Spatial relationship between soil macrofauna biodiversity and trees in Zagros forests, Iran

Abstract

One major factor in determining the spatial distribution pattern of soil macrofauna diversity in forest ecosystems is the close relationship with tree species. Information about the spatial relationship between soil macrofauna and tree diversity is scarce, especially at regional scales. To assess soil macrofauna distribution and evaluate the spatial relationships between macrofauna diversity and tree cover properties at the regional scale, a study was conducted in the Zagros forests of Iran. To investigate properties of tree cover, 83 plots (100m2) in a 100m×100m sampling grid were established. In each plot, soil macrofauna were extracted from 50cm×50cm×10cm soil monoliths located in the center of the plots. We classified soil macrofauna into two categories as total macrofauna (earthworm plus other taxa) and only earthworms. Data were analyzed using geostatistics (variograms and cross-variograms) in order to describe the spatial dependence of macrofauna and their relation to tree cover properties. Macrofauna abundance and diversity were distributed at geostatistical large range (3110 and 2110m), whereas, earthworm abundance had spatial autocorrelation at small range (691m). Macrofauna abundance and diversity were spatially related to tree cover density, diversity and evenness of tree species in addition to the density of Pyrus syriaca and Crataegus pontica at small ranges. Our results showed that tree density and diversity could be the key drivers of the spatial patterning of soil macrofauna diversity in this area. These results might be related to the conditions provided by the tree species in the surrounding environment. According to our results tree species diversity changed within a small distance (149m) creating patches that could lead to the heterogeneity of resources and microhabitats, promoting beneficial habitats for soil macrofauna. These microhabitats can provide the suitable conditions (light, moisture and litter quality) for determining the macrofauna distribution.