Study On Responses Of Rare Winter Crane's Geographic Distribution To Land Use Change In Wetlands

Shengjin Lake was located in the middle and lower reaches of the Yangtze River in Anhui Province.It was one of the important areas for wintering cranes in freshwater rivers.Since the establishment of Shengjin Lake Nature Reserve,the number of crane population has been decreasing.So the protection and restoration of crane habitats was an urgent problem to be solved.The data of crane population changes and geographical distribution from 1986 to 2015 were collected and investigated,the image data in 1986.1990,1995,2000,2004,2008,2011 and 2015 was used to evaluate crane suitability in shengjin lake.To study the response of geographical distribution of wintering rare cranes in shengjin Lake during the past 30 years,crane habitat suitability models was constructed.Finally,scientific countermeasures and suggestions was proposed for the protection and restoration of crane habitats.The main conclusions of the study were as follows:(1)The land-use in Shengjin Lake had changed significantly over the past 30 years:Land-use in Shengjin Lake was divided into forest land,water area,grassland and beach land,mudflat land,reed beach land,paddy field,dry land and construction land.The overall classification accuracy reaches 90.%.The area of forest land has gradually declined,with an overall reduction of 49.68%.The area of water areas has gradually increased,with an overall increase of 11.52%.The area of grassland has gradually increased,with an overall increase of 49.25%.The area of mudflats gradually increased,with an overall increase of 147.48%.The area of reed beach has gradually declined,with an overall decrease of 87.06%.The area of paddy fields gradually increased and the overall increase was 106.94%.The area of the dry lands gradually decreased,and the overall area decreased by 53.39%.The area of construction land has gradually increased,with an overall increase of 205.6%.The dynamic rate of change in the water area,grassland,mudflat area,paddy field and construction land was positive.The study indicates that the five types of land-use have been increasing in the past 30 years.The dynamic rate of change in forest lands,reed-flats,and dry lands was negative.In past 30 years,the greatest land-use change was construction land,followed by mudflat,and the area with the least dynamic change was water area.(2)The characteristics of geographical distribution of wintering cranes were as follow: During the wintering period,the geographical distribution of cranes was mainly distributed in grassland,mudflats,reed-flats,paddy fields and shallow-water beach lands.Grassland,mudflats,reed beach lands and paddy field were the main types to feed of cranes.Shallow water beaches were the main stopovers and overnight places for cranes.In 1986,Grus monacha,Grus leucogeranus,Grus vipio,and Grus grus were distributed in Shengjin Lake.By 2015,only Grus monacha was detected.The number of crane populations was gradually decreasing,from nearly 1200 in 1985 to about 100 in 2015.The overall distribution of cranes was distributed from all around of the Shengjin Lake.By 2015,cranes were found only on the upper lake of Shengjin Lake.(3)The evaluation results of habitat suitability of cranes were as follows: The habitat suitability evaluation of cranes was divided into five categories: suitable area,sub-optimal area,general suitable area,sub-inferior area,and unsuitable area.The results show that the habitat area of crane habitat in Shengjin Lake wetland gradually decreases from 1986 to 2015.From 1986,the proportion was reduced from 12.72% to only 1.26% in 2015.The evaluation index of habitat suitability of cranes in Shengjin Lake Wetland Reserve was 0.845,0.83,0.77,0.63,0.77,0.63,0.51,and 0.465 from 1986 to 2015.The habitat quality of cranes was declining year by year,and the correlation analysis shows that the suitability of crane habitat quality was positively correlated with the number of cranes,that is,the better the habitat quality of cranes,the more the number of cranes.(4)Responses of the geographical distribution of rare cranes to land use changes during wintering: Research shows that the geographical distribution of cranes responds to land use changes within a range of 30 m to 50 m.The geographical distribution of cranes in the past 30 years has been mainly concentrated in grassland and mudflats,Reed beach,paddy fields and waters.In the early wintering period,the cranes were mainly distributed in the mudflats for feeding and less cranes were distributed in grassland and paddy fields.In the middle of the wintering period,cranes were mainly distributed in paddy fields for feeding,and less cranes were distributed in grassland and mudflats.In the late wintering period,cranes were mainly distributed in the grassland for feeding,with a small amount distributed in paddy fields and mudflats.