| The Yellow River delta is an alluvial plain formed by the deposition of sediment carried by the Yellow River into the sea at its estuary.It is an important transition area between the Yellow River and the Bohai Sea.The formation of the Yellow River delta is inseparable from the water and sand of the Yellow River.The water and sediment in the watershed is of great significance to the formation and evolution of the delta area,the ecological environment of the watershed and the landscape pattern.Therefore,based on the water and sediment data of Lijin Hydrological station,this paper analyzes the change trend of incoming water and sediment in the Yellow River Delta basin.Using 3S technology and related software,taking Hekou District,Lijin County,Dongying District and Kenli District of Dongying City of Yellow River Delta as the study area,ENVI software was used to preprocess data,interpret and classify remote sensing images in the study area,and test their classification accuracy.Secondly,the landscape pattern indexes were calculated by FRAGSTATS software,and the characteristics of landscape pattern were analyzed from the perspectives of landscape as a whole and individual.Arc GIS software was used to calculate landscape pattern index,and dynamic attitude model,landscape transfer matrix,regional dynamic difference and other methods were used to analyze the dynamic evolution of landscape pattern in the Yellow River Delta.Based on the regression analysis,the data of runoff and sediment from Lijin Hydrological station were combined with the changes of landscape pattern in each buffer zone in the Yellow River Delta region,the relationship between runoff and sediment change and landscape pattern was discussed,and the relationship model between main landscape types and runoff and sediment transport was established.It provides a reference for the planning and management decision-making,ecological environment protection and sustainable development and utilization of the Yellow River Delta.The main conclusions are as follows:(1)The annual runoff and sediment discharge fluctuated greatly from 2000 to 2020,and the increase trend was not obvious.The stability of annual sediment concentration is poor,the fluctuation is obvious,and the trend of decline is not significant.Most of the maximum annual discharge occurred in flood season(July-October).From the point of view of the temporal heterogeneity of water and sediment,the sediment transport is more uneven in the two temporal dimensions of annual and inter-annual.In the interannual variation of water and sediment in each month,runoff is more severe from August to October,and sediment transport is more severe from September to December.(2)Arable land and water area were the main landscape components in the basin.Woodland landscape was less distributed in the basin,and the patch area had little change.Grassland and unused land were both shrinking,and the patch area of construction land was increasing.The diversity,heterogeneity and uniformity of watershed landscapes decreased,and dominant patch types existed in the landscape of the study area.(3)From 2000 to 2020,grassland decreased by 1049.31km~2at an annual rate of 3.67%,and the main directions of grassland loss were cultivated land,water area and construction land.Secondly,the landscape area changes greatly in water area,which is mainly from unused land and grassland.The dynamic attitude of construction land is the largest and that of cultivated land is the smallest.The forestland increased by 17.89km~2at an annual rate of1.37%.The unused land decreased by 774.91km~2at an annual rate of 2.80%,and752.34km~2of unused land was converted into water area,accounting for 78.64%of the area transferred out of unused land.(4)During the whole study period,the cultivated land area with the landscape gradient value in the range of 80—100 showed an overall increasing trend,the increase of unit grid area reached 0.21—0.25km~2;the decrease of grassland unit grid area reached 0.20—0.25km~2,the grassland area with the landscape gradient value in the range of 80—100decreased by 882.25km~2;the water area and construction land with the landscape gradient value in the range of 50—100 showed an increasing trend,and the maximum increase in the unit grid area of both was 0.20—0.25km~2.Among them,construction land in Dongying District has increased significantly,and cities and towns in other counties and districts have also continued to expand around;affected by the Yellow River Delta National Nature Reserve,the increase in grasslands at the mouth of the Yellow River is particularly obvious;affected by human activities,a large number of Artificial waters are developed in the north and east of the study area.From 2000 to 2020,the cultivated land landscape showed an increasing trend as a whole.The change trend of cultivated land in Hekou District and Kenli District was the same as that in the whole.The change trend of cultivated land in Dongying District and Lijin County was opposite to the overall trend.The change trend of forest land in the area is consistent with the change of the whole study area,and the relative dynamic degrees are 48.18,7.46,and 1.18 respectively.Among them,the construction of Longju Yellow River Forest Tourist Area in the western suburb of Dongying District has led to an obvious increase in forest land;the grassland landscape shows a decreasing trend.The grassland landscape in the counties also showed a decreasing trend;the overall change trend of water area and construction land was consistent with the change trend of each county,both showed an increasing trend;the change trend of unused land was consistent with the change trend of most counties,showing a decreasing trend.(5)The changes of water and sediment in the Yellow River from 2000 to 2020 had a certain impact on the landscape in the buffer zone on both sides of the Yellow River.The grassland in the 5km buffer zone was negatively correlated with annual runoff,and the regression model of various landscapes and water and sediment in the 3km buffer zone are not significant,the water area in the 1km buffer zone is positively correlated with the annual runoff,and the correlation with the annual sediment load is not significant;the seasonal changes of water and sediment have no significant impact on the landscape in each buffer zone;The correlation between the horizontal landscape index and the change of water and sediment is not significant;in the landscape index based on patch type,the grassland LPI(Largest patch index),COHESION(Patch cohesion index)within the 5km buffer zone are related to annual runoff,The annual sediment load was significantly negatively correlated,the COHESION of woodland and water was significantly positively correlated with the annual runoff,and the woodland COHESION was significantly positively correlated with the annual sediment load;1km buffer Grassland LSI(Landscape shape index)and water LPI in the area were significantly positively correlated with annual runoff and annual sediment transport.Water COHESION and PLAND(Percentage of landscape)were significantly positively correlated with annual runoff;the area of the Yellow River Delta nature reserve was significantly negatively correlated with annual runoff and annual sediment transport. |
