Stepwise and Varying Warming Impacts on Heterotrophic Respiration and Microbial Functions in Carbon Poor and Rich Switchgrass Soils
Laboratory soil incubations are used to examine soil responses to changing environment in well-controlled conditions. Stepwise warming (SW) scenario adopted in incubations compares microbial responses at two constant temperatures to simulate warming effects. However, implementing temperature fluctuations in soil-incubations (varying warming (VW) scenario) can mimic in-situ conditions. We investigate SW and VW effects on heterotrophic respiration and underlying microbial mechanisms on two switchgrass (Panicum virgatum L.) soils with contrasting soil organic carbon (SOC) content, one in middle Tennessee with low-SOC (2.05%), another in Texas with high-SOC (8.48%). Soils were incubated for 90 days under SW and VW scenarios with 10 collections. Soil heterotrophic respiration (Rs), cumulative respiration (Rc), microbial biomass carbon & nitrogen (MBC, MBN), biomass-specific heterotrophic respiration (Rss), and extracellular enzyme activities were quantified per collection. Three-way repeated measure ANOVA was conducted for each soil to test main and interactive effects of temperature (warming), warming scenario, and collection on respiration and microbial relevant variables. Results showed warming significantly increased Rs and Rc, reduced enzyme activities associated with nitrogen (N) or phosphorus (P) acquisitions in both soils but significantly increased MBC and Rss in Texas soils. Second, SW resulted in greater respiratory loss than VW in both soils. Last, warming at least doubled Rc under VW but little or no change was observed in SW. Despite positive warming effects on respiration in both soils, this study suggested contrasting warming effects of different temperature change scenarios on soil respiration likely driven by divergent responses in microbial community, enzymatic and physiological features.
Soil sciences|Climate Change
"Stepwise and Varying Warming Impacts on Heterotrophic Respiration and Microbial Functions in Carbon Poor and Rich Switchgrass Soils"
ETD Collection for Tennessee State University.