| Habitat suitability can directly affect the distribution,quantity and survival of birds,and plays an important role in the life history of birds.The national important wetland of Sugan lake plays an irreplaceable role in the construction of the special environment for the survival and safety of most birds and the transfer station for migration,and plays an important ecological function of providing habitat for bird breeding,overwintering or migration.Based on the status of inland salt marsh wetland in the Sugan lake,used Landsat series remote sensing images from 1987 to 2017,combined with field survey and sampling data,this paper analyzes the spatial and temporal pattern changes of wetland type,plant type and vegetation coverage in the study area.On this basis,used remote sensing technology and GIS spatial analysis method,the evaluation factors suitable for the specific situation of the study area are selected,the evaluation criteria of bird habitat suitability were constructed,the weight coefficients of each evaluation factor were calculated by entropy weight method and analytic hierarchy process,and the remote sensing evaluation of bird habitat suitability in the Sugan lake wetland and the 30-year study area are explored and analyzed by HSI evaluation model dynamic change of bird habitat suitability,in order to provide data support for the management decision and sustainable development of the wetland bird habitat,and then provide scientific basis for the protection,management and restoration of wetland bird breeding habitat.The results showed that:(1)The water condition and water source in the study area were different in time and space scale,the areas with high density of water system were distributed in the river channels of Quanjihe,permanent river and seasonal river in the study area,while the other areas had low density of water system;NDMI high value areas were distributed in the alluvial fan,Suganhe and Quanjihe areas,and the rest are medium and low value areas.The density of the water system in 2017 was relatively large,and the area of high-value areas of NDMI was large in 1997;the density of water systems was small in 1987,and the area of high-value areas of NDMI in 2017 was small.(2)settlements are only distributed in the peripheral area of the Sugan lake wetland,and the changes in space-time scale were not obvious;Landscape separation varies with the location of residential areas and bare land,the area with the largest landscape separation in 1997 had the smallest area,and the area with the larger landscape separation in 1987 had the largest area;spatially,areas with large landscape separation values were scattered scattered in the densely populated areas of Ahetamu,Huahaizi,and Saishenteng.(3)The NDVI value of the study area tended to be stable,the distribution area of the high-value area was relatively large in 1997,and the distribution area of the high-value area was relatively small in 2007,the change in the low-value area was not obvious;in space,the high-value areas of NDVI are concentrated in the Quanshui area,the south side of the Xiaosugan lake area,the Sugan river,and the east side of the large Sugan lake area;the low-value areas are mainly around the large and small Sugan lake areas.The levels of above-ground biomass distribution over time are inconsistent,but are mainly concentrated in 3 levels of 100-150 g/m~2,300-500 g/m~2,and 2000-3500 g/m~2.The plant communities mainly include Leymus secalinus community,Phragmites australis community,Leymus secalinus+Saussurea japonica,Leymus secalinus+Mulgedium tataricum,Leymus secalinus+Sophora alopecuroides,and Leymus secalinus,Kobresia myosuroides,Scirpus pumilus,Heleocharis intersita,Hippuris vulgaris,etc.Composition of meadow plant communities.(4)From the perspective of spatial and temporal distribution,the vegetation coverage types in the study area are mainly low and high vegetation coverage.From1987 to 1997,when the overall wetland area remained stable,the area of brackish water swamps decreased by 3963.33 hm~2;from 1997 to 2007,the total area of wetlands showed a decreasing trend.Areas of seasonal rivers,swamped meadows,brackish water swamps,herbaceous swamps,and permanent freshwater lakes decreased by 3727.44 hm~2,2010.81 hm~2,6320.43 hm~2,583.74 hm~2,and 25.44 hm~2,respectively;from 2007 to 2017,the total area of wetlands continued to increase,from64827.45 hm~2 to 67574.43 hm~2,with a growth rate of 4.24%.In terms of time,the area of SHDI high-value areas was the largest in 1997,and the area of SHDI high-value areas was the smallest in 2007;spatially,SHDI high-value areas were concentrated in areas with sufficient groundwater in the research area,respectively in the lake areas.The periphery and the Suganhe;low-value areas are concentrated in the large and small Sugan lake areas,Shanhong areas and Hehong areas.(5)The area with the best suitability for bird habitats in the Sugan lake wetland is10495.45 hm~2,which accounts for 15.62%of the total area;the area with good suitability is 18559.52 hm~2,accounting for 18.78%of the total area of the study area;the area with general suitability is 26056.27 hm~2,accounting for 26.37%of the total area;the area with poor suitability is 10423.41 hm~2,accounting for 10.56%;the area unsuitable for bird habitat is 33269.36 hm~2,accounting for 28.67%of the total area.In general,the areas with the best suitability and good suitability decreased by 14178.54hm~2,2075.68 hm~2,and the areas with moderate suitability,poor suitability,and unsuitable grades increased by 6830.37 hm~2,301.67 hm~2,respectively.Under the conditions of water,ecological disturbances,food supply and habitat environment,the suitability of bird habitat in the Sugan lake wetland showed a downward trend.By analyzing the temporal and spatial dynamics of the suitability of the important wetland bird habitats in the Sugan lake,the areas with the best suitability and good suitability have decreased,the area with the general suitability,poor suitability,and unsuitable rank has increased The area of areas with better overall suitability(best suitability,good,and general)tended to decrease,while the area of areas with poor overall suitability(poor suitability,unsuitable)showed an increasing trend.In summary,under the combined effects of four factors:water conditions,ecological disturbances,food supply,and habitat,the suitability of bird habitats in the wetland of Sugan lake has shown a downward trend,and it also reflects the bird's impact on different habitats.Selection will produce different response processes,and will also lead to disproportionate use of habitats by birds.Therefore,different habitat types in the study area will affect bird survival and fitness,resulting in suitable habitats in time and space. |
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