择伐对思茅松自然种群结构和空间分布格局的影响

思茅松是云南省重要的材脂兼用树种,而择伐是思茅松天然林管理的有效手段,也是获取木材的重要途径。基于对云南省景谷县思茅松天然林的样地调查数据,采用种群径级结构代替年龄结构、Ripley的L函数点格局等方法,对思茅松天然林在不同强度择伐10a后的种群结构和空间分布格局及其不同发育阶段在不同尺度下的相互关系进行了系统研究和分析。结果表明:择伐10a后3种类型的思茅松自然种群的胸径、树高之间呈显著的正相关且可用幂指数模拟预测模型。未择伐的思茅松种群呈衰退型,轻度择伐(12.9%)后种群呈稳定型,中度择伐(29.3%)后的种群属增长型,适当的中度择伐有利于自然种群的更新;未择伐与中度择伐后的思茅松种群分布格局整体呈随机型,但后者较前者更趋向于均匀分布,轻度择伐后的思茅松种群分布格局随着尺度的增加由随机转向聚集分布。择伐对不同径级思茅松天然林种群空间分布格局有重要影响,未择伐的思茅松自然种群随着发育阶段的发展,多数尺度上由随机分布逐渐转变为聚集分布,至大树则又以随机分布为主;轻度择伐和中度择伐的思茅松自然种群则随着发育阶段的发展而由完全的随机分布逐渐转变为聚集分布,中度择伐的聚集分布则更为明显。思茅松不同发育阶段间在所有尺度上基本都呈显著正相关,表明思茅松种群种内竞争弱,有利于种群的维持。

Influences of selective cutting on the structure and spatial distribution patterns of a natural population of Pinus kesiya var. langbianensis

Pinus kesiya var. langbianensis is an important source of timber and resin production in Yunnan Province, China. In forest management, selective cutting is an effective means of P. kesiya forest management, and is also the primary way to obtain timber. This study is based on data from sampling plots of a P. kesiya natural forest in Jinggu County, Yunnan Province. The method of substituting space for time using the L function (based on the derivatives of Ripley''s K function) was used to analyze the influence of 10 years of different selective cutting intensities on the structure and spatial distribution patterns of a P. kesiya natural forest population. This study also investigated the relationship between P. kesiya''s development stages and spatial scales. The results showed a significantly positive correlation between DBH and tree height after 10 years of selective cutting, and are used as a power model to simulate a prediction model. The P. kesiya population without selective cutting showed a decling population type. The population under low intensity selective cutting (12.9%) showed a stable type, and the diameter-class structure of the population under medium intensity selective cutting (29.3%) presented an invert "J" shape, was an expanded type, and had more individuals with the small diameter class. This indicates that medium intensity selective cutting is useful for promoting regeneration. Both P. kesiya populations without selective cutting and with selective cutting under medium intensity were randomly distributed, but the latter tended to be more regularly distributed than the former. The spatial pattern of low intensity cutting changed from random to aggregated with the increase of scale. Selective cutting intensities changed the spatial distribution patterns of different DBH classes, and also influenced the overall distribution patterns of P. kesiya. With the progression of developmental stages, the distribution of trees under no selective cutting changed from random to aggregate. For large trees, the distribution pattern was most often random; the distribution patterns under low and medium intensity cutting changed from completely random to aggregated with the development, and an aggregated distribution at medium intensity selective cutting is more apparent than low intensity selective cutting. The different growth stages of P. kesiya populations were significantly positively correlated at all scales. Intraspecific competition was weak, which had the advantage of population maintenance. Low and medium intensity selective cutting may enhance the stability of the forest community spatial structure. Medium selective cutting is more effective at forest structure maintenance than low selective cutting. Our results have important theoretical and practical implications for establishing a development plan for the sustainable management of P. kesiya forests.