南亚热带细叶云南松林大径木择伐后的空间格局

Spatial patterns of trees in a south subtropical Pinus yunnanensis var. tenuifolia forest after selective logging of large-sized trees

择伐是实现异龄林可持续经营的重要途径。它在改变物种组分与比例的同时,也改变了物种的分布及其关联。然而,很少有人关注在较长时间尺度上大径木择伐后森林群落结构的恢复状况。本研究采用双相关函数g(r)和标记相关函数kmm(r)分析了中国西南地区南盘江流域老龄林遭受大径木(DBH≥20 cm)择伐46年后形成松杉混交林的空间格局。结果表明:1)该群落生境异质性不明显,整体上呈随机分布;2)小树在很小尺度上(r=0~1 m)聚生在一起,同时种内聚集程度较高。3)6个优势种(n≥30)的空间分布随尺度的增加而趋向随机分布。其中,细叶云南松(Pinus yunnanensis var.tenuifolia)、栓皮栎(Quercus variabilis)、铁坚油杉(Keteleeria davidiana)在中小尺度上(r=0~8 m)呈轻度的聚集分布,而西南桦(Betula alnoides)呈强列的聚集分布。珍珠花(Spiraea thunbergii)和盐肤木(Rhus chinensis)几乎在所有尺度上(r=0~20 m)都是聚集分布;4)种间无明显排斥或竞争作用。据此,我们认为,大径木择伐林经过较长时间恢复后,能够形成相对稳定的结构,种内竞争已成为推动群落演替的主要驱动力。

Selective logging is an important way for sustainable management in multi-age forests.It not only changes the composition and proportion of tree species,but also alters their spatial distribution and correlation.Little attention has been paid to the restoration of forest community structure after selective logging of big trees at a long-term scale.In this study,pair correlation function g(r)and mark correlation function kmm(r)were used to analyze the spatial pattern of a pine-fir secondary forest that was formed from a forest with large-sized trees(DBH≥20 cm)being intensely harvested 46 years ago,in Nanpan River basin,southwest China.The results showed that:(1)This community showed no obvious habitat heterogeneity and presented a random distribution on the whole;(2)The small-sized trees were clustered together at very small scales(r=0-1 m),while the aggregation degree of same species was relatively high;(3)The spatial distribution of the six dominant species(n≥30)tended to be random with the increases of scale.Among them,Pinus yunnanensis var.tenuifolia,Quercus variabilis and Keteleeria davidiana showed a mild aggregation distribution at small and medium scales(r=0-8 m),Betula alnoides had a strong aggregative pattern,while Spiraea thunbergii and Rhus chinensis were clumped at most scales(r=0-20 m);(4)There was no obvious interspecific exclusion or competition.Our results indicated that the large-sized trees logged forest had formed a relatively stable spatial structure after long-term restoration and that intraspecific competition has become the main force for community succession.