The relationship between plants and environment is mainly reflected in the life history, morphology, phenology, physiology of plants. Different kinds of plants have different adaptation strategies. The southeastern of Qinghai-Tibet Plateau is among the highest forest line distribution areas and one of the most obvious climate change areas in the world. Understanding ecological and climatic indicators of the forest line in this area can offer a foundation for analyzing
the possible changes in the future climate scenario. By means of research on the basic characteristics and physiological indicators of Abies georgei var. smithii seedlings on Mt. Shergyla in southeastern Tibet, we hope to discover the response of Abies georgei var. smithii seedlings to the environment with different altitude gradients, and provide basic evidence for further explaining the response of Abies georgei var. smithii seedlings to altitude.
In this paper, we collected 350 seedlings of 7-8 years with great growth condition in the range of 3 800-4 400 m above sea level in April 2014. We measured their basic growth indexes, root activity, chlorophyll content, etc., and employed Excel 2013, R3.3.1, SPSS 21.0 and other software to analyze the data.
The results showed that: 1) The optimal growth of Abies georgei var. smithii seedlings was observed at the altitude of 3 900 m. The basic characteristics and chlorophyll content were significantly higher than the other altitudes. 2) At the altitude of 3 800 m to 4 100 m, the soluble protein content, soluble sugar content and root activity of Abies georgei var. smithii seedlings were basically stable, indicating that the environmental stress had no significant effect on the growth of Abies georgei var. smithii seedlings. 3) From the altitude of 4 200 m in the Mt. Shergyla, transition began with the forest line and tree line, and the external environment at the altitude of 4 400 m was harsh. The indexes such as seedling height, root activity and chlorophyll content declined sharply which were greatly affected by environmental stress.
In sum, the growth of Abies georgei var. smithii seedlings is largely affected by the altitude of Mt. Shergyla. The seedlings could not resist the effects of environmental stress in the range of the forest line, which resulted in short seedlings with weak energy and slow growth.