Non-systemic logging, cattle browsing and grazing with the site natural vegetation can modify tree covers in native
forests and alter the quantity and quality of organic matter entering the soil and hence its overall quality. The
objective of this study was to evaluate the effect of modifying tree covers by uncontrolled logging and grazing
processes on soil quality, in a mature and unmanaged roble (
Nothofagus obliqua
(Mirb.) Blume) forest. Soil quality
was evaluated under partly-closed (PC), partly-open (PO), and open (OP) forest covers, and two soil depths. The
indicators used were soil organic C (SOC), potential net N mineralization (N-min), and nitrification (N-NO
3), soil
microbial respiration (SMR), microbial biomass C (MBC), soil aggregates, and light fraction (LF). At 0-5 cm soil
depth SMR and MBC in PC cover was approximately 12% higher than in PO and OP covers. For the same soil depth
N-min in PC cover was 68% and 95% higher than in PO and OP covers, respectively; and for N-NO
3 PC cover was
45% higher than PO cover. OP tree cover presented a negative N-NO3 (immobilization). Dry weight for LF fraction
in OP cover (labile OM) was 90% and 67% lower respect PC and PO covers, respectively (P < 0.05). The soil quality
and the activity of its microbial processes were affected by alteration of tree cover, as well by the anthropic action
of logging and extensive grazing, the soil in OP cover was the most affected.
