Effect Of Crown Thinning On The Soil Carbon Storage Of The Korean Pine Forests By Planting Conifer And Reserving Broad-leaved Trees In Changbai Mountains Of China

As the temperate zonality climax temperate forest vegetation in northeast of China, broad leaved Korean pine forest is featured with high volume and strong ecological function etc. Unfortunately, due to over-use and destruction, it has been destroyed seriously. Therefore, how to restore the broad-leaved Korean pine forest has drawn a wide attention among scientists. The effects of liberation cutting on community structure, litter biomass, soil bulk density, soil carbon concentration, soil carbon storage and stock volume from the mid-term (33-year-old) Korean pine forest restored by planting conifer and reserving broad-leaved tree ("PCARBT") was studied by crown thinning control test method in Changbai Mountains of China. Five levels of crown thinning intensities were taken, which were no crown thinning-control, low-intensity crown thinning-25%, moderate-intensity crown thinning-50%and heavy-intensity crown thinning-75%, full-intensity crown thinning-100%(crown thinning intensity refers to the ratio of stock volume). So as to reveal the effects of crown thining on the community structure and function of Korean Pine forest by "PCARBT". The main research results were as follows.(1) The crown thinning could maintain the coniferous and broad-leaved mixed forest structure of mid-term Korean Pine forests by’PCARBT’. But with the thinning intensity increasing, the status of Korean Pine in the community was upgraded (0.364-0.732), the status of some broad-leaved trees were declined (0.231～0.012). So as to the dominant species of communities changed. For instance, the dominant species of the control, low and moderate intensity crown thinning, heavy intensity crown thinning, full-intensity crown thinning communities were Pinus koraiensis, Quercus monglica, Tilia amurensis, Ulmus pumila; P. koraiensis, Q. monglica, T. amurensis; P. koraiensis, Q. monglica, U. pumila; P. koraiensis, U. pumila respectively. Therefore, both heavy-intensity crown thinning and full-intensty crown thining could not only strengthen and enhance the position of climax of Korean pine in the community, but also accelerate the restoration process of broad-leaved Korean pine forests.(2)Low-intensity crown thinning, moderate-intensity crown thinning and heavy-intensity crown thinning reduced the stand volume (151.3±11.8～226.2±16.2m3/hm2) of the Korean pine forest restored by an approach of planting conifer and reserving broad-leaved tree by21.0%-26.3%significantly (P<0.05), while the upper full-intensity crown thinning could maintain its stand volume (increased by10.1%, P>0.05). After16years of crown thinning, low-intensity crown thinning decreased cutting annual average accumulation growth (2.76±0.17-6.85±0.49m3/a·hm2) by22.3%significantly (P<0.01), full-intensity crown thinning increase it by93.0%significantly (P<0.01). But moderate--intensity crown thinning and heavy-intensity crown thinning had no significant affect on it (-10.4%～11.0%, P>0.05). Its main mechanism was that the volume of broad-leaved trees decreased linearly, but the volume of Korean Pine under the canopy increased exponentially with crown thinning intensity increasing. So relationship between the former and the latter determined the effects of the crown thinning on stand volume.(3) The crown thinning had affect on the soil bulk density (0.83±0.02-1.15±0.03g·cm-3) and the soil carbon concentration (43.36±1.60～70.26±1.94g·kg-1) of the mid-term Korean pine forest restored by an approach of planting conifer and reserving broad-leaved tree. compared to CK. Moderate-intensity crown thinning decreased the soil bulk density by8.4%(P<0.05), but increased the soil carbon concentration (43.36±1.60～70.26±1.94g·kg-1) by14.9%(P<0.05). Heavy-intensity crown thinning and full-intensity crown thinning increased the soil bulk density by23.3%and27.1%, respectively (P<0.05), degraded the soil carbon concentration by23.7%and29.1%, respectively (P<0.05). And low-intensity crown thinning had no significant affect on it.(4) The crown thinning had greater affect on the soil carbon storage (13.12±1.57-23.46±2.03kg·m-2) density of the mid-term Korean pine forest restored by an approach of planting conifer and reserving broad-leaved tree. Compared to CK, moderate-intensity crown thinning made the soil carbon storage increase by12.8%(P<0.05), While heavy-intensity crown thinning and full-intensity crown thinning made it lower by29.9%and36.9%, respectively (P<0.05). And low-intensity crown thinning had no significant affect on it.The influence mechanism was as follows. Both heavy-intensity and full-intensity crown thinning degraded soil carbon storage significantly and increased the soil bulk density. Their synthetic action leaded to the degradation of carbon content of soil. The moderate-intensity crown thinning enhanced carbon content of soil and degraded the soil bulk density. Their combined action leaded to the improvement of soil carbon storage. The low-intensity crown thinning had no affect on carbon content of soil and soil bulk density. Therefore there was no significant impact on soil carbon storage.(5)The crown thinning had no much affect on the litter content (6.11±0.42-7.45±0.79t/hm2) and carbon content of litter (348.91±23.21-376.03±27.36g·kg-1) of Changbai Mountains mid-term of the Korean pine forest restored by an approach of planting conifer and reserving broad-leaved tree. After16years of liberation cutting, low-intensity crown thinning and moderate-intensity crown thinning enhanced the litter content by8.6%-13.7%. And heavy-intensity crown thinning and full-intensity crown thinning degraded the litter content by1.2%-6.7%. The moderate-intensity crown thinning improved the carbon content of litter by4.3%. All of low-intensity, heavy-intensity and full-intensity crown thinning degraded carbon content of litter by0.4%-3.2%. But all crown thinning had no significant affect on the litter content and carbon content. The influence mechanism was as follows. The litter content of superstratum broad-leaved tree degraded with the increase of intensity of crown thinning. But the litter content of substratum broad-leaved tree improved with the increase of intensity of crown thinning. The relationship between them determined that intensity of crown thinning had a similar affect on the input quantity of litter.(6)The crown thinning had no much affect on the litter carbon storage (2.13±0.39-2.82±0.37t·hm-2) of Changbai Mountains mid-term of the Korean pine forest restored by an approach of planting conifer and reserving broad-leaved tree. The low-intensity and moderate-intensity crown thinning enhanced the carbon storage of litter by8.1%-19.5%. The heavy-intensity crown thinning and full-intensity crown thinning degraded the carbon storage of litter by3.8%-9.8%. But all crown thinning had no significant affect on the carbon storage of litter. It indicated that the carbon storage of crown thinning got effectively recovery after16years of liberation cutting. The influence mechanism was that the style of cutting had no significant affect on the litter content and carbon content of litter of Changbai Mountains mid-term of the Korean pine forest restored by an approach of planting conifer and reserving broad-leaved tree after16years of crown thinning. And then all of styles of crown thinning had no significant affect on the carbon storage of litter.Based on the research basis above, two business models of mid-term the Korean pine forest restored by an approach of planting conifer and reserving broad-leaved tree were raised preliminary. One was carbon sink maintain of forest soil business model (maintain or enhance the soil carbon storage of forest) using crown thinning of moderate strength. The other was promotion of climax revegetation business model (promote the development and restoration of climax pinus koraiensis and maintain or improve the forest growing stock) using liberation cutting of high strength.