Effects Of Light-felling On Carbon Budget Of The Mid-term Korean Pine Forest By Planting Conifer And Reserving Broad-leaved Trees In Changbai Mountains

With the continuous development of global economy and rising density of greenhouse gases, the forest ecological system as an important part of land ecosystem, its carbon changes will directly affect the global climate change. Therefore, effective ways of forest management should be explored and more carbon be fixed in forest ecosystem, so as to improve or maintain forest carbon sink function to mitigate global climate change. Broad leaved Korean pine forest as the zonal climax temperate forest vegetation in northeast China, is featured with high volume and strong ecological function etc. Unfortunately, due to historical reasons it has been seriously destroyed. Therefore, how to restore the broad-leaved Korean pine forest has drawn a wide attention among scientists.This Paper mainly researches on the mid-term Korean pine forests by planting conifer and reserving broad-leaved tree in Changbai Mountains in northeast China(Planting of Korean pine under secondary forest in1979, at present there are33years plantation age, so called the mid-term; in view of the17years of Korean pine forests have been planted pervious to light-felling experiment was carried out in1996,by the survey of2012, pervious to light-felling test has been carried out for16years). By analyzing the carbon emission from soil respiration, net primary productivity and net carbon sequestration, and ecosystem net carbon balance under various light-felling, the Paper stipulates the way how Light-felling affects the carbon sources or sink of mid-term Korean pine forests by planting conifer and reserving broad-leaved tree, aiming at selecting out the management mode to increase forest carbon budget. Five levels of cutting intensities were taken, which were uncut sites-0%, low-intensity light-felling sites-25%,moderate-intensity light-felling sites-50%, heavy-intensity light-felling sites-75%and clear-cut sites-100%(Cutting intensity refers to the removal of upper broadleaf tree volume ratio). The main research results have shown:(1) Light-felling significantly reduce16.1%-29.8%(P<0.05) of the vegetation carbon storage (68.38±1.78～97.40±2.98t·C/hm2) of the mid-term Korean pine forest by planting conifer and reserving broad-leaved tree in Changbai Mountain, and the decrease of cutting at all intensity are similar (22.5%～29.8%) and greater than the full sunlight16.1%). The impact mechanism:the carbon storage of Pinus koraiensis with light-felling intensity increases (0.6～14.4times) under the secondary forests, while the carbon storage of upper broadleaf species is diminishing with the increase of intensity of light-felling intensity(-36.2%～-94.1%), The relationship between the two leads to reduce similar amplitude of all intensity and greater than upper clearcutting.(2)Intensive light-felling and clear-cutting can significantly reduce29.9%～36.9%(P<0.05) of the soil carbon storage(131.2±15.7～234.6±20.3t·C/hm2) of the mid-term Korean pine forest by planting conifer and reserving broad-leaved tree in Changbai Mountain, moderate light-felling can significantly increased of the soil carbon storage(12.8%, P<0.05).while low light-felling did not have a significant on the soil carbon storage(2.4%, P>0.05). The impact mechanism is:intensive light-felling and upper clear-cutting significantly reduced soil carbon content, but significantly increased soil bulk density, the comprehensive effect of the two leading to soil carbon storage decreased significantly; moderate light-felling significantly improved soil carbon content, but significantly decreased soil bulk density,the former increased is larger than the latter decreased,and soil carbon storage was increased dramatically under the comprehensive action of the two leading; low light-felling on soil carbon content and soil bulk density had no significant effect, and did not have a significant impact on soil carbon storage either.(3)The intensive light-felling and clear-cutting can significantly reduce29.8%-30.3%(P<0.05) of the ecosystem carbon storage(212.90±19.59～310.06±23.40t·C/hm2) of the medium-term Korean pine forest by planting conifer and reserving broad-leaved tree in Changbai Mountain, and low, moderate light-felling on the ecosystem carbon storage did not significantly affect(-7.8%-1.5%,P>0.05), low and moderate light-felling can maintain the ecosystem carbon storage. And the light-felling also changed the allocation pattern of ecosystem carbon storage, and sample plot is consistent with intensive light-felling, soil carbon storage accounted for about2/3, vegetation carbon storage accounted for about1/3; low, moderate light-felling to soil carbon storage accounted for about3/4, vegetation carbon storage accounted for about1/4; the upper clear-cutting to soil carbon storage accounted for about3/5, vegetation carbon storage accounted for about2/5. The impact mechanism:low, moderate light-felling significantly decreased the vegetation carbon storage, but had significant impact on soil carbon storage is not, resulting in impact of them on the ecosystem carbon is not significant; while the intensive light-felling and clear-cutting were significantly decreased the vegetation carbon storage and soil carbon storage, and significantly decreased the ecosystem carbon storage of both.(4) The intensive light-felling can significantly reduce24.7%and27.0%(P<0.05) of vegetation’s net primary productivity(6.74±0.69～8.96±0.64t·hm-2·a-1) and annual net carbon fixation (2.97±0.11～4.07±0.30t·C·hm-2·a-1) of the mid-term Korean pine forest by planting conifer and reserving broad-leaved tree in Changbai Mountain, and low, moderate light-felling and upper clear-cutting on both the impact did not significantly affect(-10.5%～0.1%and-16.0%～-2.5%,P>0.05). The impact mechanism:the intensive light-felling significantly reduced vegetation’s net primary productivity and annual net carbon fixation of tree layer and shrub layer; low, moderate light-felling significantly reduces the net primary productivity and annual net carbon fixation of tree layer, but also significantly increased net primary productivity and annual net carbon fixation of herbaceous layer; the upper clearcutting only significantly reduced the net primary productivity and annual net carbon fixation of shrub layer.(5) The intensive light-felling and upper clear-cutting light-felling significantly decreased34.1%～39.2%(P<0.05) of the soil respiration CO2emissions (24.00±4.15～39.48±5.43t·hm-2·yr-1) of Korean pine forest by planting conifer and reserving broad-leaved tree in Changbai Mountain,while moderate and low light-felling had no significant effect on the CO2emissions of soil respiration(-4.0%～-0.3%,P>0.05). The impact mechanism:the intensive light-felling and upper clear-cutting of mid-term Korean pine forest by planting conifer and reserving broad-leaved trees significantly decreased CO2emissions of soil respiration、autotrophic respiration and heterotrophic respiration in each season(spring, summer, autumn).low light-felling significantly decreased CO2emissions from soil heterotrophic respiration in spring.While moderate light-felling shed no significant influence on the CO2emissions of soil respiration、autotrophic respiration and heterotrophic respiration each season.(6) The mid-term Korean pine forests by planting conifer and reserving broad-leaved tree performance for carbon sink after light-felling16years (0.64±0.17～2.00±0.31tC·hm-2·yr-1),upper clear-cutting light-felling significantly decreased the ecosystem carbon emissions among them(111.5%, P<0.05),while moderate and intensive light-felling shed no significant influence on it(P>0.05),the low light-felling significantly improve the ecosystem carbon emission source intensity(32.6%, P<0.05).This shows that the upper clear-cutting16years later,the mid-term Korean pine forests by planting conifer and reserving broad-leaved is sink carbon of sequestration,and the upper clear-cutting can significantly increase the carbon sink.Therefore, from the consideration of maintaining China’s northeast forest carbon storage, the medium-term Korean pine forest by planting conifer and reserving broad-leaved should be taken in low, moderate light-felling more appropriate (both to maintain the ecosystem carbon), but they did not fully release the potential growth of Pinus koraiensis under canopy, will delay the broad-leaved Korean pine forest restoration process; to accelerate the northeast area of broad-leaved Korean pine forest climax vegetation restoration process and maintaining China’s northeast forest carbon sink, the medium-term Korean pine forest by planting conifer and reserving broad-leaved should take intensive light-felling or upper clear-cutting(both of them can give full play to the growth potential of Korean pine,to speed up the recovery process of broad-leaved Korean pine forest), with the continuous development of a new generation of broad-leaved Korean pine, its carbon sinks function will get improved, so from the long time scales to pervious to insentive light-felling or upper clearcutting also is feasible.