Drought legacies mediated by trait trade‐offs in soil microbiomes

Abstract

Soil microbiomes play a key role in driving biogeochemical cycles of the Earth system. As drought frequency and intensity increase due to climate change, soil microbes and the processes they control will be impacted. Even after a drought ends, microbiomes and other systems take time to recover and may display a memory of previous climate conditions. Still, the mechanisms involved in these legacy effects remain unclear, making it difficult to predict climate and biogeochemical rates in the future. Here, we used a trait-based microbiome model (DEMENTpy) to implement trade-off-mediated mechanisms that may lead to drought legacy effects on litter decomposition. Trade-offs were assumed to follow the Y-A-S framework that defines three primary life-history strategies of microorganisms: high growth Yield, resource Acquisition, and Stress tolerance. We represented cellular trade-offs between osmolytes required for drought tolerance and investment in enzymes involved in litter decomposition. Simulations were run under varying levels of drought severity and dispersal. With high levels of dispersal, no legacy effects were predicted by DEMENTpy following drought. With limited dispersal, severe drought resulted in a persistent legacy of altered community-level traits and reduced litter decomposition. Moderate drought resulted in a transient legacy that disappeared after two years, consistent with recent empirical observations in Southern California ecosystems. These results imply that greater movement along the trade-off between enzyme investment and osmolyte production resulted in stronger legacy effects. More generally, factors that shift the position of a microbiome in YAS space may alter the legacy outcome following drought. Our trait-based modeling study motivates additional empirical measurements to quantify YAS traits and trade-offs that are needed to make accurate predictions of soil microbiome resilience and functioning. Also, our study illustrates an emerging approach for representing trait trade-offs in microbiomes and vegetation that dictate ecosystem responses to drought and other environmental perturbations.

Drought soil legacy alters drivers of plant diversity-productivity relationships in oldfield systems

“…At the same time, drought-induced changes in plant physiology and/or plant community structure may contribute to drought soil legacies via indirect drought effects on the microbial community (33)(34)(35). Such drought soil legacies may affect longer-term plant community structure and function through plant-soil feedbacks (36)(37)(38), but the magnitude and persistence of drought legacies in soil microbes are currently subject to debate (39). To date, information on the influence of drought soil legacies on plant diversity-productivity relationships is lacking, and responses of plant diversity-productivity relationships to subsequent drought events are unclear.…”

Microbes, memory and moisture: Predicting microbial moisture responses and their impact on carbon cycling

“…DEMENT simulates how moisture history is likely to shape microbial traits, microbial functioning and C cycling (Wang & Allison, 2021). Under drought (Year 6), microbial communities allocate greater resources towards stress tolerance, reducing the community's biomass-specific investment in enzyme production (Figure 6a, left side).…”

“…(2020) defined trait‐based microbial strategies that putatively govern physiological responses to stress, as they are shaped by trade‐offs in resource allocation. Wang and Allison (2021) implemented these strategies in the DEMENT model to show quantitatively how trade‐offs with drought tolerance traits can lead to legacies in the microbial community capacity for decomposition (see below). This approach is powerful because it captures the intrinsic microbial properties that confer resilience and lead to legacies that affect microbial respiration.…”

“…Exposure to 6 years of moderate or severe drought (Year 6), and a subsequent 3 years of ambient conditions (Year 9) altered community‐level enzyme investment (a), drought tolerance (b) and rates of litter substrate degradation (c). Modified from Wang and Allison (2021) with permission. Dashed lines and colored bands are means and 95% confidence intervals ( n = 40), respectively…”

Responses of soil bacterial community structure and function to dry–wet cycles more stable in paddy than in dryland agricultural ecosystems

“…In addition, dry periods are accompanied by a loss of microbial diversity, meaning that some microorganisms might disappear in such conditions; conversely, rewetting of dry soil would result in a pulse of microbial activity, the so-called Birch effect (Birch, 1958). Moreover, microorganisms exhibit high resistance after experiencing water stress Fierer et al, 2003;Wang & Allison, 2021). Information on microbial diversity alone may not be adequate for understanding how community composition and assembly influence ecosystem function (Martiny et al, 2015).…”