Influence of slope and orientation on biological activities of a relict temperate forest from South-Central Chile

Abstract

Catastrophic disturbances of forest ecosystems are natural and anthropogenic phenomena that promote the natural dynamics of biocenosis and biogeochemical processes, and are the main causes of landscape fragmentation. The aim of this study was to evaluate the effect of orientation and toposequential positions on some biological activities in a relict forest community of Lapagerio-Aextoxiconetum during two seasons. Soil samples were collected from an Andisol (0-15 cm), for each toposequential position (high, medium and low slope) of a forest with orientation northeast and southwest in summer and winter. The parameters evaluated were: fluorescein diacetate hydrolysis, carbon and nitrogen biomass and activity of six enzymes related to microbiological activity: carboximethylcellulase, β-glucosidase, manganese peroxidase, urease, acid phosphatase and arylsulfatase. The results indicate that the high slope with northeast orientation showed most favourable conditions on biological activities. In turn, orientation had direct effects on the evaluated biological activities, mostly significant, due to variation in soil moisture, temperature, pH, organic matter content and nutrient availability. Urease was the only enzyme with higher activity levels in summer, because of increase in soil temperature. Biological activities were affected by seasonality, being significantly higher in winter; the differences observed for different biological parameters are attributed to microclimates that were generated under the tree canopy and mulch.