西鄂尔多斯保护区沙冬青高光谱特征分析

沙冬青是亚洲荒漠唯一的常绿阔叶灌木，由于分布范围狭小、人为调查困难、资源分布不清，加上人类活动的破坏，其数量正在不断减少。快速、准确识别其生长状况、种群动态对进一步研究沙冬青种群分布及生长监测具有重要意义。采用便携式地物光谱仪测定不同龄级沙冬青反射光谱，利用马氏距离法对其原始光谱、一二阶微分谱特征差异波段选取分析；将冠层原始及其微分光谱与叶片叶绿素含量进行分析。通过其相关性的大小理解沙冬青的生长状况与叶绿素含量间的关系。结果表明:1)不同龄级沙冬青原始光谱曲线趋势较接近，符合植被光谱特征的规律性，幼龄沙冬青反射率差异较明显；不同龄级微分光谱曲线基本一致，幼龄峰值起伏变化显著，极大峰值位于719 nm处，主要受幼龄沙冬青长势的影响；2)通过分析得出马氏距离法对不同龄级沙冬青光谱差异显著波段的选择具有显著性，且所选择波段均为光谱特征波段；3)冠层光谱与叶绿素相关性分析得出不同龄级与叶绿素的敏感波长均为<740 nm的可见光波长范围内，说明可见光波段属于沙冬青叶绿素光谱反应的敏感波；与原始光谱相比，经过导数处理的微分光谱与叶片叶绿素的相关性更高，且相关性大的波段数明显增加。

Analysis of Hyperspectral Characteristics of Ammopiptanthus mongolicus in West Ordos Nature Reserve

Ammopiptanthus mongolicus is the only evergreen broad-leaved shrub species in the Asian desert.Due to its limited distribution and the difficulty for investigations,unclear resource quantity,and the destruction of human activities,the actual situation of the occurrence of A.mongolicus is unclear.It is of significant importance to develop rapid and accurate identification methods to understand its growth status and population dynamics for the further research on the population distribution and growth monitoring.This study used a portable ground spectrometer to measure the reflectance spectra of A.mongolicus plants with different ages,and used the Mahalanobis distance method to select and analyze the characteristic difference bands of its original spectra and first-and second-order differential spectra.The original canopy and its differential spectra were compared with leaf chlorophyll.The chlorophyll content was analyzed to reveal the relationship between the growth status and chlorophyll.The results showed that 1) the original spectral curves of A.mongolicus at different ages had similar trends,which were consistent with the regularity of vegetation spectral characteristics.The reflectance of young A.mongolicus was significantly different; the differential spectrum curves of the plants with different ages were basically the same,and the peaks of young plant fluctuated significantly.The maximum peak was at 719 nm,which was mainly affected by the growth of young A.mongolicus.2) Mahalanobis distance method presented significance for the selection of the bands with significant differences in the spectrum of A.mongolicus with different ages,and the selected bands were all characteristic ones.3) Correlation analysis of canopy spectrum and chlorophyll showed that the sensitive wavelengths of different ages and chlorophyll were all within the visible light wavelength range of less than 740 nm,indicating that the visible light band belonged to the sensitive wave of A.mongolicus chlorophyll spectrum reaction; it was similar to the original spectrum.In comparison,the differential spectrum after derivative processing had a higher correlation with leaf chlorophyll,and the number of bands with high correlation significantly increased.