When applied to plant canopies, classical radiation theory for a turbid medium yields relatively simple expressions for average fluxes of absorbed radiation within an arbitrary volume of vegetation. However, due to the effects of shading and leaf angle, these averaging volumes usually contain a continuous distribution of leaf-level radiative fluxes ranging from full sun to full shade. These distributions are obscured within turbid media models and are thus usually not considered directly unless a computationally expensive leaf-resolving model is used. Consideration of the full probability distribution of absorbed radiative fluxes can yield valuable information about interactions between plant structure and function, not only for radiative fluxes but also for fluxes of radiation-dependent biophysical processes such as photosynthesis. This work presents the theoretical derivation of probability distributions of absorbed direct, diffuse, scattered, and total radiative fluxes for homogeneous canopies with varying structure. The theory is verified against predictions of a three-dimensional leaf-resolving model, and used to explore the impacts of canopy structure on the distribution of absorbed radiation.

当应用于植物冠层时，混浊介质的经典辐射理论产生了相对简单的表达式，用于表示任意植被体积内吸收辐射的平均通量。然而，由于阴影和叶角的影响，这些平均体积通常包含从全日照到全阴的叶级辐射通量的连续分布。这些分布在混浊介质模型中是模糊的，因此通常不直接考虑，除非使用计算成本高的叶子解析模型。考虑吸收的辐射通量的完整概率分布可以产生有关植物结构和功能之间相互作用的有价值的信息，不仅对于辐射通量，而且对于依赖于辐射的生物物理过程的通量，例如光合作用。这项工作提出了对具有不同结构的均匀冠层吸收的直接、扩散、散射和总辐射通量的概率分布的理论推导。该理论通过三维叶片分辨模型的预测得到验证，并用于探索冠层结构对吸收辐射分布的影响。