Abstract
Few studies have been published on the feeding ecology of Japanese soil fauna based on stable isotope analysis. Therefore, the present work aims to use this technique for studying the trophic structure of Japanese soil fauna at two coniferous forests. Significant differences were observed between investigated sites (Arahama and Gamo) in genus richness and abundance, while for Shannon diversity indexes the difference was non-significant. The isotopic signatures (δ
13C and δ
15N) of the invertebrates collected at Arahama ranged from 0.3 to 6.3‰ for δ
15N and from −27.3 to −23.3‰ for δ
13C. At Gamo, invertebrates δ
13C values ranged from −26.1 to −23.5‰ and δ
15N values ranged from 1.6 to 6.8‰. At both sites, invertebrates formed two distinct groups on the basis of combined C and N stable isotope ratios. The locations of these groups related to δ
13C values. The less enriched group (δ
13C
<
−25‰) and the more enriched one (δ
13C
>
−25‰). The range of δ
15N for the present animals exceeded two trophic levels. While, the gradual
15N enrichment within the invertebrates species may indicate the dominance of omnivory in soil food webs. The differences between sites in δ
15N confirm the importance of studying the trophic structure of soil fauna locally.