抚育间伐对栓皮栎种群空间分布格局的影响

抚育间伐是一种重要的改善林木生长条件的经营措施,对林分结构和动态具有重要影响。为研究抚育间伐对林木种群空间结构与格局影响的内在机制,以间伐和未间伐的栓皮栎人工林为研究对象,通过设置2个100 m×100 m样地并进行每木定位和调查,在采用径级结构代替年龄结构方法将栓皮栎种群划分为幼树(2 cm≤DBH<5 cm)、小树(5 cm≤DBH<13 cm)和大树(DBH≥13 cm)3个生长阶段的基础上,分别采用Ripley’s K函数衍生的g(r)函数和双变量g12(r)函数,对栓皮栎种群空间分布点格局及不同生长阶段栓皮栎种群之间的关联性进行了研究。结果表明,间伐和未间伐样地栓皮栎种群空间分布点格局分别在0-16 m和0-33 m距离尺度内呈聚集分布,而分别在大于16 m和33 m距离尺度内呈随机分布;间伐和未间伐样地栓皮栎幼树、小树和大树的株数比分别为8?741?699和261?1134?683,且间伐样地栓皮栎幼树、小树和大树种群分别在0-14、1-16、0-6 m距离尺度内呈现均匀或聚集分布,而在其他距离尺度上表现为随机分布;栓皮栎幼树、小树和大树之间仅在间伐样地0-6 m距离尺度内呈现一定的相关性,而在未间伐样地更大的距离尺度内有显著的关联性,如栓皮栎幼树和大树之间在6-38 m距离尺度上呈显著正相关。因此,抚育间伐一定程度上使得栓皮栎种群在更大距离尺度上呈现出随机分布状态,并弱化了不同生长阶段的林木栓皮栎种群的关联性,这调整了栓皮栎种群空间竞争关系,有利于大径级林木个体的培育。该研究可以为开展抚育间伐对林木种群的影响的研究提供理论依据,也可以为制定科学合理的抚育技术措施提供参考。

Effects of Forest Thinning on the Spatial Distribution Patterns of Quercus variabilis Population

Forest thinning is an important management measure to improve the growth conditions of retained trees,which has an important impact on the stand structure and dynamics.In order to explore the internal mechanism of the effects of forest thinning on the spatial structure and pattern of forest population,thinning experiment was conducted in a Quercus variabilis plantation forest,where one randomly selected 100 m×100 m quadrats at each of thinned and unthinned sites were sampled,and the information of positioning for each trees at each quadrats were surveyed.The Quercus variabilis population was divided into three age groups of sapling(2 cm≤DBH<5 cm),small tree(5 cm≤DBH<13 cm)and large tree(DBH≥13 cm)using the method that diameter of breast height(DBH)structure replaced the age structure,and the function of g(r)and g12(r)based on Ripley's K-function were then used to analyze the spatial distribution point patterns of Quercus variabilis population,and spatial associations with different growth stages of Quercus variabilis population.The results showed that the spatial point distribution pattern of Quercus variabilis population in the thinned and unthinned plots shifted from clustered on the distance scales of 0?16 m and 0?33 m,to random in the distance scales larger than 16 m and 33 m,respectively.The number ratio of saplings,small trees and large trees of thinned and unthinned plots were 8?741?699 and 261?1134?683,respectively.The spatial point distribution pattern of the saplings,small trees and large trees of Quercus variabilis population in thinned plot showed a uniform or clustered distribution pattern on distance scales of 0?14 m,1?16m,0?6 m,but a random distribution pattern on other distance scales.Only on the distance scale of 0?6 m,certain associations between saplings,small trees and large trees of Quercus variabilis were observed,and similar results could been found in larger distance scale for unthinned plot,for example,there was a significant positive correlation between the young trees and the big trees in the 6?38 m distance scale.Therefore,forest thinning shaped the Quercus variabilis population to some extent to appear a random distribution on a larger distance scale,and weakened its association between different age groups,which adjusted the spatial competition relationship of Quercus variabili spopulation,and had great benefit to the cultivation of large-scale timber.Our study could provide a theoretical basis for the study of the effects of forest thinning on forest population,and provide a reference basis for the development of scientific and reasonable forest tending technical measures.