2020 ESA Annual Meeting (August 3 - 6)

COS 220 Abstract - Potential drivers of composition and diversity of endemic plant communities along an elevation gradient in the Chilean Andes: Implications for climate change

Lucy Schroeder, Plant and Microbial Biology, University of Minnesota, Saint Paul, MN, Cathleen Lapadat, Ecology, Evolution and Behavior, University of Minnesota, Saint Paul, MN, Valeria Robles Jarpa, Facultad de Ciencias, Universidad de Chile, Santiago, Chile, Sarah E. Hobbie, Department of Ecology, Evolution, and Behavior, University of Minnesota, Saint Paul, MN, Mary T. K. Arroyo, Institute of Ecology and Biodiversity and Jeannine Cavender-Bares, Ecology, Evolution, and Behavior, University of Minnesota, Saint Paul, MN
Background/Question/Methods

Plant communities of the central Chilean Andes are of conservation importance due to high rates of endemism and risk of habitat loss. Climate change threatens plants from such high-altitude ecosystems because climate in their current range may become unsuitable for them. Additionally, migration to higher latitudes may be limited by inability to tolerate lower nutrient availability and higher sun intensity. The IPCC predicts a 3-5 °C increase in summer temperature across elevation by 2080 for this region (BAU scenario). Currently, we have limited information on how climate change will affect the composition of plant communities at different elevations. We assessed aspects of plant community composition and diversity along an elevation gradient (2400 m - 3500 m) in the central Chilean Andes. We asked 1) How do plant community composition and diversity—including taxonomic and spectral diversity—shift with altitude? and 2) What are the drivers of plant community composition and microbial processes along the elevation gradient? Spectral diversity was determined from leaf level spectroscopic measurements (400-2500 nm) across the gradient using a point-intercept method. We sampled soil cores to 10 cm depth along the elevation gradient to determine nutrient variation and the influence of microbial processes on soil nutrient availability.

Results/Conclusions

We found that taxonomic diversity (Shannon index and species richness) declined with increasing elevation, as did spectral dispersion (R2=0.31) and richness (R2=0.34) (calculated using distance-based multidimensional functional diversity indices). Plant communities showed strong zonation patterns. The highest elevation site had the largest proportion of species unique to that elevation out of the total species occurring at that site (66%). The two highest elevation sites had the first and second largest proportion of unique species relative to total species occurring at those sites. While total nitrogen concentration in the soil was relatively constant across the gradient, net nitrogen mineralization rate—the conversion of nitrogen to forms available for plants—decreased with elevation. In contrast, soil moisture increased with elevation.

Altogether, the declines in plant taxonomic and spectral diversity with altitude are associated with lower available soil nitrogen, colder temperatures, longer snow cover, and less sunshine at higher elevations. As climate warms across elevations, nitrogen mineralization rate at higher elevations may increase, facilitating plant migration and adaptation to higher altitudes. However, plants restricted to the highest elevation are likely to be adapted to cold climates with long winters and may be displaced by faster growing species adapted to warmer climates.