天目山毛竹竞争空间格局的动态分析

Competitive spatial patterns for Moso bamboo on Mount Tianmu

毛竹Phyllostachys edulis具有速生和异龄纯林结构特征,导致毛竹林内竞争十分激烈。现有研究较少关注毛竹林内个体竞争依赖距离尺度的空间异质性及其动态。以浙江天目山国家级自然保护区内毛竹为研究对象,利用2009-2015年固定样地连续调查数据,采用Hegyi竞争指数、半方差函数、Moran’s I指数、经验贝叶斯克里金插值等分析方法,研究毛竹竞争空间格局特征及其动态变化。结果表明:(1)毛竹各年竞争指数空间分布均呈现全局一般正向自相关(P<0.001),竞争强度相近的竹子相邻分布。(2)毛竹竞争指数由结构性因素产生强烈空间变异。(3)受微地形影响,毛竹竞争指数空间格局变异存在各向异性,而极端气候干扰会降低竞争的空间异质性,竞争指数空间格局变异趋于各向同性。(4)毛竹竞争变程大年长而小年短,平均变程4.306 m,可作为毛竹竞争单元半径及调控毛竹个体竞争关系的距离尺度。(5)毛竹从小年到大年时竞争加剧,从大年到小年时竞争缓和。

Moso bamboo(Phyllostachys edulis)stands,one of the most economic forest-types in China,possess many advantages over other types,such as rapid growth,wide distribution,and high production.Much research on competition of Moso bamboo,such as intraspecific and interspecific competition,the relationship between biomass and competition,and improvements of competition index,has been conducted,but this study focused on spatial variability and its dynamic analysis of bamboo competition in distance scale dependence,which has been neglected.Based on data collected from 2009-2015 in the Moso bamboo stand of Tianmu Mountain National Nature Reserve of Zhejiang Province,the Hegyi Competition Index(CI)was calculated based on Geographic Information System(GIS).Spatial semivariogram was used to analyze the auto-correlation range of CI and its anisotropy.Also Moran’s I and Empirical Bayesian Kriging(EBK)were used to describe dynamic changes in the competitive spatial pattern.Results showed that spatial distribution of CI for Moso bamboo had a significant general global autocorrelation(P<0.001).Bamboos of the same competitive intensity were distributed evenly.Also,Moso bamboo stands had strong spatial variation due to their structural features.The CI spatial pattern,influenced by micro topography,existing anisotropy,and an extreme climate,reduced spatial heterogeneity and was inclined to be isotropic.The competition range appeared inverse to change in the on-year and off-year growth cycles with the average range being 4.306 m.This range could be used as the distance scale for the basis of determining competition unit radius and for control of the Moso bamboo competitive relationship.Even though Moso bamboo competition increased from off-years to on-years,its competition lessened from on-years to off-years.These research results could provide a reference for adjusting and controlling the competitive relationships in Moso bamboo stand management.