The Result Analysis Of The Vegetation Restoration Effect Of Rare Earth Tailings Based On NDVI And Object Spectral Characteristic

The mining of rare earth produces a large number of tailings,resulting in severe soil erosion,associated water quality and geological disasters.Using the combination of engineering and non-engineering measures to carry out rare earth tailing land vegetation restoration is a common means of tailing land disaster prevention.The evaluation of the effects and causes of vegetation restoration in mining areas can provide theoretical basis for the planning and design of tailings control measures.In this paper,NDVI was taken as the research object,and the ion-type light rare earth tailing area in Xunwu county,Jiangxi province was chosen as the research area.Landsat data and meteorological data of Xunwu station from 1989 to 2015 were collected in the research area.Field investigation of typical tailing vegetation and ground object spectrum data of accumulated tailing.The NDVI value of typical vegetation was calculated,and the interannual and interannual time-history variation of NDVI in the mining area was analyzed.The response of NDVI to vegetation restoration and climate change was quantitatively evaluated,and the response mechanism was discussed.The main results are as follows:?1?The NDVI value calculation and analysis based on ground object spectrum data.The NDVI value of ground feature was calculated for measured ground feature spectral characteristics of tailings,Dicranopteris dichotoma,Miscanthus floridulus,Miscanthus,Camellia oleifera Abel,Schima superba,Bamboo,Pinus massoniana,Eucalyptus and Cinnamomum camphora.The results were 0.03,0.69,0.53,0.52,0.69,0.8,0.79,0.75,0.6,0.52,and the NDVI value of Schima superba was the highest and that of tailings was the lowest.Corresponding ground object NDVI error bars were0.018,0.155,0.119,0.134,0.042,0.057,0.024,0.088,0.008,0.016.The large error bars of Dicranopteris dichotoma,Miscanthus floridulus and Miscanthus indicate that herbaceous vegetation is more affected by seasons than trees.?2?The variation law of NDVI time history.The NDVI in the tailings of rare earth mine decreased obviously at a rate of-0.08?10a?^-11 from 1989 to 2015.The whole period can be divided into three stages:stable period?1989-2005?,violent exploitation period?2006-2008?and vegetation restoration period?2009-2015?.In the stable period,the change trend of NDVI value in the whole mining area is not significant,but fluctuates.The NDVI in shuangchating mining area decreased obviously at a rate of-0.049?10a?^-1.In the violent exploitation period,the NDVI in the whole mining area decreased obviously at a rate of-0.3?10a?^-1.The NDVI in shuangchating mining area decreased obviously at a rate of-0.63?10a?^-1.In the vegetation restoration period,the NDVI in the whole mining area decreased obviously at a rate of-0.046?10a?^-1.The NDVI in shuangchating mining area increased obviously at a rate of0.25?10a?^-1.The low-frequency signal of NDVI based on wavelet decomposition represents the stable interannual change of NDVI from 1989 to 2015,and its change rule is similar to that of the original signal of NDVI.The high-frequency signal of NDVI indicates the annual change,and the drastic change of herbaceous vegetation causes the significant fluctuation of high-frequency signal.This indicates that the main cause of vegetation change is herbaceous vegetation change.Based on this situation,the vegetation allocation mode of vegetation restoration measures can be selected for herbaceous vegetation.?3?Response of NDVI to vegetation restoration and climate change in the study area.The trend of dryness is relatively stable from 1989 to 2015.From stable period to intense mining period,the effect of dryness on NDVI in the whole mining area is-0.0097,and the effect of human activities on NDVI is-0.1303.From the violent exploitation period to the vegetation restoration period,the effect of dryness on NDVI in the whole mining area is-0.0075,and the effect of human activities on NDVI is-0.0925.From stable period to intense mining period,the effect of dryness on NDVI in Shuangchating mining area is-0.0096,and the effect of human activities on NDVI is-0.1504.From the violent exploitation period to the vegetation restoration period,the effect of dryness on NDVI in Shuangchating mining area is-0.007,and the effect of human activities on NDVI is 0.117.It can be concluded that human activities are the main factor affecting NDVI.The influence of human activities on NDVI before and after is weakened?from-0.1303 to-0.0925?.The reason was that the driving effect of rare-earth tailings restoration and treatment weakened the destructive impact of severe rare-earth mining on vegetation.The effects of tailing restoration and treatment on NDVI in the whole mining area and shuangcha ting mining area were 0.0378 and0.2674,respectively.Comparing mining area as a whole and Shuangchating mining area differences in the influence of human activities on the NDVI,shows that the overall physical measures and configuration mode vegetation restoration measures of repairing backfilling governance effect is poorer,eucalyptus configuration mode to repair effect is good,in the process of backfilling materials after management,overall mining area should be used mainly on eucalyptus vegetation configuration model for vegetation restoration measures is more scientific and reasonable.