环境及遗传背景对延河流域植物叶片和细根功能性状变异的影响

研究环境筛选作用和植物系统发育背景对植物群落构建产生的影响,有助于理解植物在生长过程中对资源的分配利用和对环境的适应规律。以延河流域3个植被带(森林带、森林草原带及典型草原带)稳定的自然植物群落为研究对象,调查了31个样地107种植物,隶属于35个科78个属,测量了6种叶片和3种细根性状。分别对3个植被带和不同植物科植物的叶片和细根性状做单因素方差分析,结果表明:叶片氮含量和细根氮含量在3个植被带间无显著差异,叶厚度、比叶面积、叶组织密度、叶片磷含量、叶片氮磷比、比根长、根组织密度在3个植被带间差异极显著。由南向北随着气候干旱的加剧,植物通过调节叶片和细根性状,表现出了不同的适应策略:森林带植物叶片相对生长速率高,根系防御力强;森林草原带植物叶片防御力强,根系相对生长速率快。不同科的植物在相同的环境条件下,对于资源的竞争力和胁迫的忍耐力也有所不同,比如豆科植物具有远远高于其他科的叶片和细根氮含量,但是对养分的利用效率并不高。GLM分析结果说明,所涉及的植物功能性状的空间变异主要来自于年均降雨量的变化及植物科的差异,如16.26%的比叶面积的变异可由年均降雨量变化解释,4.02%可由植物科的差异解释。物种水平上,叶厚度、比叶面积、叶组织密度、比根长、根组织密度、叶片磷含量是对气候干燥度变化响应敏感的植物功能性状,其空间变异主要由环境差异所致。延河流域的植物群落在形成过程中,存在明显的环境筛选效应。这表明,环境异质性在植被恢复实践中必须予以考虑。

The influence of environment and phylogenic background on variation in leaf and fine root traits in the Yanhe River catchment, Shaanxi, China

Abiotic and biotic processes may both affect plant community assembly. Our objective is to explore the relative influence of environment and phylogenic background on variations in plant functional traits in the Yanhe River catchment, Shaanxi, China. The goal is to provide helpful information related to understanding the mechanisms and interactions influencing plant adaptation as they relate to environmental factors.This study measured six leaf traits and three fine root traits of 107 species belonging to 35 families in 31 sample plots in three vegetation zones (forest, forest-steppe, steppe) on the Loess Plateau. One-way ANOVA was used to describe the variation among three vegetation zones and plant families. We then used redundancy analysis (RDA) to analyze the relationships between plant functional traits and meteorological factors. Principal component analysis (PCA) was used to detect important relationships between plant functional traits and plant families. Finally, we used a General Line Model (GLM) to evaluate the relative contribution of environmental factors and plant phylogenic background to variations in plant functional traits.The results show: (1) There were no significant differences in leaf nitrogen concentration per mass (LN) and fine root nitrogen concentration per mass (RN), but significant differences were found in leaf thickness (LT), specific leaf area (SLA), leaf tissue density (LTD), leaf phosphorus concentration per mass (LP), the ratio of leaf nitrogen concentration per mass and leaf phosphorus concentration per mass (LN:LP), specific root length (SRL), fine root tissue density (RTD)between the three vegetation zones. The values of these various parameters increased from the south to the north as climatic aridity intensified, plants adjusted plant functional traits to adapt to different environmental conditions. Plants in the forest zone had higher competitive ability with more rapid leaf growth rates and with roots having a higher resistance to stress and damage. Plants in the forest-steppe zone had higher root growth rates and had leaves with greater resistance to stress and damage. (2) Plants from different plant families used different strategies to adapt to environment; that is different species perform differently when provided with the same resources and environmental gradients; for example, leaf nitrogen concentration per mass and root nitrogen concentration per mass of Leguminosae was far greater than that of other families, but the nutrient absorption efficiency of species in the Leguminosae was not high. (3) Average annual precipitation and the mean temperature of the warmest month were two main factors which had significant effects on variations in traits along environmental gradients in the area; for example, 16.26% of the observed variance in SLA can be explained by average annual precipitation and 4.02% can be explained by plant family. The explained variance of plant functional traits varied as those same functional traits varied and there were obvious environmental screening effects in the process of the formation of plant communities in the Yanhe River watershed. Six traits, LT, SLA, LTD, LP, SRL, and RTD were sensitive to climatic aridity at the species level; the spatial variation was caused primarily by environmental differences. In conclusion, environmental heterogeneity must be considered during vegetative restoration on the Loess Plateau.