Abstract
Climate warming is likely to increase the frequency and severity of forest disturbances, with uncertain consequences for soil microbial communities and their contribution to ecosystem C dynamics. To address this uncertainty, we conducted a meta-analysis of 139 published soil microbial responses to forest disturbances. These disturbances included abiotic (fire, harvesting, storm) and biotic (insect, pathogen) disturbances. We hypothesized that soil microbial biomass would decline following forest disturbances, but that abiotic disturbances would elicit greater reductions in microbial biomass than biotic disturbances. In support of this hypothesis, across all published studies, disturbances reduced soil microbial biomass by an average of 29.4%. However, microbial responses differed between abiotic and biotic disturbances. Microbial responses were significantly negative following fires, harvest, and storms (48.7, 19.1, and 41.7% reductions in microbial biomass, respectively). In contrast, changes in soil microbial biomass following insect infestation and pathogen-induced tree mortality were non-significant, although biotic disturbances were poorly represented in the literature. When measured separately, fungal and bacterial responses to disturbances mirrored the response of the microbial community as a whole. Changes in microbial abundance following disturbance were significantly positively correlated with changes in microbial respiration. We propose that the differential effect of abiotic and biotic disturbances on microbial biomass may be attributable to differences in soil disruption and organic C removal from forests among disturbance types. Altogether, these results suggest that abiotic forest disturbances may significantly decrease soil microbial abundance, with corresponding consequences for microbial respiration. Further studies are needed on the effect of biotic disturbances on forest soil microbial communities and soil C dynamics.
Highlights
Forest ecosystems are a critical component of the global carbon (C) cycle
We focused on three abiotic disturbances and two biotic disturbances
In this study, we conducted a meta-analysis of changes in soil microbial biomass in response to forest disturbances
Summary
Temperate, and tropical forests cover ∼30% of the global land surface and store ∼1600 Pg C, accounting for up to 45% of global terrestrial carbon (Bonan, 2008). Likewise, ∼50,000 km of North American forests are harvested annually (Birdsey et al, 2006). Other common forest disturbances include storms, insect outbreaks, and pathogen infection of trees (Goetz et al, 2012). These disturbances can be grouped into abiotic (fire, harvesting, storm) and biotic (insect, pathogen) disturbances. Some forest disturbances may occur more frequently and severely as a result of climate warming. Given the large amount of C stored in forests, it is important to understand how disturbances alter ecosystem C dynamics
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