矿山恢复治理区植被物候与健康状况遥感监测

Remote sensing monitoring of vegetation phenological characteristics and vegetation health status in mine restoration areas

矿山恢复治理区植被物候与植被健康状况可以定量评价恢复治理工程实施效果,以往矿山恢复治理遥感监测多侧重于监测植被覆盖变化,忽略了对恢复治理区域植被物候特征和健康状况的评估。该研究使用时间序列哨兵2号影像,基于Savitzky-Golay滤波、动态阈值、曲率曲线等方法,以黑龙江省七台河市一玄武岩采石场及周边区域为例,分别提取了恢复治理区和正常耕作区玉米出苗期、拔节期、抽雄期、成熟期、物候期间隔长度等遥感物候指标,研究恢复治理区和正常耕作区玉米生长状态的差异。同时,提取并对比恢复治理区和正常耕作区植被红边位置指数(REIP)、归一化植被指数(NDVI)、绿色归一化植被指数(GNDVI)、陆地叶绿素指数(MTCI)、特征色素简单比值指数(PSSRA)、倒红边叶绿素指数(IRECI)、改进的叶绿素吸收指数(MCARI)和植被覆盖度(FVC)等遥感指标值,评估各遥感指标区分恢复治理区作物的能力和诊断矿山恢复治理区作物健康程度的可行性和敏感性。结果表明:1)相较正常耕作区,恢复治理区玉米关键物候期推迟,出苗期、拔节期、成熟期分别推迟了5~12、9~12和21~22 d,恢复治理区作物生长状态的差异随着作物生长阶段的推移逐步显现;2)恢复治理区和正常耕作区REIP、NDVI、GNDVI、PSSRA、IRECI和FVC等遥感指数值有明显差异,其中GNDVI指数反映恢复治理区作物的整体光谱特征更稳定,PSSRA指数对于区分恢复治理区和正常耕作区作物光谱特征差异最敏感,这种差异受两区域玉米作物叶绿素含量、叶面积指数和叶片含水量等生理信息差异的综合影响。该研究可为矿山恢复治理效果快速评估提供一种技术思路。

Plant’s health status is one of the most important indicators to evaluate restoration projects and environmental evolution of degraded land,particularly in mine restoration areas.Most studies on vegetation cover changes did not consider the phenological characteristics and health status in remote sensing monitoring,although optical remote sensing technology has been available since the 1980 s.Taking a basalt stone pit in Qitaihe City,Heilongjiang Province,China as the research area,this study aims to detect the health status of corn crops using remote sensing.Thirteen images were captured from the Sentinel-2 satellite from April to October 2020,and then reconstructed by the time-series of Normalized Difference Vegetation Index(NDVI).Different fittings were selected,including the Savitzky-Golay(S-G)filtering,double logistic(D-L)fitting,and asymmetric Gaussian(A-G)filtering.Dynamic thresholds and curvatures were used,where the phenological indicators of corn crops covered the periods of emergence,jointing,tasseling,and maturity,as well as the interval length between phenological periods.An analysis was made on the difference of corn phenological characteristics between the mine restored and normal cultivated areas.Some remote sensing spectral indices were extracted,including the Red-Edge Inflection Point(REIP),NDVI,green NDVI(GNDVI),Meris Terrestrial Chlorophyll Index(MTCI),pigment specific simple ratio(PSSRA),Inverted Red-Edge Chlorophyll Index(IRECI),Modified Chlorophyll Absorption Ratio Index(MCARI)and vegetation coverage(FVC).A systematic evaluation was made on the feasibility and sensitivity of indices to distinguish between healthy crops and sub-health crops in the restoration area.The results showed that the key phenological periods of corn was delayed in the restoration treatment area,where the emergence period was delayed by 5-12 days,while the jointing period was delayed by 9-12 days,and the maturity period was delayed by 21-22 days,compared with those in the normal cultivated areas.The phenological difference of crops gradually emerged as the crop grew.Remote sensing indicators,including the REIP,NDVI,GNDVI,PSSRA,IRECI,and FVC,can effectively distinguish the crops spectral features and the health status difference between the mine restoration and normal cultivation areas.The GNDVI received the lowest standard deviation for the restoration area(0.0935 for area A,and 0.0562 for area B),indicating the most stable indicator of the overall health status of crops.In PSSRA amplitude interval of pixels,the lower limit in the C area was 12.61%and 44.72%higher than the upper limit in the A and B areas,respectively,indicating the most sensitive among the indicators.The spectral features were related to the comprehensive influence of physiological difference between restoration and normal cultivation areas,including the leaf green content,leaf area index,and leaf water content of corn crops.This finding can provide an insightful understanding to rapidly evaluate the mine restoration using remote sensing technologies.