Quantitative Classification And Ordination Of Stellera Chamaejasme Communities In Alpine Meadow In Qilian Mountains

With the degradation of grassland,the alpine meadow ecosystem becomes more and more fragile,which directly leads to the decline of fine forage productivity and the breeding and spread of poisonous weeds.As one of the most serious poisonous plants in the Qinghai-Tibet Plateau,Stellera chamaejasme can also indicate the degree of degradation of alpine meadows.Quantitative taxonomy and sequencing analysis are often used in ecological research,so as to understand the response relationship between plant community distribution pattern and environment.The community investigation on the distribution of S.chamaejasme in degraded alpine meadow and the study of its distribution pattern and its environmental factors are of great significance to the maintenance and restoration of alpine meadow ecosystem.In this study,the degraded alpine meadow in the middle of Qilian Mountain with serious S.chamaejasme invasion was selected as the study area,and the two-way indicator species classification,except trend correspondence analysis and canonical correspondence analysis,combined with GIS spatial analysis,were used to analyze the classification characteristics of S.chamaejasme community in degraded alpine meadow,and the relationship between the distribution of S.chamaejasme community and the environment on the regional scale was discussed.The main results are as follows:(1)The investigation of degraded alpine meadow vegetation in the middle part of Qilian Mountain shows that the vegetation in this area is rare and its composition is simple.37 plant types were collected,belonging to 18 families and 30 genera.The plant samples were divided into six communities according to the number of TWINSPAN.They are:Ⅰ-Poa annua +Kobresia pygmaea + Thermopsis lanceolala + Potentilla bifurca + Gentiana straminea community;Ⅱ-S.chamaejasme + P.annua + Potentilla chinensis+ T.lanceolala + G.straminea community;Ⅲ-S.Stellera + P.annua + G.straminea + Medicago ruthenica + T.lanceolala community;Ⅳ-P.annua + S.Stellera + Anemone rivularis + M.ruthenica +Elymus nutans community;Ⅴ-E.nutans + M.ruthenica + Taraxacum mongolicum + P.anserina + Plantago asiatica community,VI-Potentilla fruticosa + P.annua + P.asiatica+ P.anserina + Caragana jubata community.Among them,communityⅠ,Ⅴand VI are nonS.chamaejasme community,and II,III and IV are S.chamaejasme community,and the coverage of S.chamaejasme is decreasing step by step.The distribution of the six communities is obvious on the DCA two-dimensional ordination diagram,which verifies that the result of TWINSPAN classification is reasonable.(2)Based on GIS spatial analysis technology,topographic,climatic and soil texture elements were extracted from the study area.Combined with soil sampling data,CCA ordination was carried out to study the response relationship between degraded alpine meadow community distribution and single environmental factor in Qilian Mountain area.The CCA ordination results of soil factors showed that the plant community distribution pattern of degraded alpine meadow in the study area was related to soil moisture content,soil p H and soil total phosphorus;the CCA ranking results of topographic factors showed that the plant community distribution pattern of degraded alpine meadow in the study area was related to altitude,topographic fluctuation and slope direction;the CCA ranking results of meteorological factors showed that the average annual mild annual precipitation had a significant impact on the distribution of degraded alpine meadow plant community in the study area.(3)The response relationship between the distribution of S.chamaejasme community and comprehensive environmental factors in degraded alpine meadow in Qilian Mountains was studied by CCA ordination of main soil,topography,meteorological factors and spatial factors selected by comprehensive single factor ranking.The results showed that the dominant environmental factor affecting the distribution of degraded alpine meadow plant community in the study area was soil moisture content,followed by annual average temperature and longitude,that is,the distribution pattern of plant community in the study area was controlled by water,heat and spatial factors.The results of species CCA ordination showed that the distribution of S.chamaejasme,P.annua,E.nutans and P.fruticosa corresponds to the distribution of S.chamaejasme community,P.annua community,E.nutans community and P.fruticosa community on the plot CCA,indicating that the distribution pattern of species can reflect the distribution pattern of the community to some extent.