The Impact Of Water Replenishment On The Habitat Suitability Of Breeding Red-crowned Cranes

In the past several years,under the disturbance of global climate change and unreasonable human activities,wetland ecosystem is facing the increased threat.Infrastructure construction(such as residential construction,road and reservoir construction,etc.)and agricultural development have changed the original hydrological pattern of wetlands.In addition,regional extreme weather phenomena have led to reduced water depth,deteriorated water quality,and decreased number of endangered species in the downstream of wetlands.In order to enhance its ecological regulation ability and improve its biodiversity,the research believes that artificial water replenishment can alleviate the water crisis of wetlands,protect species habitat,and restore the ecological function of wetlands.However,due to the complexity of wetland system,the current implementation of waterfowl biology-related water replenishment plans are more subjective,and it is impossible to define the specific water replenishment and appropriate water replenishment time.Many current studies have also pointed out that the spatial characteristics of wetland water depth and flooded area are important habitat factors affecting the habitat suitability of endangered waterfowl such as red-crowned crane.And it is difficult to obtain the hydrological dynamics such as water depth under different water replenishment conditions.Therefore,this paper firstly simulated the hydrological changes of wetlands under different water replenishment scenarios by using hydrodynamic models,and then simulated the impacts of different hydrological regimes of wetlands on the habitat suitability of waterfowls by using habitat suitability assessment models.Lastly we determined the most appropriate wetland water replenishment strategy.This paper takes Zhalong Wetland as the research area and red-crowned cranes as the research object.By collecting remote sensing data,field measured data(nest site,water flow and depth of red-crowned cranes)and some auxiliary data(DEM elevation data and meteorological data),modeling is carried out.Firstly,the MIKE21hydrodynamic model was established,and the hydrological regime(flooded area and water depth)of Zhalong Wetland was simulated according to artificial multiperiod simulation scenarios,and the influence of different upstream water inflow on the overall hydrological dynamics of the wetland was analyzed.Then,the maximum entropy(MAXENT)model was used to evaluate the effect of different habitat factors including water depth on the habitat suitability,to determine the influence of hydrological factors on the habitat suitability of red-crowned cranes during the breeding period,and to determine the optimal water replenishment quantity by classifying suitable areas.By exploring the regional hydrological dynamic characteristics under different plans of water replenishment,the study assessed the impact of hydrological regime on habitat suitability of endangered species,providing new ideas and methods for wetland water replenishment work.The main research results are as follows:(1)Through the establishment of MIKE21 hydrodynamic model,the study effectively simulated the variation of flooded range and water depth of wetland under different water replenishment scenarios.Compared with the measured hydrological records,the simulation accuracy of the model is higher,with the certainty coefficient R2 in the range of 0.85-0.97 and the Nash efficiency coefficient NSE in the range of0.81-0.96.It is proved that the results of MIKE21 hydrodynamic model can provide the basis for the subsequent habitat suitability evaluation of red-crowned cranes.(2)Based on the simulation results of the initial hydrodynamic model,11 different water replenishment schemes were set,including the time and amount of water.Finally,the model successfully outputs multiphase of wetland hydrological regime,which can be used as hydrological factors for the following habitat suitability evaluation of red-crowned cranes.(3)In this study,wetland hydrological regime(water depth and flooded range)obtained by MIKE21 model and vegetation coverage,distance from residential areas,distance from open water,distance from road were selected as habitat characteristic variables.Max Ent model is established based on 3s technology,the average area under the training curve of the output of the model is 0.872,indicating the model prediction accuracy is higher.Based on this model,we reconfirmed water depth is an important habitat characteristic of red-crowned cranes in Zhalong Wetland.The study also proves the change of suitable habitat range for red-crowned cranes under different wetland hydrological conditions.According to this,the optimal water replenishment scheme for red-crowned cranes in Zhalong Wetland during the breeding period is determined.In this study,when the water replenishment amount of Zhalong Wetland is 1.019×108m3,the maximum area for the most suitable growth of red-crowned cranes in the breeding period reaches 244.547km~2.