Chemical and microbiological changes in Norway spruce deadwood during the early stage of decomposition as a function of exposure in an alpine setting

Abstract

Alpine ecosystems are vulnerable to ever-changing environmental conditions, leading to shifts in vegetation distribution and composition with implications on soil functionality and carbon (C) turnover. Although deadwood represents an important global C stock, scarce information is available on how slope exposure influences the wood-inhabiting microbiota throughout the decomposition process in an Alpine setting. We therefore evaluated the impact of slope exposure (north-vs. south-facing sites) on physicochemical and microbiological properties (microbial abundance based on real-time PCR: fungal 18S rRNA, dinitrogen reductase [nifH]; microbial biomass: double strand DNA; and microbial activity: hydrolytic enzyme activities of the main nutrient cycles) of Picea abies wood blocks and the underlying soil in a field experiment in the Italian Alps during a three-year period. Overall, a higher abundance of fungi and nitrogen-fixing bacteria was recorded in the soil at the north-facing site where cooler and moister conditions were observed. In contrast, no exposure effects were found for these two microbial groups in the wood blocks, while their abundance increased over time, accompanied by more acidic conditions with progressing decay. The impact of exposure was also enzyme specific and time dependent for both the P. abies wood blocks and the underlying soil.ARTICLE HISTORY

Fungal communities and their association with nitrogen-fixing bacteria affect early decomposition of Norway spruce deadwood

“…Topographic features such as slope exposure may have important consequences on deadwood decomposition process 24 and on the underlying soil microbial communities as recently shown in a 2-year mesocosm monitoring of P. abies wood decomposition performed at the same experimental site in the Italian Alps [25][26][27][28] . A faster deadwood decomposition rate at the south-facing slope with respect to the north-facing one was related to a higher bacterial richness and a higher number of detected specialist operational taxonomic units (OTUs) 28 .…”

Competition and habitat filtering jointly explain phylogenetic structure of soil bacterial communities across elevational gradients

“…Several previous studies have revealed the existence of elevational patterns of bacterial community composition (Singh et al ., ; Wang et al ., ; Shen et al ., ), functional gene abundance (Bardelli et al ., ) and functional gene composition (Yang et al ., ). Along with the elevational gradient, we detected shifts in many environmental variables that may influence the bacterial phylogenetic turnover including habitat variables, such as MAT, SOM and pH, and biotic variables, such as the relative abundance of Proteobacteria and Actinobacteria .…”

Soil Slope Exposure Affects Physico-Chemical and Microbiological Properties in Soil Aggregate Size Fractions

“…Slope exposure was shown to affect not only the soil weathering and biogeochemical processes [24][25][26], but also the composition and activity of soil microbial communities [27][28][29][30][31] and soil fauna [27,32] in mountain forest soils. To date, most of our understanding about the functioning of this type of ecosystems has focused on the bulk soil.…”