Soil microbes and their response to experimental warming over time: A meta-analysis of field studies

Abstract

Numerous field studies have found changes in soil respiration and microbial abundance under experimental warming. Yet, it is uncertain whether the magnitude of these responses remains consistent over the long-term. We performed a meta-analysis on 25 field experiments to examine how warming effects on soil respiration, microbial biomass, and soil microbial C respond to the duration of warming.For each parameter, we hypothesized that effect sizes of warming would diminish as the duration of warming increased. In support of our hypothesis, warming initially increased soil respiration, but the magnitude of this effect declined significantly as warming progressed as evidenced by the two longest studies in our meta-analysis. In fact, after 10 years of warming, soil respiration in warmed treatments was similar to controls. In contrast, warming effect sizes for fungal biomass, bacterial biomass, and soil microbial C did not respond significantly to the duration of warming. Microbial acclimation, community shifts, adaptation, or reductions in labile C may have ameliorated warming effects on soil respiration in the long-term. Accordingly, long-term soil C losses might be smaller than those suggested by short-term warming studies.

Microbial responses to warming enhance soil carbon loss following translocation across a tropical forest elevation gradient

“…This loss in soil C is greater than reported from field‐based warming experiments in non‐tropical ecosystems (Lu et al ; Crowther et al ; Romero‐Olivares et al ), including a 17% decline in soil C following 26 years of 5 °C warming in a temperate forest (i.e. for comparison 0.7% loss per 1 °C warming per 5 year interval) (Melillo et al ), and an average 1% decline calculated in meta‐analyses of soil warming experiments, based predominantly on data from temperate soils and experiments that only warm the soil surface (Lu et al ; Romero‐Olivares et al ). Our extrapolation assumes that C loss (3.86% C per 1 °C warming) would linearly scale over a 4–8 °C range and would not have increased if our study continued beyond 5 years and the specified amount of warming.…”

Will heterotrophic soil respiration be more sensitive to warming than autotrophic respiration in subtropical forests?

“…Previous studies have shown that warming significantly increased soil MBC (Liu et al, ; Romero‐Olivares et al, ). The results in our study were similar (Table ).…”

“…Warming could markedly change microbial community structures in soil (DeAngelis et al, ) and trigger a shift in the use of microbial substrate (Streit et al, ). In addition, warming could have profound effects on R h and R a by changing soil moisture or microbial biomass carbon (MBC) (Heinemeyer, Tortorella, Petrovičová, & Gelsomino, ; Romero‐Olivares, Allison, & Treseder, ).…”

Disentangling effects of air and soil temperature on C allocation in cold environments: A 14C pulse‐labelling study with two plant species

“…At the ecosystem level, feedback mechanisms including carbon and nutrient dynamics will modify the initial effects we addressed. For example, many studies have found that warming effects on soil respiration decreased with time (Carey et al., ; Luo, Wan, Hui, & Wallace, ; Romero‐Olivares, Allison, & Treseder, ). The mechanisms that have been put forward as explanation include the acclimation of root metabolism (Atkin, Edwards, & Loveys, ; Burton, Melillo, & Frey, ), the exhaustion of labile soil organic matter pools that fuel microbial respiration (Caprez, Niklaus, & Körner, ; Eliasson et al., ), and a thermal adaption of soil microbial communities (Bradford et al., ; Heinemeyer, Ineson, Ostle, & Fitter, ).…”