Fractional Vegetation Cover Change And Its Ecological Effect In Panxi Area During Last 15 Years

Vegetation is an important part of terrestrial ecosystem,and the research on its ecological effect is also a hot topic in related fields.However,there are few studies on vegetation ecological effects at the large regional scale,but the relationship between regional Fractional Vegetation Cover and ecological environmental quality of the quantitative analysis can effectively make up for the deficiencies of the study.Panxi is located in the transitional zone between the Qinghai-Xizang Plateau and the Sichuan Basin,which is a typical ecological fragile region between agriculture and animal husbandry.The soil and water loss is more serious,and the ecological effect of natural vegetation restoration is increasing in recent years.Assessment and research are becoming increasingly necessary.In this paper,Landsat series remote sensing images of Panxi area in 2000,2008 and 2014 were used as data sources.Fractional Vegetation Cover inversion was obtained by linear spectral hybrid analysis.At the same time,and then the regression analysis method was used to evaluate the correlation of the Fractional Vegetation Cover and its ecological effect.The main conclusions are as follows:(1)Aiming at the characteristics of high elevation and complicated terrain,Linear Spectral Mixture Model has good adaptability to the Fractional Vegetation Cover inversion.Through the PPI extraction method and the introduction of NDMVI band,the mean RMS of the model is 0.02 or less,and the RMSE of the target image is the smallest in 2014,which is 0.005923.The accuracy of the model interpretation is the highest and the classification result is the best.In the verification of the accuracy of the verification image,the accuracy of the pixel evaluation is more than 90%,among which the accuracy of the vegetation type is the highest,which is 93.22%,which meets the requirement of accuracy evaluation.The coverage of vegetation in Panxi area is generally better.In different periods of time,Fractional Vegetation Cover is more than 80%of the total area,and the area with the highest vegetation cover is medium and high coverage vegetation.The proportion of the areas with the lowest Fractional Vegetation Cover was 1.96%,1.20%and 0.90%,respectively,with the proportion of 31.18%,43.20%and 51.57%.The average Fractional Vegetation Cover in the study area increased from 0.583 to 0.738 in 2014,showing an obvious increase trend.The area of Fractional Vegetation Cover increased by 61.76%of the total area,and the increase of the eastern part of the study area is larger than that of the western part.With the increase of Fractional Vegetation Cover,the spatial variability of the study area was also reduced.The SD decreased from 0.124 in 2000 to 0.108 in 2014,but the Fractional Vegetation Cover in the west of the study area was higher than that in the east.(2)Remote Sensing Ecological Index(RSEI),when the ecological quality information of the study area was extracted,the data was compressed effectively.The first principal component of each index contained most of its information,among which green index and heat index the contribution degree of green degree increased year by year with the increase of year,while the heat decreased.In 2000,the first principal component load of green index was-0.549,the heat index of 0.553,to 2014,the green load of-0.592,heat 0.527,the green degree of contribution in the more than heat.Compared with the EI index,the RSEI can extract the information in units of pixels,so it can be easily visualized,so it is easier to carry out quantitative research and analysis.The ecological quality of Panxi area is generally better.RSEI calculation results show that the proportion of the ecological quality in the above grade is 52.30%in 2000,and 53.95%in 2014,respectively.The proportion of "poor" ecological quality types was the smallest,and the corresponding proportion of the three periods was 2.75%,2.17%and 2.37%,respectively.Similar to the change of Fractional Vegetation Cover,the average RSEI in the region increased from 0.664 in 2000 to 0.759 in 2014,and the proportion of the area with better ecological quality was 57.35%,indicating that the ecological environmental quality also improved by years.In terms of regional spatial differences,the ecological quality of the west of the study area was better than that of the eastern part,but the increase was smaller in the western region than in the eastern region.And with the increase of RSEI,the spatial variability of ecological quality was also reduced,and the standard deviation decreased from 0.133 to 0.119.(3)This clearly indicates a significant effect of FVC on the research area,and the regression analysis showed that the Fractional Vegetation Cover had a significant positive correlation with the RSEI,and the correlation coefficients of the three different periods is 0.9340 and 0.9481.The slope of the regression model is 1.0807,1.1399 and 1.2518,respectively,indicating that the corresponding remote sensing ecological index will increase by at least 0.1%for every 0.1%increase of Fractional Vegetation Cover in the research area in each period,which shows that the local vegetation restoration has brought significant ecological effects and improved the local ecological environment quality.