| Water and grassland,as important components of terrestrial ecosystems,play an important role in the balance of natural ecosystems and human activities.Studying the temporal and spatial dynamics of grasslands and waters is an important prerequisite and basis for protecting the earth’s ecological barrier and water supply security.In this paper,the grassland in Inner Mongolia is the research area,and based on the multivariate remote sensing data such as Landsat,MODIS,Sentinel,etc.of the Google earthengine(GEE)cloud platform,this paper studies the temporal and spatial dynamic changes of grassland and water in Inner Mongolia in the past 20 years,and analyzes the land use,water and water in Inner Mongolia from 2000 to 2020.Temporal and spatial changes of grassland growth and drought and the influence of spatial distribution of waters on grassland.Provide method and data support for implementing the policy of"Scientifically carry out large-scale land greening actions and steadily restore grassland ecological environment in the No.1 Central Document in 2021.The following main results were obtained from the study:(1)According to the accuracy and actual effect of different classification schemes of random forest machine learning algorithm,spectral features and exponential features and topographic features(scheme 3,the accuracy is 92.73%)are selected for classification.During the study period,the area of different features mainly increased by 16.25%,9.67%and 42.79%respectively,including sandy land,bare land,cultivated land The area of wetland and water body decreased by 6.81%,12.60%,18.47%,7.53%and 8.72%respectively.Bare land,sandy land and cultivated land are the main transfer out land types,which are continuously transferred to other land types.The main transfer in land types of the three are grassland.At the same time,some grasslands are transferred out into forest land and artificial surface,and some bare land and sandy land are transformed with each other.(2)Using the improved normalized difference water index(MNDWI)to analyze the temporal and spatial changes of water areas,1176500 hm~2 of waters existed or existed in Inner Mongolia in the past 20 years,and the permanent water area covered 331300 hm~2,except for Bayannaoer and Ordos.The water area of Alxa League shows an increasing trend,and other league cities all decrease.From 2000 to 2010,the water area showed a decreasing trend,and it increased from 2011 to 2020.The overall change trend of the effective water area was similar to that of the whole year.Except for the insignificant correlation between the industrial output value index and the seasonal waters area(p>0.05),the correlations between the other two pairs were significantly correlated(p<0.05).Climatic factors are more likely to affect short-term seasonal water changes,while human factors will have a greater negative impact on long-term year-round waters.(3)Analysis of grass fi eld potential variation over the last 20 years by the suitability assessment selection percentile method showed fluctuating but overall good results.Grass fi elds with the worst growth potential in 2000,60.9%at medium and below levels,improved in 2005,33.3%at medium and below levels,decreased in 2010,and nearly half(49.8%)at medium and below levels,increased signi fi cantly in 2015 and 2020 compared with 2010,especially up to 80%at medium and above growth levels in 2020.At the same time,the analysis of spatial and temporal variations of prairie drought using the corrected TVDI model(tvdied)showed that in July and August 2000-2020 prairie drought was dominated by light and followed by normal,then the drought showed a fluctuating and weakening trend.Among them,the dry conditions are severe in May-July 2020,with an average arid area of 29499400hm~2,which is mainly distributed in most regions west of the great Khingan ridge.In August-September,as the temperature drops back,more rainfall occurs and the droughts in the areas with lower grass water demand are significantly relieved,the average arid area is 16219600hm~2.Rainfall was only 9.93mm in October,the dry conditions showed an increasing trend,and the mean tvdied was still low in the first affected of September,and the dry conditions were significantly aggravated in the last.(4)Different distance buffers were created around the Dai sea,dari lake,Huron lake,xiliohe River,Yellow River as well as uliansu sea to analyze the spatial distribution of waterss in relation to vegetation potential and drought.Except for Lake Huron,all other lake basins in the 5000 m range showed NDVI mean in near buffer greater than in far buffer and TVDI mean in near buffer greater than in far buffer.The difference in the means of NDVI and TVDI between different buffers was large from June to August in the vegetation growing season,and the other time gaps were small.The DAI HAI and the Yellow River showed decreasing trends in NDVI within 10000 m buffer in June August,the dari lake and xiliohe showed decreasing trends within 5000 m buffer,the uliangsu sea decreasing thrust range reached 25000m,and the increasing buffer range of TVDI means in each lake was more consistent with the decreasing buffer range of NDVI means. |
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