Soil carbon dioxide evolution, litter decomposition, and nitrogen availability four years after thinning in a Japanese larch plantation

Soil carbon dioxide (CO₂) evolution, litter decomposition, and nitrogen availability was measured four years after thinning in a 19-year-old Japanese larch (Larix leptolepis Gord.) plantation of central Korea. Four different thinning intensities [control (C), 10% (T10), 20% (T20), and 40% (T40)] were applied. There were significant differences in seasonal mean soil temperature, moisture, and CO₂ evolution among the thinning intensities. Annual soil CO₂ evolution (Mg CO₂ha ^-1) was 29.8 for C, 27.0 for T10, 24.2 for T20, and 23.8 for T40, respectively, and decreased with the thinning intensity. High soil CO ₂ evolution in the control and light thinning plots might be related to root respiration from high stand densities. After decomposing for four years, 30 and 23%, 30 and 27%, 21 and 10%, and 28 and 30% of the original needle litter dry mass and nitrogen mass remained for control, T10, T20, and T40, respectively. However, there were no significant trends with the thinning intensity. Needle litter acted as a net source for nitrogen during its 4th year of decomposition in this site. Thinning did not increase or decrease NH ₄ ⁺, NO₃ ^-, or total inorganic nitrogen concentrations, measured using the ion exchange resin bag method. Growing season sum resin inorganic nitrogen concentration (mg N bag ^-1) was 8.7 for C, 9.6 for T10, 8.6 for T20, and 9.2 for T40, respectively.