利用数字图像估测棉花叶面积指数  

Estimation of leaf area index of cotton using digital Imaging

作　　者：王方永[1] 王克如[1,2] 李少昆[1,2] 肖春华[1] 王琼[1] 陈江鲁[1] 金秀良 吕银亮[1] 

机构地区：[1]新疆兵团绿洲生态农业重点开放实验室/新疆作物高产研究中心,新疆石河子832003 [2]中国农业科学院作物科学研究所/农业部作物生理生态与栽培重点开放实验室,北京100081

出　　处：《生态学报》2011年第11期3090-3100,共11页Acta Ecologica Sinica

基　　金：国家高技术研究发展计划(863计划)(2006AA10Z207;2006AA10A302);国家自然科学基金资助项目(30860139)

摘　　要：通过3a不同种植密度、品种、施氮量和灌水量的田间试验,在棉花不同的生育期用数码相机、LAI-2000冠层仪和线性光量子传感器采集数据并进行破坏性取样测定,分析图像透光率的有效性和建立LAI估测模型,进而对图像方法、LAI-2000和破坏性取样方法进行比较和分析。结果表明:(1)在太阳高度角最大且变化最小的正午时段,数码相机测量的图像透光率与线性光量子传感器测量的冠层透光率较一致且相对稳定。(2)图像透光率能反映除吐絮期以外各时期的冠层透光状况,但是当LAI大于5时图像透光率出现饱和。(3)综合分析2009和2010年数据,建立了图像透光率估测LAI的模型(R2=0.8438,SE=0.5605);利用2007年独立试验资料检验估测模型的性能,模型检验的拟合度较高(R2=0.8767)且预测误差较小(RMSE=0.4305),当LAI>5时模型的预测能力降低。(4)数字图像、LAI-2000和破坏性取样3种方法测量的LAI值之间均呈现显著的线性相关(R2>0.85),但是图像透光率的饱和性致使当LAI>5时明显低估叶面积指数。Leaf area index （LAI） is one of the most important structural characteristics for understanding cotton （ Gossypium hirsutum L. ） growth, yield, and population structure. Destructive measurements are tedious, time consuming, and labor intensive. Modern techniques such as remote sensing and measurements from ground-based optical instruments are nondestructive and effective methods to rapidly measure LAI. The objective of this study was to determine the feasibility of using images from a common digital camera to measure LAI of cotton. We compared the results obtained using a digital camera with those obtained using a destructive sampling method and an LAI-2000 Plant Canopy Analyzer. Three field experiments were conducted with different planting densities, cultivars, nitrogen rates, and irrigation rates. A digital camera, an LAI-2000 Plant Canopy Analyzer, and an LI-191SA linear quantum sensor were used to observe the cotton canopy and record data. Leaves were also sampled destructively at their main growth stages. The digital camera images were captured looking downwards onto the canopy, and then an algorithm was used to separate the components of each image into four classes ; sunlit leaves （ SL）, sunlit soil （ SS）, shaded leaves （ ShL）, and shaded soil （ShS）. The parameter of image transmittance （Timag） was calculated from SL and SS based on the Beer-Lambert Law. The validity of Timag was analyzed and a quantitative model of Timag and LAI was developed. The three methods for determining LAI （digital imaging, LAI-2000, and destructive sampling） were compared. Analysis of the diurnal pattern of transmittance of the cotton canopy showed that the best time for measuring Timag was around solar noon, because at this time the solar elevation angle is high and remainsrelatively constant during measurements. Around solar noon, Timag was in good agreement with Tquan（ transmittance measured with a linear quantum sensor）. By analyzing the relationships among Timag, Tquuan, and diffuse non-i

关 键 词：棉花 叶面积指数 数字图像 透光率 LAI-2000 

分 类 号：S562[农业科学—作物学]