Restriction And Maintain Of Geological Environment On Richness Pattern Of Endangered Plants

The geographical pattern and formation mechanism of species diversity have long been the research focus of geobotany and global ecology.Especially in recent years,the intersection and fusion of such as ecology and geology,has provided new perspectives and methods for such studies of biodiversity.Endangered plants,as the core of global biodiversity protection and the foundation of maintaining the earth's ecological security,are not only one of the main research contents of conservation biology and plant geography,but also an important strategic resources to maintain social and economic development and boost ecological civilization construction.Therefore,it is greatly theoretical and practical significance to explore the formation and maintenance mechanism of the geographical distribution pattern of endangered plants diversity.As one of the typical microcosms of biodiversity in China,Sichuan province has a complex geological environment and distinct climatic characteristics,which has cultivated a unique habitat suitable for the long-term stable distribution of endangered plants,especially ancient relicts,where is an ideal place to study the geographical distribution pattern of endangered plant diversity.Since the 1860s,many botanists at home and abroad have carried out extensive and in-depth scientific investigation on plant resources in Sichuan,which has laid a solid foundation for studies on floristic geography and other aspects.However,there is still a lack of systematic exploration and cognition on the formation and maintenance mechanism of the richness pattern of endangered plant in the region.This thesis is supported by"The Second National Key Protected Wild Plant Resources Survey of Sichuan Province(2013?2018)",and guided by the theories of quaternary geology,plant geography,geographic information system science and other subjects,by collecting and summarizing the previous research results and field investigation,the natural distribution of relicts and paleoendemic endangered plants in Sichuan province were selected as the research objects.The research combined with basic data sources,such as Digital Geological Map of Space Data,¹⁰Be Surface Rock Erosion Data,ASTER?GDEM Data,Bio?Clim Data,HWSD Data,by using statistical data processing and analysis method as Moran's I,Semivariable Function,Correlation Analysis,Stepwise Regression,Hierarchical Partitioning,Variation Partitioning,Ecological Niche Modeling and"3S"technology.The optimal area sampling scale suitable for the study of the distribution pattern of endangered plants was selected and its spatial distribution law was discussed.The coupling relationship between geological environmental factors and the distribution pattern of endangered plants and its restrictive mechanism were analyzed and clarified.This study reveals the change process,migration rule and long-term stable distribution mechanism of endangered plants since the Last Glacial Maximum(LGM).It provides a theoretical basis for the scientific protection and rational utilization of endangered plants and the construction of the protected area system dominated by national park in Sichuan province.The main conclusions and innovations are as follows:(1)The higher richness regions of endangered plants is mainly located in Daba Mountain,Micang Mountain,Longmen Mountain,south of Qionglai Mountain,Daxiangling Mountain,east of Huangmaogeng Mountain and Dalou Mountain.However,the alpine regions such as Ruoergai grassland in the northwest of Sichuan and Que'er and Bayankala Mountain in the west of Sichuan are deficient in endangered species.Through dependence of the scale and spatial variability of the endangered plants distribution pattern contrast study,the spatial agglomeration and heterogeneity of species distribution pattern are more significant,obtained from 60km×60 kilometers(equivalent to 0.5°×0.5°)and grid sampling area scale samples.It also better showed the actual of endangered plants distribution characteristics and laws.So it is the most superior sampling scales,that suitable for the study of richness pattern of endangered plants in Sichuan Province.(2)By using optimal area sampling scale,the richness pattern of endangered plant in the study regions showed a single peak pattern on the longitude gradient,that is,the endangered plants richness increased gradually from the eastern basin to the western mountainous edge,then reduced gradually to the western Sichuan gorge and hilly plateau and plateau planation surface.The latitudinal gradient shows a linear distribution pattern of gradual decrease from south to north,but the change trend is not as obvious as that with longitude.On the vertical(altitude)gradient,endangered plants tend to be distributed in the middle and low altitude areas,while in the high-altitude areas,they are relatively few or lacking.The species richness distribution pattern shows a very obvious left-biased peak pattern and reaches the highest in the altitude range of 1800?2000m.(3)The heterogeneity of geological environment is the main factor for the formation of the richness pattern of endangered plants,and the influence degree of different geological environment factors have great different.The selected best geological,topographic and climatic models based on stepwise regression and AIC,which can explain 49.11%,45.12%and 28.57%of the total variance of endangered plants richness.Among each geological environmental models,lithologic heterogeneity,topographic relief,standard deviation of temperature seasonality have the greatest influence on richness pattern of endangered plant,followed by soil heterogeneity,earth's surface incision,precipitation of wettest month,erosion rate of earth's surface rock,coefficient of elevation variation and mean temperature of driest quarter have relatively little influence on richness pattern of endangered plant.Comparing with the predecessors'conclusion,the results of some variables have certain differences,and the author thinks that the size of sampling scale,the difference of species,the number of data points and so on may be the reasons for that lead to different research results.(4)The combination of geological,topographic and climatic variables could explain the 68.62%variance of the richness pattern of endangered plant.The habitat heterogeneity determined by the interaction of geology and topography and the redistribution of climate have a strong explanatory ability for the richness pattern of endangered plants.The independent explanatory ability of the three groups of variables is weak,which cannot well explain independently the richness pattern of endangered plants.31.38%of model residuals may reflect the influence of geo-historical events,anthropogenic activities,species evolution,and other unmeasured potential factors.In consideration of geologic origin hypothesis and habitat heterogeneity hypothesis,The author put forward“Geological Control and Restriction,GCR”views to the formation of the distribution pattern of endangered plants richness,as following:the formation of the richness pattern of endangered plants is always controlled by regional geological processes and geomorphic development.the interaction of geology and topography as well as redistribution and combination of climate by them,which has played a crucial regulatory role in controlling the formation of richness distribution pattern of endangered plants.(5)The prediction results of the potential richness of endangered plants at the present period well confirm the actual richness distribution pattern,but some regions are different from the actual survey records in the field,such as Jinsha River Basin,where may be influence of highly active neotectonic movement since 10 Ma B.P.Since the Last Glacial Maximum(LGM),the potential richness distribution area of endangered plants showed an overall trend of decrease and then increase in the study regions,and which expanded significantly after the middle Holocene(MH).The overall change pattern conforms to the pattern of“shrunk in the last ice age,and expanded after the last ice age”.Although the core areas of potential distribution in the historical period is basically consistent with the core areas of potential distribution in the current and future climatic periods,but the fragmentation of potential core habitats of endangered plants is intensified in the future climate scenario compared with historical and current climatic period.Since the LGM,the center of mass of the potential distribution of endangered plants in the study regions shifted to the southwest,low latitude and low altitude area,to begin with.After the MH,which then shifted to the north(or northwest),high latitude and high altitude area,and last till the future climate scenarios.This result shows endangered plants are more sensitive to temperature change.(6)Since the LGM,the endangered plants have maintained relatively stable distribution in E'mei Mountain and surrounding mountains,Daliang Mountain and Huangmaogeng Mountain,Dalou Mountain and surrounding mountains for a long time,which shows that these mountain areas can be regarded as long-term and stable refugia for endangered plants.The dominant climatic factors,that limit the long-term and stable distribution of endangered plants in the study area,are mean temperature of driest quarter(reflects low temperature)and precipitation of driest month(reflects drought).Moreover,Wide range of altitude and long-term stability of climate in the stable distribution area,which further promotes the formation of the refugia for endangered plants.The results further clearly support the two views that low temperature and drought are the main reasons for species retreat to refugia and climatic long-term stability is a prerequisite for plant species refugia.