延河流域植物功能性状变异来源分析

由于遗传背景对植物性状的影响，直接研究环境与植物性状的关系有一定的不确定性。因此，研究植物性状对环境变化的响应，必须明确遗传背景与环境对植物性状的相对影响，以排除遗传背景的作用。本研究以延河流域为研究区域，选取19个典型样点，调查了64种植物的6种功能性状，即比叶面积(SLA)、比根长(SRL)、叶片氮(LN)与磷含量(LP)、根的氮(RN)与磷含量(RP)，并通过野外定位信息，从已有专题信息图中获取环境数据，采用方差分析和逐步回归的方法，分析了植物性状变异来源，研究了不同科属植物对环境变化的响应。结果表明：(1)不同气候条件下，植物的SLA、LN和RP性状存在显著差异，森林区植物SLA、RP较草原区植物偏低33.02%、19.94%，而LN则高于草原区植物19.33%；不同科属植物之间SLA、SRL、LN和RN存在显著差异，豆科植物具有较高的SLA、LN、RN，分别高出研究区平均值16.33%、65.23%、97.78%，而禾本科植物SRL具有最大值，高出平均值103.11%；(2)遗传背景差异是植物性状变异的首要决定因子，遗传背景对SRL、LN、RN变异的解释比例分别达到了27.86%、32.78%、42.70%，而LP、RP则受环境因子的影响更大，环境因子对LP、RP解释比例分别达到24%、15.58%；(3)豆科Leguminosae、禾本科Poaceae、菊科Asteraceae、蔷薇科Rosaceae植物性状的环境因子逐步线性回归模型，表明不同科属的植物对环境因子是否产生响应和响应的方式均不相同，豆科和禾本科植物对区域性气候条件较为敏感，而菊科和蔷薇科植物受地形因子和土壤含水量影响较大。

Source of variation of plant functional traits in the Yanhe river watershed: the influence of environment and phylogenetic background

Identifying the impact of phylogeny and environmental change on variation in plant traits is an important component of attempts to understand the adaptability and response of vegetation to environmental change. The relationship between plant functional traits and environmental change is easier to measure with consistent phylogeny. In the study reported here we analyzed the source of variation of six plant functional traits in 47 species from 19 sample sites in the Yanhe river watershed of China. The 19 sample sites surveyed in this study were selected based on the climatic gradient, as represented by vegetation zonality. The six plant functional traits investigated were specific leaf area (SLA), specific root length (SRL), and the mass-based characteristics of leaf nitrogen concentration (LN), leaf phosphorus concentration (LP), root nitrogen concentration (RN), and root phosphorus concentration (RP). To analyze the impact of environmental change on variation in plant traits, we also selected terrain factors and soil moisture content as environmental variables. We then used variance analysis to differentiate the relative influence of phylogenetic background (as represented by plant family), climatic conditions, terrain factors, and soil moisture content on trait variation, and used a stepwise regression method to analyze the response of traits to environmental change in plants sharing a similar hereditary background. Our results include the following observations: (1) significant differences were uncovered with respect to SLA, LN, and RP under different climatic conditions. We found that SLA and RP of forest plants were 33% and 20% higher respectively, than SLA and RP of steppe plants, whereas LN of plants from steppe sites was 19% higher than that of plants from forest sites. Significant differences were also detected in SLA, SRL, LN, and RN among different families. Average SLA, LN, and RN values measured from Leguminosae species were 16%, 65% and 98% higher respectively, than average values obtained for all studied plants. Species from the family Poaceae had the highest SRL, which was 1.03-fold higher than the overall average; (2) variation of plant functional traits was mainly determined by plant phylogenetic background, which accounted for 27.86, 32.78, and 42.70% of observed variation in SRL, LN, and RN, respectively. On the other hand, LP and RP were mainly influenced by the environment, which accounted for 24% and 15.58%, respectively, of observed variation in LP and RP; (3) stepwise linear regression models revealed that species from different families responded differently to environmental factors. Members of the families Leguminosae and Poaceae were more sensitive to regional hydrothermal conditions, whereas Asteraceae and Rosaceae species were more strongly affected by local microenvironments. After removing influences attributable to phylogenetic background, we were able to clearly and reliably discern relationships between functional traits and the environment. In the Yanhe river watershed, plant phosphorus content was mainly determined by terrain factors and soil moisture content. In contrast, plant nitrogen content, SLA, and SRL were mainly affected by plant phylogenetic background. To summarize, plant phylogenetic background plays a controlling role in the influence of the environment on plant traits in the Yanhe river watershed of China.