Soil biota and fertility along a gradient of forest degradation in a temperate ecosystem

Soil biota populations are good indicators for the evaluation of soil quality, which is in line with the nutrient cycles in forest ecosystems. To the best of the authors' knowledge, responses of belowground biota to forest removal intensity have received little attention. The present study aimed to study the effect of low, moderate and high intensities of forest degradation, based on the density of standing trees, in lands covered by Carpinus betulus and Parrotia persica tree species in northern Iran on forest floor, soil properties and fauna and flora activities. In the summer season, a total of 15 forest floor and soil samples (30 x 30 x 10 cm) from each site were transferred to the laboratory. To achieve the temporal pattern of soil biota, sampling was also performed in the fall season. The activities of earthworm groups (i.e. epigeic, anecic, and endogeic) were significantly decreased in order of low > moderate > high levels of forest degradation, with higher populations in the fall season (especially epigeic earthworms). Similarly, greater activity of soil Acarina, Collembola, nematode, protozoa (especially in the fall season), bacteria and fungi (especially in the summer season) were found in forests with low intensity of degradation. Principal component analysis (PCA) indicated higher soil biological activities and fertility in the forest areas with low degradation which can be attributed to the higher density of trees, forest floor mass and quality. This research provides evidence of the strong dependence of below-ground communities on aboveground tree density in temperate forests.