The Seed Plants Differentiation And It's Response To The Uplifts In Himalayans

Based on the long-term scientific research in the area of Himalaya,and guided by multi-theories of plant geography,ecology,palynology,geology and quantitative ecology,this dissertation chose endemic species of Himalaya as research object and the impact caused by uplifting of the Himalayas on the species differentiation as main clue,and primarily focusing on three aspects:1)the composition,flora,phylogeny,and differentiation direction of endemic species;2)the impacts of environmental factors;3)evidence of palynology on species differentiation in Himalayas.By analyzing the floristic plant geography of endemic species,the extent and principle of the impacts of environmental factors on species differentiation was discussed,the leading environmental factors was determined and the impacts of uplift of Himalaya on species differentiation was qualified according to the sporopollen record of sediment profile as well.Finally,we get five conclusions.(1)The endemism of spermatophyte in Himalaya area was apparent.The 375 endemic species investigated,without species under the species level,belong to 59 family and 154 genus.Species differentiation among genus was apparent,however,there were only 3 endemic genus,Sinoleontopodium,Bolocephalus and Parapteropyrum,that were differentiated since the uplift of Himalayas.Endemic family was not founded.(2)Species differentiation among genus was apparent and the origin was complex.Endemic species mainly differentiate from species-rich families and species-rich genus.Wildly distributed species and species of tropical elements are two prominent origin of differentiation while families of temperate components were poorly differentiated.Species differentiation intensively centered on species-rich genus and it was not obvious in few-species genus and monotypic genus.Specifically,species belonged to genus center distributed in Himalaya differentiated obviously,and genus which treat research area as a distribution center mostly spread in Himalaya and its nabe.The species differentiation polarized in two ways:tropical elements and temperate elements.The tropical or subtropical areas and high mountains at low altitudes may be the two most important differentiation area.Of the temperate elements,the descendants of Laurasia seed flora have high differentiation in Himalaya region while the descendants of Gondwana flora and Tethys sea flora of the tropical elements,especially the latter,have unclear differentiation degree.(3)The Himalaya region is an important differentiation center for Tibetan spermatophyte.The endemic species in the study area account for over 50%of that in the whole Tibetan region.The differentiation of the species spreads to other areas of Tibet with the Himalaya as the center.As for monotypic genus,the differentiation center is in the Himalaya region.With regard to the differentiation within the study area,the differentiation process centers on Mo-tuo,Milin and southern valleys of Himalaya and spreads along the river.(4)The species differentiation are affected greatly by environmental factors.Environmental heterogeneity is the fundamental factor of species differentiation.Different environmental factors on different elevations have varying influences on the differentiation.Lithology,soil,geomorphological factors,temperature,light intensity and climate have great influences on differentiation in low relief terrains;geomorphological factors and climatic factors have clear effects on differentiation in middle and high mountainous area.The combination of gradient,slope aspect,lithology,vegetation,temperature,insolation is the dominant environmental factor to affect species differentiation.(5)The species differentiation has obvious hysteresis effect.As the altitudes rises,the active region of differentiation experiences three fluctuation which occurred at the altitudes of 861-1061 m,2061-2261 m,and 3861-4061 m.The species differentiation has hysteresis effects,which are as follows:1)different environmental factors cause different hysteresis effect;2)distinct hysteresis effect happens on different altitudes.In middle and high mountain area,the species differentiation lags behind the geomorphological and climatic factors at the altitudes of 800-1000m.The differentiation lags behind the lithology and soil at the altitudes of 200-400m.Though not clear,the hysteresis effect happens at the elevation of 200m.In middle and low areas,the hysteresis effect is not obvious.(6)The hysteresis period of species differentiation in Himalaya region.Based on the average uplifting rate of 5.5mm/y,during the peak period of the first and second uplifting,the differentiation lags 348000 years behind the uplifting.The violent differentiation lags 138000 years behind the third uplifting peak(since 0.9Ma),which means the differentiation happens 762000 years ago.