| Coniferous and broad-leaved mixed forest is an important forest type in Zhejiang Province, whose carbon sink function has significant impact on improving local ecological environment and economy sustainable development. In Tianmu Mountain, using typical sampling method, fifteen 30 m×30 m fixed plots were established to measure all trees whose DBH is over 5 cm. The forest crown was used for a spatially segmented scale to generate a Voronoi Diagram, to calculate and analyze the growing space and carbon storage characteristics of the trees. Results showed that:(1) In growing space area of single tree: the maximum is 120.81m2, the minimum is 0.03m2 and average is 7.60m2. In group growing space area: the maximum is 342.79m2, the minimum is 0.48m2 and average is 34.25m2. There are 4 to 5 trees around every tree on average in the group. In single dominant species, the average area of Quercus fabric is the largest and Quercus acutissima is the smallest. In group dominant species, the average area of pistacia chinensis is the largest and Castanopsis sclerophylla is the smallest. The space area is stable for dominant species of Castanopsis sclerophylla,Castanea henryi, and Quercus acutissima, but Pinus massoniana, Cunninghamia lanceolata, Quercus fabric, and Symplocos caudata have large difference in space area. On the whole, the variation trend of the average DBH and area of trees is consistent.(2) The range of nearest-tree number for target trees is 3 to 13, mostly 5, 6, and 7, and the mean is6. Every plot has same distribution. DBH has little influence in the nearest-tree number.(3) The Pinus massoniana and Quercus fabri are the main tree species which have great carbon sequestration. The carbon sink function of coniferous species is better than broad-leaved species. The carbon storage has similarly changing tend in tree height and crown width class. The changing trend presents an approximate normal curve. Most of trees have small or medium DBH, and less trees with DBH over 48cm(4) The growing space carbon density of single tree is 19.61Kg/m2 in average, and group is18.28Kg/m2 in average. And they have no obvious difference in the mean, but difference in the maximum. The growing space carbon density of single tree has a larger diversity than group.(5) Take Pinus massoniana as target tree of single tree has higher growing space carbon density.And take Pinus massoniana, Castanopsis sclerophylla, Quercus acutissima as target trees of group have higher growing space carbon density.(6) The number of nearest-tree has obvious influence on the carbon density. With the increase number of nearest tree, forest carbon density increase at first and then decrease. The carbon density reaches the maximum when nearest tree number is 5 of single tree, and 7 when it comes to the group.(7) Research between tree’s carbon density and space structure factors shows that: keep the forest in a higher mingling, lower competitive and random distribution level is good for forest carbon sink.(8) Select Pinus massoniana, Castanopsis sclerophylla, Quercus acutissima as the main species,with the trees have different ecological habits around, like: Symplocos sumuntia, Albizia kalkora,Liquidambar formosana and so on, around each tree keep nearest tree 5-7, most likely to get a higher carbon storage. When the trees have a higher mingling, neighborhood pattern appearance of natural random distribution and less competitive with the surrounding trees, forest may have a higher carbon sink capacity. |
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