Vegetation Change Monitoring From Pingshuo Surface Coal Mine Area Using Remote Sensing Technology

In an area like the Antaibao coal mine,where extensive and rapid opencast mining is going on continuously,long-term reclamation monitoring is important.Accurate information of vegetation fraction is important for assessing how mining activities affect the ecosystem in mining areas.A remote sensing method based on vegetation cover monitoring and assessment by using Landsat data sets with the temporal coverage from 1987 to 2015 was presented and applied to the Pingshuo opencast mine,Shanxi Province,China.The varying vegetation indices(VIs)were mapped,statistical evaluated and profile analyzed.(1)Normalized Difference Vegetation Index(NDVI),Normalized Difference Water Index(NDWI)and NDVI difference index(RNDVI)and profile analysis were employed in the study.The result of these analyses showed that,from 1987 to 2013,the area of NDVI<0.2,which represented bare land,increased from 25.28 km2 to 41.31 km2;the area of 0.2<NDVI<0.3,which represented low vegetation cover,declined from 75.45 km2 to 18.12km2;the area of 0.3<NDVI?0.4,which represented medium vegetation cover had irregular variation;the area of NDVI>0.4,which represented high vegetation cover,increased from 9.15 to 55.49 km2.From 1987 to 2013,46.10 km2 of vegetation degradation area was caused,which accounted for 26.41%of the study area;the vegetation increased area was 110.26 km2,which reached to 63.18%;the invariant area was 18.16 km2,which reached to 10.41%.(2)The vegetation cover area increased integrally,the rehabilitation areas significantly changed from drought to moist.It shows that the Landsat NDVI and NDWI data can be used in large coal mine area in the semi-arid area.(3)The principal components(PCs)for VIs are obtained by principal components analysis(PCA).To reduce the impact of phenology on remote sensing based vegetation monitoring,Landsat data were selected during vegetation growing season(June-October).A total of 32 pixels were selected as the survey fields during vegetation growth season in August 2010.VF of arbores canopy in the selected plots was computed.We monitored reclaimed vegetation variation through analyzing time series data of vegetation indices,which were usually applied to mine area monitoring,such as NDVI.PCA for the VIs,the accumulative ratio of contribution of the first two PCs is 91.51%,the variance contribution rate of PC1 is 84.66%,and the variance contribution rate of PC2 is 6.85%.The VF model was set up by regression analysis of SPSS based on the PC1 and PC2.T test examination showed that the field VF was correlated significantly to PC1 and PC2,the correlation coefficient R2 of the model was 0.74.The result confirmed that the PCA in the inversion of vegetation fraction worked effectively,which could be widely used.(4)In addition,we concluded that the vegetation system of South Dump,West Dump and West Enlarged Dump had gradually transformed to the natural ecosystem from 1990-2015.The vegetation in Inner Dump and Inner Enlarged Dump should be well restored.(5)Reclamation was a long-time and dynamic project,whose effect is hard to determine in short term,while remote sensing technology is an effective way to monitor the inter-annual variation of vegetation recovery.