柳杉人工林近自然改造过程中林分空间的结构变化

在四川省崇州林场进行的柳杉(Cryptomeria fortunei)人工纯林近自然森林改造过程中,将有培育前途的柳杉立木作为"目标树",其间混生的杉木(Cunninghamia lanceolata)多作为"生态目标树"予以保留,"目标树"周围影响其生长的树木作为"干扰树"予以择伐;在择伐后,又在林分中补植入楠木(Phoebe zhennan)和连香树(Cercidi-phyllum japonicum)等乡土阔叶树种,以加速其向混交林方向演替。本文采用物种隔离指数(CS)、大小分化度(T)和聚集指数(R),分析补植后林分的空间结构变化。结果表明,补植入阔叶树种后,林分的混交程度与物种隔离程度大大提高;同时,林木胸径的大小分布呈现出明显的两极分化状态;而树木的分布格局则在改造过程中保持着均匀分布的格局。这一研究有助于为人工林的近自然经营理论与实践提供有益的尝试和借鉴。

Spatial Structure Dynamic of the Close-to-Nature Forestry Management of Cryptomeria fortunei Plantation

This article reports a case of close-to-nature forest improvement in Cryptomeria fortunei plantation at Chongzhou forest farm, in southwestern China. In this investigation, the researchers selected some Cryptomeria fortunei which could be cultivated well as "target trees" , and the companion species Cunninghamia lanceolata were reserved as "ecological target trees" , other surrounding trees were selectively cut as "disturbing trees" . After selective cutting, some native broad-leaved saplings, i.e. Phoebe zhennan and Cercidiphyllum japonicum were interplanted into the stand. Thereby the stand spatial structure of Cryptomeria fortunei plantation could be optimized reasonably, so that the paces of turning pure plantation into fixed forest were anticipated to be accelerated. A detailed analysis of forest spatial structure was made after the interplanting, based on Isolation Index (CS), size differentiation (T) and aggregation index (R). Through investigating spatial structures dynamic in the process of the close-to-nature forestry management, we conclude that the degree of mingling and spatial segregation was ameliorated well after the interplanting, CS indicates complete species mingling in the stands. As for as size differentiation, it was dramatically polarized after interplanting from the values of T. The to distribution pattern was characterized as uniform pattern consistently, despite selective cutting and interplanting treated. Case study also provides initial values and stand structures for single-tree models from estimated qualitative stand characteristics. It has shown that from given spatial forest structures one can possibly conduct the close-to-nature forest management in terms of the theory and practice, however, it has yet to be proved by further appropriate analysis.