Effects of thinning on soil nitrogen mineralization in a Japanese larch plantation

We measured soil nitrogen (N) mineralization and litter decomposition for f our different thinning intensities [control (C), 10% (T10), 20% (T20), 40% (T40) thinning] during the first year after treatment in a 15-year-old Japa nese larch plantation in central Korea. Initial soil moisture content incre ased in the thinned plots. Air temperature also increased with thinning int ensity, however, soil temperature did not. Annual net N mineralization rate s (mg N kg(-1)) for C, T10, T20, and T40 were 6.7, 7.2, 6.6, and 1 1.5, res pectively. The heavily thinned plot showed higher annual N mineralization t han control, lightly and moderately thinned plots, but differences were not statistically significant. Except for the T40 treatment, the ratios of ann ual net nitrification to annual net N mineralization were greater than 100% . Dry weight and N concentration in decomposing needle litter did not show any significant patterns with thinning intensity. The current results indic ated that various levels of thinning for a young Japanese larch plantation had only a minor influence on soil N mineralization and litterfall decompos ition during the first year following thinning.