不同抚育间伐方式对平原生态林空间结构的影响

Effects of different thinning types on the spatial structure of plain ecological plantation

为探讨不同抚育间伐方式对北京市平原生态林林分空间结构的影响,在北京市通州区选取旱柳、国槐和白蜡等代表性林分布设9个固定样地。在选取目标树后,每个林分类型分别采取干扰木采伐、群团状采伐以及带状间伐,采用优化后的大小比数、角尺度和密集度3个常用的林分空间结构指标,分析平原生态林空间结构现状以及间伐对目标树及林分空间结构的影响。利用3个指标构建空间结构综合指数(CSSI)来综合评价不同间伐方式对北京市平原生态林空间结构的影响。结果表明:(1)CSSI结合了角尺度、密集度和优化后的大小比数,适用于北京平原生态林的空间结构评价。(2)以国槐、白蜡和旱柳为代表的平原生态林间伐前空间分布格局呈均匀分布,大部分林木呈中庸状态,林分比较密集,白蜡和旱柳的空间结构优于国槐。(3)抚育间伐能显著优化平原生态林空间结构,尤其对于国槐等保留密度较高的林分优化作用明显。(4)对于不同树种来说,改善空间结构的最优间伐方式不尽相同,但对于目标树空间结构单元来说,针对目标树的干扰树采伐优化程度最为明显。

In order to investigate the effects of different thinning types on the spatial structure of ecological forest in Beijing Plain,nine permanent plots were established in Tongzhou District,Beijing,including representative forest types such as Salix matsudana,Styphnolobium japonicum and Fraxinus chinensis.After selecting the target trees,each stand type was cut with interference,group and strip thinning respectively.The spatial structure of plain ecological forest and the effect of thinning on the spatial structure of target tree and stand were analyzed by using the optimized spatial ratio,angular scale and density.The Comprehensive Spatial Structure Index(CSSI)was constructed to evaluate the effects of different thinning methods on the spatial structure of ecological forest in Beijing Plain.The results indicated that:(1)CSSI combined angular scale,density,and optimized size ratios,which was suitable for the spatial structure evaluation of ecological forests in Beijing Plain.(2)The spatial distribution pattern of plain ecological forests represented by S.japonicum,F.chinensis and S.matsudana was evenly distributed before thinning,most of the trees in a moderate state.The forests were relatively dense,and the spatial structure of F.chinensis and S.matsudana was better than that of S.japonicum.(3)Thinning could significantly optimize the spatial structure of plain ecological plantation,especially for forests with high density such as S.japonicum.(4)For different tree species,the optimal thinning methods to improve the spatial structure were different,but for the spatial structure unit of target tree,the optimal degree of interference tree thinning was the most obvious.