Study On Geomorphologic Characteristics And Ecological Environmental Effects Of Dashanbao Black-Grus Nigricollis National Nature Reserve And Its Adjugate Areas

Geomorphology is the dominant factor that causes the spatial differentiation of physical geographical environment.The study of regional geomorphology and its ecological environment effect can lay a foundation and provide support for understanding the geomorphological environment of the study area,as well as carrying out the research of regional physical geography,ecology,biology,disaster prevention and control.Taking Dashanbao Black-Grus nigricollis National Nature Reserve of and its nearby areas(hereinafter referred to as Dashanbao area)as the research object,combined with field investigation,using digital elevation model data,1:200000regional geological map,1:50000 The topographic map of Dashanbao area was compiled by using Arc GIS10.2 software platform to analyze the main landforms,types,evolution and regionalization of Dashanbao area.At the same time,under the guidance of physical geography,ecology and other theories,Landsat8 was used as the data source.Combining with the related climate measured and calculated data,field survey data of vegetation,soil,the experimental data,the Black-Grus nigricollis distribution points,such as data,using linear regression method,mathematical statistics and the maximum entropy model,respectively analyzes the elevation gradient effect of climate,vegetation,soil,land use and Black-Grus nigricollis habitat effects of geomorphic,the conclusion is as follows.(1)Geomorphology and type characteristicsThe altitude class of the Dashanbao area is dominated by sub-high altitude(73.15%),followed by medium altitude(20.64%)and low altitude(6.21%).The undulation range value is 0～2874m,with an average undulation of 1240.1m.The undulation height type is dominated by large undulating mountains(38.69%),followed by medium undulating mountains(24.28%)and small undulating mountains(13.51%).The central part of the plateau is marked by a hilly plateau.The terrain decreases sharply from the central part to the west and south,and slowly decreases to the north and south.The terrain is generally higher in the north and lower in the south,higher in the east and lower in the west,higher in the northeast and lower in the southwest.Deepvalley cutting,large relief,six levels of stratified landforms.The average slope is22.9°,with slopes(28.36%)and gentle slopes(26.89%)dominating,followed by gently steep slopes(20.24%)and sharp slopes(11.01%).The semi sunny slope(25.64%)and shady slope(25.61%)are slightly higher than the semi-shady(23.95%)and sunny slope(23.42%)Gully density was 0.99km/km~2 and was higher in the east than in the west.Basic geomorphic types as the mountain and extrusive rock class denudation big ups and downs subalpine erosion(18.22%),followed by extrusive rock class denudation in the ups and downs subalpine erosion(13.82%)and extrusive rock erosion denudation greatly and subalpine(10.17%),the types of landform genesis include river landforms,gully landforms,karst landforms,gravity landforms,tectonic landforms,basaltic landforms,etc.The river valleys developed on the plateau are mostly shallow"U"shaped in cross section with small river bed gradient and gentle water flow,while those below the plateau are generally deeply narrow with mostly"V"shaped in cross section wi-th large river bed gradient and strong erosion and cutting.The average altitude and undulation height of the plateau are 3030 m and 43.12m,respectively.The basic geomorphic types are mainly subhigh altitude hills(91.06%),followed by subhigh altitude plains(8.94%).The density of disaster points at different altitudes is greatly affected by natural and human factors.From the interaction results,The altitude of 400-1000m is precipitation+distance from settlements(q=0.635),the distance from roads+precipitation(q=0.365 and 0.348)for 1000-1500m and 2000-2500m,the hypsometric index+land use(q=0.195)for 1500-2000m and 2500-3000m is distance from the road+distance from the fault(q=0.200),and 3000-3500m is hypsometric index+distance from the road(q=0.199).(2)Geomorphologic evolution and regionalizationThe geomorphic development of the landform is in its mature period,and.The average hypsometric index value is 0.501.The geomorphologic spatial differentiation is significant,and it can be divided into three geomorphologic communities:Jinshajiang large undulation subalpine canyon community(Ⅰ),Dashanbao sub-high altitude hilly plateau community(Ⅱ),and Longshuhe small undulation subalpine mountain wide valley community(Ⅲ).The average elevations of the three are 1668.8m,2878.9m and 2356m,the average undulating degrees are 2878.9m,84.6m and 255.9m,the valley densities are 0.85km/km~2,0.84km/km~2 and 1.57km/km~2,and the average HI values are:0.496,0.542,0.431,the slope is mainly gentle steep slope(28.77%),gentle slope(37.60%),gentle slope(37.83%),respectively.Slope(24.26%,29.44%,34.26%),semi-sunny slope(27.64%),negative slope(25.51%),sunny slope(25.16%),followed by semi-shady slope(27.43%),semi-shady slope(24.48%),semi-sunny slope(24.83%),respectively.The basic geomorphic types are mainly carbonate karst large undulating subalpine(17.58%),extrusive rock erosion and denudation subhigh altitude hill(86.84%),and extrusive rock erosion and denudation small undulating subalpine(41.09%).The second are large undulating carbonate karst mountain(15.17%),small undulating submountain(6.67%)and subhigh elevation hill(24.68%).(3)Ecological environmental effect of geomorphology(1)Climatic effect of altitude gradient:The difference in climate between the eastern and western slopes is obvious.The temperature and precipitation on the eastern slope and their vertical decreasing and vertical increasing rates are greater than those on the western slope,and the temperature on both the eastern and western slopes gradually decreases.the precipitation gradually increases with the increase in altitude.The vertical spectrum of climate on the western slope is south subtropical—central subtropical—north Subtropical—warm temperate—middle temperate—cold temperate.The vertical spectrum of climate on the eastern slope is warm temperate—middle temperate—cold temperate.(2)Vegetation effects of altitude gradients:The west slope from the valleys of the Jinsha and Niulan rivers to the summit of,Dushi Baobao,the vegetation consists of savanna in a dry-hot valley—warm temperate coniferous forest(Pinus yunnanensis forest,etc)—Semi-humid evergreen broadleaf fores,Warm deciduous broad-leaf forest—Emperature-coniferous forest(P.armandii forest,etc),Warm sparse trees shrub grass—Cold temperature shrub,Subalpine meadow,Subalpine swampy meadow.(3)Soil effects of altitude gradients:The west slope from the valleys of the Jinsha and Niulan rivers to the summit of Dashanbao,there are one soil vertical zones:Torrid red soils—Red earths—Yellow-brown earths—Brown earths—Dark-brown ear-ths.Soil sand content increases with altitude first decreased and then increased trend,silt content increases with altitude showed a trend of increase after decreases first and decrease the p H value increases with altitude change trend,soil organic matter and total nitrogen content increases with altitude showed atrend of the change of the"first after reduction increased,soil silicon aluminum and silicon aluminum iron rate increase with altitude all showed a trend of decrease.(4)Land use effects of geomorphic:There were significant differences in the spatial distribution patterns of land use types with different elevations,slopes,aspects and topographic level indexes.The comprehensive index of land use intensity and the index of land use diversity first decreased and then increased with the increase of elevations and slopes.(5)The habitat effect of landform in Black-Grus nigricollis:There were significant differences in the number and density of cranes at different geomorphic factor levels,which indicated that black-necked cranes had obvious selectivity to different geomorphic environments.The AUC values for the training and validation sets of the maximum entropy model were 0.880 and 0849,respectively,indicating that the model predicted the distribution of Black-Grus nigricollis at a good level.The geomorphological factor on the distribution of Black-Grus nigricollis was relief(55.6%),followed by slope position(16.8%),slope(14.2%)and altitude(7.5%).