基于高光谱遥感的退化伊犁绢蒿荒漠草地围栏恢复特征的研究

Seriphidium transiliense desert grassland belongs to the climatic type desert of Central Asia, and distributed only in Xinjiang, the western region of China. This grassland ecosystem is too vulnerable, but still suffering heavy grazing pressure, furthermore, frequent anthropogenic destruction and lack of the public protection awareness which resulting the grassland severely degraded at large. These are seriously threatening the grassland biodiversity, livestock production and oasis ecological security. At present, the method of fencing is used to degraded Seriphidium transiliense desert for self restoration, and it widely used to restoration of degraded grassland ,especially to degraded desert grassland. However, limited by the traditional method and survey precision, quite a number of fenced grassland are not track monitored effectively. That would brought hidden trouble for timely management to fenced grassland. So, by this research, the Hyperspectral Remote Sensing are used to the study of the recovery characteristics of the degraded Seriphidium transiliense desert grassland. Based on the monitoring period of month and year, monitor the vegetation, soil and climatic factor, and hyperspectral data of grass and soil in and out the fencing. Then gain the dynamic change trend and hyperspectral characteristics. And then by using HJ-HIS data, corrected by ground data and Spectral reflectance measurement data, establish HJ-HIS hyperspectral characteristics. All these research results would provide basis for dynamic monitoring of fencing Seriphidium transiliense desert grassland. Furthermore,those would provide theoretical and practical basis for timely management to fenced grassland.

伊犁绢蒿荒漠草地属于中亚气候型荒漠，在我国仅分布于新疆。该类草地生态系统脆弱，却仍然担负着极大的放牧压力，再加上人为破坏严重及保护意识低下，成为退化较为普遍、严重的地段，对草地生物多样性的保护，畜牧业生产和绿洲生态生活安全造成严重威胁。目前对该类退化草地多采用围栏封育的恢复措施，这在退化草地，尤其是退化荒漠草地恢复中得到广泛应用。然而，受传统方法及精度的限制，很多封育草地并没有很好地进行跟踪监测，这对其适时管理带来隐患。因此，将高光谱遥感术运用到该类草地恢复特征的研究中，对围栏内外草地植被、土壤和气候因子进行月际和年际动态测定，采集草土地面高光谱数据；明确草地变化趋势和各组分高光谱特征。进而，基于环境减灾卫星A星的高光谱成像仪（HJ-HIS）数据，在地面草地观测、光谱反射测量纠正的基础上，明确HJ-HIS光谱特征，为实现其高光谱遥感监测奠定基础，同时为封育草地的实时管理提供理论和技术依据。

围栏封育成为对退化草地恢复的重要措施，尤其是在退化荒漠草地的恢复中被得到广泛应用。随着我国草地围栏建设项目、草原生态保护补偿奖励机制的推进，加大了对退化草地的封育治理。然而，科学准确地获得草地恢复特征，不但是客观评价围栏效果的基础，同时对适时管理具有重要意义。高光谱遥感在精准定量识别植被、土壤中显现出了其优越性，将会在封育草地监测中发挥巨大作用。因此，本研究以集中分布在新疆的、具有重要生态及牧用价值，却处于退化前沿的伊犁绢蒿荒漠草地为对象，对其围栏恢复过程中草土特征、地面高光谱特征、HJ-HIS 光谱特征3个内容进行研究，筛选敏感指标及谱段，为提高围栏封育草地的遥感监测精度提供理论和技术依据。所得主要结论如下：.（1）退化伊犁绢蒿荒漠草地群落特征变化对围栏响应的敏感时期为春季和秋季，敏感指标为群落覆盖度和地上生物量；且监测特征物种，尤其是建群种伊犁绢蒿具有一定意义。围栏内、外土壤特征各指标大小虽然在不同月份间有差异，但变化趋势相对一致，围栏内养分含量下降季节滞后于围栏外，表层土壤理化性质反应相对敏感。.（2）围栏促进了伊犁绢蒿荒漠草地的恢复，但草土各指标变化并不与恢复年限成正比；草土地面反射光谱在5月、9月对围栏响应比较敏感。草地群落盖度、地上生物量与光谱反射率均在350~780nm和1400~2500nm波段有较高的相关性。草地土壤有机质与地面反射率在380-850 nm相关性较好，0-5 cm土层在622 nm左右更敏感。.（3）运用HJ-HSI光谱估算草地群落盖度、地上生物量的较适宜季节为春季，但这两个指标在围栏内外区域的敏感波段和估测模型具有差异。估测盖度的最佳模型精度均在85%以上：对草地退化草地围栏内以669.21 nm、765.11 nm的归一化指数构建；围栏外重度退化区域以DVI构建；围栏外中度退化区域以Rn构建。估测地上生物量的最佳模型的精度均在75%以上：退化草地围栏内以DVI构建；围栏外重度退化区域以Rn构建；围栏外中度退化区域以652.09 nm、732.01 nm的归一化值构建。