南亚热带典型针叶林改造成乡土阔叶林后林下植物功能群的变化及其环境解释

Changes of plant functional group in understory and environmental interpretation in the transformation of typical coniferous plantation to native broadleaved species plantation in south subtropical China

把针叶林改造成珍贵乡土阔叶林,是近年来亚热带人工林常见的营林措施之一。为了探究这种营林措施对林下植物功能群的影响,通过调查该地区典型针叶林和珍贵乡土阔叶林的林下植被,对比了针叶林和阔叶林之间的林下植物物种丰富度和物种组成的差异,并和环境因子进行多元分析。结果表明:(1)阔叶林林下木本、禾草、蕨类和藤本功能群的物种丰富度相对针叶林有所减少,其中红椎(Castanopsis hystrix)和米老排(Mytilaria laosensis)林的木本和禾草功能群物种丰富度的下降达到显著水平(P <0.05);(2)主成分分析(PCA)结果表明,针叶林阔叶化后其林下植物功能群发生了明显的变化;(3)冗余分析(RDA)结果揭示了叶面积指数、平均叶倾角、土壤碳氮比、土壤全磷、凋落物碳氮比和透射系数是驱动林下植物功能群变化的主要因子,分别解释了林下植被功能群变异的33%、13%、6%、5%、2%和2%。(4)针叶阔叶化引起的冠层结构变化是导致林下植物功能群变异的主因,而土壤理化性质的变化对其影响较小。

Transforming typical coniferous plantation to native broadleaved species plantation is a major management for plantation in subtropical China. To explore the effects of transforming coni- ferous to native broadleaved species plantation on the plant functional groups.in understory, we investigated the diversity and community composition of understory, and analyzed the role of environmental variables on understory functional groups by multivariable statistics in southern China. The richness of understory species （woody, gramineous, vern and vine groups） in the broadleaved plantations was lower than that in the coniferous plantations, especially for xylophyta andherb groups in the Castanopsis hystrix and Mytilaria laosenis plantations （P 〈 0.05 ）. The first principal component axis significantly separated the understory composition of plant functional groups between the coniferous and broadleaved plantations by Principal Component Analysis （PCA）. Leaf area index, average leaf angle, soil C/N, soil total phosphorus content, litterfall C/N and light transmittance well explained the variations in the understory plant functional groups by redundancy analysis （RDA）, with values of 33%, 13%, 6%, 5%, 2% and 2%, respectively. These results suggest that changes of canopy structure induced by forest transformation rather than soil physicochemical properties result in the variation of the understory plant functional groups.