The Study Of Variation In Seed And Seedling Adaptive Strategies Of Betula And Quercus With Elevation In Qinling Mountains

Venical vegetation spectmm is a crucial problem in biogeography and plant ecology. As an important part of mountain ecosystem, forest vertical zonal distribution and geo-ecological boundary were lasting topic in forest ecology study. Seed and seedling play a centre role in forest regeneration and colonize. The change of seed and seedling adaptive strategy along altitudinal gradient can help us to reveal the formation mechanism of forest vertical zonal distribution and geo-ecological boundary. Betula and Quercus were common tree species in Qinling Mountains. In this paper, total 10 species belong to Betula and Quercus were studied to reveal the relationship between plant traits and altitudinal gradient. The plant traits included morphological character of seed and appendages, biomass allocation strategy of seedling and element content in seed, seed appendages and root, stem, leaf of seedlings. The results were as follow:In the seed and appendages morphological and physiological characters of Betula species, only the ear width has a significant positive correlation with elevation. As for the Quercus species, the seed mass, cupula weight, thickness of seed coat, diameter and height of cupula put up a significantly negative correlation with the elevation. The coefficient of variation of seed width and germination percentage decreased with the rise of altitude. In the Quercus species, coefficient of variations of diameter/height and thickness of cupula are positively correlated with the altitude.All the seedling biomass traits of both genuses have no significant correlation with the altitude. In the Betula species, the coefficient of variation of stem length was negatively correlated with the altitude. As for the Quercus species, the coefficient of variation of root-shoot ratio showed the same trend.As for the seed and appendages stoichiometric characteristics, only the seed C-content of Betula species is positively correlated with the altitude, and all the stoichiometric characteristics of Quercus species have no significant correlation with the altitude. Meanwhile, the coefficients of variation of stoichiometric characteristics in both genuses also have no significant correlation with the altitude.In the seedling stoichiometric characteristics, N and C-content of cotyledon of Betula species were positively correlated with the altitude. While the coefficient of variation of N-content and C/N ratio of stem was negatively correlated with the altitude. As for Quercus species, both the seedling stoichiometric characteristics and coefficient of variation have no significant correlation with the altitude.This result showed that the low temperature in high altitude region reduced the investment on seed mass and appendages for Quercus species, but element balance in the seed was not been broke up. The low temperature in high altitude was not influenced the seed phenotypic traits of Betula species, yet Betula seed stored more carbon in high altitude region to deal with the decline of carbon absorption, which was caused by the low temperature. The biomass allocation and stoichiometric characteristics of Quercus seedlings have no significant correlation with the altitude, which means the Quercus species did not alter the biomass and resource allocation strategy in high elevation region. However, the Betula seedlings adjusted the resource allocation strategy in high elevation region. The intraspecific variations of seed and seedling were complex, and have no regularities of distribution with altitudinal gradient in different species. The reason would be the small altitude range of forest species has no enough selection pressure on seed and seedling trait, resulted in no significant correlation with the altitude or the variations were concealed by population variation.