Effect Of Thinning On Soil Physicochemical Property And Carbon Storage Of The Natural Larix Gmelinii Forest In Great Xing’an Mountains

Forest thinning has significant effects on forest system biomass and carbon storage. It is great helpful to evaluate the variation of forest carbon storage by quantitive method. The object of this study was to evaluate the effect of thinning on soil physicochemical property and carbon storage of the natural Larix gmelinii forest in Great Xing’an Mountains. Seventy years old natural Larix gmelinii forest was as the test object. And thirty-eight percent thinning was taking by two times in this forest. The results showed that:1. Thinning improved forest growth significantly. The mean DBH (diameter at breast height) and per hectare forest volume were5.44±0.30cm and65.42±4.62m3/hm2of control forest, and was9.67±0.37cm and133.31±23.51m3/hm2of thinning forest (P<0.05).2. There were no significant effects on some of the soil physicochemical properties(P>0.05), such as the soil bulk density, pH value, hydrolysable nitrogen, available phosphorus, total nitrogen, total phosphorus, total potassium and C/N ratio (total carbon/total nitrogen).But the available potassium dropped remarkably (P<0.05) after thinning.3. The total biomass and tree layer biomass increased significantly (P<0.05). Total biomass and tree layer biomass were151.52±15.06t/hm2and84.68±5.21t/hm2of control forest, and233.33±22.01t/hm2and143.20±20.14t/hm2of thinning forest.4. The carbon concentration of current year leaf litter layer was higher after thinning (P<0.05), but the others are not. The mean carbon concentration of a Larix gmelinii was49.48%. The carbon concentration of branch litter layer, shrub and herb layer, and current year leaf litter layer, was about50percent. The carbon concentration of bryophyte layer was between40percent and45percent. The carbon concentration of partly decomposed litter layer was between25percent and30percent. The carbon concentration of soil layer was between2.5percent and5.0percent.5. The carbon storage of tree layer was higher (P<0.05), and other layers not (P>0.05), after forest thinning. The order of all layers’carbon storage in control forest was that, tree layer> partly decomposed litter layer> branch litter layer> current year leaf litter layer> bryophyte layer> soil layer> shrub and herb layer. The order of organ carbon storage in tree layer was that, trunk> root> branch> leave. Tree layer and total carbon storage in control forest were41.92±2.59t/hm2and62.79±5.66t/hm2, and in thinning forest were70.86±9.94t/hm2and96.48±11.75t/hm2. Carbon storage of shrub and herb layer was higher than of soil layer.6. The effects of thinning on nitrogen storage of below-canopy layers were non-significant (P>0.05). The order of Larix gmelinii organ nitrogen concentration was that, leave>branch > trunk> root. The mean nitrogen concentration of a Larix gmelinii tree was0.186percent. The order of layer nitrogen concentration was that, bryophyte layer> shrub and herb layer> partly decomposed litter layer> current year leaf litter layer> branch litter layer> soil layer. Nitrogen concentration of shrub and herb layer higher (P<0.05), but of bryophyte layer higher (P<0.05), after thinning. The nitrogen storage order of below-canopy layers was that, partly decomposed litter layer> soil layer> bryophyte layer> current year leaf litter layer> branch litter layer> shrub and herb layer.7. The order of C/N ratio in below-canopy layers was branch litter layer> current year leaf litter layer> shrub and herb layer> bryophyte layer> partly decomposed litter layer> soil layer. The effects of thinning on C/N ratio of six layers were non-significant (P>0.05). The C/N ratio of branch litter layer was the largest (C/N=130.8) and of soil layer was the smallest(C/N=23.0).