Desiccation tolerance in dryland mosses: influences of micro- and macro-climate on carbon balance and feedbacks to biocrust communities

Kirsten K. Coe, Biology, Middlebury College, Middlebury, VT, Maya Gomez, Middlebury College, Niko Carvajal Janke, Viticulture and Enology, University of California Davis, Davis, CA, Sahalie Pittman, Middlebury College, MIDDLEBURY, VT, Theresa Clark and Lloyd Stark, University of Nevada Las Vegas

Background/Question/Methods
Dryland ecosystems account for over 40% of global land area and are projected to increase in aridity in the face of climate change. Biocrusts - communities of moss, lichen, and cyanobacteria - are critical to the function of dryland ecosystems, and mosses of the genus Syntrichia are keystone crust organisms in North America. Syntrichia mosses display a diversity of adaptations to dryland environments including desiccation tolerance: the ability dry completely and regain functioning following rehydration. Degrees of desiccation tolerance in Syntrichia can vary by both species and genotype based on climate and microhabitat conditions. To investigate how differences in microclimate and microhabitat affect desiccation tolerance within a species, we examined S. caninervis samples ex-situ from three sites along a precipitation gradient in the Sheep Creek Mountains, NV. To tease apart genetic and environmental contribution to observed differences in phenotype, we also performed a common garden experiment where field-collected samples were grown in the lab under identical conditions. We recorded post-hydration carbon balance (a functional trait related to desiccation tolerance) and measured a suite of anatomical traits to investigate differences in moss desiccation tolerance among sites.
Results/Conclusions
We found variation in carbon balance as a function of the microclimate and microhabitat of field sites such as rainfall, proximity to bushes or shrubs, and topographical aspect. The largest of these differences were between the low and high precipitation sites, and, on average, samples from the highest precipitation site expended more respiratory carbon upon rehydration compared to lower precipitation sites, however the high precipitation site genotypes also had the highest overall carbon gains following a rainfall event. We also discovered variation in leaf traits that may partially explain differential responses to desiccation and rehydration. Specifically, mosses from the highest elevation site had more robust, larger shoots containing leaves with long hair points (awns). Our common garden experiment demonstrated that the majority of these traits were genetically determined, suggesting local adaptation in sub-populations of S. caninervis. Collectively, these results indicate potential suites of environmental variables that influence desiccation tolerance in this ecologically important species of dryland moss and offer insight into the variability of genotypic responses to hydration in the face of global change.