Effect Of Liberation Cutting On The Vegetation Carbon Storage Of The Mid-term Korean Pine Forests By Planting Conifer And Reserving Broad-leaved Tree In Changbai Mountains Of China

The restoration of broad-leaved Korean Pine forest which was a climax forest in the northeast region of China is more and more paid wide attention to by scientific community and production units. The effects of liberation cutting on the community structure, growth process of Korean Pine and carbon storage from the33-year-old Korean Pine forests by planting conifer and reserving broad-leaved tree ("PCARBT") was studied by using crown thinning control test method in Changbai Mountains of China. Five levels of cutting intensities were taken, which were non-selective cutting-control, low-intensity selective cutting-25%, moderate-intensity selective cutting-50%, heavy-intensity selective cutting-75%and clear-cutting-100%(cutting intensity refer to volume percent), so as to reveal the effects of liberation cutting on the community structure and function of Korean Pine forest by "PCARBT". The results showed that:(1) The liberation cutting 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 the dominant species of communities changed. For instance, the dominant species of the control, low-, and moderate intensity light-felling, heavy intensity light-felling, clear-cutting 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.(2) Liberation cutting could significantly promote the tree height (11.0%～148.2%,58.5%～275.3%,52.3%～177.0%), DBH (6.6%～162.6%,53.7%～304.9%,45.0%～250.0%) and Individual volume (14.3%～1083.3%,203.0%～3045.5%,150.0%～2150.0%) of dominant tree, average tree and suppressed tree of Korean Pine, which were increased by a large margin with the upper crown thinning intensity increasing. In addition, the growth promoting effects of liberation cutting on the average tree and suppressed tree were generally stronger than on the suppressed tree of Korean pine.(3) Liberation cutting had different influence on the stand volume (151.3±11.8～226.2±16.2m3/hm2) and total stand volume (205.4±19.2～359.6±16.2m3/hm2)(plus the harvest volume) of the mid-term Korean Pine forests by "PCARBT" in Changbai Mountain. After liberation cutting16years, three kinds of selective cutting (low-, moderate-, and heavy-intensity selective cutting) reduced the stand volume by21.0%～26.3%significantly (P<0.05), while the upper clear-cutting could maintain its stand volume (increased by10.1%, P>0.05); Low-, and moderate-intensity selective cutting only maintain its total stand volume, while heavy-intensity selective cutting and clear-cutting significantly increased its total stand volume by about3/4and1/4than control stands. Therefore, heavy-intensity selective cutting and clear-cutting not only could bring all potentialities of Korean Pine growth into full play and improve the total stand volume significantly, but also could accelerate the restoration process of broad-leaved Korean pine forests. 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 cutting intensity increasing. So relationship between the former and the latter decided the effects of the liberation cutting on stand volume.(4) All intensity liberation cutting made its vegetation biomass (154.86±9.84～217.56±4.90t·hm-2) decrease significantly, which low-, moderate-, and heavy-intensity selective cutting decreased it by21.1%～28.8%(P<0.05), While clear-cutting made it decrease only by12.5%(P<0.05).(5) Liberation cutting had different effects on the carbon concentration of tree layer (404.53±1.28～479.64±7.22g·kg-1), shrub layer (454.87±9.82～474.52±5.82g·kg-1), herb layer (401.24±8.65～419.52±7.98g·kg-1) and litter fall layer (348.91±13.21～376.03±12.36g·kg-1) of the Korean Pine forests by "PCARBT", for instance, the carbon concentration of trunk from P. koraiensis, U. pumila and T. amurensis were decreased by2.3%～6.1%significantly (P<0.05), the carbon concentration of branches and leaves from Q. mongolica, U. pumila and T. amurensis were decreased by2.6%～12.7%significantly (P<0.05), the carbon concentration of shrub layer was decreased by3.5%～3.6%significantly (P<0.05), but the carbon concentration of branches and leaves from P. koraiensis was increased by5.4%～7.7%significantly (P<0.05).(6) Liberation cutting made its vegetation carbon storage (68.38±1.78～97.40±2.98t·C·hm-2) significantly decrease by16.1%-29.8%(P<0.05), which low-, moderate-, and heavy-intensity selective cutting decreased by22.5%-29.8%, While clear-cutting only decreased by16.1%. Therefore, in order to sequestrate more carbon, small-scale upper clear-cutting should be taken for the Korean pine forests by "PCARBT". Its main mechanism was that the carbon storage (4.74±0.17～73.21±6.33t-C/hm2) of Korean Pine planted under secondary forest canopy increased by0.6～14.4times with felling intensity increasing, but the carbon storage (5.23±1.13～88.31±3.99t-C/hm2) of the broad-leaved trees decreased by36.2%～94.1%with felling intensity increasing, the comprehensive effect of the both leads to the lowered range of carbon storage in all selective cutting stands were relatively larger than that in the clear-cutting stands.