黄土丘陵区植物叶片与细根功能性状关系及其变化

通过植物叶片功能性状(比叶面积、叶组织密度、叶氮含量)和细根功能性状(比根长、根组织密度、根氮含量)间的相互关系,分析植物对环境的适应途径；然后根据性状间的差异进行了层次聚类,将物种划分为3大功能型,并分析了不同功能型对环境的适应策略.结果表明:黄土丘陵区延河流域149种植物的叶氮含量与比叶面积和根氮含量正相关、与叶组织密度负相关,比根长与根组织密度负相关,除了根氮含量,其余根性状与叶性状不相关.此外,功能性状间关系变化和适应策略在不同功能型之间也存在差异.功能型1的植物具有最强的耐旱力和防御力；功能型3的植物具有最强的养分维持能力用以对抗营养贫瘠的环境；功能型2的植物居中,生长速率最高,具有较强的竞争力、分布最广；根据C-S-R理论,功能型1和3属于“胁迫忍耐型”策略(S策略),功能型2则属于“竞争型”(C)和“干扰型”(R)策略的综合.研究结果为黄土丘陵区植被恢复规划及物种配置等提供依据.

Comparisons of relationships between leaf and fine root traits in hilly area of the Loess Plateau, Yanhe River basin, Shaanxi Province, China

Plants use a variety of adaptive and functional strategies which help them adapt to changes in environmental conditions. Ecological success under these varied conditions may require plants to share certain common traits, which allow the classification of methods plants use to adapt to stress. The study of a plant's functional traits is currently becoming a high priority area of research in the field of plant ecology because these traits are both easy to quantify and are closely related to plant functioning. Consequently, variation in the strength or weakness of these functional traits along environmental gradients reflects variation in the relative importance of different plant adaptive mechanisms and each species' interactions with climatic, edaphic or topographic drivers. Little is known about whether, or how, this variation is reflected between aboveground and belowground organs in various species of the hilly areas of the Loess Plateau of the Yanhe River basin in Shaanxi Province in north central China. Our goal was to assess the relationships and co-variation of plant functional traits along environmental gradients, and to analyze the adaptive strategies plants use to respond to semi-arid and arid environments. We measured three leaf traits (specific leaf area, leaf tissue density, leaf nitrogen concentrations) and three fine root traits (root nitrogen concentrations, specific root length and fine root density) of 149 species in the Yanhe River watershed to study these traits and strategies. First, we analyzed the patterns of correlations among six organ-level traits and how these traits give different species similar adaptive to dealing with environmental conditions. The results show the differences in the six plant functional traits of the 149 species were closely related. Leaf nitrogen concentrations were positively correlated to specific leaf area and root nitrogen concentrations, and a negatively correlated to leaf tissue density. Specific root length was negatively related to fine root tissue density, whereas no correlation existed between leaf and root traits except for root nitrogen concentrations. Second, a hierarchical clustering method was used with all species to find dissimilarities in environmental adaptation. Based on the dissimilarity of the six traits, these species were classified into three main plant functional types (PFTs). The adaptive strategies and plant functional traits were both different among the PFTs. The species of PFT1 had smaller dense leaves, dense fine roots, and low nitrogen concentrations. The PFT2 plants had bigger leaves and a sparse number of leaves, few long fine roots and that a specific root length which was positively correlated with root nitrogen concentrations. The PFT3 group had higher leaf and fine root nitrogen concentrations and the leaf tissue density was positively correlated to fine root tissue density. Because of these different plant traits, the species of PFT1 are best adapted to an arid environment, with the greatest herbivore resistance and resistance to physical damage of the three groups. The species of PFT3 may avoid nutrient stress by having the greatest nutrient conservation efficiency, which is believed to be important in minimizing nutrient losses in a nutrient-poor environment. The PFT2 group is somewhat intermediate with a greater growth rate, higher competitive ability and wider distribution in the study area. Based on CSR Triangle theories of Grime et al., both PFT1 and PFT3 plants adopt a stress-tolerance strategy to the environment (S strategy) while PFT2 plants use a combination of competitiveness (C) and ruderality (R) strategies. By focusing on traits, our study uniquely demonstrates adaptive differentiation among species. These results will help guide the choice of species to be used in restoration planning in the hilly areas in Loess Plateau.