Abstract

The responses of heterotrophic microbial process rates to temperature in soils are often investigated in the short-term (hours to months), making it difficult to predict longer-term temperature responses. Here, we integrate the temperature sensitivity obtained from the Arrhenius model with the concepts of microbial resistance, resilience, and susceptibility to assess temporal dynamics of microbial temperature responses. We collected soils along a boreal forest climate gradient (long-term effect), and quantified exo-enzyme activities and CO2 respiration at 5, 15, and 25°C for 84 days (relatively short-term effect). Microbial process rates were examined at two levels (per g microbial biomass-C; and per g dry soil) along with community structure, to characterize driving mechanisms for temporal patterns (e.g., size of biomass, physiological plasticity, community composition). Although temperature sensitivity of exo-enzyme activities on a per g dry soil basis showed both resistance and resilience depending on the types of exo-enzyme, biomass -C-specific responses always exhibited resistance regardless of distinct community composition. Temperature sensitivity of CO2 respiration was constant across time and different communities at both units.

This study advances our knowledge in two ways. First, resistant temperature sensitivity of exo-enzymes and respiration at biomass-C specific level across distinct communities and diverse timescales indicates a common relationship between microbial physiology and temperature at a fundamental level, a useful feature allowing microbial process models to be reasonably simplified. Second, different temporal responses of exo-enzymes depending on the unit selected provide a cautionary tale for those projecting future microbial behaviors, because interpretation of ecosystem process rates may vary with the unit of observation.

Citation

Min, K., K.M. Buckeridge, S.E. Ziegler, K.A. Edwards, S. Bagchi, S.A. Billings (2016): Biomass-C specific temperature responses of microbial C transformations reveal consistency regardless of microbial community structure across diverse timescales of inquiry. American Geophysical Union 2016 Fall Meeting, San Francisco, CA.