森林与灌丛的灌木性状揭示不同的生活策略

Traits of shrubs in forests and bushes reveal different life strategies

灌木是森林和灌丛生态系统的重要组成部分,探究森林与灌丛灌木功能性状的差异,可揭示灌木在不同生境的适应策略。该研究以金华北山森林群落林下灌木层、低山灌丛和山顶灌丛共24个样地中的优势灌木为研究对象,分析叶片和小枝9个功能性状在3种生境下的总体差异,以及种间、种内变异和不同生活型的差异。结果表明:1)9个性状在3种不同生境下存在差异。林下灌木具有较大的叶面积和比叶面积,较小的叶干物质含量、叶和小枝的组织密度,低山灌丛相较于山顶灌丛具有较大的叶厚度、叶组织密度和较小的比叶面积、小枝干物质含量。2)林下灌木的比叶面积、小枝直径、小枝组织密度和小枝干物质含量的种内种间变异系数最大,低山灌丛的比叶面积、叶和小枝的干物质含量、叶和小枝的组织密度的种内种间变异系数最小。3)不同生活型间,林下常绿灌木的叶厚度、叶组织密度、叶干物质含量显著高于落叶灌木,落叶灌木的比叶面积显著高于常绿灌木,而山顶灌丛叶厚度和比叶面积的差异规律与林下灌木相同,叶组织密度和叶干物质含量的差异与其相反。4)影响灌木性状的主要因素是物种以及物种和生境的交互作用。总之,森林群落林下灌木形成较大叶面积和比叶面积,较小叶和小枝组织密度、叶干物质含量的性状组合,以快速生长而适应光照较弱、竞争作用强的林下环境,是资源获取型策略;低山灌丛和山顶灌丛具有较大叶厚度、组织密度、干物质含量和小枝组织密度和较小叶面积、比叶面积等一系列储存养分、慢速生长的性状组合,属于资源保守型策略。灌木植物性状的不同组合及其所反映的不同生活策略,对亚热带地区退化植被的生态恢复具有指导意义。

Aims Shrubs play important roles in both forest and bushland ecosystems.This study aims to identify the adaptative strategies of shrubs in different habitats by analyzing the differences in functional traits of shrubs grown in understory of forest communities and in two bushlands.Methods Nine functional traits for leaves and twigs were measured on samples collected from the dominant shrub species in 24 plots distributed in three contrasting habitats:forest understory,low mountain bushes,and bushes on the mountaintop,in Beishan Mountain of Jinhua,Zhejiang Province.The overall differences among habitats,inter-and intra-specific variations,and differences between life forms in the functional traits of shrubs were tested by statistical analysis.Important findings The nine plant traits differed for shrubs grown in the three habitats.The shrubs in forest understory had higher leaf area(LA)and specific leaf area(SLA),lower leaf dry-matter content(LDMC),leaf tissue density(LTD)and twig tissue density(TTD),while those in low mountain bushes had greater leaf thickness(LT)and LTD,smaller SLA and twig dry-matter content(TDMC),compared with shrubs from bushes on the mountaintop.The inter-and intra-specific variation coefficients of SLA,twig diameter(TD),TTD,and TDMC were greatest in shrubs of the forest understory,whereas the inter-and intra-specific variation coefficients of SLA,LDMC,TDMC,and TTD were smallest in shrubs of low mountain bushes.Among different life forms,the understory evergreen shrubs had significantly higher LT,LTD,and LDMC,and lower SLA,than that of deciduous shrubs.The differences in LT and SLA between evergreen and deciduous shrubs of the mountaintop bushes were the same as the understory shrubs,but the differences in LTD and LDMC were reversed.Species and its interaction with habitat are the major factors affecting the shrub traits.In short,compared to the shrubs from bushes,the understory shrubs in forest communities form a series of trait combinations with greater LA and SLA,and smaller LTD,TTD and LDMC for faster growth in order to adapt to the understory environment with less light and stronger competition;this is a quick investment-return(resource acquisitive)strategy.Shrubs from low mountain bushes and the mountaintop bushes are associated with a series trait combinations with greater LT,LTD,LDMC and TTD,and smaller LA,SLA for storing more nutrients and growing slower;this is a slow investment-return(resource conservative)strategy.Different combinations of shrub functional traits and their various life strategies can provide guidance to the ecological restoration of degraded vegetation in the subtropical region of China.