Structure and dynamics of the oribatid mite communities (Acari, Oribatida) in some Quercus forests, in relation with the treatments used in the control of defoliating insects

Abstract

This study was carried out in the context of some complex researches concerning the effects of long standing use of the pesticides in the control of the defoliating insects, in forest ecosystems. These investigations showed that the structural parameters of the oribatid mites' communities are obviously influenced by the stands biotic and abiotic factors, alongside some varied anthropogenic factors, such as: treatments, industrial pollution, some management measures etc. This paper includes a comparative analysis of the research results obtained in two forest stands placed in the Moldavian Plateau (Ciurea Forest District, Iasi county): Tomesti-Poieni (integrated control of the defoliating insects) and Santa (chemical control). The analysis of the faunistic material collected in these two forests has shown that, in the first stand (the control perimeter), the density, the number of species, and also the specific diversity have higher values compared to the second station. In unfavourable climatic conditions (e. g. during the winter season) it was observed a more increased decline of these parameters in the Santa forest, related to the control station. In such conditions (low temperatures, deficit of humidity etc.) the change of the vertical distribution of the effectives was observed in both stands, and a massive migration of the oribatid mites in the deeper, humiferous layer of the soil. The results gathered during the project emphasize that the chemical treatments used against the defoliating insects enhance the negative effects of some natural factors, representing an additional stressing factor on the edaphic microarthropods' communities.