不同土壤水分条件下玉米叶片/冠层气孔导度的光谱监测模型

通过玉米水分控制试验,测定不同水分条件下各生育期叶片气孔导度、叶面积指数和冠层光谱反射率等,以分析玉米叶片气孔导度的变化规律及其与光谱植被指数的相关性,从而建立基于光谱植被指数和土壤湿度的叶片气孔导度模型。结果表明：玉米在可见光区和近红外中、长波区的反射率随着土壤水分的降低而上升,但叶片气孔导度（Gs）、叶面积指数（LAI）、比值植被指数（RVI）和归一化植被指数（NDVI）随着土壤水分的下降而降低;玉米NDVI和RVI与单叶片和冠层气孔导度均呈极显著指数函数关系（P〈0.01）,且对单叶片气孔导度的拟合效果优于对冠层导度的拟合效果,而经土壤湿度订正的RVI监测模型优于NDVI监测模型。表明通过测定冠层反射光谱率可实时、迅速地定量监测玉米叶片的气孔导度,为大面积作物气孔导度估算奠定基础。

Spectral Monitoring Model of Leaf/Canopy Stomatal Conductance in Maize under Different Soil Moisture Treatments

The artificially controlled soil moisture experiments were performed in different growth periods on maize to measure the leaf stomatal conductance, leaf area index and canopy spectral reflectance. Then the changes in leaf stomatal conductance and the correlation relationships between the canopy spectral reflectance indices as well as leaf stomatal conductance were analyzed to construct leaf stomatal conductance models with considering the spectral vegetation index and soil moisture. The results indicated that the canopy reflectance of maize in visible and near medium and long infrared spectrum regions was increasing with the decreasing of soil moisture, while the stomatal conductance （Gs）, leaf area index （ LAI ）, ratio vegetation index （RVI） and normalized difference vegetation index （NDVI） were reducing. And the exponential functions and significantly positive correlations between NDVI/RVI and leaf/canopy stomatal conductance were also investigated. Furthermore, the spectral vegetation index better fitted into leaf stomatal conductance than into canopy stomatal conductance and the leaf stomatal conductance model with the consideration of RVI and soil moisture performed better than that with the consideration of NDVI and soil moisture. Thus the stomatal conductance in maize might be monitored real- timely, rapidly and quantitatively based on the canopy spectral reflectance and the work in this study could be fundamental to estimate crop stomatal conductance in large scales.