Compound-specific isotope analysis of amino acids as new tool to uncover trophic chains in soil food webs

Food webs in soil differ fundamentally from those above ground; they are based on inputs from both living plants via root exudates, and from detritus, which is a complex mixture of fungi, bacteria and dead plant remains. Trophic relationships are difficult to disentangle due to cryptic lifestyle of soil animals and inevitable microbial contributions to their diet. Compound-specific isotope analysis of amino acids (AAs) is increasingly used to explore complex food webs. The combined use of AA δ13C and δ15N values is a promising new approach to disentangle trophic relationships since it provides independent but complementary information on basal resource and trophic position of consumers. We conducted a controlled feeding study by reconstructing trophic chains from main basal resources (bacteria, fungi, plants) to primary consumers (springtails, oribatid mites) and predators (gamasid mites, spiders). We analyzed dual compound-specific isotope values in AAs of resources and consumers, simu...