A comparative study of the chemical and integrated treatments impact against the defoliating insects on the structure and dynamics of the edaphic mesofauna in two oak forests from North-Eastern Romania

The author presents in this paper some aspects about the edaphicmicroarthropods from the organic horizon of two forest soils belonging to the Ciurea Forest District, Iasi County: aanta (mixed stands mainly with oak, chemically treated against defoliating insects) and Poieni - Tomesti (Quercus robur and Quercuspetraea stands with integrated treatments). The study of edaphic microarthropods was performed both from qualitative and quantitative point of view. It considered the average of the total density of the microarthropod populations and by each taxonomic group, according to stations and subhorizons, as well as the ratio between thetaxonomical and trophic groups. The investigations concerning edaphic mesofauna consist in inventory and analysis of the mites belonging to Oribatida, Gamasida, Actinedida and Acaridida orders, of the Collembola, as well as other insects; other groups of microarthropods were taken into consideration too (pseudoscorpiones,myriapods etc). The consequences of the treatments against the defoliators on theedaphic mesofauna were performed at four different moments. Generally, lower densities were observed in the case of the chemically treated stands. The communities of the edaphic mesofauna from the integrated management treated stands are more stableduring the time. In the chemically treated stands, the densities of the microartropods vary between large limits; this instability could be assigned to this kind of treatment. The vertical distribution of the mesofauna depends on the textural characteristics of the soil, being at the same time a dynamic parameter that is modifyed according to the variation of the climatic factors.