Abstract

Soil microbial activity is affected by primary ecological variables, such as composition and density of the flora, successional stages and secondary variables, such as climatic seasons. The most important biological activities are those related to the organic matter (MO) and nutrient cycling, which allow us to detect together with some other soil physical parameters, early biochemical changes, soil compaction and biological activities originated by anthropogenic impacts. We quantified and compared a number of biological activities and the percentage of water stable aggregates under two successional stages in two growing seasons in a temperate forest of Central-Southern of Chile. The biological activities evaluated were the fluorescein diacetate hydrolysis (FDA), carbon (MBC) and nitrogen (MBN) microbial biomass and three soil enzymes activities: carboxymethyl-cellulase and B-glucosidase (both associated to carbon cycling) and acid phosphatase (related to the phosphorus cycling). In general, biological activities resulted in significant differences (p<0.05) in the two successional stages. Autumn season showed the higher values for all activities evaluated, except for MBC. In spring, the percentage of water stable aggregates was higher in both successional stages, but without significant differences between them. Our results indicate that the soil biological activities were affected by the moisture content, nutrients and MO level. In order to promote soil environmental conservation, some biological and physical indicators are very important to monitoring soil disturbance in the forest ecosystem