Edaphic variables conditioning the habitat of oribatid mites in Luvic Phaeozems under forest plantations (Buenos Aires, Argentina)

Abstract

The soil is a complex three-dimensional habitat and any changes in its structure and porosity are likely to affect the type and abundance of soil biota. Oribatid mites play an important role in the decomposition and mineralization of soil organic matter and their abundance depends on diverse soil parameters, including soil texture, organic matter content, pH, moisture, and the pore system. The aim of the present work is to analyze some of the edaphic variables that condition the habitat of oribatid mites in Luvic Phaeozems under Pinus radiata (site P) and Eucalyptus globulus (site E) plantations, in the Southeast of Buenos Aires, Argentina. Bulk density, penetration resistance, pH, moisture, pore system parameters, and oribatid abundance and species composition were analyzed. Site E had a greater total porosity than site P. The high tortuosity of the pores in both sites generates a complex habitat architecture for the development of oribatid mites. In both sites, oribatids of 70-400 μm in size predominated and were more abundant in site E. A positive correlation between the abundance of oribatids and the pore size in both sites was observed. In site E this correlation was lower for 70-600 µm (R = 0.13) or negative for 70-400 µm (R = -0.78). Therefore, the oribatid abundance could be explained by a greater complexity of the structure of the organic horizon, lower bulk density and lower penetration resistance. These conditions favor the mineralization of organic matter, and therefore food availability. On the other hand, in site P, oribatid abundance is mainly influenced by the porous system, which conditions the access to food, competition between organisms and refuge from predators. Two new species were registered for Argentina: Mesotritia elegantula and Acrogalumna longipluma.