The soil macrofauna (Diplopoda, Isopoda, Lumbricidae and Chilopoda) near tree trunks in a beechwood on limestone: indications for stemflow induced changes in community structure

Abstract

Due to stemflow water running down beech trees ( Fagus sylvatica L.) pollutants (protons, heavy metals) accumulate in the vicinity of the trunk in beech forests in central Europe. This study investigates density, biomass, species composition and depth distribution of major soil macrofauna groups (Diplopoda, Isopoda, Lumbricidae, Chilopoda) near beech trees and distant to trees in a beechwood on limestone in northern Germany each season for 1 year. Litter accumulated in the vicinity of the trunk and these localities were more acidic (average pH of 0–3 cm soil depth near to trees 3.7, distant to trees 5.3 (KCI measurement) ). Macrofauna species differentially responded to changed environmental conditions in the tree vicinity. Generally, the density of soil-inhabiting (endogeic) species was lower in the tree vicinity, whereas the density of species inhabiting predominantly the litter layer (epigeic species) was similar to or higher than that distant to trees. The most dramatic reduction occurred in the density of endogeic earthworm species which were almost absent in the tree vicinity, but the density of endogeic centipedes (Geophilomorpha) was also significantly lower in the tree vicinity. Canonical correspondence analysis showed that soil pH was an important environmental factor structuring the soil macrofauna community in the tree vicinity, whereas distant to trees soil pH was of minor importance and the faunal gradient was generally less pronounced. Depth distribution of animals indicated the retreat of most macrofauna species from deeper soil layers near the tree. Our results suggest that owing to damage of soil-inhabiting macrofauna, particularly earthworms, near to trees and concomitant reduction in bioturbation, soil humus type is changing from mull to moder.