连栽杉木人工林土壤肥力变化的主分量分析

对江西分宜县大岗山不同立地指数(12、14、16指数)、不同生长阶段(幼龄林、中龄林和成熟林)的1、2代杉木人工林23项土壤因子进行了测定,运用主分量分析筛选出评价杉木人工林土壤肥力的3个综合因子,并用主分量分析结果进一步对所选的样地进行综合评分、排序。2代杉木人工林综合得分均低于对应的1代杉木人工林,表明连栽杉木人工林土壤肥力下降的事实;1代杉木人工林不同发育阶段土壤肥力的变化趋势为：从幼龄林发育至中龄林阶段,林地综合地力呈下降趋势;从中龄林发育至成熟林阶段,林地综合地力略有回升,说明杉木人工林土壤肥力下降孕育在1代林阶段。

PCA on the Soil Degradation of the Successive Chinese Fir Plantation

23 soil factors in the different sites (site-index 12,14,16) and different growth periods (young, half-mature and mature) of the first and second generation Chinese fir plantations in Dagang Mountain, Fenyi County of Jiangxi Province,were determined.By the method of PCA, three synthesized factors were selected as targets on evaluating soil fertility in Chinese fir plantation. The results were quantified, scored and sequenced to the data-collected relevant to the soil fertility in the selected plots using PCA.The result showed that the score of all the 2~(nd) generation Chinese fir plantations were much lower than that of the 1~(st) generation. It revealed the fact that soil degradation existed in successive Chinese fir plantations. The result also showed the tendency of soil productivity of different growth period of 1~(st) rotation was that the soil productivity decreased from young to half-matured period, but raised slightly from half-matured to matured period, this meaned that 1~(st) rotation was the latent period of soil degradation of Chinese fir plantation.