摘要
归一化植被指数(NDVI)能够反映绿色植物的生长状况、监测作物长势,并与叶片尺度和冠层尺度的植被生化参数密切相关。研究方法主要是通过PROSAIL模型来分析NDVI的敏感性。在叶片尺度上,对NDVI变化的敏感性最高的参数是叶绿素含量(Cab),其次是叶肉结构参数(N);而干物质含量(Cm)和含水量(Cw)变化的敏感性较弱。在冠层尺度,NDVI对叶面积指数(LAI)的敏感性最高,其次是观测天顶角(VZA);叶倾角分布(LAD)和太阳高度角对NDVI的敏感性也较大。2017年5月16~18日野外实验采集数据及冬小麦叶片,通过实验室测得叶绿素浓度,结合2017年5月15日河北省石家庄市栾城区Landsat OLI影像,计算出采样点小麦的NDVI,建立叶绿素含量估算模型,生成栾城区冬小麦叶绿素含量分布图,得到研究区叶绿素浓度大部分在30~70μg·cm~(-2)。
Normalized Difference Vegetation Index(NDVI) can reflect the growth of green plants and be used to monitor crop growth, it is closely related to biochemical parameters of vegetation at leaf and canopy scales. The sensitivities of NDVI are analyzed basing on PROSAIL models. The results show that the sensitivity of NDVI to chlorophyll a+b content(Cab) is highest on the leaf scale, followed by leaf structure parameters(N), while the sensitivities of NDVI to dry matter content(Cm) and water content(Cw) are low. The sensitivity of NDVI to leaf area index(LAI) is highest on canopy scale, followed by the higher sensitivity of view zenith angle(VZA). Leaf angle distribution(LAD) and solar elevation angle can also cause the change of NDVI. Field data and winter wheat leaves samples are gathered on May 16~18, 2017 in Luancheng, Shijiazhuang city, the chlorophyll contents of wheat are measured in laboratory. The NDVI values are calculated using Landsat OLI image on May 15, 2017, and chlorophyll content estimation model is constructed. Chlorophyll contents in the study area are mainly 30~70 μg·cm~(-2).
引文
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