Predicting The Potential Distribution Of The Dominant Species Of The Coastal Wetland Using Maxent Model And Spatial Optimization Allocation In The Yellow River Delta,China

Due to its inherent fragility and sensitivity,coupled with the global warming and human activities such as high intensity development and utilization of coastal wetland in the Yellow River Delta.Causing many environmental problems,like that the vegetation pattern changed,the sharp decreased in biodiversity,ecosystem damaged and so on.The dominant species as an important part of the coastal wetland ecosystem which were crucial for maintaining its structure and service function.Firstly,the present situation of the coastal wetland landscape pattern of the Yellow River Delta in 2013 was analyzed.Then,soil and vegetation community were investigated using the method of kilometer grid sampling from 2008 to 2016 in the Yellow River Delta coastal wetland.In addition,using the maximum entropy?Max Ent?and the ArcGIS spatial analysis technique,the potential distribution of dominant species in the Yellow River Delta and their major environmental variables and ecological parameters were quantitatively analyzed.Combining with the dominant species potential distribution and the landscape pattern in 2013 to optimize the spatial allocation of the Yellow River Delta.The main conclusions are as follows.?1?According to the 2013 landscape pattern of the coastal wetland in the Yellow River Delta,we concluded that the wetland was the main landscape pattern and distributed along the coastline in the coastal areas in the Yellow River Delta.The area of natural wetland was 1302.28 km²,accounting for 42.4% of the total area in the Yellow River Delta and the area of man-constructed wetland was 623.64 km²,accounting for 20.3% of the total area in the Yellow River Delta.The mean average patch area of salt marsh and man-constructed wetland were larger,while the forest and construction land types were smaller.Through the percent of the landscape,we obtained that dry land,salt marsh,aquaculture pond,herb and shrub wetland were the main landscape types of the Yellow River Delta.Through the lagest patch index,we obtained that the salt marsh,dry land,aquaculture pond and construction land were the dominant landscape types of the Yellow River Delta.The number of patches and patch density of the construction land were large,while the man-constructed wetland were small.The landscape shape index of river wetland,shrub land,herb land,construction land,forest and dry land was above 20 which indicated the shape tended to be complicated.The perimeter-area fractal dimension of the salt land and reservoir was close to 1,which indicated its shape tended to be regular and it was influenced by human activities.The fragmentation of the Yellow River Delta was serious and the human activities were considered to be the most active factors affecting the evolution of wetland in the region from the landscape index including contagion index,fragmentation index,Shannon,s diversity index and Shannon,s evenness index.?2?The dominant species of the coastal wetland in the Yellow River Delta were Tamarix chinensis,Phragmites australis and Suaeda salsa.The real distribution of Tamarix chinensis and Suaeda salsa were mainly distributed in the coastal area of the Yellow River Delta.The Phragmites australis had a wider range real distribution,not only distributed in the coastal area,but also distributed along the Yellow River and inland area.The relative importance of the environmental variables was evaluated by jackknife test and environmental variables contribution in the modeling analysis.Among the environmental variables,six variables were significant contributors to the potential distribution model of Tamarix chinensis: NO₃^--N,salt,slope,Mg,altitude and NH₄⁺-N.The more influencing environmental variables to Phragmites australis were NO₃^--N,salt,total P,pH,altitude and NH₄⁺-N.NO₃^--N,salt and NH₄⁺-N were significant factors determining Suaeda salsa potential distribution.When NO₃^--N,salt,Mg and NH₄⁺-N were 0.1⁸.3 mg·kg-1,0.17⁰.26 g·kg-1,9600¹7800 mg·kg-1 and 1.9⁹.9 mg·kg-1,and altitude and slope were-1.0⁴.2 m and-0.3¹.3°,as the core potential distribution of the Tamarix chinensis.When NO₃^--N,salt,total P,pH and NH₄⁺-N were 0.1¹2.0 mg·kg-1,0.09⁰.26 g·kg-1,544⁶35 mg·kg-1,7.75⁸.28 and 1.9¹2.0 mg·kg-1,and altitude was-1.0⁴.5 m,as the core potential distribution of the Phragmites australis.When NO₃^--N,salt and NH₄⁺-N were 0.1⁵.1 mg·kg-1,0.14⁰.26 g·kg-1,1.9⁷.9 mg·kg-1,as t core potential distribution of the Suaeda salsa.The probability of presence of dominant species of coastal wetland in the Yellow River delta were positively with salt but its negatively with the other major environmental variables.?3?The model predicted core potential distribution of the dominant species in the Yellow River Delta were mainly distributed in the coastal area.In addition,among the dominant species,Phragmites australis with wider ecological amplitude,which generated a wider range of distribution.The mixed area of the dominant species accounted for 21.6%,the mixed area of Tamarix chinensis and Phragmites australis accounted for 11.0%,and Phragmites australis was widely distributed in the inland of the Yellow River Delta,accounting for 26.2% of the study area.Combining with the dominant species potential distribution map and the landscape pattern map,the Yellow River Delta was divided into planning area,natural wetland area,man-constructed wetland area,non-wetland area,man-constructed wetland restoration area and non-wetland restoration area.The restoration area of man-constructed wetland and non-wetland accounted for 33.5% of the Yellow River Delta where we should restore the ecological system.On the southwest side of the Yellow River Delta it could be planted forest.