| Environmental factors are critical for plants to survive and reproduce and the particular environments sustain particular species. Alpine species occurring in the harsh habitats are sensitive to the climatic changes and may have fast responses to the climate warming in the future. The leaf traits of the the dominant species at different altitudes and their correlations with ecological factors provide an important basis for predicting their fitness changes and distribution shifts under the climatic changes.In this thesis, I collected leaf samples of the dominant species of the forest ecosystems along the different altitudes in the temperate China, i.e., Nyingchi Sejila Mountain in Tibet, Taibai Mountain in Shanxi and Daxinganling Ao Keli Mountain in Inner Mongolia. The selected species included Abies georgei var. smithii, Larix griffithiana, Abies fargesii and Pinus pumila. I analyzed the leaves δ13C、Cmass、Carea、 Nmass、Narea、LMA、LWC, and stomatal parameters of the SD、SR、St/N、St/LM and other major leaf properties indicators of these species at different altitudes. I aimed to document the changes of these leaf traits along the altitudes. In addition, I aimed to clarify the correlations between these leaf traits, altitude and other ecological factors. Finally, a comparison was conducted across these different species and regions and I aimed to obain a general pattern through such a comparision. The main results are summarized as follow.1) The altitudinal responses of leaf traits of Abies georgei var. smithii and Larix griffithiana are different although both species occurring in the same region, in Sejila mountain in Tibet. Both the average values (-26.15‰and-26.6‰) and the variation range of leaf δ13C are lower than those of the other species in the other high-altitude regions. The δ13C variation range of Larix griffithiana is larger but the average value is lower than that of Abies georgei var. smithii. These differences may have resulted from the species-specifc adaptations or from the comprehensive effects of temperature, light, rainfall and other ecological factors because of their occurrences in different slopes.2) Leaf traits of Abies fargesii varied linearly with altitude and climatic factors of the growing season. It seems that the altitudes’climatic factors affected or determined leaf traits. A few traits, i.e.,δ13C value, nitrogen content, leaf traits may have some compensations for altitudinal changes. All changes of these leaf traits along altitudinal gradients, however, may result from the interactions between altitudes and other ecological and climatic factors.3) Leaf traits of Pinus pumila differed between mature and young trees along the atitudinal gradients and this may result mainly from age and height. Temperature is a major factor, which has an effect on the δ13C value and LWC of both types of trees along altitudinal gradients. Due to low temperature, water stress may have leaded to the increased leaf813C in this species. This may have restricted the further migration of this species to the higher altitude until the tree lines in Ao Keli Mountain. Besides, altitudinal leaf traits of this species at different developmental may have reflected to some extent the adaptions of alpine trees to extreme environments.4) The average δ13C values differ between different species with different growth forms, and distributions in temperate China. However, the average δ13C values showed a decreased trend along the regional distributios of the sampled species (e.g.28.066%o Abies georgei var. smithii,-27.666%o in Abies fargesii and-27.076%o in Pinus pumila). The contents of LMA, Narea, and other leaf traits are highly correlated with δ13C values in temperate China. However, this correlation is not obvious between δ13C value and stomatal parameters. In addition, changes δ13C values along altitudinal gradients differ between species and developmental stages. |
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