Seed Germination Strategy Of Common Species In Arid Zone Of Hexi Corridor And On The Eastern Qinghai-Tibet Plateau

Seed germination is a crucial stage in life history of plant, also an important characteristics to adapt to variable environment in order to maintain own reproduction. Seed germination directly related to the growth of individuals, expansion and maintenance of population, and other ecological processes, also have a direct impact on the distribution of vegetation, community dynamics and biodiversity. Plants in special habitat in a long-term process of natural selection may have developed unique life history strategy to adapt habitats. However, it is not known whether the random environmental factors or the inherent characteristics of species play a decisive role for this formation of mechanisms. In addition, the study on seed germination mostly concentrated in a species or a few species; obviously, the comparative study on seed germination of species between communities is still lack, in particular, the study on seed germination for different districts is very rare.In this paper, the two special zones with different topography and vegetations- the arid and semi-arid zone in Hexi Corridor and the eastern Qinghai-Tibet plateau, seed germination and dormancy characteristics of common plants species were surveyed, and the effect of ecological factors and life history characteristics on seed germination were detected, and also the effect of environmental factor including habitats, altitude, temperatures, seed storage condition on intra-species seed germination were examined. Finally, we synthesized information on phylogeny, life history and ecological factors, using unique stepwise ANOVAs to infer the correlations between seed germination and phylogeny, life history, and habitat.The result showed: 1) Final germination percentages of the 69 species from the arid and semi-arid zone in Hexi Corridor had a bimodal distribution, whereas, days to first germination was skewed toward short periods of time, indicating the main germination strategy may be rapid in response to a precipitation, or delay germination and dormant in response to the droughty habitat. Whereas the seed germination of woody species on eastern Qinghai-Tibet plateau showed a skewed distribution, tending to have more of the low germination of seed, and that indicating delay germination or dormant may have developed a major strategy. 2) In the two zone, environmental factors such as storage conditions, light, temperature and altitude may have an important effect on seed germination of some individual species. 3) Seed germination among species in Hexi Corridor was influenced by the dry and wet habitats, whereas that of woody species on eastern Qinghai-Tibet plateau scarcely be affected by habitat and altitude. 4) There was an insignificant negative correlation of germination percentage and seed size among species of arid habitat in Hexi Corridor, but that in moderate moist habitat displayed a significant negative correlation. On the eastern Qinghai-Tibet plateau, there was a significant negative correlation between germination percentage and seed size under light in woody species, whereas in darkness there was a weak correlation. 5) In the two zones, seed dispersal mode significantly influenced on seed germination, with wind-dispersed seeds germinating to higher percentages than unassisted- or vertebrate-dispersed seeds in both light and darkness. 6) In the two zones, phylogeny of species significantly influenced on germination; seed germinability varies with order and family. 7) To the comprehensive view, for the arid and semi-arid zone in Hexi Corridor, the amount of variance in final germination percentage among species for seeds incubated in light was explained by phylogeny (13.6 %), dispersal mode (11.9 %), seed size (3.6 %), and habitat (0.2 %); in darkness by dispersal mode (17.5 %), phylogeny (12.7 %), seed mass (5.7 %), and habitat (0 %); whereas growth form, seeds maturation period, flowering time and duration of flower of species had scarcely any effect on seed germination. For the eastern Qinghai-Tibet plateau, the amount of variance in final germination percentage among species for seeds incubated in light was explained by phylogeny (17.4 %), dispersal mode (19.6 %); in darkness by phylogeny (27.9 %), dispersal mode(15.3 %); in addition, the amount of variance in days to first germination in light was accounted for by phylogeny (23.8 %), dispersal mode (9.5 %); in darkness by phylogeny (15.8 %) and dispersal mode (11.1 %); but seed size, growth form, seed maturation period, habitat and altitude had scarcely any effect on variance in seed germination.We consider that there may be different seed germination strategy of species in different geographical conditions and vegetation types. The main germination strategy of species in arid and semi-arid zone may be rapid or delay germination and dormant in response to precipitation, or to the droughty habitat; whereas that of woody species on the eastern Qinghai-Tibet plateau may be delay germination and dormant in response to high altitude, long-term cold and other adverse circumstances. In addition, the inter-specific variance in seed germination of the two zones is largely dependent upon phylogeny and seed dispersal mode. We suggest that phylogeny may constrain seed germination, and since dispersal strategies may be related to phylogeny, they also constrain seed germination, that is, inherent characters of species may play a prominent role in evolution of seed germination strategy. Our results do suggest that phylogeny and life history should be taken into account when investigating the variance in seed germination or other life history attributes.