Vegetation Cover Change And Its Influencing Factors In Beijing-Tianjin-Hebei Region

This thesis takes Beijing Tianjin Hebei region as the research object,based on MODIS from 2000 to 2019 NDVI data,using pixel dichotomy model to calculate vegetation coverage,using least square fitting,piecewise linear regression,stability analysis and other methods to explore the change trend and stability of vegetation coverage of various land types and cities,combined with correlation analysis to explore the correlation between meteorological factors,human activities and vegetation coverage,using residual analysis to explore the impact of human activities on vegetation coverage In order to provide reference for Beijing Tianjin Hebei ecological environment protection,climate change research,social and economic sustainable development.The results are as follows:(1)The vegetation coverage in the study area showed an increasing trend,and the changing trends of vegetation coverage in different cities were different.The vegetation coverage of forestland was the highest,and that of construction land was the lowest.The vegetation coverage of forestland and grassland showed an increasing trend,while that of other land types showed a decreasing trend.The stability analysis showed that the vegetation in the study area was mainly slightly fluctuated(39.65%),the severe fluctuated(21.1%)mostly concentrated around the construction land,and the relatively stable area(28.46%)mainly concentrated in woodland and grassland.(2)The temperature and precipitation in the study area showed an increasing trend.Annual and seasonal vegetation coverage was mainly positively correlated with temperature and precipitation.Precipitation has a promoting effect on FVC,and air temperature has a promoting effect on FVC in spring and growing season,and the correlation between FVC and precipitation is stronger.(3)The water resources in the study area showed an increasing trend,and the water consumption of groundwater exploitation and primary industry showed a decreasing trend.The vegetation coverage was mainly positively correlated with the amount of water resources.There was a strong correlation between the vegetation and surface water in many cities,and the overexploitation of groundwater had no significant effect on the vegetation coverage.Population density and per capita GDP showed an increasing trend.In most cities,FVC showed no significant negative correlation with population density and no significant positive correlation with per capita GDP,indicating that population growth in most cities in the study area had a certain inhibiting effect on vegetation coverage,while per capita GDP growth had a weak promoting effect on vegetation coverage.(4)The comprehensive contribution of human activities to vegetation coverage was68.68%.The areas with high contribution were mainly in the plain area and Zhangjiakou City,and the areas with high contribution of meteorological factors were mainly distributed in the Yanshan-Taihang Mountains.Among all land use types,the contribution of human activities to vegetation coverage of construction land was the highest,accounting for 87.43%,while that of woodland was the lowest(32.39%).The severe and moderate inhibition was mainly distributed in construction land,while the mild inhibition was mainly distributed in cultivated land.The areas where human activities played a promoting role were mainly distributed in woodland and grassland.The residual trend analysis showed that the influence of human activities had an increasing trend.