The saline grasslands, a suitable environment for maintaining the functional relationships of the edaphic mesofauna?

Abstract

This study represents a continuation of research carried out in Danube Delta Biosphere Reserve, within the Core Program, financed by the Romanian Ministry of Research and Innovation. Communities of edaphic microarthropods in halophilic ecosystems of D.D.B.R. have been investigated to assess their vulnerability. The analysis was performed qualitatively and quantitatively, on systematic and trophic groups, in a space-time dynamic. The obtained results have shown that the structural features of edaphic mesofauna depend both on the vegetation and the biopedoclimatic conditions, in general the halophilic habitats being restrictive for most edaphic microarthropods. The highest density is observed in a salinized wet meadow, characterized by a great floral diversity. The lowest population abundance was recorded in the grassland with the poorest vegetation, where Salicornia europaea is the only dominant species. The analysis of the relationships between the trophic groups highlights the dominance of the detritomicrophytophages versus zoophages, a situation that is usually found in meadow ecosystems. The analysis of the seasonal dynamics of the mesofauna as a whole revealed that in most of the studied ecosystems, under summer drought conditions there was a decrease in the total number of edaphic mesofauna (1.6-4.3 times), the most significant decrease (2 -20 times) being the number of springtails that are known to be susceptible to edaphic dryness. The numerical ratio between oribatid mites and springtails (the main groups of detritomicrophytophages) is in most cases supraunitary, indicating that in the nutrient cycling the humification processes are predominant.