Evaluation of the enzymatic activity and diversity of soil microorganism in Andean temperate forests degradation gradient

Soil microorganism are an essential component of forest ecosystem. Microbes and plant release enzymes that catalyse reactions needed to decomposed soil organic matter and crucial to release nutrient in available forms. Therefore, soil enzymes are relevant indicators of microbial activity and nutrient cycling in forest ecosystems. Anthropic disturbances in natural forest, such as logging and exotic livestock, modify the structure and composition of forest thereby altering the structure and activities of soil microbial communities.

Here we determine the effect of these disturbances on the enzymatic activity (Dehydrogenase-DHA; Phosphatase Acid-AP; Ureasa-UA) and the microbial diversity using a forest degradation gradient of native temperate forest dominated by Nothofagus dombeyi, Nothofagus obliqua and Nothofagus alpina. In addition we quantify C:N:P nutrient reservoirs, stoichiometry and available pools. Preliminary results suggest a higher activity of the DHA enzyme in degraded forest dominated by N. obliqua. AP and UA showed no relationship with the phosphorus and total nitrogen reservoirs. Forest degradation modify microbial communities, C:N:P stoichiometry, total and available nutrient pools, where the biggest pool of total C and N was registered on low degraded condition and decrease as degradation condition increase from medium to high degraded forest (74.44%; 65.35%; 48.05% for total C and 3.71; 3.41; 3.24 for total N respectively). Inverse relation was registered for total P pool were the highest pool was registered on high degraded condition (14963ppm; 13092ppm and 11299ppm from high to low degraded condition). Degraded sites were dominated mainly by members of Gammaproteobacteria, Alfaproteobacteria, Acidobacteria and Bacteroidia. Chitinophagaceae and Burkholderiacea were not detected in degraded plots, which suggest that some of the specialised functions carried by this groups could be lost. With respect to fungi Ascomycota and Basidomicota Phylum dominated the soil profiles. A species of the genus Clonostachys (Bionectriaceae) was identified, an endophyte fungus that acts as a saprophyte, also known to be a parasite of other fungi and some nematodes.

This research contributes to a better understanding of the direct effects of anthropic disturbances on the biogeochemical functioning of temperate forests and their relationship to the activity and composition of microbial communities.

Acknowledgment: Proyecto Reforestación Enel – UdeC