Study On Carbon Stock Of Vegetation And Its Affecting Factors In Xuzhou

Based on the data of Forest Management Inventory in2009, Biomass expansion factor andaverage biomass methods are used to estimate the total biomass, presenting the distribution trendof carbon storage and density of forest vegetation in Xuzhou. Analysis the influence degree ofcarbon storage in different factors, including the forest age, stand density, thinning and otherfacters on the Platyclatdus orientalis plantation in Xuzhou city. A preliminarily discussed thechange mechanism on carbon storage of the Platyclatdus orientalis Plantation.The results showedthat:(1) In2009, Xuzhou forest vegetation carbon storage is6.45Tg, carbon storage of arborforest is the highest, about5.45Tg; Secondly is the shrub, odd tree and economic forest, arerespectively0.34Tg,0.31Tg and0.34Tg, the above four respectively84.46%,5.32%,5.30%and4.75%account for the total vegetation carbon storage.(2) The carbon storage of forest vegetation in Xuzhou increases0.51Tg between2005and2009, with an average annual increase by0.13Tg and an average annual growth rate of2.54%;The average density of forest vegetation carbon increases from25.85Mg· hm-2in2005to27.37Mg· hm-2in2009. This result suggests that, Xuzhou forest is "carbon sink" from2005to2009,and it will play a more and more important role of carbon sequestration in the future.(3) The arbor forest biomass and carbon storage of different counties' forest vegetationgenerally present a gradual increasing trend from city to suburb and to exurb in Xuzhou. But thecarbon density decreases gradually from the city to the exurb. The uneven distribution of acreageand volume of dominant species is a common phenomenon, resulting in the differencedistribution of carbon storage in Xuzhou. The sum of poplar and cypress carbon storage is5.35Tg, accounts for98.16%of the total forest vegetation carbon storage in Xuzhou, showing thetwo dominant species have great contribution to the carbon storage of forest vegetation inXuzhou.(4) The distribution rule of arbor forest carbon storage of forest vegetation in Xuzhou is:broad-leaved forest＞coniferous forest＞coniferous and broad-leaved mixed forest; andmiddle-age forest＞per-matured forest＞young growth forest＞matured forest＞over-matureforest; and high canopy density＞middle canopy density＞low canopy density. The distributionrule of arbor forest carbon density of forest vegetation in Xuzhou is: coniferous forest＞coniferous and broad-leaved mixed forest＞broad-leaved forest; and over-mature forest＞matured forest＞per-matured forest＞middle-age forest＞young growth forest; and middlecanopy density＞high canopy density＞low canopy density. (5) In2009, the carbon emission including energy consumption, transportation,construction, farmland utilization, residents living and population breathing, amounts to46.52million t, per capita4.86t in Xuzhou. The forest vegetation reducts CO₂accounted for1.00%bycarbon emission. It showed that the forest vegetation has some effect on the carbon emission inXuzhou.(6)Three different stands density of P. orientalis plantation unit area average carbonstorage were as follow:94.11t/hm²and (1679individual/hm²),79.06t/hm²and (2250individual/hm²),73.32t/hm²and (3074individual/hm²), in which the carbon stocks of treelayer, understory shrub, herb layer and litter layer are decreased with the stand density increasing,the proportion of Carbon reserves in the soil layer in the system was increased with the increasein stand density.(7)Three different age of P. orientalis forest plantation ecosystems per unit area averagecarbon stocks were as follows: the40a P. orientalis forest plantation is90.67t/hm²,48a P.orientalis forest plantation is82.60t/hm²and55a P. orientalis forest plantation is109.54t/hm²,the individual of P. orientalis plant biomass showing a rising trend with the stand ageincreased, the proportion of Tree layer of carbon reserves in the total ecosystem carbon storageshowing a clear upward trend with the ages increase, the biomass of Various organs of the treelayer with the increase of forest age increase. The results of soil organic carbon storage indifferent ages of P. orientalis Plantation as follow: the40a P. orientalis Plantation is60.67t/hm²,48a is48.12t/hm²,55a is56.00t/hm².(8)The secondary thinning plots (76.36t/hm²)>the carbon reserves in first thinningplots(73.30t/hm²)> the carbon reserves of original thinned plots(68.54t/hm²), in which the treelayer of carbon reserves is as follow: the first thinning plots(37.35t/hm²)> the secondarythinning plots (30.42t/hm²)> the original thinned plots(28.13t/hm²), in the secondary thinningplot the carbon reserves tree layer was significantly reduced, the individual biomass wassignificantly increased. The carbon stocks of soil layer showed that: the layer of soil carbon stockchanges for thinning secondary (39.38t/hm²)> original thinning (36.09t/hm²)> first thinning(32.47t/hm²). The prediction conclusions is moderate thinning can increase the carbon storage inP. orientalis Plantation ecosystems.(9)Response of fine root biomass to stand density was in conformity with the changeregularity of arbor layer, soil profile and ecosystem carbon reserves under different stand density.The change regularity showed the reponse was the most obvious under low density, while lestobvious under the high density. The fine root morphology represented that the diameter of lever1st and2nd root decreased, root length shortened after getting longer, while the diameter of the fifth root increased with decreased stand density.(10)The response of fine root biomass to the first thinning was concordant with the law ofecosystem carbon reserves, they were both noticeably decreasing after thinning, except the slightincreasing of carbon reserves after the first thinning; fine root biomass were decreasing afterthe second thinning, having the similar tendency with carbon reserves in arbor layer. But carbonreserves in soil profile and ecosystem were increasing. Carbon backing to the soil profile alsodecreased. After the second thinning, diameter of lever3and4fine lever has become largerwhile that of lever5were decreased. Root length of lever4and5were increasing, capacity ofuptaking, transportation and extending to the soil were greatly improved.(11) Fine root biomass was obviously decreasing with the increasing age of the stand.Similar to the changes in soil profile of different tree ages, carbon reserves in arbor layer andecosystem increased as the the tree ages increased. Fine root shape showed that the diameter oflever2root got small after getting larger. Diameter and length of lever4and5fine root weredecreased firstly, and then increased.