Study On Temporal And Spatial Changes Of FVC In Fen River Basin From 2001 To 2017

This study based on MODIS NDVI remote sensing data,combined with dimidiate pixel model,the trend line analysis,correlation analysis,GIS spatial analysis and significance testing method,The dynamic change characteristics of vegetation cover in the Fen River basin are illustrated from the time scale and space scale,and the temporal and spatial relationship between vegetation cover and climate factors and topography factors is studied with the help of DEM topography data and the contemporaneous climate data as quantitative index,and the effect of human factors on the development of vegetation cover is discussed.The main conclusions were as follows:(1)On the whole,the vegetation coverin the Fen River basin showed an obvious increasing trend year by year.In the annual changes,except for luliang mountain range and Taiyuan basin,the annual changes in other areas showed obvious seasonality and regularity,and the inter-annual changes showed an increasing trend.The vegetation distribution law of the whole basin is relatively uniform,and the development status is good.Areas with FVC of 0.6 or above account for more than 60% of the whole watershed,and water bodies or very low FVC accounts for only about 3%.(2)The annual maximum FVC increased from 0.55 in 2001 to 0.72 in 2017.Although it fluctuates slightly,the overall increase of the annual maximum FVC in the basin reflects,to some extent,the harvest of the agricultural areas in the region and the effectiveness of shanxi's environmental protection policies.(3)The research on the relationship between FVC and the spatial distribution and time variation of meteorological factors shown that the temperature in the Fen River shown a rising trend,and the temperature is decreasing from north to south.Precipitation shown a fluctuating trend,with a large range of change.In 2003,the highest is about 650 mm,and in 2015,the lowest is about 350 mm.The distribution was characterized by low north and high south.Analysis of the relationship between vegetation coverage and the change of temperature,precipitation,the annual average temperature and annual average vegetation coverage was basically consistent except in 2003.In 2015,the average temperature reached a 17-year high.At the same time,the vegetation coverage has reached the highest,It is proved that the response of temperature with the change of vegetation coverage is relatively timely and significant,there is a certain lag between precipitation and vegetation change,and the overall trend of precipitation is well consistent with the change trend of vegetation coverage.The temperature reached the trough in 2003,but the precipitation was abundant and the vegetation coverage did not decline.This shown that the increase in rainfall properly makes up for the lack of temperature,and at the same time,vegetation coverage is greatly affected by the change in precipitation,but it is not the only decisive factor.(4)Choose the vegetation coverage of 2001 and 2017,through the analysis of the DEM terrain data and vegetation coverage,it can be seen that the minimum height of the Fen river is taiyuan basin and linfen basin,the second is the connection between the interior and the mountains,the highest point is the mountain range on both sides of the basin.The distribution shown that the north is high and the south is low,which is consistent with the temperature distribution.The change of vegetation coverage also increased with the increase of elevation,reaching the maximum when the elevation reaches 2000 m.There are many low-slope areas in taiyuan basin,linfen and yuncheng,other areas have higher slope.As the slope increases,the vegetation coverage also increases.The distribution in the slope direction was more uniform in the study area,and the vegetation coverage was the highest in the non-slope and overlying slopes,which was related to the duration of sunshine and the intensity of nutrient absorption.Compare 2001 to 2017,the vegetation coverage rate of all terrains increased significantly in terms of interannual changes.Especially in low elevation and gentle slope areas,human activities are more obvious,indicating that human factors have improved vegetation coverage significantly.(5)Through the analysis of the change of cultivated land area and relevant policies,it was found that the cultivated land area increases first and then decreases,The Fen river basin protection policy is also increasing year by year,these are the important factors of increasing vegetation coverage year by year.