不同间伐强度对南亚热带杉木人工林林下植物功能群的影响

Effects of different thinning intensities on undergrowth plant functional groups in subtropical Cunninghamia lanceolata plantations

间伐作为我国森林经营的主要措施之一,对提高森林生态系统内部生物多样性起着不可忽视的作用。然而,不同间伐强度对森林林下植物功能群的影响程度尚不明确。以广西凭祥热林中心经过4种不同强度抚育间伐8年后的杉木人工林为研究对象(轻度间伐ST,34%;中度间伐MT,50%;重度间伐HT,74%;不进行间伐的对照,CK),对林下植被及其环境因子进行调查和测定。研究结果表明:不同间伐强度对禾草植物功能群的物种丰富度均无显著影响(P>0.05),MT显著增加杂草植物功能群的物种丰富度(P<0.05),HT显著提高蕨类植物功能群的物种丰富度(P<0.05),ST显著增加木本植物功能群的物种丰富度(P<0.05),与CK相比,ST、MT和HT均能显著增加藤本植物功能群的物种丰富度(P<0.05);不同间伐强度对禾草和木本植物功能群的重要值均无显著影响(P>0.05),但HT显著降低了杂草植物功能群的重要值(P<0.05),ST显著降低了蕨类植物功能群的重要值(P<0.05),ST显著增加藤本植物功能群的重要值(P<0.05)。主成分分析(PCA)表明,ST和HT的林下植物功能群组成和分布与对照组相比均发生了显著的变异。方差分解分析(Variation partitioning analyses)结果显示,林分和土壤因子对林下植物功能群变异的解释率相似,二者在决定杉木人工林林下植物功能群变异中都起着重要作用。

As one of the main plantation management strategies,thinning plays an important role in improving biodiversity of forest ecosystem in China.However,the effects of different thinning intensities on undergrowth plant functional groups are still unclear.We investigated the changes of four different thinning intensities for eight years(slight thinning,ST,34%;moderate thinning,MT,50%;heavy thinning,HT,74%;no thinning control,CK)on the understory vegetation and its related environmental factors in Cunninghamia lanceolata plantations in subtropical China.We found that the different thinning intensities had no significant influence on the grass species richness of plant functional groups(P>0.05).MT significantly increased weed species richness of plant functional groups(P<0.05),while HT significantly increased fern species richness of plant functional groups(P<0.05).ST significantly increased the species richness of woody plant functional groups(P<0.05).The ST,MT and HT could significantly increase vine species richness of plant functional groups(P<0.05).In addition,the different thinning intensities had no significant effect on the important values of the functional groups of grass and woody plants(P>0.05),but HT significantly reduced the important values of the functional groups of weeds(P<0.05).Meanwhile,the ST significantly decreased the important values of the functional groups of ferns(P<0.05),and ST significantly increased the important values of the functional groups of vines(P<0.05).Principal component analysis(PCA)showed that the composition and distribution of understory plant functional groups of ST and HT were significantly different from those of the no thinning control groups.Overall,the interpretation rates of forest and soil factors on the variation of understory plant functional groups that examined by the variation partitioning analyses were similar.And the forest and soil factors could jointly determine the variations of understory plant functional groups in Cunninghamia lanceolata plantations.