西山国家森林公园人工侧柏林种内与种间竞争的数量关系

Quantitative relationships of intra-and interspecific competition of Platycladus orientalis plantation in Beijing Xishan National Forest Park

为了解北京西山国家森林公园人工侧柏中幼龄林的群落结构及生长状况,运用Hegyi的单木竞争指数计算分析了人工侧柏林对象木和竞争木间的种内和种间竞争强度。结果表明:1)随着物种间距离的增大,人工侧柏中幼龄林总竞争强度的增量逐渐减少,从而确定影响对象木的最佳竞争范围是6m。2)在最佳竞争影响范围内,侧柏林物种间竞争压力更多地来自于种内竞争,占总竞争的73.03%;种间竞争强度不大,占总竞争的26.97%,其中种间竞争强度较大的树种主要是天然更新的刺槐,在4m范围内与侧柏物种的竞争强度最大,在营造侧柏和刺槐的混交林中,要保证株间距在4m以上。3)随着侧柏对象木胸径的增大,所受到的总体竞争指数逐渐减小,胸径在15cm以内所受到的竞争强度较大,侧柏中幼龄林所受到的竞争强度与其对象木胸径之间的关系符合幂函数关系。

In order to investigate the growth status and structure of middle and young stands of Platycladus orientalis plantation in the Beijing Xishan National Forest Park, the intra- and interspecific competition intensity was analyzed between target and competitive tree species using the Hegyi＇ s competition index （CI）. The results showed that 1 ） the competition intensity increment of middle and young P. orientalis stands became smaller with the increasing distance between species, indicating that the optimal competition distance of the target trees is 6 m. 2 ） Within the optimal competition distance, the competition stress to the middle and young stands mainly came from the interspecific competition, which accounted for 73.03 percent of the total; the intraspecific competition was weak, accounting for 26. 97 percent of the total competition. The most competitive species with P. orientalis was natural renewal Robinia pseudoacacia. The competitive intensity between P. orientalis and R. pseudoacacia reached maximum within d m limits. Thus in order to avoid intensive competition, the interval distance of mixed forest of P. orientalis and R. pseudoacacia should be set above 4 m. 3 ） The competition intensity of P. orientalis became declined with the increase of DBH and the stress reached the maximum when DBH of target trees was less than 15 cm. The relationship between competition intensity and DBH of the target trees followed the relationship of power function.