Soil enzyme response to vegetation disturbance in two lowland Costa Rican soils

Conversion of forests to intensive agriculture often leads to degradation of weathered soils. The effects of two intensities of vegetation management on soil beta-glucosidase (beta-GLC) and phosphomonoesterase (PME) activities were studied on two river-terrace soils of differing fertility in Costa Rica. After approximately four years of annual harvest or continuous vegetation removal to bare soil, soil organic matter carbon (SOM-C), microbial biomass carbon (Mb-C), beta-GLC and PME activity were reduced. Effects of continuous cropping to bare soil on Mb-C, beta-GLC and PME were greater in the more weathered, acidic, Al-rich, P-limited upper-terrace soil than in the more neutral, base cation-rich lower-terrace soil. In contrast, more SOM-C was lost in the lower terrace. The annual harvest treatment produced intermediate decreases in SOM-C, Mb-C, beta-GLC and PME on upper-terrace soils, intermediate reduction in lower terrace beta-GLC, and no significant effect on lower terrace Mb-C or PME. beta-GLC activity was the most sensitive indicator of treatment effect and may be a suitable alternative to Mb-C or SOM-C as a measure of change in soil health. (C) 1999 Elsevier Science Ltd. All rights reserved.