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Dryad

The use of plant, bacterial and fungal resources in soil food webs of ecto- and arbuscular mycorrhiza-dominated deciduous forests

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Jul 17, 2025 version files 211.20 KB

Abstract

Soil food webs, driven by complex interactions among plants, microbes, and invertebrates, are crucial for carbon and nutrient cycling in forest ecosystems. Over the last decade, it has become evident that forests dominated by arbuscular mycorrhizal fungi (AMF) or ectomycorrhizal fungi (EMF) differ in their litter chemistry and microbial community composition, leading to different carbon and nutrient cycling. Still, the role of soil invertebrates in soil food webs of AMF- and EMF-dominated forests remains undescribed. Here, we tested whether trophic positions (TP) and basal resources of nine soil invertebrate groups (Araneae, Chilopoda, Collembola, Diplopoda, Diptera, Isopoda, Lumbricina, Mesostigmata, and Oribatida) are different in AMF- (maple and/or ash) and EMF-dominated (beech and/or oak) deciduous forests. We addressed this question using compound-specific stable isotope analysis of carbon and nitrogen in amino acids (CSIA-AA) – a novel method that allows precise estimation of the TP and basal resource use (bacteria, fungi, plants) of consumers in field conditions. Plant- and microbial-derived resources of soil invertebrates generally varied little between AMF and EMF-dominated forests. We only found a slight tendency of soil invertebrates in AMF-dominated forests relying more on fungal-derived resources (ca. 2% difference) and more on bacteria-derived resources in EMF-dominated systems (ca. 2% difference). Most of the variation in resource use was explained by the taxonomic identity of invertebrates, independently of the forest type and location. Mesofauna, particularly Collembola and Oribatida, were key consumers of fungi (relative contribution 49-72.1%), while macrofauna (except earthworms) relied more on plant resources (relative contribution 42.1-58.9%), suggesting that different size compartments of soil food webs predominantly use different basal resources. Earthworms and Myriapoda (Chilopoda and Diplopoda) had the highest proportions of bacteria-derived essential amino acids (relative contribution 23.2-35.2%). TPs of taxa remained largely consistent across mycorrhizal types (except for an elevated TP of Isopoda in EMF-dominated forests), suggesting similar vertical organisation of soil food webs across the studied forests. Overall, our study shows that TPs and basal resource use of soil fauna vary little across temperate deciduous forests, being mainly explained by the faunal taxonomic identity.