Abstract

This study was undertaken to measure certain carbon (C) fluxes in secondary Nothofagus forests with different levels of degradation (degraded-DEF, partly-degraded-PDF and undisturbed-UNF forests). Litter decomposition was determined using the litterbag method. Leached soil solution was collected with tension lysimeters at 80 cm depth, and soil respiration evaluated in situ with the soda lime technique for CO2 absorption. Soil samples were taken at 0-5, 5-20 and 20-40 cm depths to determine the amount of microbial respiration. Soil temperatures at a depth of 0-20 cm were higher in DEF than UNF (12.9 vs. 11.4°C in the Andes, and 12.1 vs. 9.6°C in the Coastal Mountains, respectively). The same trend was observed for the air temperature above the ground (+5 cm) (13.2 vs. 11.8°C in the Andes, and 12.3 vs. 10.1°C in the Coast, respectively). Soil moisture percentages were slightly higher in the UNF than DEF, but generally did not show significant differences. In the Andes Mountains, rates of litter decomposition were lower in UNF and higher in DEF (21.8 and 14.1% remaining residue weight after 30 months, respectively), while in the Coastal Mountain Range, these values were 22.6 and 13.9%, respectively. On the other hand, total soil respiration was greater in UNF than DEF (0.37 vs. 0.32 g CO2 h-1 m-2, respectively) in the Andes, and 0.44 vs. 0.36 g CO2 h-1 m-2, respectively, in the Coast. Regarding soil microbial respiration at 0-5 cm depth, a significant difference was only observed in the Coastal Mountains, with 2.44 and 3.71 cm3 CO2 h-1 100 g dry soil-1 in DEF and UNF, respectively. Despite not obtaining significant differences in the NO3- and NH4+ contents in soil leachates, a trend of higher content was found in the undisturbed soils. The overall soil organic carbon (SOC) and N contents at 0-40 cm depth decreased significantly in the order UNF˃PDF˃DEF. The presence of greater plant coverage and number of species in undisturbed forests favored the productivity of the ecosystem, conserving nutrients and sequestering more carbon in the vegetation and soil.