Compositional and Functional Shifts in Microbial Communities Due to Soil Warming

TLDR

Microbial decomposition is typically modeled with first‑order kinetics, yet experimental data indicate that temperature increases the pool of substrate carbon available for respiration while having little effect on the rate constants. The study investigates whether soil warming alters microbial community composition, with dominant populations at higher temperatures able to metabolize substrates not used by communities at lower temperatures. Using phospholipid fatty acid (PLFA) and lipopolysaccharide fatty acid (LPS‑OHFA) analyses, the authors compared microbial respiration kinetics in soils incubated from 5 °C to 25 °C to assess compositional and functional changes. Temperature treatments produced significant differences in substrate pools and PLFA/LPS‑OHFA biomarkers for Gram‑positive and Gram‑negative bacteria, demonstrating that warming shifts microbial community composition and function and may alter soil organic matter decomposition in ways not accounted for by current simulation models.

Abstract

Abstract Microbial decomposition processes are typically described using first‐order kinetics, and the effect of elevated temperature is modeled as an increase in the rate constant. However, there is experimental data to suggest that temperature increases the pool size of substrate C available for microbial respiration with little effect on first‐order rate constants. We reasoned that changes in soil temperature alter the composition of microbial communities, wherein dominant populations at higher temperatures have the ability to metabolize substrates that are not used by members of the microbial community at lower temperatures. To gain insight into changes in microbial community composition and function following soil warming, we used molecular techniques of phospholipid fatty acid (PLFA) and lipopolysaccharide fatty acid (LPS‐OHFA) analysis and compared the kinetics of microbial respiration for soils incubated from 5 to 25°C. Substrate pools for microbial respiration and the abundance of PLFA and LPS‐OHFA biomarkers for Gram‐positive and Gram‐negative bacteria differed significantly among temperature treatments, providing evidence for a shift in the function and composition of microbial communities related to soil warming. We suggest that shifts in microbial community composition following either large seasonal variation in soil temperature or smaller annual increases associated with global climate change have the potential to alter patterns of soil organic matter decomposition by a mechanism that is not considered by current simulation models.