Soil fertility determines whether ectomycorrhizal fungi accelerate or decelerate decomposition in a temperate forest

Abstract

Ectomycorrhizal (ECM) fungi can both accelerate and decelerate decomposition of organic matter in forest soils, but a mechanistic understanding of this differential influence is limited.Here, we tested how ECM fungi affect decomposition along a natural fertility gradient in a temperate forest of European beech. Trees were girdled to reduce belowground carbon supply to the soil.Girdling shifted soil fungal community composition and decreased hyphal biomass production and soil CO 2 efflux, indicating a reduced ECM fungal activity. Girdling also affected decomposition processes, but the effects depended on fertility. Our results indicate that ECM fungi decelerate decomposition under conditions of low fertility while under conditions of high fertility ECM fungi and their host roots have an accelerating effect.We conclude that both acceleration and deceleration of decomposition of organic matter by ECM fungi can occur within a forest, with soil fertility determining the direction and magnitude of these effects. We suggest a positive feedback between fertility, stand productivity and soil carbon and nitrogen dynamics that is mediated to a large extent by ECM fungi.

Responses of vascular plant fine roots and associated microbial communities to whole‐ecosystem warming and elevated CO2 in northern peatlands

“…In ecosystems where nutrients are scarce, as is the case at the SPRUCE experimental site (Hobbie et al ., 2017), fungi compete for limited labile carbon and nitrogen supplies (Kaye & Hart, 1997; Schimel & Weintraub, 2003). Thus, when nitrogen is limited, the presence of ECM can decelerate decomposition by suppressing saprotrophs (Averill & Hawkes, 2016; Mayer et al ., 2023). As ECM are supplied carbon by their host plants, they are shown to allocate more resources to nitrogen acquisition (Terrer et al ., 2016; Pellitier et al ., 2021).…”

Biochar and manure additions increased above‐ and belowground wood decomposition, and soil enzyme activities in a sandy loam soil

“…Further, organic matter decomposition rates are a function of soil biotic and abiotic properties that can be altered by soil amendments (Mayer et al, 2023;Tie et al, 2022). For example, altered soil C or organic matter contents caused by soil amendments or other forest management can result in soil microbial process changes and subsequent decomposition rate and nutrient cycling alterations through the production of a variety of soil enzymes, for example, acid phosphatase, cellulase, α-glucosidase, β-glucosidase, N-acetyl-β-Dglucosaminidase, and aryl sulfatase (Mayer et al, 2023), because these enzymes mainly drive the degradation of lignin, cellulose, and hemicellulose of the substrates (Albiach et al, 2000;Fatemi et al, 2016;Zhang et al, 2018). Therefore, although soil organic amendment effects on soil microbial activities, for example, decomposition, is difficult to distinguish due to the various substrate qualities in numerous studies (Jastrow et al, 2007;Zhao et al, 2023), organic matter decomposition can be an effective index of forest soil quality changes associated with soil amendment additions.…”

“…In general, high organic matter decomposition rates on and in forest soils are generally linked to higher site and soil productivity (Mayer et al., 2023; Wang et al., 2010). Further, organic matter decomposition rates are a function of soil biotic and abiotic properties that can be altered by soil amendments (Mayer et al., 2023; Tie et al., 2022). For example, altered soil C or organic matter contents caused by soil amendments or other forest management can result in soil microbial process changes and subsequent decomposition rate and nutrient cycling alterations through the production of a variety of soil enzymes, for example, acid phosphatase, cellulase, α‐glucosidase, β‐glucosidase, N‐acetyl‐β‐D‐glucosaminidase, and aryl sulfatase (Mayer et al., 2023), because these enzymes mainly drive the degradation of lignin, cellulose, and hemicellulose of the substrates (Albiach et al., 2000; Fatemi et al., 2016; Zhang et al., 2018).…”

“…In general, high organic matter decomposition rates on and in forest soils are generally linked to higher site and soil productivity (Mayer et al., 2023; Wang et al., 2010). Further, organic matter decomposition rates are a function of soil biotic and abiotic properties that can be altered by soil amendments (Mayer et al., 2023; Tie et al., 2022).…”