Abstract:

It is important to monitor the drought degree of crop for reasonable irrigation. In the study, taking spring wheat in semi-arid region of the Loess Plateau as research object, the feasibility of monitoring drought of spring wheat based on the retrieved parameters of PROSAIL model was probed by analyzing the response of model simulated spectral reflectance to input parameters, the relationships between input parameters of model and drought degrees as well as spectrum simulation accuracy under different drought stress. The results show that each input parameter of PROSAIL model had a different response range to canopy spectra reflectance of spring wheat. The spectra response range of chlorophyll a and b content (Cab) was 476-730 nm, for leave area index (LAI) they were 400-750 nm, 800-1 000 nm and 1 330-2 500 nm, and for equivalent water thickness (EWT) and leaf mass per area (LMA) they were 1 874-1 891 nm and 2 331-2 356 nm, respectively. The correlation between input parameters of PROSAIL model and crop drought degree was significant. The deviations between the measured and estimated canopy spectra reflectance of spring wheat were significantly different in different bands. The deviations between them for the bands less than 1 400 nm were about 11.5%, while for the band greater than 1 400 nm they were about 69%, and the overall deviation was about 30%. The explanation of PROSAIL model to EWT and LMA wasn’t sufficient, which was a main cause to form the deviation. It was debatable to monitor the drought of crop by using the retrieved parameters of PROSAIL model. Therefore, the increase of the explanatory ability of PROSAIL model to EWT and LMA is necessary.

Key words: PROSAIL model, spring wheat, drought degrees, physiological parameters, applicability

摘要：

监测半干旱区作物的旱情对合理灌溉有重要意义。本文以黄土高原半干旱雨养农业区春小麦为研究对象，以模型模拟光谱对输入参数的响应、模型输入参数与干旱程度的关系以及不同旱情下光谱模拟精度为切入点，探讨基于PROSAIL模型反演参数指征春小麦旱情的可行性。结果表明：春小麦冠层光谱对于PROSAIL模型主要输入参数具有不同的光谱响应区间，其中叶绿素含量Cab的光谱响应区间为476～730 nm，叶面积指数LAI的主要响应区间为400～750 nm、800～1 000 nm和1 330～2 500 nm，等效水厚度EWT的响应区间在1 874～1 891 nm，干物质含量LMA的主要响应区间在2 331～2 356 nm。PROSAIL模型的输入参数与干旱程度有显著相关性。模型模拟的半干旱区春小麦冠层光谱的误差在1 400 nm前后差异显著，在1 400 nm之前模拟误差为11.5%，1 400 nm之后模拟误差为69%，总体误差约30%。模型对于等效水厚度和干物质含量的解释不够充分是导致模拟误差的主要原因之一。以PROSAIL模型反演参数监测黄土高原半干旱区春小麦旱情值得商榷。

关键词: PROSAIL模型, 春小麦, 旱情, 生理参数, 适用性