Impacts Of Land Use Changes On The Habitat Of Red-crowned Crane In Songnen Plain Under The Background Of Intensive Agriculture

Red-crowned crane(Grus japonensis)is a large wetland dependent wading bird mainly distributed in East Asia area.In our country,it is a grade One national protection animal.On the one hand,Songnen plain is an important commodity grain base in our country,but also the main breeding and migration ground of red-crowned cranes.In recent years,with the progress of science and technology and the increase of human demand for agriculture,intensive agriculture has gradually become an important cause of land use change in Songnen Plain,leading to obvious changes in the pattern and pattern of land use in the region.Among them,man-made development activities dominated by reclamation and natural factors such as climate and hydrology have led to the degradation and loss of natural wetlands.It is an important factor that directly or indirectly affects the habitat quality of red-crowned cranes.A large area of wetland has been transformed into farmland,paddy fields and other agricultural production and construction industrial land.The drastic change of land use type greatly affected the habitat selection and utilization of red-crowned cranes.Compared with the historical records,the distribution range of red-topped cranes has been significantly reduced,from widespread distribution in Songnen Plain to concentrated distribution in wetland in the core area of the reserve,and gradually increasing the intensity of use of farmland habitat.Therefore,based on the multidisciplinary theories of geography,landscape ecology,bird ecology and nature reserve science,this study analyzed the remote sensing images of Songnen plain in different periods(1990,1995,2000,2005,2010,2015 and 2020)and determined the habitat selection factors of red-crowned cranes in different life stages.Furthermore,the temporal and spatial characteristics of habitat distribution of red-crowned cranes under the background of intensive agriculture were elucidated,and the progressive effects of land use type and pattern changes on habitat selection of red-crowned cranes in Songnen Plain were understood,providing a strong basis for the conservation and management of red-crowned crane population and its habitat.The main research results are as follows:(1)During the 30 years from 1990 to 2020,the land use types in Songnen Plain were mainly grassland,cultivated land,marshland and building land,and the change rates and spatial distribution of the 8 land types were different.In the past 30 years,the maximum change of grassland in Songnen plain was 9038.67 km~2.The rest are 5146.19 km~2of construction land,4654.37 km~2of cultivated land,4121.5 km~2of forestland,3945.33 km~2of water area,1728.12 km~2of marshland,1420.45 km~2of saline-alkali land and 630.37 km~2of unused land.In terms of proportion,the proportion of cultivated land,building land and saline-alkali land has been increasing,while the proportion of grassland,marshland and water area has been decreasing.Through the analysis of the transfer matrix,the alternate evolution of different land use types in Songnen Plain in the past 30 years was relatively drastic,which was mainly manifested as:marsh to cultivated land and grassland,grassland to cultivated land and saline-alkali land,and cultivated land to woodland.(2)From 1990 to 2020,during the spring migration period,elevation and land use/cover type(habitat type)were the most important environmental factors affecting habitat selection of red-crowned cranes.With the increase of years,the disturbance of red-crowned cranes on roads became less and less obvious.Red-crowned cranes prefer to choose marshland and occasionally use cultivated land.Road is the main environmental variable avoided by red-crowned cranes in habitat selection.Other environmental variables played an auxiliary role in spring habitat selection of red-crowned cranes.(3)From 1990 to 2020,during the breeding period,land use/cover type(habitat type)and distance from road were the most important environmental factors affecting nest site selection during the breeding period of red-crowned cranes.The nesting habitat of red-crowned crane during breeding period has absolute preference for marshland.At the microhabitat scale,nest site selection was mainly affected by human disturbance distance,vegetation height,distance of reeds remaining,and water depth around the nest.At the landscape scale,the breeding site selection of red-crowned cranes was mainly related to swamp factors at a larger spatial scale,while it was related to dispersal degree at a smaller spatial scale.Other environmental variables had little effect on habitat selection of red-crowned cranes in spring.(4)From 1990 to 2020,distance to road,distance to arable land and land use/cover type(habitat type)were the key environmental factors influencing habitat selection during migration of cranes.Red-crowned cranes prefer marshland and farmland far away from roads,and gradually use cultivated land habitat.Other environmental variables have little influence on the habitat selection of red-crowned cranes in autumn.(5)The area of suitable habitat for red-crowned cranes has been decreasing year by year in the past 30 years.During the migration period in spring,in 1990,the area of suitable area(including high-suitable area and medium-suitable area)was 10138.74km~2,accounting for4.38%of the total area of the study area.In 2020,the area of the suitable area was 4021.86km~2,accounting for 1.74%of the total area of the study area.During the breeding season,1990,the area of suitable area was 3182.4km~2,accounting for 3.37%of the total area of the study area.In 2020,the area of the suitable area was 890.14km~2,accounting for 0.94%of the total area of the study area.During the autumn migration period,in 1990,the area of suitable area(including high-suitable area and medium-suitable area)was 7661.46km~2,accounting for3.31%of the total area of the study area.In 2020,the area of the suitable area was 1814.9km~2,accounting for 0.79%of the total area of the study area.From the perspective of the spatial distribution of suitable habitat,the habitat showed serious fragmentation,and the suitable area shrank to high latitude as a whole.Red-crowned cranes are concentrated in nature reserves where they breed in the suitable habitat of Songnen Plain,including Zhalong,Xianghai,Wuyuer River and other national nature reserves.(6)There are three gaps in the conservation of suitable habitat for red-crowned crane in Songnen Plain,including Lindian-anda,Tailai-Dumeng and Meilisida-Fuyu.Based on the above research results,the management suggestions of establishing a habitat protection mechanism for red-crowned cranes in Songnen Plain with the national park as the main body and the natural protected area network as the supplement were put forward.