Spatial point patterns and effects of density dependence in secondary poplar-birch forest, Changbai Mountains, China

以长白山5.2 hm²次生杨桦林样地为研究对象，利用空间点格局分析的双相关函数g（r）以及随机标签零模型和案例-对照设计法，探讨了树木种群空间格局及其密度制约效应。研究结果表明：生境异质性对不同生活型以及不同树种的成熟个体在大尺度范围上具有强烈影响。剔除生境异质性带来的影响后，在14个常见树种中有12个树种在小尺度上呈显著的空间聚集分布格局；随着空间尺度的增加聚集性分布树种数量急剧下降，在18 m尺度上聚集率下降到0。全部14个常见树种均呈现出显著的密度制约效应，表明密度制约是调节温带森林树木种群空间结构的主要作用机制。此外，密度制约与物种多度呈负相关，与亚林层和灌木层树种的同种聚集强度呈正相关。并且随着空间尺度增大受密度制约影响的树种百分比逐渐减小，14个常见树种中有11个在0-1 m处达到最大的密度制约强度。;Taking 5.2 hm² secondary poplar-birch forest plot in Changbai Mountains as the research object, the pair-correlation function g(r) of the spatial point pattern analysis and the random label null model and case-control design method were used to discuss the spatial pattern of tree populations and its density dependence effect. The results showed that the L(r) function is more suitable for analyzing whether there is habitat heterogeneity in a research plot. Habitat heterogeneity had a strong impact on mature individuals with different life forms and different tree species on a large scale. This showed that when studying the spatial pattern, the impact of habitat heterogeneity on the research results should be fully considered. After excluding the impact of habitat heterogeneity, 12 of the 14 common tree species showed the significantly spatial aggregation distribution pattern on a small scale. With the increasing of spatial scale, the number of aggregated distribution tree species decreased sharply, and the aggregation rate dropped to 0 on the 18 m scale. The 14 common tree species all exhibited significant density dependence effects, indicating that density dependence was the main mechanism for regulating the spatial structure of temperate forest tree populations. In addition, density dependence was negatively correlated with species abundance and positively correlated with the same species aggregation intensity of sub-forest and shrub layer species. And with the increasing of spatial scale, the percentage of tree species affected by density dependence gradually decreased, and 11 of 14 common tree species reached the maximum density dependence intensity at 0-1 m.