基于冠层结构的油菜群体光分布模拟研究

Based on the earlier rapeseed (Brassica napus L.) morphological model established by our group, the rapeseed canopy and organs (including leaves, stems, flowers and siliques) were taken as object, and a canopy structure model will be established by measuring the canopy structure and light distribution under different plant-type cultivars, nitrogen, and density treatments, using the method of 3D digitalization and system analysis, and the technology of dynamic and mathematical modeling, investigating the quantitative expression of organs' two dimension morphology (including the curvature of organs themselves) and their relative position (including the relative position between leaf and stem, and between silique and stem, etc.); on this base, a dynamic model of organs' comprehensive extinction area index at different canopy depths will be established by dividing the canopy into two parts and accumulating the areas of various organs; and then, the calculate method of the canopy structure parameters, such as organ angle distribution function and area projection function, will be studied, the dynamic model of extinction coefficient at different canopy depths will be established, and the canopy-structure-based simulation of population light distribution will be achieved by combining the simulation method of mathematical function with three-dimensional structure. Through the above research, the following two key scientific issues will be solved: (1) the calculation of canopy structure parameters and the quantitation of organs' extinction effect; and (2) combination of the method for light distribution calculation by three-dimensional structure with the Beer's law.

在本项目组已有油菜形态模型基础上，以油菜冠层及植株器官（叶、茎、花及角果）为研究对象，提取不同株型品种、氮肥和密度处理下油菜冠层结构及光分布等信息，利用3D数字化与系统分析等方法、动态与数学建模等技术，研究各器官自身的弯曲等二维形态，以及叶片与茎干、角果与茎干等器官之间相对位置关系的定量表达，并构建油菜冠层结构模型；在此基础上，通过截分冠层、积分器官面积等方法建立油菜冠层任意高度各器官综合消光面积指数动态模型；进而研究各器官倾角分布函数和投影面积函数等冠层结构参数计算方法，建立油菜冠层任意高度处消光系数动态模型，并采用数学函数模拟和三维结构模拟相结合的方法，实现基于冠层结构的油菜光分布模拟。通过上述研究，拟解决以下两个关键科学问题：（1）冠层结构参数计算与各器官消光作用的定量；（2）三维结构模型与比尔定律计算光分布的结合。

油菜是世界上最重要的油料作物之一，也是我国唯一的冬季油料作物，保持油菜生产的稳定、持续增长对国民经济健康发展具有重要意义。基于冠层结构的光分布模拟可为高光效群体的设计与调控提供高效而精确的手段，是作物生长模型和形态模型的结合点，也是功能-结构植物模型研究的重要突破口。为定量油菜冠层结构进而较机理的模拟光分布，本研究基于2011到2015年4季不同品种、移栽密度及施肥水平油菜田间试验，通过观测不同品种和处理油菜茎、叶和果等器官形态参数，并分析上述参数与对应器官生物量间关系，构建了包括叶长[LLj(i)=sqrt(DWLBj(i) ∙LLDWCNj) ]、最大叶宽[LWMaxj(i)=sqrt(DWLBj(i) ∙LWDWCNj) ]、叶柄长[LPL j(i)=LP0+LP1×LL j(i) ]、叶曲线[f(x) = Lci∙x2+ cot(TA)∙x]、茎长[SLm(i)=Sa∙WDSm(i)+Sb]、轴长[RLm(i)=Ra∙WDRm(i)+Rb]、分枝曲线[fr(x) = Rci∙x2+ cot(RTA)∙x]、果长[SL(i)=SLa∙WDSL(i)+SLb) ]、果粗[SW(i)=SWa∙SL(i)+SWb]等在内的基于生物量的油菜器官形态参数模型，进而分析了茎、叶位高，构建了冠层结构模型，模拟了器官消光面积。在此基础上，利用截分冠层、积分器官面积等方法定量了冠层结构对消光参数的影响，建立油菜冠消光面积指数[KAh(i)= KLSAh(i)+ KPAh(i)]、器官倾角分布函数[f(θL)]及消光系数(Kd)模型，最终通过比尔定律实现了光分布模拟。上述研究连接了生物量、器官形态、冠层结构、冠层消光参数及冠层光分布，实现了冠层结构参数与各器官消光作用的定量模拟，以及两种计算光分布方法（微观的三维结构模型与宏观的比尔定律）的结合，为通过生物量将油菜生长模型与形态结构模型结合提供了机理性较强的方法，为建立油菜功能-结构模型奠定了基础。