生境异质性对鼎湖山常绿阔叶林群落功能多样性的影响

Effects of habitat heterogeneity on community functional diversity of Dinghu Mountain evergreen broad-leaved forest

关键词:  群落生态学, 功能多样性, 生境异质性, 群落共存机制, 适应性策略

Key words:  community ecology, functional diversity, habitat heterogeneity, species co-existence mechanisms, adaptive strategy

摘要:

物种共存机制一直以来是群落生态学的研究热点。为了探讨异质生境条件下鼎湖山常绿阔叶林群落功能多样性变化,找到其变化的主要环境驱动因子,该研究利用位于鼎湖山20 hm²监测样地第2次群落调查数据并选择代表不同生境(海拔和地形)的27个样方(20 m×20 m),于2013年夏季在样地内所选样方中测定所有胸径≥1 cm树种的叶片功能性状。所测性状包括形态学性状(比叶面积、叶片干物质含量、叶面积以及叶片长宽比)和化学计量学性状(叶片碳、氮、磷的含量),结合地形和土壤数据并通过分析功能多样性随环境梯度的变化,探讨了环境过滤和竞争在鼎湖山群落物种共存中的相对重要性。结果表明:功能分歧度和群落权重平均值与环境因素关系密切,尤其是海拔、凹凸度和土壤养分。环境条件较好区域(微尺度高海拔、高凹凸度和土壤养分含量)的植物采取统一的养分有效保存(低SLA,高LDMC)的适应策略(功能分歧度低),环境过滤所起作用更强; 植物在相反的环境条件下,采取快速生长策略(高SLA,低LDMC),能够更好地适应环境的变化,且性状变化是多样的(功能分歧度高),在该条件下竞争作用更为显著。叶面积和叶片氮含量的分歧度在环境条件较好的区域增大,这与其他功能性状不一致,说明不同生态位轴(环境因素)影响不同性状的分歧度变化,并且在局域尺度上植物为了更好地适应环境变化采取了多样的适应策略。

Abstract:

Species co-existence mechanisms have long been one of the core topics in community ecology. To explore the changes in community functional diversity of Dinghushan evergreen broad-leaf forest under the heterogeneous habitats and to find out the main driving factors of the functional diversity varations, based on the second community survey data of the 20 hm² forest dynamics plot in Dinghushan National Nature Reserve, 27 subplots(20 m×20 m)were selected according to the changes of relative elevation and topograph. These 27 subplots can stand for the heterogeneous habitats in Dinghushan evergreen broad-leaved forest. Leaf functional traits of all the trees with DBH(diameter at breast height)≥1 cm in the 27 subplots were measured to calculate the functional diversity(functional dispersion and community weighted mean are caculated as the functional diversity in this paper)during the summer of 2013. The measured traits included morphological traits(specific leaf area, leaf dry matter content, leaf area and leaf lenth to leaf width ratio)and stoichiometric traits(leaf carbon, nitrogen, phosphorus content). Combining with the topographic and soil information, we analysed the main environmental factors that influence the variation of functional diversity. To elucidate the relative importance of environmental filtering and competitive interactions for species co-existence of Dinghushan evergreen broad-leaved forest, we inferred the shifts in functional diversity patterns across environmental gradients. The results indicated that functional divergence and community-weighted mean were in close relation with environmental factors, especially elevation, convexity and soil fertility. In the optimal environmental conditions(high relative elevation, high convexity and higher soil nutrient content), plants adopt the similar(functional divergence decreased)adaptive strategy of efficient conservation of nutrient(low SLA, high LDMC), which suggested that environmental filtering played a stronger role; while in the adverse environmental conditions(low relative elevation, low convexity and lower soil nutrient content), the traits were various(functional divergence increased)and use fast growing strategy(high SLA, low LDMC), since competitive interactions might play a key role. The functional divergence of leaf area and leaf nitrogen contents increased in better environmental conditions(high relative elevation, high convexity and higher soil nutrient content), and these two traits(leaf area and leaf nitrogen content)were opposite to the others(specfic leaf area, leaf dry matter content, leaf length to leaf width ratio, leaf carbon and phosphorus content). These results indicated that different niche axes(environments)had different importances in the changes in functional traits dispersion, and illustrated that we could use plants diverse strategies to adapt to heterogeneous environments in local scale.