【作者】 周伟；

【导师】 关庆伟；

【作者基本信息】 南京林业大学 ， 生态学， 2012， 博士

【摘要】 本文依据2009年的徐州市森林资源二类清查数据，分别运用生物量换算因子连续函数法和非蓄积换算法估算徐州市森林植被生物量，研究了徐州市森林植被碳储量和碳密度分布规律；分析了林分密度、林龄、间伐等因素对徐州市侧柏人工林碳储量的影响程度；从细根生物量和形态角度，初步探讨了侧柏人工林生态系统碳储量变化的机理。结果表明：（1）2009年徐州市森林植被碳储量6.45Tg，乔木林碳储量最高，为5.45Tg；其次是灌木林、四旁树和经济林，分别为0.34Tg、0.34Tg和0.31Tg，四者分别占植被总碳储量的84.46%、5.32%、5.30%和4.75%。乔木林是植被碳储量的最主要贡献者。（2）2005～2009年间徐州市森林植被碳储量共增加0.51Tg，年均增加0.13Tg，年均增长率2.54%；4年间森林植被平均碳密度由2005年的25.85Mg·hm-2增加到了2009年的27.37Mg·hm-2。这表明2005～2009年，徐州市森林是CO₂的一个“汇”，随着时间的变化，徐州市森林将发挥越来越大的固碳功能。（3）徐州市的森林植被乔木林生物量和碳储量大致呈现从市区—近郊—远郊方向逐渐增加的趋势；碳密度呈现从市区向远郊逐渐降低的趋势。徐州市各优势树种面积、蓄积分布不均，造成碳储量有所差异。杨树和柏类的碳储量之和达5.35Tg，所占比例之和占全市总碳储量的98.16%，显示了这两种优势树种碳储量对徐州市森林植被碳储量有极大贡献。（4）徐州市森林植被乔木林碳储量分布规律：阔叶林＞针叶林＞针阔混交林；中龄林＞近熟林＞幼龄林＞成熟林＞过熟林；高郁闭度＞中郁闭度＞低郁闭度。碳密度分布规律：针叶林＞针阔混交林＞阔叶林；过龄林＞成熟林＞近龄林＞中龄林＞幼龄林；中郁闭度＞高郁闭度＞低郁闭度。（5）2009年徐州市能源消耗、交通运输、建筑施工、农田利用、居民生活和人口呼吸六个方面的碳排放量共计4652.11万t，人均4.86t/人。森林植被碳储量年均增加0.13Tg，相当于同期碳排放量的1.00%，即减排贡献率也为1.00%，说明森林植被对城市碳排放有一定的消弱作用。（6）3种林分密度单位面积平均碳储量分别为：94.11t/hm²（1679株/hm²）、79.06t/hm²（2250株/hm²）和73.32t/hm²（3074株/hm²）。其中，乔木层、林下灌草层和枯落物层的碳储量随着林分密度增加在系统中所占比重逐渐减小，土壤层碳储量随林分密度增加在系统中所占比重呈增加趋势。（7）3种林龄的侧柏人工林生态系统其单位面积平均碳储量分别为：40年生侧柏林碳储量为90.67t/hm²，48年生为82.60t/hm²和55年生为109.54t/hm²。侧柏单株生物量随林龄增加呈明显上升趋势，乔木层碳储量在系统碳储量中所占比重随林龄增加呈明显上升趋势，乔木层各器官生物量随林龄增加而增加。不同林龄侧柏人工林土壤有机碳储量结果为：40年生侧柏林为60.67t/hm²，48年生侧柏林为48.12t/hm²，55年生侧柏林为56.00t/hm²。（8）间伐两次侧柏林碳储量（76.36t/hm²）>间伐一次侧柏林碳储量（73.30t/hm²）>未间伐侧柏林碳储量（68.54t/hm²），其中乔木层碳储量为：间伐一次（37.35t/hm²）>间伐两次（30.42t/hm²）>未间伐（28.13t/hm²），土壤层碳储量为间伐两次（39.38t/hm²）明显高于未间伐（36.09t/hm²）和间伐一次（32.47t/hm²）。可见，适度的间伐可以增加系统碳储量。（9）不同林分密度细根生物量的变化与不同林分密度下的乔木层、土壤层以及生态系统碳储量变化规律一致，均为低林分密度下最大，高林分密度下最小。细根形态随林分密度的降低表现为低级根中的1、2级根直径变小，根长先变长后变短；而高级根中的5级根直径变粗。（10）1次间伐细根生物量与土壤层和生态系统碳储量的变化规律一致，均表现为间伐后明显减少，但乔木层碳储量在一次间伐后略有增加；细根生物量在两次间伐后减少，这与乔木层碳储量有相似规律，但两次间伐后土壤层和生态系统碳储量却有所增加。两次间伐后，3、4级根直径变粗，5级根直径变小；4、5级根平均根长变长，吸收、运输和延伸能力均增强，5级根寿命缩短，归还到土壤中碳增多。因此，适度间伐不但不会减少细根生物量反而有利于整个生态系统碳储量的增加。（11）细根生物量随林龄的增加明显减少与不同林龄下土壤层碳储量的变化规律类似，乔木层和生态系统碳储量随林龄的增加而增加。细根形态随林龄的增加表现为2级根直径先变粗后变细，4、5级根直径和根长均先变小后变大。综上所述，城市是大气中CO₂的主要来源，城市植被是较大的“汇”。徐州市城市森林植被对固定城市中排放的CO₂有较大贡献，但不同类型森林植被的碳储量有所差异；适度间伐等经营措施可以提高城市人工林生态系统的碳储量；侧柏人工林细根的结构和功能变化与系统碳储量变化具有较高一致性，这可能是导致系统碳储量变化的主要因素之一。更多还原

【Abstract】 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.更多还原