An agroecological approach for Danube Delta Biosphere Reserve: structure of edaphic mesofauna community in agricultural crops and the surroundings natural ecosystems

Abstract

As part of a larger research developed within the Core Program and dedicated to the natural and anthropogenic ecosystems of the Danube Delta Biosphere Reserve, this study aims to investigate the edaphic mesofauna in several agricultural ecosystems and in the meadows of their vicinity. In both natural and anthropogenic ecosystems, edaphic mesofauna in interrelation with soil microorganisms actively participates in the processes of degradation of vegetal necromass. The comparative analysis of edaphic microarthropod communities indicates that agroecosystems do not provide favorable conditions for their development, with the densities being the smallest, while higher values have been noted in meadows, especially in non-grazed ones. In both agroecosystems and meadows, the mites dominate the rest of the microarthropods. Among the mites, the predominance of thrombidiforms is observed both in meadows (42% and 54% respectively) and in most agricultural crops (38-89%). In non-grazed meadows and in some agricultural crops, oribatids are predominant (39% - 66%). Among thrombidiforms, tydeid - mites with a diversified trophic regime - are common to crops and meadows. They were found in most of the samples from investigated agroecosystems and also in meadows, but with great representation only in the last category. The ratio of the main detritomicrofitophagous groups (oribatids / collembolans), a good bioindicator of the quality and humification stage of an organic substrate, was superior in most of the examined plots being subunit in only 23% of cultures and in a pasture. On the basis of all these findings it can be appreciated that humification is predominant, and the nutrient cycle is slower in almost all the considered plots. The study also reveals that the influence of agroecosystems on neighboring natural ecosystems at the level of edaphic mesofauna communities has not been confirmed.