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Using Rhizoplaca as a new approach to alpine lichenometry

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Using Rhizoplaca as a new approach to alpine lichenometry
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Mountain plants ( lcsh )
Lichen communities ( lcsh )
Lichenology ( lcsh )
Geological time ( lcsh )
Geological time ( fast )
Lichen communities ( fast )
Lichenology ( fast )
Mountain plants ( fast )
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Lichenometry is a useful tool when ages of a surface are unknown. As a discipline, lichenometry needs to overcome uncertainties in the understanding of lichen biology. Rhizocarpon geographicum is generally the lichen of choice for these studies as it is fairly ubiquitous. Other lichens can and have been used for these types of studies, but are used in conjunction with R. geographicum or other lichens. Rhizoplaca chrysoleuca may be used as an alternate species in areas lacking R. geographicum because it will not grow in a particular area or the substrate in question is not old enough to have substantial R. geographicum growth. While R. geographicum is well-studied, the same cannot be said for R. chrysoleuca. Growth curves R. chrysoleuca have not been established to any extent like they have been for R. geographicum. The alluvial fan in Rocky Mountain National Park created by a dam breach in 1982 makes an ideal setting to start establishing a growth curve for R. chrysoleuca. Age of the substrate is known and had been previously unexposed inside a glacial moraine. Growth over the last 28 years can be measured and the data generated by this study can be used by others to help establish a robust growth curve for R. chrysoleuca.
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by Jennifer Shanteau.

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Full Text
USING RHIZOPLACA AS A NEW APPROACH TO ALPINE
LICHENOMETRY
by
Jennifer Shanteau
B.S., Metropolitan State College of Denver, 2005
A thesis submitted to the
University of Colorado Denver
in partial fulfillment
of the requirements for the degree of
Master of Science
Environmental Sciences
2012


2012 Jennifer Shanteau
All rights reserved.


This thesis is for the Master of Science
degree by
Jenifer Shanteau
has been approved
by
Casey Allen
Jon Barbour
Frederick Chambers
Date


Shanteau, Jennifer (M.S., Environmental Sciences)
Using Rhizoplaca as a New Approach to Alpine Lichenometry
Thesis directed by Assistant Professor Casey Allen
ABSTRACT
Lichenometry is a useful tool when ages of a surface are unknown. As a
discipline, lichenometry needs to overcome uncertainties in the
understanding of lichen biology. Rhizocarpon geographicum is generally
the lichen of choice for these studies as it is fairly ubiquitous. Other
lichens can and have been used for these types of studies, but are used in
conjunction with R. geographicum or other lichens. Rhizoplaca
chrysoleuca may be used as an alternate species in areas lacking R.
geographicum because it will not grow in a particular area or the substrate
in question is not old enough to have substantial R. geographicum growth.
While R. geographicum is well-studied, the same cannot be said for R.
chrysoleuca. Growth curves R. chrysoleuca have not been established to
any extent like they have been for R. geographicum.
The alluvial fan in Rocky Mountain National Park created by a dam breach
in 1982 makes an ideal setting to start establishing a growth curve for R.
chrysoleuca. Age of the substrate is known and had been previously
unexposed inside a glacial moraine. Growth over the last 28 years can be
measured and the data generated by this study can be used by others to
help establish a robust growth curve for R. chrysoleuca.
This abstract accurately represents the content of the candidates thesis. I
recommend its publication.
Approved:
Casey Allen


ACKNOWLEDGEMENT
I wish to thank my advisor, Casey Allen, for his patience, understanding,
and input towards the completion of this thesis. Also, I am grateful to
Austen Cutrell for his assistance in trekking up to Rocky Mountain
National Park on many occasions to collect data.


TABLE OF CONTENTS
Figures..........................................................viii
Pictures...........................................................ix
Chapter
1. Introduction.....................................................1
1.1 What are Lichens?...............................................1
1.2 Classification..................................................1
1.3 Photobiont/Mycobiont Components.................................2
1.4 Habitat and Regional Preference.................................3
1.5 Anatomy and Morphology..........................................6
1.6 Reproduction and Substrate Establishment........................9
1.7 Nutrient Acquisition...........................................10
1.8 Environmental Importance.......................................12
1.9 Ecological Importance to Other Organisms.......................14
1.10 Lichenometry and Environmental Monitoring.....................15
1.11 Comparison of 2 Species.......................................17
1.11.1 Rhizocarpon geographicum....................................17
1.11.2 Rhizoplaca chrysoleuca......................................19
VI


2. Methods
21
3. Results..........................................................26
4. Conclusion.......................................................31
5. Future Directions................................................35
Bibliography........................................................36
vii


LIST OF FIGURES
Figure
1 Study Area Topographical Map...................................22
2 Lichen Sizes of all Samples Taken.............................27
3 Average Diameter per Site.....................................27
4 Lichen Diameter vs. Boulder Size..............................28
5 Average Size by Aspect........................................29
6 Average Size by Quadrant.......................................29
7 Extrapolated Growth Curve......................................30
viii


LIST OF PICTURES
1 Crustose Lichens..................................................7
2 Foliose Lichens..................................................7
3 Fruticose Lichens................................................8
4 Rhizocarpon geographicum........................................18
5 Rhizoplaca chrysoleuca..........................................20
6 Debris Field....................................................22
7 Other Lichen Species............................................23
IX


1. INTRODUCTION
1.1 WHAT ARE LICHENS?
Difficult to classify, lichens are a unique combination of fungus, algae,
and/or cyanobacteria. Able to shape landscapes and add nutrients to the
environment, they are an important component to all ecosystems. One of the few
organisms able to withstand the icy Antarctic climate, their presence enables
researchers to learn more about not only our own planet, but how life may
possibly exist on others.
1.2 CLASSIFICATION
Lichens are classified as fungi, even though they may consist of organisms
from 3 different kingdoms. An estimated 13,500 to 17,000 different species of
lichen can be found throughout the world (Nash, Introduction, 2008). It is
generally accepted that lichens evolved after their components fungi, algae, and
cyanobacteria. Lichens are polyphyletic, evolving separately over time. During
this time, lichenization and delichenization occurred between species of fungi,
algae, and cyanobacteria. Nash (Introduction, 2008) defines lichenization as the
acquisition of fixed carbon from a population of minute, living algal and/or
cyanobacterial cells. Taylor et al. (1995) have dated fossil lichen to -400 million
years ago, and Yuan, Xiao, & Taylor (2005) to -600 million years ago. Lichen
1


fossils have been found in Tertiary sites (65-1.5 mya), some even preserved in
amber. Fossils such as these are rare and difficult to find. It is possible that this
type of relationship between fungus and algae/cyanobacteria is even older, but no
evidence has been found yet to substantiate this (Honegger, Mycobionts, 2008).
1.3 PHOTOBIONT/MYCOBIONT COMPONENTS
Two core components form lichens. A photobiont, the autotrophic
component, is either an algae or cyanobacteria species (Friedl & Biidel, 2008).
The mycobiont, the fungal component, makes up the bulk of the lichen.
Lichenized fungi and non-lichenized fungi have no discernible differences. Unlike
the photobionts, the mycobionts differ from other fungi only in their nutrition
source.
Algae comprise the photobiont in approximately 90% of known lichens;
the remainder is comprised of cyanobacteria (Friedl & Biidel, 2008). Trebouxia
are a free-living species of algae and are associated with many lichenized fungi,
presumably forming a relationship easily (Honegger, Morphogenesis, 2008).
Algae and cyanobacteria utilize photosynthesis to produce either sugar alcohols
(algae) or glucose (cyanobacteria) (Friedl & Biidel, 2008). Algae are eukaryotic
cells, where they have a separate nucleus to hold DNA, and chloroplasts
photosynthesize the sugar alcohols. Cyanobacteria are prokaryotic cells that
photosynthesize in thylakoids and have circular DNA not contained in a separate
membrane. Photosynthesis in algae is possible with only water vapor available,
but in cyanobacteria, higher water content is needed to have net results (Friedl &
2


Biidel, 2008). This allows algal lichen to thrive in drier environments, and can be
attributed to the higher frequency found. When joined with a fungus, the
photobionts morphology is significantly changed, and the only way to
definitively identify the species is through DNA analysis.
The relationship between the photobiont and mycobiont is a mutual
symbiotic relationship, where the photobiont and the mycobiont both benefit from
the others presence. However, some lichens are parasitic in relation to how they
acquire their photobiont (Honegger, Mycobionts, 2008). The parasitic lichen
removes the photobiont from the host lichen and incorporates it into itself. Some
parasitic lichen completely destroy the host, others depend on the host their entire
lifetime to provide photobiont cells. The mechanism by which lichens typically
acquire their photobiont is not understood at this point (Honegger,
Morphogenesis, 2008), but established lichen symbiotes re-acquire their
photobionts after fungal reproduction. Other lichens reproduce asexually, where
symbiotic propagules contain both the photobiont and mycobiont.
1.4 HABITAT AND REGIONAL PREFERENCE
Most lichen species are terrestrial, found typically growing on trees, rocks,
and in soil. Few lichens are found living in streams or marine intertidal zones
(Nash, Introduction, 2008). These species, because they are infrequently found,
have yet to be studied well. Lichens are most important in polar and sub-polar
regions, as they are typically the dominant autotroph, but in other ecosystems, are
not normally the main contributors to primary productivity or mineral cycling.
3


Although most lichen species are terrestrial, many of the algae and
cyanobacteria species are aquatic when outside of their lichen incarnation (Nash,
Introduction, 2008). When paired with a fungus, these organisms are able to live
in less moist and higher solar intensity environments outside of the water
environment. The mycobiont helps protect the photobiont from desiccation and
the higher levels of solar light. Lichens are poikilohydric, where the lichens water
content is dependent upon surrounding moisture conditions. This is in contrast to
most plants, which are homoiohydric, who can maintain their moisture content
regardless of environmental conditions. Due to this poikilohydric nature (Nash,
Nutrients, Elemental Accumulation, and Mineral Cycling, 2008), lichens can
influence the cycling of water in their habitat. By preventing soil evaporation in
areas like the Arctic and Antarctic where they grow in mats on the soil surface,
water is unable to return to the atmosphere, creating a drier environment. Lichens
can absorb about 7.5% of incoming rainfall in one California oak forest, observed
over a three-year period (Nash, Nutrients, Elemental Accumulation, and Mineral
Cycling, 2008). This does not allow for water to reach other organisms or the soil
in the forest, thereby diverting any water exchange with the atmosphere. In coastal
deserts, the absorption effects of fog and dew has yet to be determined, but
influence over the water cycle is likely. As part of biological soil crusts in semi-
arid and arid deserts (see Habitat section), lichens absorb rainfall and aid in water
penetrating the soil in areas where a calcium carbonate layer would otherwise
prevent the movement of water into the soil (Nash, Nutrients, Elemental
Accumulation, and Mineral Cycling, 2008). This also keeps water from returning
to the atmosphere.
4


Lichens thrive in habitats or on substrates where higher plants are unable
to establish or have not yet established (Green, Nash, & Lange, 2008). These
habitats have little to no precipitation in the form of rainfall, and have high
humidity, fog, or dew that lichens are able to use as the primary source of water.
Low temperatures in the polar and alpine zones pose a threat to vascular and other
plants, but those lichens that do not contain cyanobacteria as their photobiont are
able to survive in these harsh environments. Lichens that live in Antarctica have
been shown to survive temperature extremes of -60C to -70C (Green, Nash, &
Lange, 2008). Areas that are humid and have warm overnight temperatures are not
suitable for lichen. Lichens are sensitive to air pollution and habitats with
changing landscapes, such as agricultural and high traffic areas in forests. Few
lichens are found in these environments.
Lichens are also found in living in communion with other organisms such
as free-living cyanobacteria, algae, moss, and fungi in biological soil crusts
(BSCs), an important contributor to desert ecosystem function (Belnap, 2003).
These soil crust communities are also known as cryptobiotic, cryptogamic,
microbiotic, or microphytic soil crusts (Belnap, 2003). Soil crusts can be
described as keystone communities (Eldridge, 2000) that dramatically alter abiotic
environments into living ecosystems over time (Viles, 2008). BSCs are essential
to their ecosystem as they influence species diversity, nutrient cycling, and
community structure (Viles, 2008). Belnap (2003) discusses that albedo changes
induced by lichen and moss crusts also play an important role in the crust
ecosystem. These crusts reduce the reflected light by up to 50%, compared to soils
without crusts, increasing surface temperatures. This increase helps balance the
5


rates of nitrogen and carbon fixation, soil water evaporation, microbial activity,
uptake of nutrients by plants, plant growth, and seed germination.
1.5 ANATOMY AND MORPHOLOGY
The anatomy of lichens varies by species, but there are a few similarities
shared by all. The thallus, as defined by Encylopsedia Britannica, is composed of
filaments or plates of cells...and is a simple structure that lacks specialized tissues
typical of higher plants, like stems, leaves, and conducting tissue and is the main
structure of lichen. Algal cell distribution within the thallus is either
homoiomerous or heteromerous (Biidel & Scheidegger, 2008). In homoiomerous
arrangements, algal and fungal cells are evenly distributed throughout the thallus.
Algal cells in a heteromerous arrangement are placed between layers of fungal
cells. They are not evenly distributed among the fungal cells, giving a more
complex arrangement. Heteromerous arrangements are more typically found than
the homoiomerous arrangement since this arrangement gives more protection to
the photobiont from both the sun and from desiccation when it is more completely
surrounded by mycobiont cells. Some lichens also have a prothallus structure that
is photobiont free, and may be a white, dark brown or black zone between
aerolated thallus structures and around the growing perimeter.
The morphology of the thallus puts lichens into three groups crustose,
foliose, and fruticose (Biidel & Scheidegger, 2008). Crustose lichens adhere
tightly to their substrate completely, and removal completely destroys the lichen.
Foliose lichens are flat, leaf-like structures that only partially attached to the
6


substrate, sometimes only at one point on the lichen. Fruticose lichens are shrubby
looking, with lobes that can be flat or cylindrical.
7


Picture 3 Fruticose Lichen
Many fundamental questions remain about lichen morphogenesis. How
fast is the growth rate of the thallus after establishment on a substrate? How long
does this establishment take is it possible for the propagule to be removed before
it has a chance to adhere to the substrate? How long after growth begins can the
lichen be detected on a substrate? How successful is establishment how many
propagules produced by mature lichen actually end up becoming a mature lichen?
These questions can hamper the legitimacy of lichenometry, since many of these
issues can influence the estimated age of lichens.
8


1.6 REPRODUCTION AND SUBSTRATE ESTABLISHMENT
Reproduction of lichens typically follows the fungal life cycle, modified to
include the symbiotic arrangement, with the photobiont reproductive cycle
reduced or eliminated completely. Lichens reproduce both sexually and asexually,
however Fahselt (2008) states that it is still a poorly understood discipline.
Propagules of lichens disperse dependent upon species and location
(Seaward, 2008). Some are carried by wind, dispersing lichen spores to new
habitats. Water may also transport some lichen propagules, but this area is not
well-studied. Invertebrates help facilitate transport as well. Some feed on or
shelter in lichen thalli, where propagules adhere to the organism and are carried
away and deposited elsewhere. Propagules can be dispersed in a local area when
carried by a terrestrial organism; flying invertebrates carry propagules to areas
further away, facilitating larger scale dispersal. Some slugs and snails can disperse
propagules by ingestion and leaving them behind in droppings. Vertebrates also
play a role in dispersing lichen spores as propagules can become attached to fur
and carried away. Some birds also use lichens as nesting material.
Establishment of lichen propagules on a substrate has a few criteria that
must be met (Brodo, Sharnoff, & Shamoff, 2001). The substrate must be suitable
for that species; however, only a few species have very specific requirements.
Environmental conditions also must be suitable for the particular lichen species.
There also must be space available on the substrate. Areas already high in lichen
density or soils with higher plant growth will inhibit a lichen propagule from
establishing itself on that substrate.
9


Once attached to a suitable substrate, thallus development begins.
Development and organization of thallus structure is specific to the species of
lichen (Honegger, Morphogenesis, 2008) and studies on this aspect of
development are ongoing. The time between settling on a suitable substrate and
the start of growth has been difficult to determine.
Many lichens have antibacterial and antifungal defenses that help defend
against intrusion on their home (Seaward, 2008). Most of these compounds have
been found in mature thalli, but it is reasonable to assume that propagules also
possess the ability to fend off bacterial and fungal growth to aid in their own
development into a mature thalli.
1.7 NUTRIENT ACQUISITION
Lichens obtain most of their nutrients from the air and sometimes from the
substrate to which they are attached (Nash, Nutrients, Elemental Accumulation,
and Mineral Cycling, 2008). In contrast, higher plants typically utilize the soil as
the sole means of obtaining nutrients. It is not, however, well known what specific
nutrient lichens typically require. Culturing lichens in the laboratory has proved
difficult, especially when many lichens are partial to a specific substrate and
reproduction of environmental factors in the lab is equally challenging. It has been
found that phosphorus is the limiting factor in lichen growth as no gaseous form is
available and must come from another source.
Many nutrients come from the substrate to which the lichen is attached
(Nash, Nutrients, Elemental Accumulation, and Mineral Cycling, 2008). Fog and
10


dew are another source of nutrients as these typically have a higher concentration
of various nutrients than rainwater, as this is more diluted. Particles in the air
adhere to the falling water droplets, however, dew forming on lichen surfaces has
more opportunity to collect particles, as well as fog, since these water droplets are
not moving through the air at a rapid speed. Likely this is the major source of
airborne nutrients that the lichen receives.
Dust deposition of airborne particles also gives lichens additional
nutrients, but is not thought to be a significant source, since the dust particles must
be solubilized in order to be utilized by the lichen (Nash, Nutrients, Elemental
Accumulation, and Mineral Cycling, 2008). In areas with low humidity and
precipitation, dust particles would not be a substantial source of nutrients.
However, some lichens have been shown to have high levels of pollutants and it is
believed this is the manner in which these particles, such as radioactive elements
from nuclear testing and industrial processes, are accumulated in the lichen.
Due to this observation that lichens seem to accumulate pollutants coupled
with no mechanism to remove them, they have become important in tracking
deposition of pollutants (Nash, Nutrients, Elemental Accumulation, and Mineral
Cycling, 2008). Since they are slow-growing and stay intact throughout their
lifetime (as opposed to vascular plants, which shed leaves and such during the
course of their life cycle), new growth and new pollutant concentrations are
available for measurement every year, allowing for long-term research.
Absorption of pollutants through the whole surface of the lichen is possible since,
unlike higher plant life, they do not have a waxy cuticle that does not allow such
particles to enter. Due to this, lichens are capable of accumulating elements at
11


higher levels than they require. How much pollutants and nutrients are being
deposited can be measured when compared to normal accumulation levels
observed in lichens from other areas.
These monitoring studies include deposition of metals such as nickel,
copper, zinc, mercury, lead, uranium, and arsenic (Nash, Nutrients, Elemental
Accumulation, and Mineral Cycling, 2008). Organic particles are also monitored,
including chlorinated hydrocarbons, polychlorinated biphenyls (PCBs), polycyclic
aromatic hydrocarbons (PAHs), and dioxins. Many of these organic molecules and
metals are not useful in the life cycle of the lichen; however, those that are include
inorganic substances like nitrogen and sulfur. Not only can concentrations of the
pollutants entering the environment be determined, but so can the distance certain
pollutants travel before deposition, ascertaining airborne times for those
pollutants.
Drawbacks to using lichens as environmental models include needing
better understanding of taxonomy, utilizing consistent methodologies of research,
and overcoming the depletion of lichens during research and bioassays (Nash,
Nutrients, Elemental Accumulation, and Mineral Cycling, 2008).
1.8 ENVIRONMENTAL IMPORTANCE
Lichens have many environmental roles, including pedogenesis,
biodeterioration, and nutrient cycling (Seaward, 2008). Lichens accumulate
various nutrients that eventually end up in the environment at the end of their life
cycle and these elements are then bioavailable for other organisms. Availability of
12


these elements to other organisms is not immediate, since lichens are such slow
growing and long living organisms. Over time, however, their contributions can
transform abiotic rocks into soil capable of supporting more advanced organisms.
Lichens transform rocks by both physical and chemical weathering
processes, helping create small particles that make up soils. Lichens infiltrating
cracks, subsequently contracting and expanding (Seaward, 2008) accomplishes the
physical processes of weathering. Major chemicals secreted by lichens capable of
degrading minerals are oxalic acid and a variety of phenolic acids. These acids
react with minerals in the rock to form metal complexes, many times in the form
of calcium oxalate. Most biodeterioration due to lichens is measured on a long-
term (geologic) scale, but some have a relatively short time-table, most notably on
historic monuments or artworks (such as frescoes and statues). Lichens convert up
to one millimeter of calcium carbonate into calcium oxalate every six years. Using
this chemical transformation, historians and archaeologists can verify ages of
these structures.
Lichen-assisted weathering of rocks is not only important to the
bioavailability of nutrients, but Schwartzman and Volk (1989) postulate that they
are also responsible for the habitable temperature of the Earth. As lichens
weathered rock during the Precambrian, they removed carbon dioxide from the
atmosphere, sequestering it in biomass. Weathering of rock by lichens also
released different silicates, which react with carbon dioxide and water, forming
bicarbonates, removing more carbon dioxide from the atmosphere. Carbon
dioxide removal, coupled with reduction of volcanic outgassing, led to cooler
temperatures. Biotic weathering, with lichens playing a central role, adds to soil
13


formation more than abiotic weathering. Abiotic factors contributing to
weathering include water, and to a lesser degree, wind. Depending upon the
location, rates of bioweathering are 10-1,000 times that of abiotic weathering.
Complex soil formation ceases without bioweathering. Any weathered rock would
wash away with rains, and stabilization of soils stop without biota to hold them in
place, as would soil water retention. This shifts precipitation patterns, creating
deserts in low-lying areas. Without lichens, temperatures would be higher than
current temperatures by 30-45C. At these temperatures, only thermophilic
bacteria survive.
The extensive loss of lichens may contribute to climate change locally
(Nash, Nutrients, Elemental Accumulation, and Mineral Cycling, 2008). In areas
that have large expanses of lichen cover, a major die-off due to anthropogenic
interferences would mean that no lichen cover on rocks or soils would absorb sun
radiation. Higher temperatures locally result as rocks and soils would warm up
during the day and keep the local area warmer as the rock cools slowly at night.
The rocks and soils may also reflect light, warming the surrounding atmosphere,
trapping heat in conjunction with greenhouse gases.
1.9 ECOLOGICAL IMPORTANCE TO OTHER ORGANISMS
Lichens are ecologically important to many invertebrates and vertebrates.
South African bagworm larvae (Seaward, 2008) use quartz crystals to construct
the bag in which they live. These quartz crystals are loosened from the clay by the
lichen. Some invertebrates use lichens as a camouflage, placing thalli on
14


themselves. These lichens may use the invertebrate as a substrate and continue to
grow. Birds utilize lichens as nesting material and some will only use a specific
species to construct their nest. Some species of flying squirrels also make nests
out of lichens, and also use as food. There are quite a few mammals that utilize
lichens as a food source. Deer, gazelles, mountain goats, polar bears, marmots,
monkeys, and others use the lichens only as a supplement to their diet, as many
lichens are smaller and their nutrient content is not ideal as a primary source for
larger mammals. Reindeer and caribous winter diet is approximately 50% lichen,
and while lichens are not a good source of protein, calcium, or phosphorus, they
can provide enough nutrition for reindeer and caribou to endure the winter.
1.10 LICHENOMETRY AND ENVIRONMENTAL MONITORING
Lichen biology remains a poorly understood research field, and when it
comes to using lichens as accurate dating mechanisms (i.e., lichenometry),
controversies abound. However, in many instances, such as dating late-Holocene
glacier fluctuations (Loso & Doak, 2006), lichenometry represents the only
appropriate method. Another related issue revolves around the accuracy of
statistical analyses of lichen size and their growth rate determinations. Knowing
the exact deposition time of debris from a washed out glacial moraine in Rocky
Mountain National Park (RMNP)such as the Lawn Lake flood in 1982
embodies an excellent site to conduct lichenometry studies. By using the exact
date and time this flood occurred in RMNP, a number of previously unstudied
factors about lichens, lichenometry, and climate change can be determined.
15


Further, using such a young site with a precise time of exposure can give valuable
insight into current lichenometry controversies.
Lichens are useful in environmental monitoring as they reflect changes in
environment (Seaward, 2008), especially when that change is due to
anthropogenic factors. Loss of specific species sensitive to particular
environmental changes can help identify those changes and aid in mitigating them.
Determination of glacial retreat rates, snowmelt rates, flooding, seismic
landslides, etc. by lichenometry may be the most appropriate method. This, along
with mapping and remote-sensing, aids in monitoring of these changes in
conjunction with monitoring of other known environmental changes, allowing
scientists to model future changes and recommend steps to mitigate further issues.
Using lichenometry as a technique, it is possible to measure climate
change responses of lichens. Armstrong (2004), for example, discusses
lichenometry as a method for studying glacial fluctuations caused by rapid
warming periods. This technique has shown that during periods of warming,
glaciers recede rapidly, exposing new surfaces that are subsequently colonized by
lichens. This method can then, in turn, aid in a better understanding climatic
responses of surrounding biota. Lichens are useful for climate change studies in
colder climates with harsh environmental conditions. As the first colonizers after
glacial retreat (Sancho, Green, & Pintado, 2007), lichens are the most abundant
plant life in these areas. Their growth rates correlate to favorable environmental
factors, including temperature and moisture. The studies Armstrong (2004)
discusses (McCarroll, 1993; Harrison and Winchester, 2000; Oerlemans, 1994)
contribute valuable data to further validate climate change impacts on glacial
16


retreats over the last century by comparing growth rates of lichens with increasing
temperatures associated with global climate change (Sancho, Green, & Pintado,
2007) .
Lichen growth rates applied to surface dating characterizes the basis for
lichenometry and typically uses crustose lichens (Palmqvist, Dahlman, Jonsson, &
Nash, 2008), although foliose lichens (Noller & Locke, 2000) have also been
used. Other dating techniques, such as radiocarbon or other elemental dating
techniques, are less accurate at dating recent (<500 years) events (Armstrong,
2004), and even less useful when rocks are the medium. Conversely, lichens can
grow on surfaces for up to 1000 years (Palmqvist, Dahlman, Jonsson, & Nash,
2008) , yet calibration with known dated surfaces remains key to growth curve
formation (Loso & Doak, 2006). Since lichens usually grow in a circular
formation, the diameter of the lichen can be used to determine the growth rate
when the age of the substrate is known (Noller & Locke, 2000).
1.11 COMPARISON OF TWO LICHEN SPECIES
1.11.1 RHIZOCARPON GEOGRAPHICUM
Also known as yellow map lichen, R. geographicum is classified as a
cosmopolitan taxa (Galloway, 2008), which are found on all continents and most
islands. This does not mean, however, that it will be found in all areas of said
continent or island. Crustose lichen completely attaches to its substrate; R.
geographicum is easily distinguishable with a patterned yellow and black thallus
17


that is map-like and typically found growing on siliceous rocks and favors alpine
and arctic habitats (Brodo, Sharnoff, & Sharnoff, 2001). R. geographicum is the
lichen of choice when performing lichenometric studies. Bradwell & Armstrong
(2007) reviewed multiple studies, giving 0.1 mm yr'1 to 0.5 mm yr'1 growth rate
for R. geographicum depending upon the habitat the lichens were found. Their
own study revealed a higher average growth rate (0.65 mm yr'1), and included
differences between thallus size and growth rate, giving a parabolic growth rate as
opposed to a linear growth rate assumed in many studies. Only two studies have
shown this type of growth curve, therefore, more studies into the relationship
between thallus size and yearly growth are needed.
Picture 4 Rhizocarpon geographicum (yellow) found outside study area.
18


1.11.2 RHIZOPLACA CHRYSOLEUCA
Orange rock-posy is the common name for R. chrysoleuca. This lichen is
typically found on granitic rock and is fairly ubiquitous across western North
America (Brodo, Sharnoff, & Shamoff, 2001). A foliose lichen, the thallus can be
pale yellow-green to yellow-grey in color, with apothecia disks of pale to dark
orange. R. chrysoleuca attaches to the substrate by a central holdfast, but
sometimes appears as more of a crustose lichen. Another Rhizoplaca species is
similar in morphology, but lifting of the thallus edges identifies the lichen as R
chrysoleuca and not R subdiscrepens, which is a crustose lichen. Very few
studies have been conducted with R. chrysoleuca, as it is not as cosmopolitan as
R. geographicum. One study using multiple species to establish growth curves to
determine water level changes (Timoney & Marsh, 2004) report growth rates for
R. chrysoleuca between 0.32 0.89 mm yr'1 when a lag time of 5.9 years is used
(see Results section for discussion of lag time). The Timoney & Marsh paper
references three unpublished studies for these growth rates. It is apparent that
more study is needed for this particular species, and can be useful if other lichens
are not present in abundance for lichenometric studies.
19


Picture 5 Rhizoplaca chrysoleuca used in study.
20


2. METHODS
The Lawn Lake Dam, an earthen dam constructed in 1903, after years of
disrepair, failed on July 15, 1982, sending 219 million gallons of water into the
Roaring River (Town of Estes Park, 2010). This torrent of water broke through a
glacial moraine, intact from the last ice age, sending literally tons of debris
including large boulders from the glacial tilldown to Horseshoe Park. Most of
this debris deposited at this site, though water continued to wash down through the
Cascade Lake Dam, flooding the town of Estes Park, and finally stopping in the
Estes Lake (Town of Estes Park, 2010).
Horseshoe Park (elevation 8500 to 8610 feet) in Rocky Mountain National
Park (Map 1) sits at the deposition point for many large boulders and sediments
washed down from the Lawn Lake Dam flood. Many of these boulders were part
of a glacial moraine that the flood destroyed and had, as such, no previous
exposure to lichens. As such, this site was chosen to conduct studies on lichen
colonization. Initially, this study was to determine if there were any climate
change impacts on lichens, however, the lichen typically used for lichenometric
studies was not found in any abundance at this site. Without an established growth
curve for the lichen eventually sampled here, the decision was to establish a
growth curve for R. chrysoleuca as an alternative to R geographicum in younger
sites or those sites lacking A. geographicum.
21


Picture 6 View of the debris field just above the sampling area, showing the deposition of
boulders after the flooding event in 1982.
Figure 1 Topographical map of study area outlined in orange.
22


Before gathering data, random areas of the site were sampled for lichen
diversity (not recorded). It was decided at that point that while R. geographicum is
the better species for conduction of lichenometric studies, there were almost none
found within the boundaries of the debris field. The most abundant lichen that
could be identified definitively to the species level was Rhizoplaca chrysoleuca.
Other genera or species encountered within the boundaries of the debris field
include Xanthoparmelia, Umbilicaria, and unidentified brown, grey/black, and
orange crustose lichens.
Picture 7 Other species were considered for the study, but were not as abundant as
Rhizoplaca.
When conducting this study, a few assumptions were made following Noller
and Locke (2000).
1. The substrate had not been colonized by lichens before final deposition
and had not been moved since deposition
2. Diameter of lichens reflect annual growth
3. The growth rate of lichens is linear
23


4. No lag time for colonization (establishment of lichen on the substrate took
place soon after deposition)
Thirteen 8m x 8m plots were randomly selected within the boundaries of the
debris field. The entire site was segmented into 4 quadrants using the Roaring
River and Old Fall River Road as transects (these transects can be seen in Figure
1). The largest lichens were measured within each plot, as recommended in Innes
study (1984). A 12m buffer between the sampling sites and any hiking paths or
roads was used to minimize any anthropogenic influence on lichen growth. This
site is a popular hiking area and easily accessible for all levels of hikers in Rocky
Mountain National Park, colonization by lichen would ultimately be inhibited by
people climbing on boulders. Boulder sizes less than 30cm were not sampled, as it
appeared than little to no R. chrysoleuca grew on smaller boulders or rocks. Close
to the Roaring River, no lichens were found, either due to flooding in the spring or
the small size of the rocks and boulders.
Any R. chrysoleuca that was growing closely with another R chrysoleuca was
not measured unless there was a clear delineation between the two lichens. Since
R. chrysoleuca do not completely attach to the substrate, it was usually possible to
distinguish a separation between two lichens. In the cases where it seemed they
were growing together, they were excluded from sampling (Refsnider & Brugger,
2007).
For each sampling site, GPS coordinates were taken at the four comers of the
plot, the lichens measured using digital calipers, the size of the boulder was
recorded, as well as which aspect the lichen was facing (north, south, top of
boulder, etc.). In some sampling sites, few lichens were encountered, and only the
24


largest five were recorded, measuring on the longest axis of the lichen (Innes,
1984). The majority of the sampling sites had numerous lichens, and up to 14
lichens in each sampling site were recorded. The largest 5 lichen from each
sampling site were averaged. The averages of each site were then combined to
give an overall average lichen size for the entire debris field.
Another method considered for this project was discussed in Timoney &
Marsh (2004). As R. geographicum was not available at their study site, multiple
species were used to determine age of the water-formed trimlines. A growth curve
was constructed incorporating those species found. For this project, however, the
use of R. chrysoleuca exclusively was determined the best course of action as it
was easily identified and found in all areas sampled. Other lichens, such as those
species of genera Xanthoparmelia and Umbilicaria were not used as they were not
either found in many of the sites sampled, or in the case of Umbilicaria, species
were indistinguishable from each other. R. geographicum were rarely found
within the boundaries of the debris field. The conclusion was that this species was
either unable to establish in this area, or their growth was much slower and had
not achieved a sufficiently large enough size to be easily seen.
25


3. RESULTS
The average size o/R. chrysoleuca from all 13 sites, with 65 total lichens
measured, is 32.35 mm 3.22 mm. Assuming a linear growth from exposure in
1982, the average growth per year is 1.15 mm. As seen in Figure 2, the lichen
diameter of all samples taken fall between 25.59 and 42.99 mm. The average
value for these data is 32.35 4.18 mm and the median is 31.92 4.18 mm. The
few outliers do not have a significant impact on diameter mean and will be
included in subsequent analyses. The averages of lichen diameter per site (Figure
3) have a mean of 32.47 3.22 mm. Using the averages of all samples is not
significantly different than using the average of the means of each site. Following
the recommendation of Innes (1984), the mean of the five largest lichen of each
sample site will be used for reporting.
Timoney and Marsh (2004) established a lag time by comparing lichen
growth in a cemetery near their study site. At this site, surfaces were exposed at
different times, with lichenized and non-lichenized surfaces to compare. At the
project site, there were non-lichenized surfaces, but many were eliminated due to
size or proximity to potentially anthropogenic disturbances. Therefore, a lag time
was not determined due to this and the fact that all of the substrate available for
lichen colonization was exposed from the glacial moraine at the same time.
26


Rhizoplaca chrysoleuca
£
£,
4-*
OJ
E
TO
b
46.00
44.00
42.00
40.00
38.00
36.00
34.00
32.00
30.00
28.00
26.00
24.00
22.00
20.00
0
10 20 30 40 50 60 70
Sample number
Figure 2 Lichen sizes of all samples taken.
Figure 3 Averages of diameter by site (5 samples per site).
27


Lichen Diameter vs. Boulder Size
Figure 4 Comparing boulder size to the diameter of all lichen found on each boulder._
There was a varying degree of boulder size among the sampling sites, and
all lichen measurements were compared against the size of boulder on which it
was found (Figure 5). There is no significant effect on lichen size compared to
boulder size. While McCarroll (1994) found a more significant role played on
lichen size (using R. geographicum) when boulder size is taken into account, he
also shows that sampling a variety of boulder sizes has no significant effect on
mean lichen size.
28


Figure 5 Comparing sample aspect and size. Numbers above aspect diameter represent
number of samples.
Average Size by Quandrant
Northeast Southwest Southeast Northwest
Figure 6 Comparison of lichen diameter with quadrant sampled.
When looking at the impacts of aspect (Figure 6) and quadrant (Figure 7)
on lichen growth, there are significant effects. When the lichen was located on the
north, east, south, northeast, or top of the boulder, the size was significantly larger
than those located on the southwest, southeast, northwest, or west facing lichen.
29


(Some boulders were large enough or flat on the top that it was difficult to
determine which way the lichen was facing, these lichens were assigned a top of
the boulder aspect.) There are significant differences in growth when compared to
the four quadrants the lichens grew in the debris field. The northwest and
southeast quadrants have a higher growth rate than the northeast and southwest
quadrants. In all areas, vegetation was similar and shading from these small trees
and bushes probably did not have a large impact.
Extrapolated Growth Curve
R2 = 0.9973
Measured Diameter
-----Extrapolated Growth
Year
Figure 7 Extrapolated growth curve for 100 years growth.
Assuming a linear and infinite growth, the extrapolated growth curve
(Figure 8) can be used to determine the age of a substrate where R. chrysoleuca is
found. When using the initial colonization as 0 mm and the growth of 1.155 mm
yr'1, the growth curve shows that if the lichen measures 97 mm, the substrate has
been exposed for 80 years.
30


4. CONCLUSION
In order to understand more about using lichenometry and validate its
usefulness as a dating method when other methods cannot be used, more is
understanding of lichen growth is necessary. This study is by no means complete,
but is a starting place to finding alternative lichens for sites that do not have
established Rhizocarpon geographicum, whether due to age of the site or
unsuitable habitat. There is no documentation of the growth limit or average
lifespan for R. chrysoleuca and only one reference to annual growth is mentioned
in Timoney and Marsh (2004). The ability to use multiple species for a location
would only help establish a more concrete time of exposure for determination of
deposition or exposure of a substrate.
Using growth curves from one site to date another site requires similar
macroclimatic, elevation, substrate, and vegetative cover conditions. Since many
lichens have specific growth requirements, these criteria will most likely be met at
a location if a particular lichen is found. Each case is different, however, so there
will not be any universal growth curve for every lichen. The best possible growth
curve is based on a comparison of lichen growth on a substrate of known age in
the same or adjacent area for the unknown substrate.
Differences seen in the growth in different quadrants may be an indication
of earlier colonization. For purposes of growth curve construction, it is assumed
that colonization takes place shortly after the substrates initial exposure. This is
not necessarily what happens, as Timoney and Marsh (2004) show, but even their
review of other studies show that lag time is inconsistent. Another reason for the
31


dichotomy between the sites may be that the climactic conditions in those areas
differ enough to affect growth. The two quadrants with lower growth may not
receive the same amount of sunlight, precipitation, or the substrate may have
different composition than the two quadrants with higher growth. The fact that
neither of the lower or higher growth quadrants is adjacent to each other makes it
difficult to infer the cause for the significant difference seen in growth, unless
microclimatic factors are vastly different in each area.
Much of the literature cited here, in particular Noller and Locke (2000),
Innes (1984), and McCarroll (1994), state that the largest lichen are the idealized
specimens for that particular habitat fast-growing and quickest to establish on
the substrate, therefore giving the best possible growth curve to estimate age of
the substrate. In light of this, should the lichens in the lower growth quadrants be
excluded from the analyses? The largest growth quadrant (northwest) has an
average of 34.69 mm and 95% confidence interval of 27.49 42.49 mm. The
smallest growth quadrant (northeast) has an average of 30.12 mm. Since the
lowest growth falls well within the 95th percentile of the largest growth quadrant,
it should not be excluded from further analyses.
Aspect also seems to have an effect on growth of R. chrysoleuca in this
location. The most abundant growth is found with lichens growing on the top of
the boulders with an average growth of 33.41 mm, and a 95% confidence interval
of 23.95 42.87 mm. As described in the data section, the top of the boulder
aspect was used when the lichen faced no discernible direction due to the size or
shape of the boulder. The southwest aspect had the least growth with an average
32


of 30.11 mm. Again, as the lowest growth falls well within the 95th percentile of
the largest growth quadrant, it should not be excluded from further analyses.
Since both aspect and quadrant can be ruled out with having an effect on
the growth of R. chrysoleuca in this particular area, other sites with similar habitat
and climate should be able to use this preliminary data to help construct a more
robust growth curve for R. chrysoleuca. Since less is known of R. chrysoleuca's
growth rate than R. geographicum, possibly due to a shorter life span for R.
chrysoleuca than R geographicum, or that R. chrysoleuca is a primary colonizer
and is subsequently outcompeted by later succession of other species, it is difficult
to draw concrete conclusions. Using R. chrysoleuca may be a good alternative at
younger sites where R. geographicum may not have had a chance to establish or
had enough time to grow.
There are other questions that came up during this project, but are not able
to be answered with the current data. Is lag time a factor? This would have large
implications on the growth rate. A lag time of 5.9 years, as Timoney and Marsh
(2004) suggests at their Northern Alberta site, would have a sizable impact on the
growth curve. This would change the average yearly growth rate from 1.155 mm
(assumed 28 years to grow to current size) to 1.464 mm (22.1 years to grow to
current size).
We assume a linear growth rate, but it is likely that there is a more
parabolic curve to R chrysoleuca growth. Bradwell and Armstrong (2007)
reviewed data from previous studies for R. geographicum and showed that growth
rates were higher when the lichen was younger, and slowing down as the lichen
aged. Previous growth curves using a linear relationship to age and time would
33


have to be recalibrated to reflect these new findings, and ages of substrates would
have to be re-evaluated. Since this study only has data from one point in time, it is
not possible to construct a curve reflecting possible changes in growth rate.
Under-studied areas of lichen biology hinder accurate growth curve
production for species of lichen. Reproduction, transportation of propagules,
morphogenesis, lag time of establishment on a substrate, and even understanding
of lichen taxonomy are all areas that need further study. These uncertainties
should not invalidate lichenometry, since some assumptions can be made using
current knowledge to make a case for legitimacy. Lichenometry may not yet be an
exact science, but the field is continuing to grow. With more research in these
areas, the use of lichens can become a legitimate dating tool, useful in situations
where other dating techniques will not yield results.
34


5. FUTURE DIRECTIONS
Despite the aforementioned issues, the information found here can help
future studies. In this particular study, many questions can be answered about R.
chrysoleucas annual growth by re-visiting the site annually and repeating
measurements in the same areas. With repeated sampling, a better curve can be
constructed, allowing more accurate dating to take place at sites with unknown
age. This can also help answer the question of whether these lichens have linear or
parabolic growth.
In addition to re-evaluating growth for R. chrysoleuca, monitoring of the
site can also yield results for establishment time of R geographicum, as a few
specimens were found in this outing. Continued monitoring may produce more
observations of this species, resulting in not only calculated lag times, but
questions about climate change impacts on both lichen growth and the
surrounding environment can be answered.
With ongoing studies of lichen biology, such as morphogenesis,
reproduction, and taxonomy, these growth studies will strengthen the field of
lichenometry. Establishing more consistent methodologies of research for all who
conduct these studies will bring more validity to the field and streamline the
process of gathering data so that future studies are more widely accepted as a
dating technique.
35


BIBLIOGRAPHY
Armstrong, R. (2004). Lichens, Lichenometry, and Global Warming.
Microbiologist, September, 32-35.
Bradwell, T., & Armstrong, R. A. (2007). Growth Rates of Rhizocarpon
geographicum Lichens: A Review with New Data from Iceland. Journal of
Quaternary Science, 22(4), 311-320.
Brodo, I. M., Shamoff, S. D., & Sharnoff, S. (2001). Lichens of North America.
New Haven and London: Yale University Press.
Biidel, B., & Scheidegger, C. (2008). Thallus Morphology and Anatomy. In T. H.
Nash III (Ed.), Lichen Biology (pp. 40-68). Cambridge: University Press.
Fahselt, D. (2008). Individuals and Populations of Lichens. In T. H. Nash III
(Ed.), Lichen Biology (pp. 252-273). Cambridge: University Press.
Friedl, T., & Biidel, B. (2008). Photobionts. In T. H. Nash III (Ed.), Lichen
Biology (pp. 9-26). Cambridge: University Press.
Galloway, D. J. (2008). Lichen Biogeography. In T. H. Nash III (Ed.), Lichen
Biology {pp. 315-335). Cambridge: University Press.
Green, T. G., Nash, T. H., & Lange, O. L. (2008). Physiological Ecology of
Carbon Dioxide Exchange. In T. H. Nash III (Ed.), Lichen Biology (pp.
152-181). Cambridge: University Press.
Honegger, R. (2008). Morphogenesis. In T. H. Nash III (Ed.), Lichen Biology (pp.
69-93). Cambridge: University Press.
Honegger, R. (2008). Mycobionts. In T. H. Nash III (Ed.), Lichen Biology (pp. 27-
39). Cambridge: University Press.
Innes, J. L. (1984). The Optimal Sample Size in Lichenometric Studies. Arctic
and Alpine Research, 16, 233-244.
Loso, M. G., & Doak, D. F. (2006). The Biology behind Lichenometric Dating
Curves. Oecologia, 147, 223-229.
McCarroll, D. (1994). A New Approach to Lichenometry: Dating Single-Age and
Diachronous Surfaces. The Holocene, 4, 383-396.
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Nash, T. H. (2008). Introduction. In T. H. Nash III (Ed.), Lichen Biology (pp. 1-8).
Cambridge: University Press.
Nash, T. H. (2008). Nutrients, Elemental Accumulation, and Mineral Cycling. In
T. H. Nash III (Ed.), Lichen Biology (pp. 234-251). Cambridge: University
Press.
Noller, J. S., & Locke, W. W. (2000). Lichenometry. Quaternary Geochronology:
Methods and Applications, 261-272.
Palmqvist, K., Dahlman, L., Jonsson, A., & Nash, T. H. (2008). The Carbon
Economy of Lichens. In T. H. Ill (Ed.), Lichen Biology (pp. 182-215).
Cambridge: University Press.
Refsnider, K. A., & Brugger, K. A. (2007). Rock Glaciers in Central Colorado,
U. S.A., as Indicators of Holocene Climate Change. Arctic, Antarctic, and
Alpine Research, 39, 127-136.
Sancho, L. G., Green, T. G., & Pintado, A. (2007). Slowest to Fastest: Extreme
Range in Lichen Growth Rates Supports Their Use as an Indicator of
Climate Change in Antarctica. Flora, 202, 667-673.
Seaward, M. R. (2008). Environmental Role of Lichens. In T. H. Nash III (Ed.),
Lichen Biology (pp. 274-298). Cambridge: University Press.
Taylor, T. N., Remy, W., & Kerp, H. (1995, November 16). The Oldest Fossil
Lichen. Nature, 378, 244.
thallus. (n.d.). Retrieved January 24, 2012, from Encylopsedia Britannica:
http://www.britannica.com/EBchecked/topic/589870/thallus
Timoney, K. P., & Marsh, J. (2004). Lichen Trimlines in Northern Alberta:
Establishment, Growth Rates, and Historic Water Levels. The Bryologist,
107(4), 429-440.
Town of Estes Park. (2010). The Lawn Lake Flood. Retrieved February 19, 2010,
from Town of Estes Park:
http://www.estesnet.com/Hydroplant/the_lawn_lake_flood.aspx
Yuan, X., Xiao, S., & Taylor, T. N. (2005). Lichen-Like Symbiosis 600 Million
Years Ago. Science, 308, 1017-1020.
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Full Text

PAGE 1

USING RHIZOPLACA AS A NEW APPROACH TO ALPINE LICHENOMETRY by Jennifer Shanteau B.S. Metropolitan State College of Denver, 2005 A thesis submitted to the University of Colorado Denver in partial fulfillment of the requirements for the degree of Master of Science Environmental Sciences 2012

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2012 Jennifer S hanteau All rights reserved.

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This thesis is for the Master of Science degree by Jenifer Shanteau has been approved by Casey Allen Jon Barbour Frederick Chambers Date

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Shanteau, Jennifer (M.S., Environmental Sciences) Using Rhizoplaca as a New Approach to Alpine Lichenometry Thesis directed by Assistant Professor Casey Allen ABSTRACT Lichenometry is a useful tool when ages of a surface are unknown. As a discipline, lichenometry needs to overcome uncertainties in the understanding of lichen biology. Rhizocarpon geographicum is generally the lichen of choice for these studies as it is fairly ubiquitous. Other lichens can and have been used for these types of studies, but are used in conjunction with R. geographicum or other lichens. Rhizoplaca chrysoleuca may be used as an al ternate species in areas lacking R geographicum because it will not grow in a particular area or the substrate in question is not old enough to have substantial R. geographicum growth. While R. geographicum is well studied, the same cannot be said for R chrysoleuca Growth curves R. chrysoleuca have not been established to any extent like they have been for R. geographicum The alluvial fan in Rocky Mountain National Park created by a dam breach in 1982 makes an ideal setting to start establishing a grow th curve for R chrysoleuca A ge of the substrate is known and had been previously unexposed inside a glacial moraine. G rowth over the last 28 years can be measured and the data generated by this study can be used by others to help establish a robust growt h curve for R. chrysoleuca recommend its publication Approved: Casey Allen

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ACKNOWLEDGEMENT I wish to thank my advisor, Casey Allen, for his patience, understanding, and input towards the completion of this thesis. Also, I am grateful to Austen Cutrell for his assistance in trekking up to Rocky Mountain National Park on many occasions to collect data.

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vi TABLE OF CONTENTS ...... .viii Pictures ................................................................. .................................ix Chapter 1. Introduction........................................................................................ 1 1. 1 What are Lichens?.............................................. ..............................1 1. 2 Classification.................................................................................... 1 1. 3 Photobiont/Mycobiont Components..................... ..............................2 1. 4 Habitat and Regional Preference....................................................... 3 1. 5 Anatomy and Morphology.................................. ...............................6 1. 6 Reproduction and Substrate Establishment.................... ....................9 1. 7 Nutrient Acquisition................................................................. ...... 10 1. 8 Environmental Importance...... ........................... ............................. 12 1. 9 Ecological Importance to Other Organisms.... .. ...............................1 4 1.1 0 Lichenometry and Environmental Monitoring........... .....................1 5 1.1 1 Comparison of 2 Species................................. ..............................1 7 1.1 1 .1 Rhizocarpon geographicum ........................................................ 1 7 1.1 1 .2 Rhizoplaca chrysoleuca .. ............................... ......... ....................19

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vii 2. Methods........................................................... ............................... 21 3. Results ........................ ............................................. ........................26 4. Conclusion....................................................................................... 31 5. Future Directions..............................................................................35 Bibliography ............................................................ ............................. 36

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viii LIST OF FIGURES Figure 1 Study Area Topographical Map........ ... ................. ..............................22 2 Lichen Sizes of all Samples Taken............ ... ....... ...............................27 3 Average Diameter per Site......................... ... ....... ..............................27 4 Lichen Diameter vs. Boulder Size.............. ... ....... ........ ......................28 5 Average Size by Aspect.............................. ... ...... ..............................29 6 Average Size by Quadrant........................... .. ...... ...............................29 7 Extrapolated Growth Curve....... .................. ... ......................... ...........30

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ix LIST OF PICTURES 1 Crustose Lichens.............. ... ................................. ...............................7 2 Foliose Lichens................... ... .............................. ...............................7 3 Fruticose Lichens................... ... .......................................................... 8 4 Rhizocarpon geographicum ....... ... ........................ ..............................1 8 5 Rhizoplaca chrysoleuca ................ ... .......................... ........................20 6 Debris Field.................................... .. .................. ...............................22 7 Other Lichen Species........................ ... ............... ..............................23

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1 1. INTRODUCTION 1. 1 WHAT ARE LICHENS ? Difficult to classify, lichens are a unique combination of fungus, algae, and/or cyanobacteria. Able to shape landscapes and add nutrients to the environment, they are an important component to all ecosystems. One of the few organisms able to withstand the icy Antarctic climate, their presence enables researchers to learn more about not only our own planet, but how life may poss ibly exist on others. 1. 2 CLASSIFICATION Lichens are classified as fungi, even though they may consist of organisms from 3 different kingdoms. An estimated 13,500 to 17,000 different species of lichen can be found throughout the world (Nash, Introduction, 2008) It is generally accepted that lichens evolved after their components fungi, algae, and cyanobacteria. Lichens are polyphyletic, evolving separately over time. During this time, lichenization and delichenization occurred between species of fungi, algae, and cyanobacteria. Nash (Introduction, 2008) acquisition of fixed carbon from a population of minute, living algal and/or cyanobacterial (1995) have dated fossil lichen to ~400 million yea rs ago, and Yuan, Xiao, & Taylor (2005) to ~600 million years ago. Lichen

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2 fossils have been found in Tertiary sites (65 1.5 mya), some even preserved in amber. Fossils such as these are rare and difficult to find. It is possible that this type of relationship between fungus and algae/cyanobacteria is even older, but no evidence has been f ound yet to substantiate this (Honegger, Mycobionts, 2008) 1. 3 PHOTOBIONT / MYCOBIONT COMPONENTS T wo core components form lichen s A photobiont, the autotrophic component, is either an algae or cyanobacteria species (Friedl & Bdel, 2008) The mycobiont, the fungal component, makes up the bulk of the lichen. Lichenized fungi and non lichenized fungi have no discernible differences. Unlike the photobionts, the mycobionts differ from other fungi only in their nutrition sourc e. Algae comprise the photobiont in approximately 90% of known lichens; the remainder is comprised of cyanobacteria (Friedl & Bdel, 2008) Trebouxia are a free living species of algae and are associated with many lichenized fu ngi, presumably forming a relationship easily (Honegger, Morphogenesis, 2008) Algae and cyanobacteria utilize photosynthesis to produce either sugar alcohols (algae) or glucose (cyanobacteria) (Friedl & Bdel, 2008) Algae are eukaryotic cells, where they have a separate nucleus to hold DNA, and chloroplasts photosynthesize the sugar alcohols. Cyano bacteria are prokaryotic cells that photosynthesize in thylakoids and have circular DNA not contained in a separate membrane. Photosynthesis in algae is possible with only water vapor available, but in cyanobacteria, higher water content is needed to have net results (Friedl &

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3 Bdel, 2008) This allows algal lichen to thrive in drier environments, and can be attributed to the higher frequency found. When joined with a fungus, the definitively identify the species is through DNA analysis. The relationship between the photobiont and mycobiont is a mutual symbiotic relationship, where the photobiont and the mycobiont both benefit from the others presence. However, some lichens are parasitic in relation to how they acquire their photobiont (Honegger, Mycobionts, 2008) T he parasitic lichen removes the photobiont from the host lichen and incorporate s it into itself Some parasitic lichen completely destroy the host, others depend on the host their entire lifetime to provide photobion t cells. The mechanism by which lichens typically acquire their photobiont is not understood at this point (Honegger, Morphogenesis, 2008) but established lichen symbiotes re acquire their photobionts after fungal reproduction Other lichens reproduce asexually, where symbiotic propagules contain both the photobiont and mycobiont. 1. 4 HABITAT AND REGIONAL PREFERENCE Most lichen species are terrestrial, found typically growing on trees, rocks, and in soil. Few lichens are found living in streams or marine intertidal zones (Nash, Introduction, 2008) These species, because they are infrequently found, have yet to be studied well. Lichens are most important in polar and sub polar regions, as they a re typically the dominant autotroph, but in other ecosystems, are not normally the main contributors to primary productivity or mineral cycling.

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4 Although most lichen species are terrestrial, many of the algae and cyanobacteria species are aquatic when outs ide of their lichen incarnation (Nash, Introduction, 2008) When paired with a fungus, these organisms are able to live in less moist and higher solar intensity environments outside of the water environment. The mycobiont helps protect the photobiont from desiccation and the higher levels of solar light. Lichens are poikilohydric, where the lichens water content is dependent upon surrounding moisture conditions. This is in contrast to most plants, which are homoiohydric, who can maintain their moisture content regardless of environmental conditions. Due to this poikilohydric nature (Nash, Nutrients, Elemental Accumulation, and Mineral Cycling, 2008) lichens can influence the cycling of water in their habitat. By preventing soil evaporation in areas like the Arctic and Antarctic where they grow in mats on the soil surface, water is unable to return to the atmosphere, creating a drier environment. Lichens can absorb about 7.5% of incoming rainfall in one California oak forest, observed over a three year period (Nash, Nutrients, Elemental Accumulation, and Mineral Cycling, 2008) This does not allow for water to reach other organisms or the soil in the forest, thereby diverting any water exchange with the atmosphere. In coastal deserts, the absorption effects of fog and dew has yet to be determined, but influence over the water cycle is likely. As part of biological soil crusts in semi arid and arid deserts (see Habitat section ), lichens absorb rainfall and aid in water penetrating the soil in areas where a calcium carbonate layer would otherwise prevent the movement of water into the soil (Nash, Nutrients, Elemental Accumulation, and Mineral Cycling, 200 8) This also keeps water from returning to the atmosphere.

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5 Lichens thrive in habitats or on substrates where higher plants are unable to establish or have not yet established (Green, Nash, & Lange, 2008) These h abitats h ave little to no precipitation in the form of rainfall, and have high humidity, fog, or dew that lichens are able to use as the primary source of water Low temperatures in the polar and alpine zones pose a threat to vascular and other plants, but those lichens that do not contain cyanobacteria as their photobiont are able to survive in these harsh environments. Lichens that live in Antarctica have been shown to survive temperature extremes of 60C to 70C (Green, Nash, & Lange, 2 008) Areas that are humid and have warm overnight temperatures are not suitable for lichen. Lichens are sensitive to air pollution and habitats with changing landscapes, such as agricultural and high traffic areas in forests. Few lichens are found in these environments. Lichen s are also found in living in communion with other organisms such as free living cyanobacteria, algae, moss, and fungi in biological soil crusts (BSCs), an important contributor to desert ecosystem function (Belnap, 2003). These soil crust communities are also known as cryptobiotic, cryptogamic, microbiotic, or microphytic soil crusts (Belnap, 2003). Soil crusts can be described as keystone communities (Eldridge, 2000) that dramatically alter abiotic environments into living ecos ystems over time (Viles, 2008). BSCs are essential to their ecosystem as they influence species diversity, nutrient cycling, and community structure (Viles, 2008). Belnap (2003) discuss es that albedo changes induced by lichen and moss crusts also play an i mportant role in the crust ecosystem. These crusts reduce the reflected light by up to 50%, compared to soils without crusts, increasing surface temperatures. This increase helps balance the

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6 rates of nitrogen and carbon fixation, soil water evaporation, mi crobial activity, uptake of nutrients by plants, plant growth, and seed germination. 1. 5 ANATOMY AND MORPHOLOGY The anatomy of lichens varies by species, but there are a few similarities shared by all. filaments or plates of cells...and is a simple structure that lacks specialized tissues typical of higher plants, like stems, leave s, and conducting tissue and is the main structure of lichen. Algal cell distribution within the thallus is either homoiomerous or heteromerous (Bdel & Scheidegger, 2008) In homoiomerous arrangements, algal and fungal cells are evenly distributed throughout the thallus. Algal cells in a heteromerous arrangement are placed between l ayers of fungal cells. They are not evenly distributed among the fungal cells, giving a more complex arrangement. Heteromerous arrangements are more typically found tha n the homoiomerous arrangement since this arrangement gives more protection to the photo biont from both the sun and from desiccation when it is more completely surrounded by mycobiont cells. Some lichens also have a prothallus structure that is photobiont free, and may be a white, dark brown or black zone between aerolated thallus structures and around the growing perimeter. T he morphology of the thallus puts lichens into three groups crustose, foliose, and fruticose (Bdel & Scheidegger, 2008) Crustose lichens adhere tightly to their substrate completely, and removal completely destroys the lichen. Foliose lichens are flat, leaf like structures that only partially attached to the

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7 substrate, sometimes only at one point on the lichen. Fruticose lichens are shrubby looking, with lobes that can be flat or cylindrical. Picture 1 Crustose Lichens Picture 2 Foliose Lichens

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8 Picture 3 Fruticose Lichen Many fundamental questions remain about lichen morphogenesis. How fast is the growth rate of the thallus after establishment on a substrate? How long does this establishment take is it possible for the propagule to be removed before it has a chance to adhere to the subst rate? How long after growth begins can the lichen be detected on a substrate? How successful is establishment how many propagules produced by mature lichen actually end up becoming a mature lichen? These questions can hamper the legitimacy of lichenometr y, since many of these issues can influence the estimated age of lichens.

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9 1. 6 REPRODUCTION AND SUBSTRATE ESTABLISHMENT Reproduction of lichens typically follows the fungal life cycle, modified to include the symbiotic arrangement, with the photobiont reproductive cycle reduced or eliminated completely. Lichens reproduce both sexually and asexually, however Fahselt (2008) states that it is still a poorly understood discipline. Propagules of lichens disperse depende nt upon species and location (Seaward, 2008) Some are carried by wind, dispersing lichen spores t o new habitats. Water may also transport some lichen propagules, but this area is not well studied. Invertebrates help facilitate transport as well. Some feed on or shelter in lichen thalli, where propagules adhere to the organism and are carried away and deposited elsewhere. Propagules can be dispersed in a local area when carried by a terrestrial organism ; flying invertebrates carry propagules to areas further away facilitating larger scale dispersal Some slugs and snails can disperse propagules by ingestion and leaving them behind in droppings Vertebrates also play a role in dispersing lichen s pores as p ropagules can become attached to fur and carried away. Some birds also use lichens as nesting material. Establishment of lichen propagules on a substrate has a few criteria that must be met (Brodo, Sharnoff, & Sharnoff, 2001) The substrate must be suitable for that species; however, o nly a few species have very specific requirements. Environmental conditions also must be suitable for the particular lichen species. T here also must be space available on the substrate. Areas already high in lichen density or soils with higher plant growth will inhibit a lichen propagule from establishing itself on that substrate.

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10 Once attached to a suitable substrate, thallus development begins. Development and organization of thallus structure is specific to the species of lichen (Honegger, Morphogenesis, 2008) and studies on this aspect of development are ongoing The time between settling on a suitable substrate and the start of growth has been difficult to determine Many lichens have antibacterial and antifungal defenses that help defend against intrusion on their home (Seaward, 2008) Most of these compounds have been found in mature thalli, but it is reasonable to assume that propagules also possess the ability to fend off bacterial and fungal growth to aid in their own development into a mature thalli. 1. 7 NUTRIENT ACQUISITION Lichens obtain most of their nutrients from the air and sometimes from the substrate to which they are attached (Nash, Nutrients, Elemental Accumulation, and Mineral Cycling, 2008) In contrast, h igher plants typically utilize the soil as the sole means of obtaining nutrients. It is not, however, well known what specif ic nutrient lichens typically require. Cul turing lichens in the laboratory has proved difficult, especially when many lichens are partial to a specific substrate and reproduction of environmental factors in the lab is equally challenging It has been found that phosphorus is the limiting factor in lichen growth as no gaseous form is available and must come from another source. Many nutrients come from the substrate to which the lichen is attached (Nash, Nutrients, Elemental Accumulation, and Mineral Cycling, 2008) Fog and

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11 dew are another source of nutrients as these typically have a higher concentration of various nutrients than rainwater, as this is more diluted. Particles in the air adher e to the falling water droplets, however, d ew forming on lichen surfaces has mor e opportunity to collect particles, as well as fog, since these water droplets are not moving through the air at a rapid speed. Likely this is the major source of airborne nutrients that the lichen receives. Dust deposition of airborne particles also give s lichens additional nutrients, but is not thought to be a significant source, since the dust particles must be solubilized in order to be utilized by the lichen (Nash, Nutrients, Elemental Accumulation, and Mineral Cycling, 2008) In areas with low humidity and precipitation, dust particles would not be a substantial source of nutrients. However, s ome lichens have been shown to have high levels of pollutants and it is believed this is the manner in which these particles, such a s radioactive elements from nuclear testing and industrial processes, are accumulated in the lichen. Due to this observation that lichen s seem to accumulate pollutants coupled with no mechanism to remove them, they have become important in tracking deposition of pollutants (Nash, Nutrients, Elemental Accumulation, and Mineral Cycling, 2008) Since they are slow growing and stay intact throughout their li fetime (as opposed to vascular plants, which shed leaves and such during the course of their life cycle), new growth and new pollutant concentrations are available for measurement every year, allowing for long term research. A bsorption of pollutants throug h the whole surface of the lichen is possible since, unlike higher plant life, they do not have a waxy cuticle that does not allow such particles to enter. Due to this, l ichens are capable of accumulating elements at

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12 higher levels than they require. H ow mu ch pollutant s and nutrients are being deposited can be measured when compared to normal accumulation levels observed in lichens from other areas These monitoring studies include deposition of metals such as nickel, copper, zinc, mercury, lead, uranium, an d arsenic (Nash, Nutrients, Elemental Accumulation, and Mineral Cycling, 2008) Organic particles are also monitored, including chlorinated hydrocarbons, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and dioxins. Many of these organic molecules and metals are not useful in the life cycle of the lichen; however, those that are include inorganic substances like nitrogen and sulfur. Not only can concentrations of the pollutants entering the environment be determined, but so can the distance certain pollutants travel before deposition, ascertaining airborne times for those pollutants. Drawbacks to using lichens as environmental models include needing better understanding of taxonomy, utilizing consistent methodologies of research, and overcoming the depletion of lichens during research and bioassays (Nash, Nutrients, Elemental Accumulation, and Mineral Cycling, 2008) 1. 8 ENVIRONMENTAL IMPORTANCE Lichens have many environmental roles, including pedogenesis, biodeterioration, and nutrient cycling (Seaward, 2008) Lichens accumulate various nutrients that eventually end up in the environment at the end of their life cycle and these elements are then bioavailable for other organisms. Availability of

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13 these elements to other organisms is not immediate, since lichens are such slow growing and long living organisms. Over time, however, their contributions can transform abiotic rocks into soil cap able of supporting more advanced organisms. Lichen s transform rocks by both physical and chemical weathering processes, helping create small particles that make up soils. L ichen s infiltrating cracks, subsequently contracting and expanding (Seaward, 2008) accomplishes the physical processes of weathering. Major chemicals secreted by lichens capable of degrading minerals are oxalic acid and a variety of phenolic acids These acids react with minerals in the rock t o form metal complexes, many times in the form of calcium oxalate. Most biodeterioration due to lichens is measured on a long term (geologic) scale, but some have a relatively short time table, most notably on historic monuments or artworks (such as fresco es and statues). Lichens convert up to one millimeter of calcium carbonate into calcium oxalate every six years. Using this chemical transformation, historians and archaeologists can verify ages of these structures. Lichen assisted weathering of rocks is n ot only important to the bioavailability of nutrients, but Schwartzman and Volk (1989) postulate that they are also responsible for the habitable temperature of the Earth. As lichens weathered rock during the Precambrian, they removed carbon dioxide from t he atmosphere, sequestering it in biomass. Weathering of rock by lichens also released different silicates, which react with carbon dioxide and water, forming bicarbonates, removing more carbon dioxide from the atmosp here. Carbon dioxide removal, coupled w ith reduction of volcanic outgassing led to cooler temperatures. Biotic weathering, with lichens playing a central role, adds to soil

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14 formation more than abiotic weathering. Abiotic factors contributing to weathering include water, and to a lesser degree, wind. Depending upon the location, rates of bioweathering are 10 1,000 times that of abiotic weathering. Complex soil formation ceases without bioweathering. Any weathered rock would wash away with rains, and stabilization of soils stop without biota to h old them in place, as would soil water retention. This shifts precipitation patterns, creating deserts in low lying areas. Without lichens, temperatures would be higher than current temperatures by 30 45C. At these temperatures, only thermophilic bacteria survive. The extensive loss of lichens may contribute to climate change locally (Nash, Nutrients, Elemental Accumulation, and Mineral Cycling, 2008) In areas that have large expanses of lichen cover, a major die off due to an thropogenic interferences would mean that no lichen cover on rocks or soils would absorb sun radiation. Higher temperatures locally result as rocks and soils would warm up during the day and keep the local area warmer as the rock cools slowly at night The rocks and soils may also reflect light, warming the surrounding atmosphere, trapping heat in conjunction with greenhouse gases. 1. 9 ECOLOGICAL IMPORTANCE TO OTHER ORGANISMS Lichens are ecologically important to many invertebrates and vertebrates. South African bagworm larvae (Seaward, 2008) use quartz crystals to construct the bag in which they live. These quartz crystals are loosened from the clay by the lichen. Some invertebrates use lichens as a camouflage, placing t halli on

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15 themselves. T hese lichens may use the invertebrate as a substrate and continue to grow. Birds utilize lichens as nesting material and some will only use a specific species to construct their nest. Some species of flying squirrels also make nests o ut of lichens, and also use as food. There are quite a few mammals that utilize lichens as a food source. Deer, gazelles, mountain goats, polar bears, marmots, monkeys, and others use the lichens only as a supplement to their diet, as many lichens are smaller and their nutrient content is not ideal as a primary source for and while l ichens are not a good source of protein, calcium, or phosphorus, they can provide enough nutr ition for reindeer and caribou to endure the winter. 1.1 0 LICHENOMETRY AND ENVIRONMENTAL MONITORING Lichen biology remains a poorly understood research field, and when it comes to using lichens as accurate dating mechanisms (i.e., lichenometry), controv ersies abound. However, in many instances, such as dating late Holocene glacier fluctuations (Loso & Doak, 2006) lichenometry represents the only appropriate method. Another related issue revolves around the accuracy of statistical analyses of lichen size and their growth rate determinations. Knowing the exact deposition time of debris from a washed out glacial mor aine in Rocky Mountain National Park (RMNP) such as the Lawn Lake flood in 1982 embodies an excellent site to conduct lichenometry studies. By using the exact date and time this flood occurred in RMNP, a number of previously unstudied factors about lichens lichenometry, and climate change can be determined.

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16 Further, using such a young site with a precise time of exposure can give valuable insight into current lichenometry controversies. Lichens are useful in environmental monitoring as they reflect changes in environment (Seaward, 2008) especially when that change is due to anthropogenic factors. Loss of specific species sensitive to particular environmental changes can help identify those changes and aid in mitigating them. Det ermination of glacial retreat rates snowmelt rates, flooding, seismic landslides, etc. by lichenometry may be the most appropriate method This, along with mapping and remote sensing, aids in monitoring of these changes in conjunction with monitoring of o ther known environmental changes, allowing scientists to model future changes and recommend steps to mitigate further issues. Using lichenometry as a technique, it is possible to measure climate change responses of lichens. Armstrong (2004) for example, discusses lichenometry as a method for studying glacial fluctuations caused by rapid warming periods. This technique has shown that during periods of warming, glaciers recede rapidly, exposing new surfaces that are subseq uently colonized by lichens. This method can then, in turn, aid in a better understanding climatic responses of surrounding biota. Lichens are useful for climate change studies in colder climates with harsh environmental conditions. As the first colonizers after glacial retreat (Sancho, Green, & Pintado, 2007) lichens are the most abundant plant life in these areas. Their growth rates correlate to favorable environmental factors, including temperature and moisture. The studies Armstrong (2004) discusses (McCarroll, 1993; Harrison and Winchester, 2000; Oerlemans, 1994) contribute valuable data to further validate climate change impacts on glacial

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17 retreats over the last century by comparing grow th rates of lichens with increasing temperatures associated with global climate change (Sancho, Green, & Pintado, 2007) Lichen growth rates applied to surface dating characterizes the basis for lichenometry and typically uses crustose lichens (Palmqvist, Dahlman, Jonsson, & Nash, 2008) although foliose lichens (Noller & Locke, 2000) have also been used. Other dating techniques, such as radiocarbon or other elemental da ting techniques, are less accurate at dating recent (<500 years) events (Armstrong, 2004) and even less useful when rocks are the medium. Conversely, lichens can grow on surfaces for up to 1000 years (P almqvist, Dahlman, Jonsson, & Nash, 2008) yet calibration with known dated surfaces remains key to growth curve formation (Loso & Doak, 2006) Since lichens usually grow in a circular formation, the diameter of the lichen can be used to determine the growth rate when the age of the substrate is known (Noller & Locke, 2000) 1.1 1 COMPARISON OF TWO LICHEN SPECIES 1.1 1 .1 RHIZOCARPON GEOGRAPHICUM Also known as yellow map lichen, R. geographicum is classified as a cosmopolitan taxa (Galloway, 2008) which are found on all continents and most islands. This does not mean, however, that it will be found in all areas of said continent or island. Crustose lichen completely attaches to its substrate; R. geographicum is easily distinguishable with a patterned yellow and black thallus

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18 that is map like and typically found growing on siliceous rocks and favors alpine and arctic habitats (Brodo, Sharnoff, & Sharnoff, 2001) R. geographicum is the lichen of choice when performing lichenometric studies. Bradwell & Armstrong ( 2007) reviewed multiple studies, giving 0.1 mm yr 1 to 0.5 mm yr 1 growth rate for R. geographicum depending upon the habitat the lichens were found. Their own study revealed a higher average growth rate (0.65 mm yr 1 ), and included difference s between thallus size and growth rate, giving a parabolic growth rate as opposed to a linear growth rate assumed in many studies. Only two studies have shown this type of growth curve, therefore, more studies into the relationship between thallus size and yearly growth are needed. Picture 4 Rhizocarpon geographicum (yellow) found outside study area.

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19 1.1 1 .2 RHIZOPLACA CHRYSOLEUCA Orange rock posy is the common name for R. chrysoleuca This lichen is typically found on granitic rock and is fairly ubiquitous across western North America (Brodo, Sharnoff, & Sharnoff, 2001) A foliose lichen, the thallus can be pale yellow green to yellow grey in color, with a pothecia disks of pale to dark orange. R. chrysoleuca attaches to the substrate by a central holdfast, but sometimes appears as more of a crustose lichen. Another Rhizoplaca species is similar in morphology, but lifting of the thallus edges identifies the lichen as R. chrysoleuca and not R. subdiscrepens which is a crustose lichen. Very few studies have been conducted with R. chrysoleuca as it is not as cosmopolitan as R. geographicum One study using multiple species to establish growth curves to determine water level changes (Timoney & Marsh, 2004) report growth rates for R. chrysoleuca between 0.32 0.89 mm yr 1 when a lag time of 5.9 years is used (see Results section for discussion of lag time) The Timoney & Marsh paper references three unpublished studies for these growth rates. It is apparent that more study is needed for this particular species, and can be useful if other lichen s are not present in abundance for lichenometric studies.

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20 Picture 5 Rhizoplaca chrysoleuca used in study.

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21 2. METHODS The Lawn Lake Dam, an earthen dam constructed in 1903, after years of disrepair, failed on July 15, 1982, sending 219 million gallons of water into the Roaring River (Town of Estes Park, 2010) This torrent of water broke through a glacial moraine, intact from the last ice age, sending literally tons of debris including large boulders from the glac ial till down to Horseshoe Park Most of this debris deposited at this site, though water continued to wash down through the Cas cade Lake Dam, flooding the town of Estes Park, and finally stopping in the Estes Lake (Town of Estes Park, 2010) Horseshoe Park (elevation 8500 to 8610 feet) in Rocky Mountain National Park (Map 1) sits at the d eposition po int for many large boulders and sediments washed down from the Lawn Lake Dam flood. Many of these boulders were part of a glacial moraine that the flood destroyed and had, as such, no previous exposure to lichens. As such, this site was chosen to conduct s tudies on lichen colonization. Initially, this study was to determine if there were any climate change impacts on lichens, however, the lichen typically used for lichenometric studies was not found in any abundance at this site. Without an established grow th curve for the lichen eventually sampled here, the decision was to establish a growth curve for R. chrysoleuca as an alternative to R. geographicum in younger sites or those sites lacking R. geographicum

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22 Picture 6 View of the debris field just above the sampling area, showing the deposition of boulders af ter the flooding event in 1982. Figure 1 Topographical map of study area outlined in orange.

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23 Before gathering data, random areas of the site were sampled for lichen diversity (not recorded). It was decided at that point that while R. geographicum is the better species for conduction of lichenometric studies, there were almost none found within the boundaries of the debris field. The most abundant lichen that could be identified definitively to the species level was Rhizoplaca chrysoleuca Other genera or species encountered within the b oundaries of the debris field include Xanthoparmelia Umbilicaria and unidentified brown, grey/black, and orange crustose lichens. Picture 7 Other species were considered for the study, but were not as abundant as Rhizoplaca When conducting this study, a few assumptions were made following Noller and Locke (2000) 1. The substrate had not been colonized by lichens before final deposition and had not been moved since deposition 2. Diameter of lic hens reflect annual growth 3. The growth rate of lichens is linear

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24 4. No lag time for colonization (establishment of lichen on the substrate took place soon after deposition) Thirteen 8m x 8m plots were randomly selected within the boundaries of the debris field The entire site was segmented into 4 quadrants using the Roaring River and Old Fall River Road as transects (these transects can be seen in Figure 1). study (1984) A 12 m buffer between the sampling sites and any hiking paths or roads was used to minimize any anthropogenic influence on lichen growth. T his site is a popular hiking area and easily accessible for all levels of hikers in Rocky Moun tain National Park, colonization by lichen would ultimately be inhibited by people climbing on boulders. Boulder sizes less than 30cm were not sampled, as it appeared than little to no R. chrysoleuca grew on smaller boulders or rocks. Close to the Roaring River, no lichens were found, either due to flooding in the spring or the small s ize of the rocks and boulders. Any R. chrysoleuca that was growing closely with another R. chrysoleuca was not measu red unless there was a clear delineation between the two lichens. Since R. chrysoleuca do not completely attach to the substrate, it was usually possible to distinguish a separation between two lichens. In the cases where it seemed they were growing togeth er, they were excluded from sampling (Refsnider & Brugger, 2007) For each sampling site, GPS coordinates were taken at the four corners of the plot, the lichens measured using digital calipers, the size of the boulder was reco rded, as well as which aspect the lichen was facing (north, south, top of boulder, etc.). In some sampling sites, few lichens were encountered, and only the

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25 largest five were recorded, measuring on the longest axis of the lichen (In nes, 1984) The majority of the sampling sites had numerous lichens, and up to 14 lichens in each sampling site were recorded. The largest 5 lichen from each sampling site were averaged. The averages of each site were then combined to give an overall average lichen size for the entire debris field. Another method considered for this project was discussed in Timoney & Marsh (2004) As R. geographicum was not available at the ir study site, multiple species were used to determine age of the water formed trimlines. A growth curve was constructed incorporating those species found. For this project, however, the use of R. chrysoleuca exclusively was determined the best course of act ion as it was easily identified and found in all areas sampled. Other lichens, such as those species of genera Xanthoparmelia and Umbilicaria were not used as they were not either found in many of the sites sampled, or in the case of Umbilicaria species were indistinguishable from each other. R. geographicum were rarely found within the boundaries of the debris field. The conclusion was that this species was either unable to establish in this area, or their growth was much slower and had not ach ieved a sufficiently large enough size to be easily seen.

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26 3. RESULTS The average size of R. chrysoleuca from all 13 sites, with 65 total lichens measured, is 32.35 mm 3.22 mm. Assuming a linear growth from exposure in 1982, the average growth per yea r is 1.15 mm. As seen in Figure 2 the lichen diameter of all samples taken fall between 25.59 and 42.99 mm. The average value for these data is 32.35 4.18 mm and the median is 31.92 4.18 mm. The few outliers do not have a significant impact on diamete r mean and will be included in subsequent analyses. The averages of lichen diameter per site (Figure 3 ) have a mean of 32.47 3.22 mm. Using the averages of all samples is not significantly different than using the average of the means of each site. Follo wing the recommendation of Innes (1984) the mean of the five largest lichen of each sample site will be used for reporting. Timoney and Marsh (2004) established a lag time by comparing lichen growth in a cemetery near their study site. At this site, surfaces were exposed at different times, with lichenized and non lichenized surfaces to compare. At the project site, there were non lichenized surfaces, but many were eliminated due to size or proximity to potentially anthropogenic disturbances. Therefore, a lag time was not determined due to this and the fact that all of the substrate available for lichen colonization was exposed from the glacial moraine at the same time.

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27 Figure 2 Lichen sizes of all samples taken. Figure 3 Averages of diameter by site (5 samples per site). 20.00 22.00 24.00 26.00 28.00 30.00 32.00 34.00 36.00 38.00 40.00 42.00 44.00 46.00 0 10 20 30 40 50 60 70 Diameter (mm) Sample number Rhizoplaca chrysoleuca 25 27 29 31 33 35 37 39 41 0 2 4 6 8 10 12 14 Diamter (mm) Site Number Rhizoplaca chrysoleuca Average per site

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28 Figure 4 Comparing boulder size to the diameter of all lichen found on each boulder. There was a varying degree of boulder size among the sampling sites, and all lichen measurements were compared against the size of boulder on which it was found (Figure 5 ). There is no significant effect on lichen size compared to boulder size. While McCarroll (1994) found a more significant role played on lichen size (using R. geographicum ) when boulder size is taken into account, he also shows that sampling a variety of boulder sizes has no significant effect on mean lichen size. R = 0.0439 20 25 30 35 40 45 50 0 100 200 300 400 500 Lichen Diameter (mm) Boulder Size (cm) Lichen Diameter vs. Boulder Size

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29 Figure 5 Comparing sample aspect and size. Numbers above aspect diameter represent number of samples. Figure 6 Comparison of lichen diameter with quadrant sampled. When looking at the impacts of aspect (Figure 6) and quadrant (Figure 7) on lichen growth, there are significant effects. When the lichen was located on the north, east, south, northeast, or top of the boulder, the size was significantly larger than those located on the southwest, southeast, northwest, or west facing lichen. 7 2 12 3 8 3 5 7 18 R = 0.9045 28 29 30 31 32 33 34 35 Diamter (mm) Average Size by Aspect R = 0.9257 27 28 29 30 31 32 33 34 35 36 Northeast Southwest Southeast Northwest Diameter (mm) Average Size by Quandrant

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30 ( Some boulders were large enough or flat on the top that it was difficult to the boulder aspect.) There are significant differences in growth when compared to the four quadran ts the lichens grew in the debris field. The northwest and southeast quadrants have a higher growth rate than the northeast and southwest quadrants. In all areas, vegetation was similar and shading from these small trees and bushes probably did not have a large impact. Figure 7 Extrapolated growth curve for 100 years growth. Assuming a linear and infinite growth, the extrapolated growth curve (Figure 8 ) can be used to determine the age of a substrate where R. chrysoleuca is found When using the initial colonization as 0 mm and the growth of 1.155 mm yr 1 the growth curve shows that if the lichen measures 97 mm, the substrate has been exposed for 80 years. R = 0.9973 0 20 40 60 80 100 120 140 Lichen size mm Year Extrapolated Growth Curve Measured Diameter Extrapolated Growth

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31 4. CONCLUSION In order to understand more about using lichenometry and validate its usefulness as a dating method when other methods cannot be used, more is understanding of lichen growth is necessary. This study is by no means complete, but is a starting place to findi ng alternative lichen s for sites that do not have established Rhizocarpon geographicum whether due to age of the site or unsuitable habitat. There is no documentation of the growth limit or average lifespan for R. chrysoleuca and o nly one reference to annual growth is mentioned in Timoney and Marsh (2004) The ability to use multiple species for a location would only help establish a more concrete time of exposure for determination of deposition o r exposure of a substrate. Using growth curves from one site to date another site requires similar macroclimatic elevation, substrate, and vegetative cover conditions. Since many lichens have specific growth requirements, these criteria will most likely be met at a location if a particular lichen is found. Each case is different, however, so there will not be any u niversal growth curve for every lichen. The best possible growth curve is based on a comparison of lichen growth on a substrate of known age in the same or adjacent area for the unknown substrate. D ifferences seen in the growth in different quadrants may be an indication of earlier colonization. For purposes of growth curve construction, it is assumed that colonization takes place shortly after the substrates initial exposure. This is not necessarily what happens, as Timoney and Marsh (2004) show but even their review of other studies show that lag time is inconsistent. Another reason for the

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32 dichotomy between the sites may be that the climactic conditions in those areas differ enough to affect growth. The two quadrants with lower growth may not receive the same amount of sunlight, precipitation, or the substrate may have different composition than the two quadrants with higher growth. The fact that neither of the lower or higher growth quadrants is adjacent to each other makes it difficult to infer the cause for the significant difference seen in growth unless microclimatic factors are vastly different in each area Much of the literature cited here, in particular Noller and Locke (2000) Innes (1984) and McCarroll (1994) state that the largest lichen are the idealized specimens for that particular habitat fast growing and quickest to establish on the substrate therefore giving the best possible growth curve to estimate age of the substrate. In light of this, should the lichens in the lower growth quadrants be excluded from the analyses? The largest growth quadrant (northwest) has an average of 34.69 mm and 95% confidence interval of 27.49 42.49 mm. The smallest growth quadrant (northeast) has an average of 30.12 mm. Since the lowest growth falls well within the 95 th percentile of the largest growth quadrant, it should not be excluded from further anal yses. Aspect also seems to have an effect on growth of R. chrysoleuca in this location. The most abundant growth is found with lichens growing on the top of the boulders with an average growth of 33.41 mm, and a 95% confidence interval of 23.95 42.87 mm As described in the data section, the top of the boulder aspect was used when the lichen faced no discernible direction due to the size or shape of the boulder. The southwest aspect had the least growth with an average

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33 of 30.11 mm. Again, as the lowest gr owth falls well within the 95 th percentile of the largest growth quadrant it should not be excluded from further analyses. Since both aspect and quadrant can be ruled out with having an effect on the growth of R. chrysoleuca in this particular area, other sites with similar habitat and climate should be able to use this preliminary data to help construct a more robust growth curve for R. chrysoleuca. Since less is known of growth rate than R. geographicum possibly due to a shorter life sp an for R. chrysoleuca than R. geographicum or that R. chrysoleuca is a primary colonizer and is subsequently outcompeted by later succession of other species, it is difficult to draw concrete conclusions. Using R. chrysoleuca may be a good alternative at younger sites where R. geographicum may not have had a chance to establish or had enough time to grow. There are other questions that came up during this project, but are not able to be answered with the current data. Is lag time a factor? This would have large implications on the growth rate. A lag time of 5.9 years as Timoney and Marsh (2004) suggests at their Northern Alberta site, would have a sizable impact on the growth curve. This wo uld change the average yearly growth rate from 1.155 mm (assumed 28 years to grow to current size) to 1.464 mm (22.1 years to grow to current size). We assume a linear growth rate, but it is likely that there is a more parabolic curve to R. chrysoleuca gr owth. Bradwell and Armstrong (2007) reviewed data from previous studies for R. geographicum and showed that growth rates were higher when the lichen was younger, and slowing down as the lichen aged. Previous growth curve s using a linear relationship to age and time would

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34 have to be recalibrated to reflect these new findings, and ages of substrates would have to be re evaluated. Since this study only has data from one point in time, it is not possible to construct a curve reflecting possible changes in growth rate. Under studied areas of lichen biology hinder accurate growth curve production for species of lichen. Reproduction, transportation of propagules, morphogenesis, lag time of establishment on a substrate, and even u nderstanding of lichen taxonomy are all areas that need further study. These uncertainties should not invalidate lichenometry since some assumptions can be made using current knowledge to make a case for legitimacy. Lichenometry may not yet be an exact sc ience, but the field is continuing to grow. With more research in these areas, the use of lichens can become a legitimate dating tool, useful in situations where other dating techniques will not yield results.

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35 5 FUTURE DIRECTIONS Despite the aforementioned issues, the information found here can help future studies. In this particular study, many questions can be answered about R. annual growth by re visiting the site annually and repeating measurements in the same areas. With rep eated sampling, a better curve can be constructed, allowing more accurate dating to take place at sites with unknown age. This can also help answer the question of whether these lichens have linear or parabolic growth. In addition to re evaluating growth for R chrysoleuca monitoring of the site can also yield results for establis h ment time of R. geographicum as a few spec imens were found in this outing. C ontinued monitoring may produce more observations of this species, resulting in not only calculated lag times, but questions about climate change impacts on both lichen growth and the surrounding environment can be answered. With ongoing studies of lichen biology, such as morphogenesis, repro duction, and taxonomy, these growth studies will strengthen the field of lichenometry. Establishing more consistent methodologies of research for all who conduct these studies will bring more validity to the field and streamline the process of gathering da ta so that future studies are more widely accepted as a dating technique.

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36 BIBLIOGRAPHY Armstrong, R. (2004). Lichens, Lichenometry, and Global Warming. Microbiologist, September 32 35. Bradwell, T., & Armstrong, R. A. (2007). Growth Rates of Rhizocarpon geographicum Lichens: A Review with New Data from Iceland. Journal of Quaternary Science, 22 (4), 311 320. Brodo, I. M., Sharnoff, S. D., & Sharnoff, S. (2001). Lichens of North America. New Haven and Lo ndon: Yale University Press. Bdel, B., & Scheidegger, C. (2008). Thallus Morphology and Anatomy. In T. H. Nash III (Ed.), Lichen Biology (pp. 40 68). Cambridge: University Press. Fahselt, D. (2008). Individuals and Populations of Lichens. In T. H. Nash II I (Ed.), Lichen Biology (pp. 252 273). Cambridge: University Press. Friedl, T., & Bdel, B. (2008). Photobionts. In T. H. Nash III (Ed.), Lichen Biology (pp. 9 26). Cambridge: University Press. Galloway, D. J. (2008). Lichen Biogeography. In T. H. Nash III (Ed.), Lichen Biology (pp. 315 335). Cambridge: University Press. Green, T. G., Nash, T. H., & Lange, O. L. (2008). Physiological Ecology of Carbon Dioxide Exchange. In T. H. Nash III (Ed.), Lichen Biology (pp. 152 181). Cambridge: University Press. Honeg ger, R. (2008). Morphogenesis. In T. H. Nash III (Ed.), Lichen Biology (pp. 69 93). Cambridge: University Press. Honegger, R. (2008). Mycobionts. In T. H. Nash III (Ed.), Lichen Biology (pp. 27 39). Cambridge: University Press. Innes, J. L. (1984). The Opt imal Sample Size in Lichenometric Studies. Arctic and Alpine Research, 16 233 244. Loso, M. G., & Doak, D. F. (2006). The Biology behind Lichenometric Dating Curves. Oecologia, 147 223 229. McCarroll, D. (1994). A New Approach to Lichenometry: Dating Sin gle Age and Diachronous Surfaces. The Holocene, 4 383 396.

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37 Nash, T. H. (2008). Introduction. In T. H. Nash III (Ed.), Lichen Biology (pp. 1 8). Cambridge: University Press. Nash, T. H. (2008). Nutrients, Elemental Accumulation, and Mineral Cycling. In T. H. Nash III (Ed.), Lichen Biology (pp. 234 251). Cambridge: University Press. Noller, J. S., & Locke, W. W. (2000). Lichenometry. Quaternary Geochronology: Methods and Applications 261 272. Palmqvist, K., Dahlman, L., Jonsson, A., & Nash, T. H. (2008). Th e Carbon Economy of Lichens. In T. H. III (Ed.), Lichen Biology (pp. 182 215). Cambridge: University Press. Refsnider, K. A., & Brugger, K. A. (2007). Rock Glaciers in Central Colorado, U.S.A., as Indicators of Holocene Climate Change. Arctic, Antarctic, a nd Alpine Research, 39 127 136. Sancho, L. G., Green, T. G., & Pintado, A. (2007). Slowest to Fastest: Extreme Range in Lichen Growth Rates Supports Their Use as an Indicator of Climate Change in Antarctica. Flora, 202 667 673. Seaward, M. R. (2008). Env ironmental Role of Lichens. In T. H. Nash III (Ed.), Lichen Biology (pp. 274 298). Cambridge: University Press. Taylor, T. N., Remy, W., & Kerp, H. (1995, November 16). The Oldest Fossil Lichen. Nature, 378 244. thallus. (n.d.). Retrieved January 24, 2012 http://www.britannica.com/EBchecked/topic/589870/thallus Timoney, K. P., & Marsh, J. (2004). Lichen Trimlines in Northern Alberta: Establishment, Growth Rates, and Historic Water Levels. The Bryologist, 107 (4), 429 440. Town of Estes Park. (2010). The Lawn Lake Flood Retrieved February 19, 2010, from Town of Estes Park: http://www.estesnet.com/Hydroplant/the_lawn_lake_flood.aspx Yuan, X., Xiao, S., & Taylor, T. N. (2005). Lichen Like Symbiosis 600 Million Years Ago. Scie nce, 308 1017 1020.