Nematode community indices for microhabitat type and large scale landscape properties

Abstract

Nematode community indices have been broadly used to assess and monitor soil conditions. Most studies focused on agricultural or other disturbed soils and were usually applied at local-field scale. In this study, we focused on the variation of nematode community indices across fine (among microhabitats) and landscape level scales with the aim to identify indices or combinations of indices that are efficient at distinguishing microhabitats and landscape properties. We calculated nematode community indices in five microhabitats to account for variability in basal resources/organic input (soils, mosses on soil, mosses on rocks, as well as mosses on the lower and the upper part of trees trunks). The different microhabitats were located across the landscape in sites that differed in vegetation cover type (forested and non-forested), altitude (low, high) and aspect (North, East, South).Results of our models showed that microhabitat type could be predicted by all indices except the Maturity Index (MI) and the Fungivore/Bacterivore (F/B) ratio. Soil could be distinguished from mosses by the higher Plant Parasitic Index (PPI) and Enrichment Index (EI) and the lower Channel Index (CI). The different moss microhabitats could be distinguished from each other by the Summed Maturity Index (SMI) the Structure Index (SI) as well as the Basal Index (BI). At the larger scale, among landscape properties, variation by altitude was more pronounced compared to vegetation cover type and aspect. Samples originated from low altitudes were characterized by higher EI and F/B ratio. Indices for predicting landscape properties of the site a sample was taken from were more efficient when analyzed separately within each microhabitat. The interaction of the BI and the F/B ratio was able to predict vegetation cover type in soils while the same holds for BI, SI and their interaction in mosses. We conclude that nematode community structure is strongly shaped by variation in basal resources in the different microhabitats and microhabitats can be well predicted by most nematode community indices. Landscape properties constitute gradients of exposure of basal resources to ambient conditions, which affects basal resource transformations and availability. This variation across the landscape can also be predicted by some nematode community indices.