Consequences of drought tolerance traits for microbial decomposition in the DEMENT model

Abstract

The frequency and intensity of drought are expected to increase in the future, yet the consequences for soil microbial communities and functioning remain unclear. Processes such as decomposition could be maintained if microbial communities become more drought tolerant. However, increased drought tolerance might involve physiological costs with uncertain consequences for ecosystem processes. Here we used the trait-based model DEMENT to quantify the sensitivity of microbial traits, community dynamics, and litter decomposition to variation in drought tolerance costs. These costs were imposed as a physiological tradeoff between drought tolerance and carbon use efficiency. We ran simulations across a range of drought tolerance costs and with climate forcing from ambient and drought treatments in a Southern California grassland that experiences seasonal summer drought. As expected, zero or low costs of tolerance allowed droughttolerant taxa to increase in abundance under ambient simulation conditions. More drought tolerant communities had greater microbial biomass but lower extracellular enzyme investment due to biological feedbacks involving enzyme production. These two responses counteracted one another, leaving decomposition unchanged relative to virtual microbial communities with no drought tolerance. Simulated decomposition rates were one-third lower under drought treatment, but there were no differences in microbial drought tolerance compared to simulations forced with ambient climate. This model result suggests that seasonal drought is a more important environmental filter than reduced precipitation during the wet season in our Mediterranean climate system. Overall, our simulations indicate that microbial community responses to drought are not likely to increase decomposition rates, even if CUE costs are low. Using the simulation approach described

Physiological adaptations of leaf litter microbial communities to long-term drought

“…The observations of community shifts suggests environmental pressures that select for taxa that can survive the physiological stress imposed by drought [36][37][38][39] . The community shifts could also be ascribed to the indirect effect of drought-induced changes in plant litter chemistry acting as a selection pressure 7,21 .…”

Spatial Control of Carbon Dynamics in Soil by Microbial Decomposer Communities

“…A model-based analysis demonstrated that adaptive microbial responses to C limitation and water stress might emerge from microbial traits related to dormancy and production of extracellular polymeric substances (Brangarí et al, 2018). The importance of community-level regulation and microbial trait trade-offs was highlighted by trait-based modeling of litter decomposition (Kaiser et al, 2015;Allison and Goulden, 2017).…”

Defining trait-based microbial strategies with consequences for soil carbon cycling under climate change

“…We anticipate that these approaches will improve our understanding of the physiological constraints facing microbes under anthropogenic influence. By linking population-level response traits to community Figure 3: Summary of the proposed trait-based framework incorporating microbial life history strategies into the DEMENT model to predict community response and its ecosystem consequences under environmental change (adapted from Allison and Goulden, 2017). and ecosystem processes, our life history theory can improve predictive understanding of soil C responses to future climatic change.…”

“…Yield in the model is a function of multiple factors, including substrate type and stoichiometry, enzyme production rates, uptake investment, and temperature. The most recent version of DEMENT also includes a simple representation of drought stress tolerance (Allison and Goulden, 2017). After incorporating trait tradeoffs derived from omics or other data sources for individual taxa, DEMENT projects community responses and carbon cycling consequences under simulated environmental conditions.…”