高精度作物冠层结构模型的构建及应用

发布时间：2018-07-11 09:37

本文选题：功能-结构模型 + 叶曲面模型　；参考：《中国农业大学》2016年博士论文

【摘要】：基于精确的植物结构模型,可实现对植物冠层光能利用等的精确分析。本文通过获取高精度的叶曲面信息,构建了玉米和烟草的精确冠层结构模型。为解决精确冠层结构模型所带来的巨大计算量的问题,探索植物精确冠层结构模型的合理简化方案,本文系统地评估了叶曲面网格简化对植物结构及光截获的影响。基于构建的植物结构精确模型对两种简化的植物结构模型进行了精度评估。基于精确的烟草冠层结构模型,结合光分布模型和光合模型,进行了大田烟草群体冠层结构优化的评估。主要内容如下：1.进行了玉米和烟草的大田实验。在玉米灌浆期和烟草打顶后,采用三维激光扫描仪精确测定了具有复杂形态的玉米和烟草叶片,构建了高精度的三维叶曲面和植株结构模型。采用顶点消除法和边折叠法对扫描获取的高精度的叶曲面网格进行不同程度的精简,根据选定的五个指标,系统评估了不同的简化方法和简化率对叶形态的影响；采用三维光分布模型模拟了作物冠层的光截获,分析了叶曲面网格简化对光截获模拟的影响。结果表明,对叶曲面网格进行适度简化,基本不会改变叶片的结构参数,对叶片光截获模拟没有显著影响。当简化率过大后,叶片形态误差和光截获模拟误差均显著增加。与顶点消除法相比,边折叠法能够更好地保持原始叶片的曲面形态特征,但会损失更多的叶缘信息。2. 通过对精确叶曲面模型上的褶皱进行逐步简化,构建了两种具有不同褶皱程度的简化叶曲面模型。在叶片和冠层两个尺度上研究了褶皱对植物结构与光截获能力的影响。结果表明,叶曲面褶皱会显著改变叶片形态和叶倾角。叶缘褶皱对叶倾角的影响与叶倾角的大小有关。当叶倾角较小时,叶缘褶皱会使叶倾角增加,当叶倾角较大时,叶缘褶皱则会使叶倾角降低。对于烟草叶片,叶曲面褶皱还能够改变冠层的叶倾角分布函数。在叶片尺度上,叶缘褶皱和非叶缘褶皱均会使单个叶片的光截获率降低,对于烟草叶片,其光截获率最大降幅可达30%。在冠层尺度上,叶曲面褶皱能够使太阳辐射射入冠层的更深处,增加冠层中下部的相对光强,从而使冠层的光分布更加均匀。3. 基于精确的烟草冠层结构模型、光分布模型和光合模型进行虚拟实验。通过调整株距、行距、行向和烟株留叶数,构建了不同的烟草群体冠层结构模型,模拟了不同天空条件下各个烟草群体冠层的光截获量和日潜在光合同化量。结果表明,种植行距增至110cm、株距增至60 cm后烟草群体的日潜在光合同化量不再明显增加,种植行向为南北向(±20。)时烟株群体的光截获量最大。在烟株现有留叶情况下,去掉顶部2片叶和底部2片叶不会降低烟草群体的净潜在光合同化量,且因改善了烟株的受光环境而有利于剩余叶片产质量的提高。
[Abstract]:Based on the accurate plant structure model, the utilization of light energy in plant canopy can be analyzed accurately. In this paper, the accurate canopy structure model of maize and tobacco was constructed by obtaining high precision leaf surface information. In order to solve the problem of huge computational cost caused by accurate canopy structure model and to explore a reasonable simplification scheme of plant precise canopy structure model, the effect of leaf surface mesh simplification on plant structure and light interception is systematically evaluated. The accuracy of two simplified plant structure models was evaluated based on the constructed plant structure precise model. Based on the accurate model of tobacco canopy structure, combined with light distribution model and photosynthesis model, the canopy structure optimization of tobacco population in field was evaluated. The main content is as follows: 1. Field experiments on corn and tobacco were carried out. After filling period of maize and topping of tobacco, three dimensional laser scanner was used to accurately measure the complex shape of maize and tobacco leaves, and a high precision 3D leaf surface and plant structure model were constructed. The vertex elimination method and the edge folding method are used to simplify the leaf surface mesh with high precision obtained by scanning. According to the selected five indexes, the effects of different simplification methods and simplification rate on leaf morphology are systematically evaluated. Three dimensional light distribution model was used to simulate the light interception of crop canopy. The effect of leaf surface mesh simplification on the simulation of light capture was analyzed. The results show that the reasonable simplification of leaf surface mesh will not change the structural parameters of the blade and has no significant effect on the simulation of leaf light capture. When the simplification rate is too large, both the leaf shape error and the light interception simulation error increase significantly. Compared with the vertex elimination method, the edge folding method can keep the surface morphology of the original blade better, but it will lose more information of the blade edge. Two simplified leaf surface models with different fold degrees were constructed by simplifying the fold on the precise leaf surface model step by step. The effects of folds on plant structure and light interception were studied at leaf and canopy scales. The results showed that leaf surface fold could significantly change leaf morphology and leaf inclination. The influence of leaf margin fold on leaf inclination is related to the magnitude of leaf inclination. When the dip angle is small, the leaf edge fold will increase the leaf inclination angle, and when the leaf dip angle is large, the leaf edge fold will make the leaf dip angle decrease. For tobacco leaves, leaf surface folds can also change the leaf inclination distribution function of the canopy. In leaf scale, leaf margin fold and non-leaf fold can decrease the light interception rate of single leaf, and the maximum light capture rate of tobacco leaf can reach 30%. On the scale of the canopy, the leaf curved fold can make the solar radiation into the deeper part of the canopy, increase the relative light intensity in the middle and lower part of the canopy, and make the light distribution of the canopy more uniform. 3. Based on the accurate model of tobacco canopy structure, light distribution model and photosynthetic model, virtual experiments were carried out. The canopy structure models of different tobacco populations were constructed by adjusting the plant spacing, row direction and the number of leaves left in tobacco plants. The light interception amount and the potential daily light contract amount of different tobacco populations under different sky conditions were simulated. The results showed that the daily potential photocontractual amount of tobacco population increased from 110 cm to 110 cm and from 60 cm to 60 cm, but the row direction was from south to north (卤20. 05). The light interception of tobacco population was the largest. The removal of the top 2 leaves and the bottom 2 leaves did not reduce the net potential light contract amount of tobacco population under the condition of the existing leaves of tobacco plants, and the improvement of the light receiving environment of the tobacco plants was beneficial to the increase of the yield and quality of the remaining leaves.
【学位授予单位】：中国农业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S513;S572

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