The impact of post-fire salvage logging on microbial nitrogen cyclers in Mediterranean forest soil

摘要

Highlights•Salvage logging post-fire affects the properties of Mediterranean forest soil.•Tree retention post-fire increases pools ofnifH,amoA-B,amoA-Arch,nirK&nosZ.•OM, avP, N & aggregate stability impact N cycler abundance in forest soil post-fire.•Microaggregates are hotspots for N cyclers particularly under salvage logging.•Greater N cycling can support post-fire re-vegetation improving ecosystem recovery.Graphical abstractDisplay OmittedAbstractForest fires are a regular occurrence in the Mediterranean basin. High severity fires and post-fire management can affect biological, chemical and physical properties of soil, including the composition and abundance of soil microbial communities. Salvage logging is a post-fire management strategy, which involves the removal of burnt wood from land after a fire. The main objective of this work was to evaluate the impact of post-fire salvage logging and microaggregation on soil microbial communities, specifically on the abundance of nitrogen cyclers and, thus, the potential of the soil for microbial nitrogen cycling. The abundance of nitrogen cyclers was assessed by quantification of microbial nitrogen cycling genes in soil DNA, includingnifH(involved in nitrogen fixation),nirS/KandnosZ(involved in denitrification),amoA-B andamoA-Arch (involved in bacterial and archaeal nitrification, respectively). It was demonstrated that salvage logging reduced bacterial load post-fire when compared to tree retention control and resulted in significant changes to the abundance of functional bacteria involved in nitrogen cycling. Microbial gene pools involved in various stages of the nitrogen cycle were larger in control soil than in soil subjected to post-fire salvage logging and were significantly correlated with organic matter, available phosphorous, nitrogen and aggregate stability. The microaggregate fraction of the soil, which has been associated with greater organic carbon, was shown to be a hotspot for nitrogen cyclers particularly under salvage logging. The impact of post-fire management strategies on soil microbial communities needs to be considered in relation to maintaining ecosystem productivity, resilience and potential impact on climate change.