Abstract

以不同林分密度(1800、3000、4500株/hm<sup>2</sup>)杉木林为研究对象, 通过野外调查、样品采集和室内分析, 研究不同林分密度杉木林生态系统碳密度及其分配特征。结果表明:1)三种林分密度杉木林生态系统碳密度分别为131.54、161.42、172.69 t/hm<sup>2</sup>, 随林分密度增大而升高, 且具有显著差异(P < 0.05)。杉木林碳密度表现为土壤层>乔木层>林下地被物层。土壤有机碳储量占总碳储量的比例最大(53.11%-67.37%), 其次是树干、树根、树皮(25.89%-35.74%), 高密度杉木林分有利于树干、树皮、树根碳密度分配比例的增加。2)乔木层, 树干、树皮、宿留枯枝及宿留枯叶碳密度随林分密度增大而升高, 鲜枝及鲜叶碳密度随林分密度增大先升高后降低, 且均具显著差异(P < 0.05);树干、树皮碳密度随树体高度的升高而降低, 鲜枝鲜叶碳密度集中于树体中上部(8 m≤h≤10 m), 宿留枯枝枯叶碳密度集中分布于树体中部(4 m≤h≤8 m)。3)随着林分密度的增大, 不同径级根碳密度呈上升趋势, 且不同径级根碳密度随林分密度变化差异达显著水平(P < 0.05);不同径级间碳密度:根头>粗根>大根>中根>小根>细根, 根头和粗根占比最大(57.38%-70.84%)。4)林下植被碳密度随林分密度增大不断降低, 而林下凋落物碳密度随林分密度增大呈逐渐上升趋势, 且具显著差异(P < 0.05)。5)土壤层碳密度随土壤深度增加逐渐降低, 不同林分密度土壤层碳密度没有显著差异(P>0.05)。综上所述, 适当增加林分密度有利于提高杉木林生态系统的碳密度。;Cunninghamia lanceolata plantation with densities of 1800, 3000 and 4500 plants/hm<sup>2</sup> were employed to investigate the carbon density and its distribution characteristics of C. lanceolata forest ecosystem under different stand densities through field investigation, sample collection and analysis. The results showed that: 1) the carbon density in the C.lanceolata ecosystem with stand densities of 1800, 3000 and 4500 plants/hm<sup>2</sup> were 131.54 t/hm<sup>2</sup>, 161.42 t /hm<sup>2</sup> and 172.69 t/hm<sup>2</sup>, respectively, and increased significantly with the increase of stand densities (P < 0.05). The carbon density of C. lanceolata forest followed the order of soil layer > tree layer > understory layer. Soil organic carbon storage accounted for the largest proportion of total carbon storage (53.11%-67.37%), followed by trunk, root and bark (25.89%-35.74%). High stand density could increase the carbon density distribution portion in trunk, bark and root. 2) The carbon density of tree layer, trunk, bark and persistent withered branches and leaves increased with the increase of stand densities, while the carbon density of fresh branches and leaves displayed first increase and then decrease tendency with the increasing stand densities, which all showed significantly decreased with the increase of stand densities (P < 0.05). The carbon density of trunk and bark decreased with the increase of tree height. The carbon density of fresh branches and leaves were relatively high in the middle and upper part of tree (8 m≤h≤10 m), while for withered branches and leaves, higher carbon density was observed in the middle of the tree (4 m≤h≤8 m). 3) The carbon density in roots of different diameter increased significantly with the increase of stand densities (P < 0.05). The carbon density among different roots diameter was as follows: root head > coarse root > big root > middle root > small root > fine root, and root head and coarse root accounted for the largest portion (57.38%-70.84%). 4) The carbon density of undergrowth vegetation decreased with the increase of stand densities, while the opposite trend was observed for litter, which showed significantly decreased with the increase of stand densities (P < 0.05). 5) The carbon density of soil layer decreased with the increase of soil depth, and no significant difference was observed for different stand densities (P>0.05). 6) In summary, appropriate increase stand density is beneficial to improve the carbon density of C. lanceolata forest ecosystem.

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