| Casuarina plantations are widely distributed over the coastal region of Southeastern China. From late October 2007 until the end of July 2008, tests were carried out in Zhejiang, Fujian, Guangdong, Guangxi and Hainan provinces (autonomous regions)to investigate the biomass and productivity of Casuarina plantations. In these tests, a total of 32 plots were set up and 33 standard wood were determined for biomass. On this basis, the structure of the biomass, biomass model, spatial and temporal variations of productivity, latent productive capacity were studied comprehensively according to Casuarina plantations.The conclusions were as follow:(1) The form of math lnW = a + blnX was used to estimate the relationship between Casuarina biomass of each component and the measured diameter at breast height (DBH) and diameter at breast height by the square of height (D2H)tree biomass according to Casuarina plantations in the four areas, Guangdong Lufeng, Guangdong Wuchuan and Dianbai, Guangxi Qinzhou and Hainan Wenchang (12 years old). Both the two regression models (DBH based and D2H based models) have high correlation coefficient (R). Meanwhile, the relationship for the total of 33 standard wood were also estimated, and the correlation coefficient was highly significant.(2) The vertical distribution characteristics of the above ground biomass in different growth stages of Casuarina trees were the following: Clear length of young growth was almost at 2 ~ 4m, and the crown was of different shape due to the size of stand density (the densely populated stand was similar to conical-hour, when the sparsely populated was similar to cylindrical); Clear length of medium-aged stand was almost at 4 ~ 6m, and soon showed that pruning to 6 ~ 8m, and crown shapes were similar to rotating parabolic type; height of natural pruning of mature stand was, nearly 1 / 2 tree height, and crown shapes varied.(3) Biomass of Casuarina plantations increased with the increasing age, but there was differences between various stands. Biomass of 5-year-old and 7-year-old Casuarina stands were 106.46 t ? hm-2 and 109.29 t ? hm-2, an average of 107.88 t ? hm-2; biomass of medium-aged stands ranged from 67.98 to 171.91 t ? hm-2, with an average of 135.41 t ? hm-2; biomass of mature stands ranged from 193.4 to 297.59 t ? hm-2, an average of 242.65 t ? hm-2.(4) The distribution of organ biomass of Casuarina young growth was the trunks (60.86%)> branches (15%)> roots (12.6%)> leaves (11.54%), middle-age stage was the trunks (64.33%)> roots (14.81%)> branches (14.21%)> leaves (6.65%), and mature stage was the trunks (69.00%)> roots (15.30%)> branches (11.38%)> leaves (4.33%). Casuarina from young to middle-age and to the mature stage, the proportion of trunks biomass gradually increased from 60.86% to 64.33% and to 69.00%; proportion of branches biomass gradually decreased from 15% to 14.21% and to 11.38%; proportion of leaves biomass decreased from 11.54% to 6.65% and to 4.33%; proportion of roots biomass increasd from 12.6% to 14.81 and to 15.30%. (5) The relationship between the biomass of various organs of Casuarina plantations in various growth stages was different. The ratio of trunk and crown was the young growth (2.31) |
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