Evaluation Of The Effects Of Different Water Replenishment Conditions On The Habitat Of Typical Summer Migratory Birds In Shallow Lake Wetlands

The abundant and diverse habitat conditions in Baiyangdian Lake provide good conditions for waterfowl to find food and habitat.Since 1997,the ecological water supplement work of Baiyangdian Lake has achieved remarkable results.However,the terrain of Baiyangdian Lake is complex,and there are many factors affecting the habitat.The spatial heterogeneity characteristics of bird habitat under different water supplement conditions are still lacking of quantitative research.Based on Landsat series remote sensing images and field survey,this thesis analyzes the spatial-temporal change characteristics of Baiyangdian wetland landscape under different water replenishment conditions in typical years.Based on the construction of habitat suitability index(HSI)evaluation model,the temporal and spatial changes of heron habitats in Baiyangdian Lake from April to August under different water replenishment conditions and the reasons for their impacts were analyzed quantitatively.The habitat network was constructed with the single foraging distance of waterfowl as the threshold,and the landscape connectivity index and patch importance index were used to analyze and evaluate the landscape connectivity,important habitat patches and key node location change characteristics.Clarifying the distribution and change of waterfowl habitat is of great significance for maintaining the diversity of wetland waterfowl species and improving the quality of ecological environment.The research results have certain scientific significance for the monitoring and protection of summer migratory bird population in Baiyangdian.The main conclusions are as follows:(1)From the perspective of landscape area change,the area of construction land has a small change within the year.The area of deep water has a downward trend over time.The area of reed terraces and cultivated land has an overall upward trend over time.The area of shallow water has an overall upward trend from April to June and a significant decline from June to August.From the perspective of landscape type transfer,from April to June,shallow water and reed terraces are mainly transferred into the landscape,while cultivated land and deep water are mainly transferred out of the landscape.The transformation areas are mainly distributed along the line from Shaoche Lake in the north to Yangjiao Lake in the south,Laowang Lake in the middle,and Xiaobai River estuary in the east to the southeast.From June to August,the cultivated land is mainly transferred into the landscape,while the deep water and shallow water are mainly transferred out of the landscape.The regional distribution of the cultivated land transferred into the landscape is mainly Shaoche Lake in the north,Lianhua Lake in the northeast and Yangjiao Lake in the south.(2)Baiyangdian water level is closely related to the suitable habitat area of herons.In April,the suitable habitat area of herons in the middle and high places showed a single peak change with the water level,reaching the maximum when the water level was 7.21 m,about79.76km2;From May to August,the area of medium and high suitable habitats for herons increases with the decrease of water level.When the water level is lower than 6.33 m,the area of medium and high suitable habitats decreases gradually with the decrease of water level.The location of recharge is the main reason that affects the spatial and temporal pattern of the suitable habitat for herons.The water supplement at a single inlet,such as Xiaobai River and Baigou River respectively,has significantly improved the habitat suitability of Shaoche Lake in the north of the lake area,and the water supplement from Fuhe River has significantly improved the habitat suitability of Zao Lake in the west;The water is replenished at several entrances from Baohe River,Fuhe River and Baigou River,which has the most significant effect on improving the habitat suitability of the whole lake area.(3)From the perspective of changes in the year,whether the water is replenished at a single inlet or multiple inlets,from April to July,with the passage of time,the water level gradually drops,the number of large patches gradually decreases,the area gradually increases,and the IIC and PC indexes show an overall upward trend,indicating that the habitat patches in the lake area gradually tend to be integrated;In August,the number of habitat patches increased gradually,the area decreased sharply,the IIC and PC index decreased sharply,and the habitat tended to be fragmented.From the perspective of inter annual comparison,the higher the water level is,the more serious the fragmentation of patches is;The higher the water level,the more integrated the habitat patches.