Spatial And Temporal Evolution Of Wetland Types And Landscape Patterns In Beihaizi National Wetland Park

As an important part of terrestrial ecosystem,wetland plays an irreplaceable role in protecting biodiversity,rare animal and plant resources and maintaining regional ecological balance.The inland river basin in northwest China is a fragile region of ecological environment in our country.It is of great significance to understand the formation of the spatial distribution pattern of inland river wetland due to its topography,groundwater depth,salt accumulation of surface soil,and hydrological characteristics such as lakes and rivers connected with wetlands.The eco-hydrological process of inland river wetland controls the basic ecological pattern and ecological process in the basin,especially the basic vegetation distribution pattern and succession process,thus affecting the transformation of land use/cover types.Therefore,the study of land use/cover change and wetland landscape pattern is of great significance to understand the origin of wetland landscape evolution and the formation mechanism of wetland landscape spatial distribution pattern.In view of this,this article is based on community survey with the method of investigation and remote sensing technology,by interpreting the five issues of remote sensing images from 2007 to 2017,to select comprehensive dynamic attitude,transfer matrix,the landscape pattern index analysis method,and the area change and spatial and temporal distribution pattern of wetland types in Jinta Beihaizi national wetland park were studied.To explore the distribution and response mechanism of vegetation functional groups in different habitats,and the relationship between wetland landscape change and wetland landscape fragmentation is quantitatively analyzed,and It also provides a theoretical basis for the management and protection of local wetland resources and the restoration of wetland vegetation.The results are as follows:(1)From the perspective of spatial and temporal changes,the landscape types in beihaizi national wetland park have significant changes,and the total area of gobi desert and sandy land showed a downward trend,with the proportion decreasing from 62.45%to 31.18%,and the wetland area showed an upward trend,with the proportion increasing from 37.55% to 68.75%.Among them,the lake area increased by 100% and the area of the marsh decreased by 18.16%.In terms of dynamic transfer,there were significant transfer changes among different land use types in the study area from 2007 to 2017,and the transfer area varied greatly in different time periods,which wasgenerally manifested as the transfer from non-wetland to wetland,and the transfer change area from 2014 to 2017 was significantly higher than that in other time periods.In terms of quantity change,the comprehensive dynamic attitude of land use shows a significant difference,and the overall change range is the largest from 2009 to 2011,which is 19.80%,which is more drastic than other study periods.(2)In the comparison of wetland types,the change of lake wetland was the most obvious from 2007 to 2017,and the area of lake wetland increased significantly.The area of herbaceous marshes wetland showed a trend of decreasing first and then increasing,with an overall decrease of 25.64%.The area of inland salt marsh showed a trend of increasing first and then decreasing,with an overall decrease of 2.30%.In terms of transfer and change,the transfer between wetland types was more drastic,and the herbaceous marsh wetland and inland salt marsh wetland were mainly transferred to lake wetland.In terms of dominant plant,Phragmites australis+Typha minima,Phragmites australis+Calamagrostis pseudophragmites,and Tamarix chinensis-Leymus secalinus+Phragmites australis are dominated in herbaceous marsh wetland.Phragmites australis+Lycium ruthenicum and Phragmites australis+Alhagi sparsifolia are dominated in inland salt marsh.Nitraria tangutorum+Kareliniacaspia is dominated in sand.(3)From the analysis of meteorological factors,the average annual precipitation showed a decreasing trend and the average annual temperature showed an increasing trend in Beihaizi wetland from 2007 to 2017,but the impact on the landscape pattern change of Beihaizi wetland was not significant.For hydrological factors,the annual discharge of the Yuanyangchi Reservoir in the upper reaches of the Beihaizi Wetland has an upward trend,which has a very significant positive correlation with the area of lake wetlands.Groundwater resources have also been fully replenished,and the landscape pattern of wetlands has changed accordingly.The area of dominant plant is also mainly affected by the water coming from the upstream reservoir,which is not significantly related to temperature and precipitation.The water coming from the upstream has changed the original living environment in the park,and the changes in habitats have led to the corresponding distribution of vegetation functional groups Adjustment.(4)From 2007 to 2017,the overall landscape pattern of Beihaizi wetland changed significantly.At the landscape level,the number of patches and the Shannon's diversity index show a decreasing trend,the aggregation index and the contagion index show anincreasing trend,the shape of the landscape tends to be regular,and the patches are aggregated.At the level of patch types,the number of patches and patch density of each landscape types gradually decreased,and the dominant landscape changed from the Gobi in 2007 to the lake wetland in 2017.In terms of landscape fragmentation,with the decrease in the number of landscape patches and the contagion index,large-area patches dominate,and the space is continuously distributed.The spatial connectivity of landscape patches is enhanced,and the degree of fragmentation is gradually weakened.On the whole,the wetlands in the study area changed from a patchy and mosaic-based spatial pattern to a highly continuous and cluster-based spatial pattern.