Effects of Air-Drying and Rewetting on Extractable Organic Carbon, Microbial Biomass, Soil Respiration and β-Glucosidase and β-Galactosidase Activities of Minimally Disturbed Soils Under Mediterranean Conditions

Abstract

The objectives of this study were: (1) to evaluate the effect of air-drying or air-drying and rewetting on microbial biomass carbon (MBC), extracted organic carbon (EOC), basal soil respiration (BSR), the evolution of the respiration process (ERP) and β-glucosidase and β-galactosidase activities in ten native soils with minimal anthropogenic disturbance in Catalonia (NE Spain); and (2) to determine whether air-drying or air-drying and rewetting are accurate sample pre-treatment procedures when the above properties are used to evaluate the quality of the soils. In order to assess the effect of air-drying on the MBC, BSR, ERP and the β-glucosidase and β-galactosidase activities of field-moist soils, the values of these parameters were determined after the field-moist soil samples had been air-dried for one week at room temperature. To evaluate the effect of air-drying plus rewetting on the β-glucosidase and β-galactosidase activities of field-moist soils, air-dried samples were rewetted to 60% of their water holding capacity and kept in the dark at 28°C for 7 days before the assays were performed. In the case of EOC, air-dried values were compared with those of air-dried plus rewetted samples. The results showed that air-drying caused a reduction in the MBC and an increase in the BSR of field-moist soil samples. Rewetting air-dried soils generally increased the activity of the two enzymes. The values of MBC and of β-glucosidase and β-galactosidase activities in air-dried soils had the same ranking as in field-moist soils, whereas air-drying plus rewetting led to a change in the ranking of both enzyme activities compared with field-moist samples. β-glucosidase was probably more protected by humic colloids than β-galactosidase.