| In a long process, plants evolved many strategies both in physiological and morphological traits in response to viarable environmental conditions, which in turn benifited minimize the adverse environmental impact on the plants, such variations representing the quantitative relationship between plants and enviromental conditions called plant functional traits. However, up to now, it is still a challenging issue to understand the relationship between plant functional traits and enviromental factors for plant ecologists. Knowledge of the variation within and among the widespread species at large spatial scales offer unique opportunities to observe evolutionary progress, and also provides an important step to identify and determine the relative importance of biotic and abiotic factors that promote phenotypic differentiation. Recently, plant ecologists have been interested in quantifying how the leaf nitrogen and phosphorus content varied at biome scale, to further explore the nutritional status of the communities at local site, as well as the plant response mechanism and adaptation strategies under global change. Although these previous similar studies have greatly improved our understanding of the variations and patterns of leaf N and P in terrestrial plants, one area for which there have been few data reported in the peer-reviewed international literature is China, particularly for the Tibetan Plateau, which represented one of the largest alpine forests in the world.On the other hand, based on the previous studies and experience data, plant ecologists summarized the relationships between plant traits and climatic variations, then raised the leaf economics spectrum theroy (LES). As proved by the substantial researches and experience data, the world leaf economic spectrum (LES) revealed a striking consistent pattern of correlations among leaf traits. However, the spectrum of leaf morphology and physiology resluted from geographical and enviromental heterogeneity, such as temperature, light and water conditions, or the inherent differences among species were still unknown. Therefore, we evaluate these questions by collecting the seeds of forest species grown under controlled conditions. Furthermore, we also test whether the parameters of light-response curve can accurately predicated from leaf traits of the LES. The main results and conclusions obtained in the present study run as follows:(1) Our analysis indicated that multiple factors can covary with the overall pattern of morphological traits. Although most of morphological traits showed high supported by local natural selection and genetic factor, the local natural selection was much stronger. Moreover, the analysis of potential driving force showed that most of morphological traits had negative correlation with PET. These resluts may be further indicated that the natural distribution of P. tabulaeformis populations was consequentially constrained by the favoured humid conditions at mid-altitude region.(2) The stoichiometry in the forest biome of China showed that leaf N concentrations (average14.4mg g-1) was both significant lower than that of753terrestrial plant species (average18.6mg g-1) in China and1251world terrestrial plant species (average18.3mg g-1). Although the leaf P concentrations in our study was average1.1mg g-1, nearly identical to that previous reported. Leaf N:P ratio is an indicator of the relative limitation of N vs P (N:P ratio<14often indicate N limitation and N:P>16frequently signify P limitation). Therefore, the N:P ratio in this study was14.2, which revealed that N concentration are relatively low, furthermore, the relative stable N:P ratio across China’s forest biome.(3) Leaf stoichiometry in Qinghai-Tibetan Plateau (QTP) was markedly different from other three forest biomes. Although the leaf from QTP exhibited as same level of leaf P (1.2mg g-1) as other forest biomes, leaf N concentration (11.9mg g-1) was even much lower. In Tibetan Plateau, the relatively low temperature significantly depressed the decomposition rate of plant litter, furthermore, it is also a major restraint on the nutrient cycling between plant and soil. However, the lasted study revealed that there existed another explanation for such variation. The composition of species in community-scale could influence the geographic patterns in leaf N and P, as environment filters determine the possible species pool with biogeographic region though leaf traits, then different species composition will lead to local-scale and biome-scale difference in N:P ratio.(4) We also found that climate variable (MAT) had a significant linear relationship correlation with leaf N, P and their ratios. Since we took genus identity into consideration, it showed strong influence on N, P and N:P ratio in the forest biome of China. This result further indicated that the temperature is the major determinates of stoichiometry in forest biome of China, may indirectly influenced on the composition of leaf traits at community level.(5) The forest species had much less scatter under controlled conditions than that in the original GLOPNET data. The scatter in the controlled conditions was moderate to the LES, except for daytime respiration (Rd). It is further indicated the plant functional traits may be contributed to plants adapting to the environment and shaping their own genetic survival strategy. Since both QE and Isat significant covaried with LMA, there exised possbility that the parameters of light-response curve can accurately predicated from leaf traits of the LES. However, the reasons for these mechanism are unknown, it is possible in practice require further empirical evaluation. |
PDF Full Text Request