川西南山地云南松过熟林上层枯立木和活立木竞争强度研究

The Competition Intensity between Withered and Living Standing Trees in the Upper Layer of Overmature Pinus yunnanensis Forest in the Mountainous Area of Southwest Sichuan

邻体干扰是种群自疏的原因。但在云南松过熟林中,邻体干扰是否影响到枯立木的死亡呢?本文选用Weiner指数、Hegyi指数和张跃西指数计算竞争强度,研究了云南松过熟林径级相当的枯立木和活立木的邻体竞争强度。将8 m范围内邻体分为三类:云南松、壳斗科类和其它类,分别占42.83%、20.65%、36.52%(枯立木)和44.29%、22.49%、33.22%(活立木)。分别受枯立木和活立木周围邻体的分布格局差异的影响,邻体对云南松枯立木的种内竞争和种间竞争相当,对云南松活立木的竞争以种内竞争占优势。邻体对云南松枯立木的竞争强度小于活立木的,但不存在统计学上的显著差异。由于枯立木死亡后大小不变,三个指数所得枯立木竞争强度均大于枯立木死亡时的竞争强度。因此,活立木的竞争强度比目前枯立木死亡时受到的竞争强度还要大,这表明枯立木死亡受邻体竞争影响的可能性较低。由于Weiner指数、Hegyi指数和张跃西指数的构建参数不同,同样数据所得竞争强度各不相同,随距离的变化趋势也各异,但在计算云南松枯立木和活立木竞争强度时获得了一致结果。

Neighborhood interference（NI） is the reason for population self-thinning lematic whether the neighborhood interference will have an on the death of withered overmature forest. Three competition indices were used to analyze the neighborhood in forest. It is prob- standing trees in the competition between the withered and living standing trees, which have the same DGL. The neighborhoods around objective trees within 8m were compartmantalized into three types ：Pinus yunnanensis, Fagaceaea and other shrubs. The results showed that, withered standing trees of P. yunnanensis, Fagaceaea and the others occupied 42.83%, 20.65% and 36.52% respectvely and their living standing tree occupied 44.29%, 22.49% and 33.22% respectively. For withered standing trees, intra-specific competition and inter-specific competition were similiar （ p 〉 0.05 ） and for living trees, intra-specific competition was bigger than inter-specific competition （ p 〈 0.05 ）. Although the competition effect for withered standing trees was larger than that for living standing trees, but there was no significant difference in statistics（ p 〉 0.05 ）. Meanwhile, withered standing trees had stopped growing, but the growth of neighborhood would release. Therefore, the competition indices, when the tree died, would be lower than the measured indices. Based on the information above, the competitive effect leading withered standing trees to the death was not a fact. Weiner index, Hegyi index and Zhang Yuexi index were different models including different parameters, and hence the use of the same data would get different results. And yet the results were identical when the three competitive indices were used for analyzing the neighborhood competition between the withered and living standing trees.