| Abstrakt: |
Net N mineralization, nitrification, and N uptake were monitored in the A (0–8 cm) and B (8–30 cm) soil horizons from 1997 to 1999 across a chronosequence of upland hardwood forest stands in southern Indiana, USA. Stand ages were 1, 6, 12, 31, and 80–100 years at the beginning of the study. Contrary to previous studies, there was no apparent stimulation of N mineralization due to harvesting. The highest rates of N mineralization, nitrification, and N uptake were in the mature forest stand. Rates of N cycling were greater in the A than the B horizon by concentration (g kg−1), but the greater depth and bulk density of the B horizon led to insignificant differences by area (kg ha−1). N mineralization, nitrification, and N uptake all correlated significantly with each other, and average annual rates of N mineralization balanced well with N uptake in most stands of the chronosequence. N cycling seemed to be subject to strong internal regulation at all stages of stand development. Analyses of the spatial and temporal variability in N cycling properties or processes would provide further insights in the effects of harvesting on N cycling in these forest stands. [Copyright &y& Elsevier] |
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