Influence of thinning on carbon storage in a Japanese larch(larix kaempferi)plantation in Yangpyeong, central Korea

This study was conducted to determine the carbon (C) contents in a Japanese larch (Larix kaempferi) plantation with four different thinning intensities over 12 years in Yangpyeong, central Korea. Thinning was applied in April of 1997 [control, no thinning (2250 trees/ha)], light thinning (T10, 10% thinning, 2000 trees/ha after thinning), moderate thinning (T20, 20%thinning, 1750 trees/ha after thinning), and heavy thinning (T40, 40% thinning, 1200 trees/ha after thinning)]. We measured individual tree DBH (cm) in November, 2009 and calculated biomass using the allometric regression equation. Forest floor (litter and coarse woody debris (CWD)) and soils, litter and soils up to 30 cm were collected and analyzed. Even though tree survival rate during 12 years was highest in the heavy thinning plot (T40), vegetation C content (Mg C/ha) was significantly higher in the light thinning plot (T10) than the other plots: 58.5 for control, 64.9 for T10, 60.4 for T20, and 55.8 for T40, respectively. Moreover, total soil C content (Mg C/ha) was higher in the moderate thinning plot (T20), however, there was no significant difference among the other plots; 56.2 for control, 57.8 for T10, 63.7 for T20, and 62.3 for T40. C contents of forest floor (litter plus CWD) were largest in the control plot, which might be influenced by the individual tree species competition; 11.9 for control, 10.2 for T10, 10.1 for T20, and 6.6 for T40, respectively. Total ecosystem C content was higher in the moderate thinning plot (T20) than those in other thinned and unthinned plots: 125.2 for control, 131.2 for T10, 132.4 for T20, and 125.9 for T40, respectively. Moderate thinning treatment (T20) seemed more effective to conserve total ecosystem C content while the individual tree growth (mean DBH and height) was higher in the heavy thinning plot (T40).