Studies On Poa Pratensis Population Structure Characteristic And Environment Factor Of Different Communities In The Source Region Of Yangtze River, Yellow River And Lancang River

The source region of the Yangtze River,Yellow River and Lancang River(short for SRYYL) are located in Qinghai-Tibetan plateau.It is the biggest highland genebank in the world,the spices are very richer.It has very significant meaning for improving idioplasm resource bank,increasing breeding material and supplying fine grass seed to restore degraded grassland that we have sought local grass seed to adapt to SRYYL.The Poa pratensis is graminaceous rhizome needle grass,its rhizome are very stronger,the nutrition value is very higher.Now it is used as grass seed to conserve water and soil,graze and mow grassland and degraded grassland restoration.Through searching the geographic distribution of P.pratensis population in the field of SRYYL,the species of composition,biodiversity,morphological characteristic and environmental factors of P.pratensis are studied.The the position and function of P.pratensis population on vegetation restoration are proposed.The results are as follows:The geographical distribution of P.pratensis population is wider,it can grow in the elevation of 3365m～4500m.The suitable habitat for P.pratensis is shrub meadow,river floodplain,river side mountain slope and under the forest.It can also grow in the acid,neutral and alkaline soil.The principal factors of P.pratensis geographical distribution is organic material,organic carbon and total phosphorus,the chemical factor is the Ph value.The type of distribution of P.pratensis in the SRYYL is P.pratensis+ Geranium spp.,P.pratensis+Elymus nutans,Potentilla anserina+P.pratensis, Ligularia virgaurea+P.pratensis,P.anserina+ Aconitum tanguticum+P.pratensis, Deyeuxia spp.+P.pratensis,E.nutans+P.pratensis, Carex moocroftii+P.pratensis,P.pratensis+Capsellabursa-pastoris,P.anserina+L.virgurea,P.pratensis+ Polygonum sibiricum,P.fruticosa+ Scirpus distigmaticus.The community diversity is that the colorful difference is appeared by the composition,structure,function and dynamic of community.The alfa and beta diversity index of P.pratensis are increased with the increase of elevation.In the same climate zone,the plant morphology has plastic to the environment change in the different geographical situation.The analysis of morphological variation is the one of basic methods that identify ecotype differentiation and genetic variation study.After the analysis of morphological variation of P.pratensis is SYRRL,it can be divided by three types:Jiuzhi type,Dari type and Maqin type.The P.pratensis community is in the phase of herbs and forbs of degraded alpine meadow.At the same time the P.pratensis population is in the dominant spices position,subordinate spices position and company spices position.So,we can replant P.pratensis and other grass seed to change the structure and composition of plant community,improve community environment,cause it to develop to subclimax community succession,reach the stabler state.We can apply fertilizer,improve soil nutrition condition,enable degraded grassland with the link of soil and vegetation system together to reach the stabler subclimax and climax state.