Characterizing the distribution and ecological roles of Xanthoparmelia chlorochroa, a vagrant lichen of the Mountain West

In this study, I collected data and compared models to understand the distribution, abundance and annual productivity of a common vagrant lichen in Wyoming grasslands, Xanthoparmelia chlorochroa.;The focus of Chapter 1 is the investigation of the environmental drivers of presence and abundance of Xanthoparmelia chlorochroa. I use maximum entropy modeling to predict presence in the western United States based on records from herbaria along with a suite of environmental variables. I then use GLM modeling of field data of Xanthoparmelia abundance to predict mean biomass per area within the suitable habitat. I find that lichen biomass matches and even exceeds that of vascular plants in many situations, with maximum rates of biomass for X. chlorochroa of 256 g/m 2 in sites where it is most abundant, compared to the 127 g/m 2 estimates of total above-ground vascular plant productivity in these communities.;In Chapter 2 I examine the growth rates for this species and use these measurements to estimate annual productivity for this lichen, while accounting for the fluctuations in the total biomass of the species across its range. I measured changes in biomass of 336 individual lichens to estimate monthly and annual increases in growth. I then estimate landscape scale annual lichen productivity in these grassland ecosystems. I also make some interspecific comparison of growth rates and estimate the time required, given these growth rates, to attain the observed local accumulation on the landscape.