空间竞争指数在华北土石山区天然次生林的应用

Application of spatial competition index to the natural secondary forest of rocky mountain area in Northern China

为了揭示森林群落内林木竞争关系,对比分析不同空间竞争指数的特点与关系,采用大小比数和开敞度对木兰围场国有林场管理局域内天然次生林林木竞争强度进行定量分析。研究结果显示:研究区天然次生林林分内各树种大小分化较为明显,平均大小比数为0.476;林分内不同种群和林木个体生长空间分配并不均匀,差异较大,全林分开敞度为0.282,处于不足状态;树种大小比数与开敞度呈负相关关系,但其相关性显著程度存在差异。大小比数与开敞度计算结果存在差异,且这一差异主要受控于两种指数对参照木与相邻木距离的不同处理方法。大小比数全面考虑了参照木与相邻木之间的大小关系,但忽略了参照木与相邻木之间的干扰程度随二者距离增大而降低的特性;开敞度虽然考虑了参照木与相邻木之间的距离,却又将参照木与相邻木抽象为没有大小的点与线,忽略了二者之间的大小关系。

In order to reveal the arbor competitive relationships in forestry community, we contrastively analyzed the characteristics and relationships of spatial competition indexes ; The competition intensity of natural secondary forest was quantitatively analyzed in Forest Bureau of Mulan Weichang by using neighborhood comparison （NC） and opening degree （OD）. The results indicated that there were an obvious size differentiation of each species, the average NC was 0. 476; Growing space distribution was not uniform and with a great discrepancy, OD of the total stand was 0.282 that showed a insufficient growing space. There was a negative correlation rela- tionship with significant differences in the degree between NC ＆ OD and opening degree according to the correla- tion analysis. The calculation result differences of NC ＆ OD were mainly controlled by respective treatment of the distance between reference tree and its neighbors. NC took a comprehensive consideration on magnitude between reference tree and neighboring trees, ignoring the property that annoyance level between reference tree and its neighbors decreased with the increasing of their distances. Compared with NC, OD did consider the intervals be- tween reference tree and adjacent trees, but it abstracted reference tree and its neighbors into point and lines without dimension.