Phattaralerphong J, Sathornkich J, Sinoquet H
UMR PIAF INRA-UBP, Site de Crouelle, 234 Avenue du Brézet, 63100 Clermont-Ferrand, France.
Tree Physiol. 2006 Sep;26(9):1123-36. doi: 10.1093/treephys/26.9.1123.
A method for computing leaf area of isolated trees from perspective photographs was developed. The method is based on gap fraction inversion. Photographs are discretized into picture zones where gap fraction is computed from image processing. Canopy volume and leaf area density associated with each picture zone are computed from geometrical considerations and inversion of gap fraction equations. Total leaf area and the vertical profile of leaf area are computed from the product of associated volume and its density. The method has been implemented in software called Tree Analyser, written in C++. The method has been tested by comparison with direct estimation of leaf area of three-dimensional (3D) digitized trees of walnut, peach, mango, olive and rubber. Estimated leaf area was sensitive to picture discretization, individual leaf size and leaf inclination distribution. Optimal size of picture discretization was 17 times projected leaf size. Total leaf area was estimated by using a set of eight photographs taken around the tree in the main horizontal directions: deviation ranged from -11% in peach tree to +5% in rubber tree. The method allows fast and nondestructive monitoring of leaf area of individual tree canopies. The next version of the method will include the estimation of 3D leaf area distribution within the canopy.
开发了一种从透视照片计算孤立树木叶面积的方法。该方法基于间隙率反演。照片被离散化为图像区域，通过图像处理计算间隙率。根据几何关系和间隙率方程的反演计算与每个图像区域相关的冠层体积和叶面积密度。总叶面积和叶面积的垂直分布通过相关体积与其密度的乘积来计算。该方法已在名为Tree Analyser的用C++编写的软件中实现。通过与核桃、桃子、芒果、橄榄和橡胶树的三维（3D）数字化树木叶面积的直接估计进行比较，对该方法进行了测试。估计的叶面积对图像离散化、单叶大小和叶倾角分布敏感。图像离散化的最佳大小是投影叶大小的17倍。通过在树木周围主要水平方向拍摄一组八张照片来估计总叶面积：偏差范围从桃树的-11%到橡胶树的+5%。该方法允许对单个树冠的叶面积进行快速且无损的监测。该方法的下一版本将包括冠层内三维叶面积分布的估计。
