Abstract Detail

Ecology

Gray, Jesse [1], Smith, Melinda [2].

Climate change impacts on population dynamics in tallgrass prairie: Implications for species codominance.

Two C4 grass species, Andropogon gerardii and Sorghastrum nutans, together account for the large majority of individuals, biomass, and possibly genetic diversity in plant communities of the tallgrass prairies of the Central US. As co-existing species with similar functional traits and what appears to be overlapping niches, it is not clear what mechanisms facilitate their co-dominance, but it may partly rely on the high variability of environmental conditions that characterize grassland ecosystems. We found asynchrony in population dynamics in which A. gerardii begins each growing season at higher tiller densities, with attrition of tillers starting mid-season. Concurrent gains of S. nutans tillers results in A. gerardii becoming less dominant by the end of most growing seasons. We hypothesized that this differentiation in tillering strategies causes each species to be most vulnerable to unfavorable environmental conditions during different parts of the growing season, thus enabling their coexistence by preventing an inter-annually consistent competitive advantage of either species. A greenhouse experiment confirmed that the timing of water availability has different effects on each species. Monitoring intra- and interannual dynamics of the species in the field over eight growing seasons, we found that greater plot-level tiller density asynchrony was associated with higher population densities of S. nutans and aggregate tiller densities of both species. Experimental increases in temperature and rainfall variability were associated with decreased population-level asynchrony, as well as greater declines in population density and overall community productivity, suggesting this mechanism of co-dominance may rely on current and historic levels of environmental variability, and may be vulnerable to projected increases in that variability with climate change.

1 - Colorado State University, Biology, 1878 Campus Delivery, Fort Collins, CO, 80523, United States
2 - Colorado State University, 1878 Campus Delivery, Fort Collins, CO, 80523, United States

Keywords:
none specified

Presentation Type: Oral Paper
Session: 31, Ecology Section - Population Biology
Location: 106/Mayo Civic Center
Date: Tuesday, July 24th, 2018
Time: 4:00 PM
Number: 31010
Abstract ID:370
Candidate for Awards:Ecological Section Best Graduate Student Paper