择伐强度对杉阔混交人工林空间结构的影响

利用混交度、角尺度及以大小比数为权重的空间优势度和树种优势度4个空间结构参数,对比分析不同强度(中度34.4%、强度47.1%和极强度69.5%)择伐下杉阔混交人工林林分空间结构变化,探讨择伐强度对杉阔混交人工林空间结构的影响.结果表明:从混交程度看,择伐强度越大,越易导致林木单种聚集.与伐前相比中度择伐后林分和主要树种的平均混交度都有所增加,强度和极强度择伐后林分平均混交度明显降低,杉木平均混交度增加而木荷则显著降低;不同择伐强度在一定程度上都改善了林木的空间分布格局,中度择伐后林分的单木聚集分布改善最为明显;从空间优势看,中度或强度择伐能够维持及提高林分和主要树种空间优势度,有利于发挥林分生长潜力.综合来看,中度择伐后林分空间结构趋于合理,建议采用中度择伐作为优化杉阔混交人工林林分空间结构的有效手段.

Influence of Selective Intensity on Stand Spatial Structure of Cunninghamia lanceolata-Broadleaved Mixed Plantation

To analyze the effect of selective logging on stand spatial structure of Cunninghamia lanceolata-broadleaved mixed plantation, four kinds of structure parameters were used, including mingling degree, uniform angle index,spatial and species advantage degree based on the neighborhood comparison. The experimental stand were harvested by selective cutting of different intensities(medium intensity of 34. 4%,high intensity of 47. 1%and over-high intensity of 69. 5%). We analyzed the changes of stand spatial structure after selective cutting,the results showed that aggregation of congeneric trees was easier to happen under higher intensity cutting. In addition,the mingling degree of stand improved under the cutting intensity while reduced under cutting intensity. In terms of mingling degree of Cunninghamia lanceolata and Schina superba,the both increased under medium intensity cutting. In stands under high intensity and over-high intensity cutting, Cunninghamia lanceolata surrounded by more different species than before while Schina superba. Then we found that selective cutting,to some extent,improved the spatial distribution situation and the aggregation distribution changed obviously under medium intensity cutting. Furthermore,the results also indicated that stand and species spatial advantage degree in uncut stand were lower than before while medium and high intensity cutting showed advantage to maintain and enhance stand growth potential. Comprehensively, we should take medium intensity of selective cutting as an effective method to optimize spatial structure of Cunninghamia lanceolata-broadleaved mixed plantation.