Comparing the soil macro-fauna in two oak-wood forests: does community structure differ under similar ambient conditions?

Abstract

Summary Taxa, specimen richness and biodiversity were compared in the forest floor of two old natural oak forests in the Mediterranean region in the Galil mountains and in the Golan Heights. The study sites, about 35 km (by air) apart, had similar tree species composition, similar climatic and micro-climatic conditions, but different soil physical texture. The fauna was extracted from samples of leaf litter and top soil. Decomposition parameters (organic matter, nitrogen, calcium, phosphorus) and climatic conditions (precipitation, air and forest floor temperature, leaf litter and top soil water content) were measured. The dynamics of taxa moving between the leaf litter and top soil, were determined. The two forests did not differ significantly in biodiversity, taxa and specimen richness, except for the taxa numbers in the soil phase. However the forest floor community composition differed. Thus, oligochaetes were more abundant in the Golan whereas diplopods, isopods and hymenoptera were more abundant in the Galil, and gastropods were found exclusively in the Galil. In both forests, no correlation was found between specimen richness and the decomposition parameters, though some groups (oligochaetes, arachnids and insects) were influenced by mineral levels. In both forests, climate affected the dynamics of taxal vertical movement. Moreover, in both forests, (leaf litter and top soil), specimen richness and biodiversity index were low during the dry season and high during the wet season. The influence of climatic changes on the taxa composition and vertical movement, were similar in the two forests. We conclude that in similar forest types under similar climatic conditions, the soil composition and texture do not directly affect biodiversity and fauna richness. The soil texture has a direct influence on the relative abundance of certain animal taxa.