Effects of Density Control on the Spatial Structure of Pinus tabulae f ormis Plantation | 密度调控对油松人工林空间结构的影响

Chinese. 【目的】旨在探索密度调控对油松人工林空间结构的影响。【方法】以实施间伐后6种保留密度下油松（Pinus tabulaeformis Carr.）人工林样地植被群落调查数据为基础，利用角尺度、混交度和大小比数来分析华北土石山区油松人工林空间结构。【结果】结果表明：研究区油松人工林林分混交度和角尺度随密度增大呈减小趋势，林分大小比数呈波动型变化趋势，但各密度油松人工林林分大小比数相差不大，分布较均匀，林木分化程度较高；油松人工林空间分布格局整体呈均匀分布，但随保留密度的减小向随机分布演替，保留密度最小的林分（540 株？hm-2）已经向异龄混交林发展。【结论】密度调控使林分空间结构趋于优化合理状态，建议引进蒙古栎（Quercus mongolica Fisch. ex Ledeb.）等乡土树种，伐除角尺度较小林木来改变树种组成及竞争关系，以促进油松人工林演替。

English. 【OBJECTIVE】 The objective of the study was to explore the effects of density control on the spatial structure of Pinus tabulaeformis plantations. 【METHOD】 Based on the vegetation community investigation data of the six samples with reserve density of P. tabulaeformis plantation after thinning, the uniform angle index , mingling degrees and neighborhood comparison index were used to analyzed the spatial structure characteristics of P.tabulaeformis plantations in the rocky mountain area of Northern China. 【RESULTS】 The results indicated that the mingling index and uniform angle index of P. tabulaeformis plantations decreased with the density increase. Neighborhood comparison of plantations with different density showed a fluctuating tendency with indistinctive differentiation and uniform distribution. The differentiation degree of plantations is higher. The plantations distributed uniformly as a whole, but transformed to random distribution pattern with the reserve density decrease. The minimum density （540 strains ？hm-2） had been in the succession process to uneven-aged and mixed forest. 【CONCLUSION】Density control made the spatial structure optimized and reasonable. It was suggested that the succession of P. tabulaeformis plantations can be promoted by changing the species composition and competition relationship, such as instructing Quercus mongolica Fisch. and other native species, removing the trees with smaller uniform angle index.