为研究水稻土的光谱特征及其对不同土壤组分的响应规律, 研究采集江西省发育于红粘土(RC)和红砂岩(RS)的两个水稻土时间序列为研究对象。 以水稻土时间序列为研究对象的优势在于, 样本有相同的土地管理背景, 母质和种稻时间成为土壤发育过程中的两个主导差异因素, 进而能够对土壤有机质(SOM)和母质特征在光谱上的响应特征进行研究。 使用Cary 5000分光光度计采集样品在350～2 500 nm波段的漫反射光谱信息, 并从土壤层次、 成土时间和成土母质三个方面, 论述了在VNIR波段水稻土中的主要有机质和无机矿物组成的光谱响应特征和规律。 实验结果表明: 对于单一母质的时间序列土壤样品而言, SOM增加是人为水耕条件下土壤演变的重要趋势之一, 用PC_1 Score表征的整体反射率与SOM含量间可建立精度较高的模型(R2RC=0.91, R2RS=0.79), 且在SOM含量低值区也能保证较高精度; 1 400, 1 900和2 200 nm三个波段处的吸收强度主要与母质中的矿物有关, 在土壤剖面中下层土壤受人为作用较弱、 土层吸收强度较大, 且相同母质的土壤光谱, 在这三个波段有相同的吸收峰强度比值, 可作为判断母质同质的依据; 母质成分的差异会显著影响土壤光谱的波形以及吸收强度, 在建模中充分考虑母质因素将使模型更具解释性。

To investigate spectral characteristics of different soil compositions, eight soil profiles from two paddy soil chronosequences developed on red clays and red sandstones respectively were collected in Jiangxi Province. A total of 37 soil samples were taken from each soil horizons of the profiles. The paddy soil chronosequences were chosen mainly because all soil profiles have the same land management and thus parent materials and rice cultivation time would be two major soil formative factors. This makes it possible to study spectral response characteristics of soil organic matter (SOM) and parent material characteristics. We measured diffuse reflectance spectra data of soil samples using the Cary 5000 spectrophotometer at 350～2 500 nm spectral range. Spectral response characteristics of SOM and inorganic minerals in paddy soils were analyzed according to different soil horizons, soil forming times and parent materials. Experiment results showed that for soil samples from a single parent material, overall reflectance presented by PC_1 score can be calibrated for soil organic matter (SOM) content with high precision(R2RC=0.91, R2RS=0.79), even though the SOM content was low (not more than 20 g·kg-1). The absorption strength (AS) at 1 400, 1 900 and 2 200 nm was mainly affected by the minerals inherited from parent materials. And the more the sample was near to bottom of a soil profile, the higher the AS value. Samples with the same mineral components had the similar AS ratio among these three wavelength locations. The differences in parent materials can significantly affect spectral curve shape and spectral absorption strength. To make the calibration more interpretative, parent material factors should be considered.