Effect of Thinning Intensity on Soil Nitrogen Dynamics in Pinus densiflora Stand

The effects of thinning intensity on soil N dynamics of Red pine (Pinus densiflora S. et Z.) stands were investigated in four short-term thinning experiments in southern Korea. The measurement was conducted 7 years after the thinning treatment and the thinning intensity ranged from heavy thinning to no thinning. All thinned sites had higher average extractable NH4+ and NO4--N ranges than that of the control, and the average of the lightly thinned site was significantly higher than that of the control for the other two thinning treatment. Average NH4+ concentrations were higher than the average NO3- concentrations in all study sites, and the of extractable NH4+ concentrations were higher in the growing season of Jun and July, and then declined in the late summer and fall seasons. Nitrification rates were comparatively low and net N mineralization differed significantly by thinning management, and showed seasonal variations. For net N mineralization and nitrification rate during the study period, the lightly thinned site had a significantly higher average than the other three sites.