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Polyploidy, or whole genome duplication, is a common phenomenon in plants, but the establishment and persistence of mixed-ploidy populations remains a paradox. This dissertation explores factors that contribute to the persistence and establishment of mixed-ploidy populations in nature. The first chapter investigates the role of unreduced gametes in neopolyploid establishment and finds that variability in their formation rate can have a significant impact on polyploid establishment and persistence. The second chapter searches for evidence of soil microbes exhibiting ploidy-specificity, a pre-condition for microbe-mediated niche differentiation, a possible stabilizing mechanism contributing to ploidy coexistence. Finally, the third chapter tests for microbe-mediated niche differentiation in a mixed-ploidy population of Larrea tridentata. Using a plant-soil feedback experiment this chapter demonstrates that microbe-mediated niche differentiation­­­ can facilitate the coexistence of different ploidy levels. Overall, this dissertation demonstrates there are complex and interrelated factors that contribute to the persistence and establishment of mixed-ploidy populations in nature.

Drylands cover 45% of the terrestrial surface and are expanding rapidly due to anthropogenic drivers. Altered precipitation regimes, atmospheric nitrogen deposition, and wildfire will likely have significant consequences in these regions where ecological processes are limited by water and nitrogen. In this dissertation, I explored temporal dynamics of net primary production (NPP) and related above- and belowground processes under several environmental change drivers in the Sevilleta National Wildlife Refuge, central New Mexico, USA. Located in the northern Chihuahuan Desert, this region experiences strong seasonal precipitation patterns driven by the North American Monsoon, historically characterized by frequent small rain events hypothesized to benefit microbial processes, such as nitrogen mineralization. Climate models predict a shift to a more extreme precipitation regime characterized by fewer, but larger rain events hypothesized to benefit plant production. Yet, it remains unclear how drylands will respond to increased precipitation variability and other drivers of environmental change. To address this knowledge gap, I explored daily and seasonal responses of plant available nitrogen and related belowground parameters to altered rainfall size and frequency using a long-term rainfall manipulation experiment. Next, I explored long-term responses of aboveground NPP (ANPP) and plant community composition to these altered rainfall patterns, along with chronic nitrogen enrichment. In contrast to long-standing ecological theories, small frequent rain events stimulated the greatest amounts of plant available nitrogen and ANPP, and when combined with nitrogen enrichment, led to the greatest shift in plant community composition following a wildfire. A more extreme growing season rainfall regime decoupled microbial and plant processes, and only when nitrogen limitation was alleviated did ANPP respond strongly to large infrequent rain events. Finally, I explored spatiot

Terrestrial ecosystems are critical to human and ecological processes but many gaps in our knowledge remain regarding how terrestrial plant communities assemble and respond to global change. I used field experiments distributed around the world, including long-term experiments from the Sevilleta National Wildlife Refuge (SNWR) in New Mexico and deserts of the southwestern U.S., to evaluate the consequences of drought and other abiotic stressors on plant communities. Dominant grasses were particularly important for the productivity and structure of grasslands at SNWR. In general, the structure of desert plant communities had high resistance to extreme drought, though grasses and other perennial species were most negatively impacted. Global change drivers altered the beta diversity of plant communities both locally and among sites. Continued study of how communities respond to abiotic disturbances is of increasing importance as we try to conserve modern ecosystems and predict the consequences of anthropogenic global change.

Small mammals in hot deserts often avoid heat via nocturnality and fossoriality and are thought to have a limited capacity to dissipate heat using evaporative cooling. Research to date has focused on thermoregulatory responses to air temperatures (Ta) below body temperature (Tb). Consequently, the thermoregulatory performance of small mammals exposed to high air temperatures is poorly understood, particularly responses across geographic and seasonal scales. We quantified the seasonal thermoregulatory performance of four cricetid rodents (Neotoma albigula, N. lepida, Peromyscus eremicus, P. crinitus) exposed to high Ta, at four sites in the Mojave Desert. We measured metabolism, evaporative water loss and Tb using flow-through respirometry. When exposed to Ta ≥ Tb, rodents showed steep increases in Tb, copious salivation and limited evaporative heat dissipation. Most individuals were only capable of maintaining Ta-Tb gradients of ~1 °C resulting in heat tolerance limits (HTL) ranging from Ta = 43-45°C. All species exhibited a thermoneutral Tb of ~35-36 °C, and Tb increased to maximal levels of ~ 43°C. Metabolic rates and rates of evaporative water loss increased steeply in all species as Ta approached Tb. We also observed significant increases in resting metabolism and evaporative water loss from summer to winter at Tas within and above the thermoneutral zone. In contrast, we found few differences in the thermoregulatory performance within species across sites. Our results suggest that cricetid rodents have a limited physiological capacity to cope with environmental temperatures that exceed Tb and that a rapidly warming environment may increasingly constrain their nocturnal activity.

Drylands cover 45% of the terrestrial surface and are expanding rapidly due to anthropogenic drivers. Altered precipitation regimes, atmospheric nitrogen deposition, and wildfire will likely have significant consequences in these regions where ecological processes are limited by water and nitrogen. In this dissertation, I explored temporal dynamics of net primary production (NPP) and related above- and belowground processes under several environmental change drivers in the Sevilleta National Wildlife Refuge, central New Mexico, USA. Located in the northern Chihuahuan Desert, this region experiences strong seasonal precipitation patterns driven by the North American Monsoon, historically characterized by frequent small rain events hypothesized to benefit microbial processes, such as nitrogen mineralization. Climate models predict a shift to a more extreme precipitation regime characterized by fewer, but larger rain events hypothesized to benefit plant production. Yet, it remains unclear how drylands will respond to increased precipitation variability and other drivers of environmental change. To address this knowledge gap, I explored daily and seasonal responses of plant available nitrogen and related belowground parameters to altered rainfall size and frequency using a long-term rainfall manipulation experiment. Next, I explored long-term responses of aboveground NPP (ANPP) and plant community composition to these altered rainfall patterns, along with chronic nitrogen enrichment. In contrast to long-standing ecological theories, small frequent rain events stimulated the greatest amounts of plant available nitrogen and ANPP, and when combined with nitrogen enrichment, led to the greatest shift in plant community composition following a wildfire. A more extreme growing season rainfall regime decoupled microbial and plant processes, and only when nitrogen limitation was alleviated did ANPP respond strongly to large infrequent rain events. Finally, I explored spatiot

Small mammals in hot deserts often avoid heat via nocturnality and fossoriality and are thought to have a limited capacity to dissipate heat using evaporative cooling. Research to date has focused on thermoregulatory responses to air temperatures (Ta) below body temperature (Tb). Consequently, the thermoregulatory performance of small mammals exposed to high air temperatures is poorly understood, particularly responses across geographic and seasonal scales. We quantified the seasonal thermoregulatory performance of four cricetid rodents (Neotoma albigula, N. lepida, Peromyscus eremicus, P. crinitus) exposed to high Ta, at four sites in the Mojave Desert. We measured metabolism, evaporative water loss and Tb using flow-through respirometry. When exposed to Ta ≥ Tb, rodents showed steep increases in Tb, copious salivation and limited evaporative heat dissipation. Most individuals were only capable of maintaining Ta-Tb gradients of ~1 °C resulting in heat tolerance limits (HTL) ranging from Ta = 43-45°C. All species exhibited a thermoneutral Tb of ~35-36 °C, and Tb increased to maximal levels of ~ 43°C. Metabolic rates and rates of evaporative water loss increased steeply in all species as Ta approached Tb. We also observed significant increases in resting metabolism and evaporative water loss from summer to winter at Tas within and above the thermoneutral zone. In contrast, we found few differences in the thermoregulatory performance within species across sites. Our results suggest that cricetid rodents have a limited physiological capacity to cope with environmental temperatures that exceed Tb and that a rapidly warming environment may increasingly constrain their nocturnal activity.

Genetic and phenotypic variation can have different patterns within a species if it has populations with contrasting histories. Populations can have discrete differences that are shaped by different evolutionary scenarios, but within each population, range, or region, traits and association with fitness can also be affected by both edaphic and landscape variation. For my dissertation, I surveyed and experimentally analyzed variation and adaptive potential in Sahara mustard (Brassica tournefortii), a desert annual that has endemic, invasive, and agricultural populations in Africa, Asia, and the Americas. Although my multi-trait analysis generated complex results, my findings can be applied to other Brassica that have both wild and agricultural populations. B. tournefortii has both adaptive and maladaptive evolutionary potential that can be harnessed for conservation, invasive species control, and crop development.

It has long been assumed that fishes were unimportant in the diet of past Pueblo people in the U.S. Southwest. Yet, small numbers of fish remains are consistently recovered from Late pre-Hispanic/Early Historic archaeological sites in the Middle Rio Grande of New Mexico. The end of drought conditions may have impacted food choice and fishing decisions during this time. I use behavioral ecology to understand how fishing could have been an optimal food-getting strategy for Ancestral Pueblo farmers. Stable isotope analysis offers a way to account for environmental change. I provide a refined 13C Suess correction model to support the analysis of past fishing. The presence of aquatic ecological stability in the protohistoric Middle Rio Grande is revealed using stable isotope analysis and the refined 13C Suess correction model. Fish body size estimations provide a way to evaluate whether environmental conditions impacted the health of fishes and Ancestral Pueblo food choice. Stable isotope analysis and body size estimation suggest Ancestral Pueblo fishing strategies were associated with energy maximizing and risk reducing foraging behavior linked with environmental change. This mix of foraging goals could be significant in the development of fishing behavior throughout human history, and the analysis of Ancestral Pueblo fishing charts a course to change the human/fish narrative across the globe.

Join a Museum educator and a mycologist to learn more about the amazing structures and functions that plants and animals have to survive in Utah habitats. Use observation skills to discover animals that live in different habitats and dig in to the adaptations of the porcini mushroom.

Genetic and phenotypic variation can have different patterns within a species if it has populations with contrasting histories. Populations can have discrete differences that are shaped by different evolutionary scenarios, but within each population, range, or region, traits and association with fitness can also be affected by both edaphic and landscape variation. For my dissertation, I surveyed and experimentally analyzed variation and adaptive potential in Sahara mustard (Brassica tournefortii), a desert annual that has endemic, invasive, and agricultural populations in Africa, Asia, and the Americas. Although my multi-trait analysis generated complex results, my findings can be applied to other Brassica that have both wild and agricultural populations. B. tournefortii has both adaptive and maladaptive evolutionary potential that can be harnessed for conservation, invasive species control, and crop development.

The existence of microbial activity hotspots in temperate regions of Earth is driven by soil heterogeneities, especially the temporal and spatial availability of nutrients. Here we investigate whether microbial activity hotspots also exist in lithic microhabitats in one of the most arid regions of the world, the Atacama Desert in Chile. While previous studies evaluated the total DNA fraction to elucidate the microbial communities, we here for the first time use a DNA separation approach on lithic microhabitats, together with metagenomics and other analysis methods (i.e., ATP, PLFA, and metabolite analysis) to specifically gain insights on the living and potentially active microbial community. Our results show that hypolith colonized rocks are microbial hotspots in the desert environment. In contrast, our data do not support such a conclusion for gypsum crust and salt rock environments, because only limited microbial activity could be observed. The hypolith community is dominated by phototrophs, mostly Cyanobacteria and Chloroflexi, at both study sites. The gypsum crusts are dominated by methylotrophs and heterotrophic phototrophs, mostly Chloroflexi, and the salt rocks (halite nodules) by phototrophic and halotolerant endoliths, mostly Cyanobacteria and Archaea. The major environmental constraints in the organic-poor arid and hyperarid Atacama Desert are water availability and UV irradiation, allowing phototrophs and other extremophiles to play a key role in desert ecology.

Uncertainties surround the extent to which diversity can mitigate the effects of climate change and anthropogenic activity on ecosystem functions. In desert grasslands, changes to water availability and soil nitrogen, two primary resources that limit ecosystem processes, can have lasting impacts on nutrient cycling. We used grass litter from Bouteloua eriopoda, Bouteloua gracilis, Pleuraphis jamesii, and Sporobolus spp. to assess the effects of soil resources on single- and multi-species decomposition in a Chihuahuan Desert grassland in central New Mexico, USA. Litterbags were deployed in a factorial experiment that manipulated rain pulse size (5- vs. 20-mm) and frequency (weekly vs. monthly), and soil nitrogen content during the monsoon season. Decay did not significantly differ among pulse-sized thresholds. We found significant differences among species so that the more palatable grasses, B. gracilis and P. jamesii, decayed faster (k = 0.48 y-1 and 0.33 y-1, respectively) than B. eriopoda (k = 0.24 y-1). Although not significant, the decay of litter mixtures was enhanced in the 5-mm·week-1 (k = 0.53 y-1) and 20-mm·month-1 (k = 0.499 y-1) treatment relative to the water control (k = 0.31 y-1) when nitrogen was not limiting. Nitrogen immobilization persisted only in B. eriopoda and litter mixtures after one year. Future changes in rainfall regimes will have limited impacts on nutrient cycling in desert grasslands at current rates of atmospheric nitrogen deposition. However, high rates of nitrogen deposition will likely intensify the effect of pulse-sized thresholds on nutrient cycling. We conclude that species composition is critical for ecosystem functioning.

Few studies have examined inoculum potential of ectomycorrhizal fungi (EMF) in the absence of plant hosts, yet persistence of these fungi may be paramount to resilience of Pinus edulis and other mycorrhizal plant species. We conducted a study in which seven sites were selected in northwestern New Mexico with known dates of P. edulis extirpation and a lack of regeneration. Age classes included: two sites extirpated 10-20 years ago, two extirpated 55-65 years ago, two extirpated 500+ years ago, and one extirpated 11,000+ years ago. At each site, two plots were paired: an extirpated plot and the nearest live adult P. edulis stand. Soil samples were collected from each plot at 0-5 cm and 20-25 cm depths from four locations. Pinus edulis seedlings were inoculated with field soils in a greenhouse bioassay to measure EMF inoculum potential. Colonization by EMF occurred across sites, and inoculum potential decreased significantly from zero to 16+ years post extirpation. Tree biomass was unaffected by EMF colonization. Communities of EMF in extirpated and live plots differed significantly and were dominated by Geopora, Rhizopogon, and Tomentella. Geopora was the only genus found in sites older than 65 years and possibly arrived by dispersal. Trees grown in soils collected from 0-5 cm had significantly greater colonization rates and associated EMF diversity. Sites where P. edulis was extirpated via drought had less diverse EMF communities dominated by Geopora. The results of this study will help guide restoration efforts for P. edulis and other ectomycorrhizal tree species.

Few studies have examined inoculum potential of ectomycorrhizal fungi (EMF) in the absence of plant hosts, yet persistence of these fungi may be paramount to resilience of Pinus edulis and other mycorrhizal plant species. We conducted a study in which seven sites were selected in northwestern New Mexico with known dates of P. edulis extirpation and a lack of regeneration. Age classes included: two sites extirpated 10-20 years ago, two extirpated 55-65 years ago, two extirpated 500+ years ago, and one extirpated 11,000+ years ago. At each site, two plots were paired: an extirpated plot and the nearest live adult P. edulis stand. Soil samples were collected from each plot at 0-5 cm and 20-25 cm depths from four locations. Pinus edulis seedlings were inoculated with field soils in a greenhouse bioassay to measure EMF inoculum potential. Colonization by EMF occurred across sites, and inoculum potential decreased significantly from zero to 16+ years post extirpation. Tree biomass was unaffected by EMF colonization. Communities of EMF in extirpated and live plots differed significantly and were dominated by Geopora, Rhizopogon, and Tomentella. Geopora was the only genus found in sites older than 65 years and possibly arrived by dispersal. Trees grown in soils collected from 0-5 cm had significantly greater colonization rates and associated EMF diversity. Sites where P. edulis was extirpated via drought had less diverse EMF communities dominated by Geopora. The results of this study will help guide restoration efforts for P. edulis and other ectomycorrhizal tree species.

Uncertainties surround the extent to which diversity can mitigate the effects of climate change and anthropogenic activity on ecosystem functions. In desert grasslands, changes to water availability and soil nitrogen, two primary resources that limit ecosystem processes, can have lasting impacts on nutrient cycling. We used grass litter from Bouteloua eriopoda, Bouteloua gracilis, Pleuraphis jamesii, and Sporobolus spp. to assess the effects of soil resources on single- and multi-species decomposition in a Chihuahuan Desert grassland in central New Mexico, USA. Litterbags were deployed in a factorial experiment that manipulated rain pulse size (5- vs. 20-mm) and frequency (weekly vs. monthly), and soil nitrogen content during the monsoon season. Decay did not significantly differ among pulse-sized thresholds. We found significant differences among species so that the more palatable grasses, B. gracilis and P. jamesii, decayed faster (k = 0.48 y-1 and 0.33 y-1, respectively) than B. eriopoda (k = 0.24 y-1). Although not significant, the decay of litter mixtures was enhanced in the 5-mm·week-1 (k = 0.53 y-1) and 20-mm·month-1 (k = 0.499 y-1) treatment relative to the water control (k = 0.31 y-1) when nitrogen was not limiting. Nitrogen immobilization persisted only in B. eriopoda and litter mixtures after one year. Future changes in rainfall regimes will have limited impacts on nutrient cycling in desert grasslands at current rates of atmospheric nitrogen deposition. However, high rates of nitrogen deposition will likely intensify the effect of pulse-sized thresholds on nutrient cycling. We conclude that species composition is critical for ecosystem functioning.

Advances in DNA sequencing and data analysis make it possible to address questions in population genetics and evolution at the genomic level. Fungi are excellent subjects for such studies, because they are found in diverse environments, have short generation times, can be maintained in culture and have relatively small genomes. My research employed genetic approaches using a variety of sequencing technologies and methods of analysis to explore questions in fungal evolution. In one study, I explored the genetics behind differences in thermotolerance between isolates of Neurospora discreta from Alaska and New Mexico. Isolates from the two states exhibited differences in maximal growth temperature, with New Mexico isolates being substantially more thermotolerant than isolates from Alaska. Genomic scale comparisons of progeny from crosses between isolates from New Mexico and Alaska indicated that two regions, one on chromosome III and another on chromosome I, are responsible for differences in thermotolerance. Examination of these regions revealed numerous differences between the New Mexico and Alaska isolates at nucleotide and amino-acid levels; and it identified candidate genes for being important for differences in maximal growth temperatures. In a second study, I explored the genomic differences between pathogenic and endophytic isolates in the genus Monosporascus. Culture and sequence-based surveys of root associating fungi at the Sevilleta National Wildlife Refuge (SNWR) revealed the ubiquitous presence of members of this genus. Although M. cannonballus is known as a severe pathogen of melon roots in agricultural settings, all of the host plants associating with Monosporascus species in natural settings appeared to be disease free. Complete genome sequences were obtained from three M. cannonballus isolates, an M. ibericus isolate and six SNWR isolates. Comparative genome analyses revealed that

eDNA is a relatively new but promising tool for characterizing biological communities. Currently, the two most common eDNA analyses used by biologists are qPCR and metabarcoding. qPCR is more established, using primers to target a single species. Metabarcoding targets multiple species using one primer set. This allows metabarcoding to more broadly characterize community assemblages and potentially detect rare or low-density species. As a new technology, several methodological questions need to be answered. For example, standard protocol uses only a fraction of DNA extracted from a sample, in PCR reactions. Are rare species thus going undetected? To address this, we examined whether we might find different species in one versus two PCR replicates from the same eDNA sample. Duplicate 4L water samples were collected from seven sites on Fossil Creek, AZ. Samples were filtered, DNA was extracted, PCR was performed in duplicate using primers that amplified a hypervariable region of the 16S rRNA gene that can be used to identify vertebrate species. Sequencing was performed on a Illumina MiSeq FGX Forensic Genomics System. Sequence analysis identified 14 vertebrate species, including six fish, six mammals, and two herpetofauna. The most common species were found in every PCR replicate, whereas sequences associated with rare species were often found in only one of the two PCR replicates. POSTER PRESENTATION URI SIG GRANT AND ARIZONA SPACE GRANT AWARD

Advances in DNA sequencing and data analysis make it possible to address questions in population genetics and evolution at the genomic level. Fungi are excellent subjects for such studies, because they are found in diverse environments, have short generation times, can be maintained in culture and have relatively small genomes. My research employed genetic approaches using a variety of sequencing technologies and methods of analysis to explore questions in fungal evolution. In one study, I explored the genetics behind differences in thermotolerance between isolates of Neurospora discreta from Alaska and New Mexico. Isolates from the two states exhibited differences in maximal growth temperature, with New Mexico isolates being substantially more thermotolerant than isolates from Alaska. Genomic scale comparisons of progeny from crosses between isolates from New Mexico and Alaska indicated that two regions, one on chromosome III and another on chromosome I, are responsible for differences in thermotolerance. Examination of these regions revealed numerous differences between the New Mexico and Alaska isolates at nucleotide and amino-acid levels; and it identified candidate genes for being important for differences in maximal growth temperatures. In a second study, I explored the genomic differences between pathogenic and endophytic isolates in the genus Monosporascus. Culture and sequence-based surveys of root associating fungi at the Sevilleta National Wildlife Refuge (SNWR) revealed the ubiquitous presence of members of this genus. Although M. cannonballus is known as a severe pathogen of melon roots in agricultural settings, all of the host plants associating with Monosporascus species in natural settings appeared to be disease free. Complete genome sequences were obtained from three M. cannonballus isolates, an M. ibericus isolate and six SNWR isolates. Comparative genome analyses revealed that

In light of climate change and projections of increasing temperatures and aridity in the North American southwest, it is essential to understand how consumer populations will respond to changes in the resource landscape. Rainfall varies in timing and intensity and therefore the timing, proportion, phenology, and abundance of C3 and C4 plant resources vary seasonally and annually. Here we examine rodent resource use in the Chihuahuan desert and focus on two distinct precipitation pulses in this system, where spring C3 plants increase production in response to winter rains and C4 plants respond to summer monsoons. We used the distinct carbon isotope ratios of the C3 and C4 plant photosynthetic types to quantify resource use and diet breadth by measuring δ13C in blood plasma and assessed relative trophic level by measuring δ15N. We compared resource use across three years with different precipitation regimes and C3 and C4 abundances. We observed a generally increasing use of C4 derived carbon, as C4 vegetation became more available and C3 decreased. However, diets were generally composed of a greater proportion of C3 derived carbon. Heteromyid rodents exhibited a greater overall reliance on C3 resources. When C3 resources were not available, we observed a division of resources among heteromyids, and the cricetid rodents maintained generally greater than 50% C4 use and higher peaks in C4 use. We observed a community wide shift to C3 resources when abundant, even in the presence of abundant C4 resources. Diet breadth was most constrained and dietary overlap was greatest when C3 plants were abundant and highly utilized. Onychomys arenicola, the most insectivorous species, showed the least variation in C3/C4 usag

Plant-microbial interactions are ubiquitous and yet the consequences of these interactions on plant population and community dynamics are relatively unknown. Here, we used two different classes of plant-microbial interactions to examine their effects on key plant population and community characteristics such as commonness and rarity, competition and coexistence, as well as community stability. Vertically-transmitted endophytes had stage-dependent effects on the population growth of two grass species Poa sylvestris and Poa alsodes, and generally increased host population growth rates. However, it was the intrinsic demographic advantage of P. sylvestris that allowed its population to grow at a much faster rate compared to P. alsodes rather than endophyte benefits. In a greenhouse experiment, we showed that plant-soil microbial feedbacks were important in regulating the strength of self-limitation, or negative frequency dependence, of a strong competitor Bouteloua gracilis. These negative feedbacks increased the potential for its coexistence with Bouteloua eriopoda. In a field experiment, we showed that fungal-driven plant-soil feedbacks between B. gracilis and B. eriopoda may help explain long term patterns of spatial variation in temporal stability between these two species. Negative plant-soil feedbacks for B. gracilis could promote locally stable plant communities, and this effect was stronger when it was at low frequency in the community. Finally, next-generation sequencing of root-associated fungal communities from the two preceding studies revealed strong differences in composition among different growth conditions as well as cultivation periods. In addition, experimental inoculation methods in the greenhouse and field reliably altered the root-associated fungal communities of test plants.

The Southwestern United States is currently experiencing severe drought, resulting in the mortality of many tree species. Piñon-juniper woodlands are an extensive biome in the Southwest, and are highly vulnerable to extended periods of drought that lead to tree mortality. Specifically, Pinus edulis populations are decreasing due to increasingly arid conditions. I used dendrochronology to investigate how tree growth rings of Pinus edulis reflect severe drought in living and dead trees. I also investigated how severe drought affects Pinus edulis along an altitudinal gradient. Tree core samples were taken from currently living and dead trees, as well as from trees at three elevations separated by 100 m in elevation. Growth rings were cross-dated and measured, and widths were statistically compared between all living and dead trees to find years where growth may have differed. Widths were also compared between the three elevation sites. I sought to differentiate between two mortality-related hypotheses: 1) trees that died had a lifetime of underperforming compared to surviving trees and lacked the resources to deal with severe drought, or 2) trees that died consistently outperformed surviving trees and in doing so were closer to physiological limitations when stressed. I also hypothesized that, across elevations, trees at lower elevations would exhibit less growth and greater variability in growth compared to higher elevations. My results indicate that trees that died began to experience decreased growth compared to surviving trees following the drought of the 1950s, and that they had a higher variability in growth that was highly correlated with precipitation. I also found that trees at higher elevations had a higher variability in their growth, while trees at lower elevations may not be able to tolerate severe drought and may periodically die and then re-establish. Using tree rings offers the chance to compare growth patterns to known cli

Life in seasonally dry areas strongly depends on pulses of precipitation during certain portions of the year. This is particularly relevant for Tropical savannas on the Caribbean coast of Colombia that have been converted from Tropical Dry Forests and subjected to permanent agricultural and grazing practices that in turn induce changes in nutrient status in these systems. Several studies have presented evidence for a shift in C and N dynamics following forest conversion, including a decrease in total soil organic carbon and changes in nitrogen status, but the consequences of forest conversion on soil microbial processes are poorly understood. No studies have examined the composition, succession and responses of fungal communities in this region. My analysis of monthly and daily rainfall totals indicate that “Sabanas” can be classified as pulse driven ecosystems, because dry conditions predominate even in the wet season, when days with precipitation are followed by several days with no precipitation. This work showed that time after treatment and not treatment alone affected the species composition of the fungal community. The results from the analysis of the 71 core species revealed that while certain indicator species were present at specific time points, the general pattern was that of a highly resistant and resilient fungal community inhabiting highly perturbed soils in this savanna. Finally, the dynamics of the composition and abundance of this fungal community seems to derive from a combination of factors involving interactions between precipitation and the types of carbon sources available during the decomposition process.

The fire-grazing interaction is well studied in mesic grasslands worldwide, but research is lacking in semiarid systems. In addition, the fire-grazing interaction reduces the invasion of exotic forage species in mesic grasslands by increasing the scale of grazing selection and may be a tool to control invasive plants in other grasslands. We examined the principal drivers and feedbacks of the fire-grazing interaction on the strength of cattle grazing selection, forage quantity and quality, and vegetation structure and composition in two pastures in northeast Montana at The Nature Conservancy’s Matador Ranch. We also determined the influence of time since fire, within the context of the fire-grazing interaction, on cover and herbicide efficacy of crested wheatgrass (Agropyron cristatum [L.] Gaertner), an introduced perennial grass with numerous negative impacts on grassland habitat. Cattle showed significant preference, use, and grazing utilization in recent burned patches that declined as time since fire increased. Cattle selection was driven by significantly increased forage quality in recent burns. Cattle established low forage quantity in recent burned patches, but the extent to which it was maintained varied with precipitation. Forage quality decreased with time since fire as forage quantity increased. Forage production returned to unburned levels after two years since fire, demonstrating that the mixed grass prairie is resilient to the fire-grazing interaction. Species composition was influenced primarily by site and year, though bare ground and litter were influenced by the fire-grazing interaction. The fire-grazing interaction shifted grazing preferences from being plant specific to patch specific in recent burns. The fire-grazing interaction maintained stable cover of A. cristatum in recent burned patches while it increased two fold elsewhere. Herbicide substantially reduced cover of A. cristatum regardless of years since fire, though plant mortality at the l

Life in seasonally dry areas strongly depends on pulses of precipitation during certain portions of the year. This is particularly relevant for Tropical savannas on the Caribbean coast of Colombia that have been converted from Tropical Dry Forests and subjected to permanent agricultural and grazing practices that in turn induce changes in nutrient status in these systems. Several studies have presented evidence for a shift in C and N dynamics following forest conversion, including a decrease in total soil organic carbon and changes in nitrogen status, but the consequences of forest conversion on soil microbial processes are poorly understood. No studies have examined the composition, succession and responses of fungal communities in this region. My analysis of monthly and daily rainfall totals indicate that “Sabanas” can be classified as pulse driven ecosystems, because dry conditions predominate even in the wet season, when days with precipitation are followed by several days with no precipitation. This work showed that time after treatment and not treatment alone affected the species composition of the fungal community. The results from the analysis of the 71 core species revealed that while certain indicator species were present at specific time points, the general pattern was that of a highly resistant and resilient fungal community inhabiting highly perturbed soils in this savanna. Finally, the dynamics of the composition and abundance of this fungal community seems to derive from a combination of factors involving interactions between precipitation and the types of carbon sources available during the decomposition process.

The Southwestern United States is currently experiencing severe drought, resulting in the mortality of many tree species. Piñon-juniper woodlands are an extensive biome in the Southwest, and are highly vulnerable to extended periods of drought that lead to tree mortality. Specifically, Pinus edulis populations are decreasing due to increasingly arid conditions. I used dendrochronology to investigate how tree growth rings of Pinus edulis reflect severe drought in living and dead trees. I also investigated how severe drought affects Pinus edulis along an altitudinal gradient. Tree core samples were taken from currently living and dead trees, as well as from trees at three elevations separated by 100 m in elevation. Growth rings were cross-dated and measured, and widths were statistically compared between all living and dead trees to find years where growth may have differed. Widths were also compared between the three elevation sites. I sought to differentiate between two mortality-related hypotheses: 1) trees that died had a lifetime of underperforming compared to surviving trees and lacked the resources to deal with severe drought, or 2) trees that died consistently outperformed surviving trees and in doing so were closer to physiological limitations when stressed. I also hypothesized that, across elevations, trees at lower elevations would exhibit less growth and greater variability in growth compared to higher elevations. My results indicate that trees that died began to experience decreased growth compared to surviving trees following the drought of the 1950s, and that they had a higher variability in growth that was highly correlated with precipitation. I also found that trees at higher elevations had a higher variability in their growth, while trees at lower elevations may not be able to tolerate severe drought and may periodically die and then re-establish. Using tree rings offers the chance to compare growth patterns to known cli

Plant-microbial interactions are ubiquitous and yet the consequences of these interactions on plant population and community dynamics are relatively unknown. Here, we used two different classes of plant-microbial interactions to examine their effects on key plant population and community characteristics such as commonness and rarity, competition and coexistence, as well as community stability. Vertically-transmitted endophytes had stage-dependent effects on the population growth of two grass species Poa sylvestris and Poa alsodes, and generally increased host population growth rates. However, it was the intrinsic demographic advantage of P. sylvestris that allowed its population to grow at a much faster rate compared to P. alsodes rather than endophyte benefits. In a greenhouse experiment, we showed that plant-soil microbial feedbacks were important in regulating the strength of self-limitation, or negative frequency dependence, of a strong competitor Bouteloua gracilis. These negative feedbacks increased the potential for its coexistence with Bouteloua eriopoda. In a field experiment, we showed that fungal-driven plant-soil feedbacks between B. gracilis and B. eriopoda may help explain long term patterns of spatial variation in temporal stability between these two species. Negative plant-soil feedbacks for B. gracilis could promote locally stable plant communities, and this effect was stronger when it was at low frequency in the community. Finally, next-generation sequencing of root-associated fungal communities from the two preceding studies revealed strong differences in composition among different growth conditions as well as cultivation periods. In addition, experimental inoculation methods in the greenhouse and field reliably altered the root-associated fungal communities of test plants.

Plant-microbial interactions influence biogeochemical cycles. Plants and biological soil crusts are primary producers in drylands. Biocrusts include cyanobacteria, lichens, mosses, algae, fungi, bacteria, and archaea on the soil surface, some of which fix atmospheric nitrogen. I investigated controls on biocrust carbon fluxes and their contribution to ecosystem fluxes, the incorporation of plant-derived carbon into biocrusts, and the role of soil fungi in promoting performance of plants and biocrusts. Biocrusts responded to temperature and moisture differently by biome. Biocrusts in grasslands/shrublands contributed >25% of total summertime ecosystem respiration, but biocrusts in savannas/woodlands contributed <1%. Biocrusts contributed <2% to GPP in any biome. To augment their native photosynthesis, biocrusts may include 16% plant-derived carbon. Fungal connections improved plant and biocrust performance and reduced differences in the CN ratio between organisms compared to when connections were impeded. Investigation of interactions among biocrusts, plants, and fungi has improved understanding of resource cycling in drylands.

Plant-microbial interactions influence biogeochemical cycles. Plants and biological soil crusts are primary producers in drylands. Biocrusts include cyanobacteria, lichens, mosses, algae, fungi, bacteria, and archaea on the soil surface, some of which fix atmospheric nitrogen. I investigated controls on biocrust carbon fluxes and their contribution to ecosystem fluxes, the incorporation of plant-derived carbon into biocrusts, and the role of soil fungi in promoting performance of plants and biocrusts. Biocrusts responded to temperature and moisture differently by biome. Biocrusts in grasslands/shrublands contributed >25% of total summertime ecosystem respiration, but biocrusts in savannas/woodlands contributed <1%. Biocrusts contributed <2% to GPP in any biome. To augment their native photosynthesis, biocrusts may include 16% plant-derived carbon. Fungal connections improved plant and biocrust performance and reduced differences in the CN ratio between organisms compared to when connections were impeded. Investigation of interactions among biocrusts, plants, and fungi has improved understanding of resource cycling in drylands.

Mammalian distributions are constantly changing. Some distributional shifts reflect habitat change, climate change, and human transplantations; thus, such shifts are due to actual expansions or contractions of populations. However, other species ranges that appear to shift as the result of new records being added to known distributional limits actually might reflect populations that previously were undetected due to a lack of past surveys or species that are difficult to detect. In 2013, multiple techniques were employed to document mammalian distributional records in southwestern Kansas and northwestern Oklahoma. We discovered three new county records in Morton County, Kansas (Crawford’s Desert Shrew, Notiosorex crawfordi; American Beaver, Castor canadensis; and Eastern Fox Squirrel, Sciurus niger), with Crawford’s Desert Shrew also representing the first records of the species in Kansas. We documented five new county records in Cimarron County, Oklahoma (Least Shrew, Cryptotis parva; American Parastrelle, Parastrellus hesperus; Wapiti, Cervus canadensis; White-tailed Deer, Odocoileus virginianus; and Eastern Fox Squirrel, Sciurus niger). The Eastern Fox Squirrel and Least Shrew likely are expanding their distribution in this region along the Cimarron River, whereas the Wapiti, White-tailed Deer, and American Beaver likely are recolonizing the area after extirpation during the last century. Occurrence of Eastern Fox Squirrels in Elkhart, Kansas, and Boise City, Oklahoma, might represent human introductions. The American Parastrelle and Crawford’s Desert Shrew likely have gone undetected at those sites and have not recently experienced range expansions. Our results demonstrate the importance of continued surveys using various methods to document mammals. Both counties have been intensively surveyed for mammals, indicating that targeted surveys and various techniques are important to document distributional shifts as well as rare or difficult to capture species. Unde

Habitat loss and fragmentation are the leading causes of biodiversity loss and are considered to be the principal threats to the sustainability of the biosphere. Historically, fragmentation literature focuses on direct anthropogenic disturbances, such as deforestation and urbanization. However, many ecosystems now face novel disturbances, such as the invasion of non-native species and climate change-induced disturbances, further exasperating the rate of habitat loss and fragmentation. Thus, it is critical to understand the influence of these novel disturbance events on biodiversity in order to identify the long-term consequences of global change. My dissertation focused on two types of landscapes facing novel disturbances: 1) the invasion of an exotic plant species in California’s Coachella Valley, and 2) altered fire regimes in Joshua Tree National Park (JTNP). Sahara Mustard (Brassica tournefortii; hereafter mustard), has invaded habitats throughout the arid southwestern United States, including five distinct sand habitats in the eastern Coachella Valley, California. I examined trends in ground-dwelling arthropod community structure concurrent with mustard invasion within those habitats from 2003‒2011. I found strong negative relationships with arthropods and mustard even when controlling for non-target environmental correlates and for potential factors that we suspected of mediating mustard effects. My second study site took place in JTNP, where wildfire was once non-existent or exceedingly rare. However, fires are now increasingly common due to the invasion of non-native grass species – an invasion facilitated by climate change and an on-going nitrogen soil deposition from urban California. This altered fire regime has left behind varying patterns of landscape heterogeneity. Within this landscape, I quantified the influence of fire-induced spatial heterogeneity on ground-dwelling arthropods and small mammal communities. I found that community patterns of both ar

Patch burn‐grazing is a rangeland management strategy that exploits the attraction of grazing animals to recently burned areas in order to achieve management objectives. When fire is applied to a landscape in a patchy manner, leaving some patches unburned, the resulting grazing animal activity, forage utilization, and animal impact are patchily distributed within that landscape as well. Areas that have been recently burned tend to be characterized by the highest levels of grazing animal activity while areas that have gone the longest without burning tend to be characterized by the lowest levels of grazing animal activity. This can be advantageous for a multitude of reasons related to wildlife conservation, livestock productivity, herbaceous fuel management, invasive species management, and woody plant control. The following annotated bibliography lists resources about patch burn‐grazing in North America. The bibliography includes all citations known by us of research conducted within the context of patch burn‐grazing as an explicit management strategy. Included in the bibliography are papers representing original research, review and synthesis papers, theses (10), and a dissertation. In instances where the research in a thesis or dissertation was subsequently published, we include the citation for the published article(s) but not for the original thesis or dissertation. We did not include reports or extension publications although many valuable publications of this type exist on this topic. For additional resources such as extension publications, look at the Great Plains Fire Science Exchange website or university extension websites in the region.

Throughout Canyonlands, naturally occurring sandstone basins called "potholes" form tiny ecosystems inhabited by a surprising collection of animals. Join ranger Karen Henker for an introduction to these animals and some their remarkable adaptations.

Biological Soil Crust is a living groundcover that forms the foundation of plant life in Canyonlands and the surrounding area. Join ranger Karen Henker and learn about this critical - and fragile - component of the high desert ecosystem.

Biological Soil Crust is a living groundcover that forms the foundation of plant life in Canyonlands and the surrounding area. Join ranger Karen Henker and learn about this critical - and fragile - component of the high desert ecosystem.

Throughout Canyonlands, naturally occurring sandstone basins called "potholes" form tiny ecosystems inhabited by a surprising collection of animals. Join ranger Karen Henker for an introduction to these animals and some their remarkable adaptations.

Drylands typically have distinctive vegetative patterns that reflect the underlying physical landscape. We use a geopedological classification to organize the landscape into five categories from broad scale to fine scale: (1) physiographic divisions which describe regional topography, such as mountains and basin floors; (2) regolith type which identifies residuum versus transported sediments; (3) parent materials which describe mineralogy; (4) landforms which provide meso-scale descriptions of topography; and (5) soil texture, a fine-scale variable important for infiltration, erodibility, and available water holding capacity. The study was conducted in a 1753 km2 area of the White Sands Missile Range and easternmost Jornada Experimental Range and revealed the following. (1) At the broadest scale, mesquite is dominant on the basin floor when the parent material is siliceous sand, but (2) biological soil crust becomes dominant in the basin floor when the parent material is gypseous. (3) Creosotebush is dominant on rocky soils of the piedmont slopes regardless of parent material, but (4) grasslands become dominant on the bajadas upslope in the semiarid zone and into the semiarid mountain uplands regardless of bedrock type. This method provides a way of supplementing ecologic-edaphic studies and provides a framework within which mechanisms can be explored.

As drought conditions spread across the United States, concerns over water supplies, water use, and water management policies are growing and possible contributing environmental factors are continually being scrutinized. This thesis examines Death Valley as an analog for Southern Nevada and utilizes NASA EOS data, combined with ancillary climate data, to assess the effect of decadal climate variability on groundwater storage in the Death Valley area. Historical climate data, combined with satellite imagery observations, were compiled and calculated for analyses. Conclusions derived from statistical analyses infer trends between GRACE (Gravity Recovery and Climate Experiment) satellite data and fluctuating levels of recharge and groundwater storage, as well as climatic changes in temperature and rainfall. The observations show seasonal variations in ground water thickness of up to 10 cm from the mean, correlated directly to seasonal temperature variability. Connections were also observed between temperature and precipitation with a correlation factor of -0.5. The relationship between precipitation and groundwater thickness change is also evident, with a correlation factor of 0.4 where evaporation and delayed aquifer response are likely impacting direct correlation. The research illustrates how and which environmental factors are impacting the groundwater storage in Death Valley. Due to the similarity of climates between Death Valley and Southern Nevada, this research may be used as an analogy illustrating the impact of climate variability in Southern Nevada. The research, combining GRACE satellite observations and downscaled historical climate data will show any adverse effects that climate variability may be having on the area, including the impact it has on aquifers, and the impact it has on Death Valley's water supply in general.

As a fundamental component of the developing discipline of conservation biogeography, broadscale analyses of biotic assembly and disassembly across multiple temporal and spatial scales provide an enhanced understanding of how geologic transformations and climate oscillations have shaped extant patterns of biodiversity. As with any scientific field, there are limitations in the case of biogeographic historical reconstructions. Historical reconstructions are only as robust as the theoretical underpinnings of the methods of reconstruction (including data collection, quality, analysis, and interpretation). Nevertheless, historical reconstructions of species distributions can help inform our understanding of how species respond to environmental change. My dissertation takes a critical look at the current state of biotic-level biogeographic analyses across an array of spatio-temporal scales and I use the North American warm deserts as a model system to both develop and test biogeographic methods. In particular, I address the biogeographic issue of pseudo-congruence (similar biogeographic patterns produced by historically dissimilar events) and develop potential approaches to reduce the issue of pseudo-congruence in biotic-level analyses. I review potential confounding issues that could produce pseudo-congruence in climate change-based biogeographic analyses and I incorporate temporal components into complex biogeographic theories and methods to reduce pseudo-congruence in biogeographic analysis. My dissertation goals and approaches are described in Chapter 1, which serves as an introduction. In Chapter 2, I provide a summary of paleoclimatic patterns and processes in the North American deserts. A refined understanding of paleoclimatic pattern and process can facilitate the generation of enhanced hypotheses about how biotas are altered by climate change events, particularly in cases where climate change events occurring at different times and scales could produce pseudo-co

Desertification of the East Asian drylands and the consequent dust transport have been serious concerns for adjacent Asian countries as well as the western United States. Tree planting has been considered one applicable strategy to mitigate the desertification. However, the desired effect of the tree planting would not be brought to fruition unless the newly planted trees change the coupling characteristics between the land and the atmosphere. Based on this perception, we attempt to clarify the effects of vegetation on the coupling strength between the atmosphere and land surface, and we suggest the most efficient areas of tree planting for desertification mitigation in East Asia. Using regional vegetation-atmosphere coupled model simulations, coupling strength with and without vegetation was computed and compared with each other. An increased vegetation fraction reduces the coupling strength in June, July, and August (JJA), primarily due to decreased evapotranspiration variability. This effect is pronounced over the Manchurian Plains and the highly populated areas of Beijing and Tianjin. The reduced coupling strength tends to weaken feedback between soil moisture and precipitation as a maintenance mechanism of warm season droughts in the midlatitudes and subsequently decrease the probability of droughts, a finding that is reflected in the enhanced JJA mean soil moisture. However, some drylands like the eastern edges of the Gobi desert present marginal or even opposite changes in coupling strength, meaning a limited effect of vegetation on relieving droughts. Therefore, given limited financial and human resources, acupuncture-like afforestation, i.e., concentrated tree planting in a particular region where the coupling strength can be substantially reduced by vegetation, is an effective strategy to secure long-standing desertification mitigation.

Trends in the mid-continent population of sandhill cranes (Grus canadensis) indicate that the species is increasing. A large proportion of this population winters in northern Mexico where possible conflicts between local inhabitants and cranes can occur. We conducted interviews of 40 rural inhabitants living near wetlands used by cranes in three Mexican states. All interviewees had knowledge of cranes and were capable of describing them. The arrival of cranes affected 43% of interviewees. The negative effects were mainly destroyed crops with a subsequent diminished production. Seventy percent of those affected implemented scare tactics to deter the birds, while others (15%) did nothing to mitigate crop losses and accepted such damages. While sandhill cranes continue to increase, conflicts with humans are expected to rise. Our results provide information about human attitudes toward cranes and can serve as the basis for future conservation guidelines.

The Lane Mountain milkvetch, Astragalus jaegerianus, is an endangered species that exists in fragmented populations in the Mojave Desert. UCLA monitored populations have declined by 76% since 1999 due to drought. Reintroduction experiments support this idea: supplemental water increased seedling survivorship. Phenological studies suggest that between-year differences in A. jaegerianus phenology are pronounced, and controlled by annual differences in precipitation. Seed production per plant is highly variable. Study plants had significant reproductive potential that was unrealized in 2011 and 2012. High precipitation in 2011 is a likely explanation for increases in seed production in some plants, but the strong negative effect of herbivory on other plants appears to have overwhelmed the positive effect of precipitation on seed production. The soil seed bank may be categorized as low, persistent, and largely restricted to the area beneath host shrubs with active A. jaegerianus. Seed dispersal is low. The post-dispersal seed bank, significantly declined in 2011 despite increases in precipitation. Decreases in soil seed density are attributable to two factors: (1) a decrease in seed production due to increases in herbivory, and (2) an increase in seed predation due to high seed predator populations and an extended fruit dehiscing period., The original document contains color images.

I investigate the phylogeography of the relict and lowland leopard frogs (Rana onca; R. yavapaiensis) inhabiting the Mojave and Sonoran deserts. In Chapter 1, I summarize literature describing taxonomy, phylogenetics, and the possible effects of Quaternary climate change on distribution. Examples of phylogeographic patterns from generally co-distributed organisms are provided to develop background for interpreting the structure. In Chapter 2, I investigate the phylogeography of these frogs using mitochondrial DNA data. The analysis supports a previously determined phylogenetic break between taxa however further dividing R. yavapaiensis into two lineages. I estimate a possible Early Pleistocene divergence of R. onca and R. yavapaiensis, followed by a Middle Pleistocene separation of the western Grand Canyon population of R. yavapaiensis from the main R. yavapaiensis clade. Demographic/network analyses indicate population/range expansion for R. yavapaiensis. Species distribution models suggest that these frogs may not have greatly shifted ranges since the last glacial maximum.

This thesis examines the death of mulga (Acacia aneura) adjacent to a mine haul road in the north-eastern Goldfields of Western Australia. The death of trees along roadsides in the arid and semi-arid regions of Australia is often referred to as a ‘road shadow effect’ and is thought to occur because of sheetflow blockage. As sheetflow redistributes water across the land surface (rather than into channels) any impediment to flow is likely to have consequences for vegetation downslope of the impediment. The study was important as many mining companies in semi-arid Western Australia have reported tree deaths along their mine haul roadsides and the problem has also been identified across other areas of Western Australia including grazing land and road verges. The haul roads at many mines are watered to suppress dust and the water is often hypersaline. This study compared vegetation and soil parameters at sites up and downslope of both the haul (treated) and control roads to ascertain whether factors additional to sheetflow contributed to roadside tree deaths. At each site, a series of adjoining quadrats was established perpendicular to the road. The data collected at each site was analysed on a quadrat by quadrat basis to establish trends with increasing distance from the road edge. Where possible analysis techniques which could test for differences between control and treated sites or upslope and downslope sites and the interaction between sites were used as this would address the aims of the study. If data were normally distributed either two-way Analysis of Variance or t-tests were carried out and where data were not normally distributed the non-parametric Mann Whitney Utest was performed. The significant differences noted in several vegetation parameters between up and downslope sides of both the control and treated roads provided a good argument for road presence leading to road shadow effect. These differences included a greater proportion of dead and recently dead

High desert plants and animals are adapted to their environment in many different ways. This lesson has been designed specifically to connect with the Utah State Science Core Curriculum for 7th grade. However, the lesson also meets standards for 5th grade and high school biological science with some minor adjustments in teaching style and depth of content. The Arches National Park Field Trip in a Box provides the lesson plans, materials and background for you to teach your students about either: Geology, Desert Adaptations or Microorganisms. Each box includes suggestions of locations you may want to conduct your field trip lessons and introductory activities and assessment activities. Each topic is tied to the core curriculum for the State of Utah.

Microorganisms play a vital role in the high desert ecosystem. They are everywhere! This lesson has been designed specifically to connect with the Utah State Science Core Curriculum for 6th grade. However, the lesson’s emphasis on inquiry and practicing the steps of the scientific method makes it appropriate for higher grades with some minor adjustments. The Arches National Park Field Trip in a Box provides the lesson plans, materials and background for you to teach your students about either: Geology, Desert Adaptations or Microorganisms. Each box includes suggestions of locations you may want to conduct your field trip lessons and introductory activities and assessment activities. Each topic is tied to the core curriculum for the State of Utah.

Open-File Report 2009–1102: Habitat modeling is an important tool used to simulate the potential distribution of a species for a variety of basic and applied questions. The desert tortoise (Gopherus agassizii) is a federally listed threatened species in the Mojave Desert and parts of the Sonoran Desert of California, Nevada, Utah, and Arizona. Land managers in this region require reliable information about the potential distribution of desert tortoise habitat to plan conservation efforts, guide monitoring activities, monitor changes in the amount and quality of habitat available, minimize and mitigate disturbances, and ultimately to assess the status of the tortoise and its habitat toward recovery of the species. By applying information from the literature and our knowledge or assumptions of environmental variables that could potentially explain variability in the quality of desert tortoise habitat, we developed a quantitative habitat model for the desert tortoise using an extensive set of field-collected presence data. Sixteen environmental data layers were converted into a grid covering the study area and merged with the desert tortoise presence data that we gathered for input into the Maxent habitat-modeling algorithm. This model provides output of the statistical probability of habitat potential that can be used to map potential areas of desert tortoise habitat. This type of analysis, while robust in its predictions of habitat, does not account for anthropogenic changes that may have altered habitat with relatively high potential into areas with lower potential.

High desert plants and animals are adapted to their environment in many different ways. This lesson has been designed specifically to connect with the Utah State Science Core Curriculum for 7th grade. However, the lesson also meets standards for 5th grade and high school biological science with some minor adjustments in teaching style and depth of content. The Arches National Park Field Trip in a Box provides the lesson plans, materials and background for you to teach your students about either: Geology, Desert Adaptations or Microorganisms. Each box includes suggestions of locations you may want to conduct your field trip lessons and introductory activities and assessment activities. Each topic is tied to the core curriculum for the State of Utah.

Microorganisms play a vital role in the high desert ecosystem. They are everywhere! This lesson has been designed specifically to connect with the Utah State Science Core Curriculum for 6th grade. However, the lesson’s emphasis on inquiry and practicing the steps of the scientific method makes it appropriate for higher grades with some minor adjustments. The Arches National Park Field Trip in a Box provides the lesson plans, materials and background for you to teach your students about either: Geology, Desert Adaptations or Microorganisms. Each box includes suggestions of locations you may want to conduct your field trip lessons and introductory activities and assessment activities. Each topic is tied to the core curriculum for the State of Utah.