Study On The Relationship Of Seed Size And Altitude And Climate Factors On The Eastern Qinghai-Tibet Plateau

Seed size play a role in seed germination and seedling recruitment, then affect the structure of plant communities and species distribution. Because of pressure of phylogeny, environment and biological attributes, there are several magnitude variations in seed size within a flora, particularly in the flora which consists of complex communities. But so far, studies on the relationship between seed size and altitude, climatic variables were mostly focused on a simple plant species, study among species is rare, and not a consistency had been reached. In this paper, a series research were used to analyze the relationship between seed size and altitude, on the eastern Qinghai-Tibetan Plateau, and assessed responses of seed size of 9 common families to climate variables. The results showed:1. On the eastern of Qinghai-Tibetan Plateau, frequency of species decrease significantly with increasing altitude. Bur it increases at the altitude of 3000m. Species of different growth forms distribute unbalanced with increasing altitude, trees are more universal below 3000m, but herbs are more universal above 3000m.2. There is significantly negative relationship between the variation in seed size and altitude in the flora, and seed size decreases with altitude. The effect of altitude on seed size has different patterns among growth forms, and altitudinal gradient in seed size of herbs is similar with the flora, but there is no significant relationship between the variations in seed size of trees or shrubs and altitude.3. Under different taxonomy levels, the variability of seed size is different too. Within family, altitude pressure imposes notable effect on seed size of 23.3% families. But within genus, different genus has different altitudinal gradient in seed size. Compared to seed size of species collected from lower altitude regions, seed size of 40.9% lower species have larger seed, 19.7% small, and 39.4% no alteration.4. For the 9 common families in the flora, climatic variables play a significant role in 5 of 9 families, and temperature, precipitation and sunshine have significant effects on seed size of the plants of Poaceae, but no significant effect on seed size of the plants of Cyperaceae,Fabaceae,Scrophulariaceae and Gentianaceae. The annual total precipitation and the total precipitation of the growing season only impose significant effect on seed size of the plants of Poaceae and Apiaceae. And seed size of the plants of Ranunculaceae and Asteraceae response significantly to sunshine, whereas seed size of the plants of Rosaceae response to the change of sunshine and temperature notablely.