Soil and saproxylic species (Coleoptera, Collembola, Araneae) in primeval forests from the Northern part of South-Easthern Carpathians

Abstract

In 2006-2007 we carried out faunal investigations in the vernal, estival and autumnal seasons in the scientific reserve "Codrul Secular Giumalău" using quantitative sampling methods. We identified 189 species of Coleoptera, 70 of Collembola and 20 of Araneae. Of these, 11 phytophagous, 18 myceto/xylo-mycetophagous, 9 mixophagous, 18 xylo- and cambio-xylemophagous, 38 saproxylophagous, 125 (55 Coleoptera, 70 Collembola) detritivorous (sapro-, copro- and necrophagous), 60 (40 Coleoptera, 20 Aranea) predators/parasitoids. Hymenaphorura polonica Pomorski, 1990 (Collembola), and Leiodes rhaeticus Erichson, 1845 (Coleoptera, Leiodidae), are recorded for the first time in the Romanian fauna. The rare species and characteristic species for the old primeval spruce forests are analysed for each studied taxonomic group. The species richness and faunal diversity from the Giumalău primeval spruce forest are compared with those of other very well preserved forests from the Carpathians scientific reserves (Codrul Secular Slătioara, Pietrosul Rodnei). The species abundances were used to compute the similarity indexes between the sampled sectors of forest and to perform Cluster Analysis. We observed that the dead wood in the 2nd-6th phases of decomposition has a great influence not only on the saproxylic species but also on the soil fauna like ground beetles (Carabidae) that use the logs as ecologic microrefuges (winter refugees or diurnal refugees). The structure of the soil fauna is influenced by wood extraction from the forest ecosystem or by natural perturbations, this consisting in the appearance of opportunistic species as Orchesella pontica (Collembola) and in decreasing of species richness of Carabidae (Coleoptera).