The role of spatial averaging scale in leaf-to-canopy scaling of non-linear processes in homogeneous canopies

Canopy biophysical models require averaging fluxes over some spatial scale (sub-leaf, leaf, sub-crown, crown, whole-canopy, etc.). Choice of averaging scale can be important when modeling processes like stomatal conductance and photosynthesis that have a non-linear response to environmental variables such as light interception. The model results archived here were used to quantify errors in canopy-level flux simulations due to averaging scale choice. A detailed leaf-resolving model was used to simulate light interception for a series of homogeneous canopies with differing canopy structure. Radiation model parameters and non-linearity of the light response were also varied. Averaging over individual leaves and over various sub-leaf resolutions were compared with averaging approaches used in multi-layer and two-leaf canopy models.

冠层生物物理模型（Canopy biophysical models）需在特定空间尺度（亚叶片、叶片、亚冠层、冠层、全冠层等）上对通量进行平均。当模拟气孔导度（stomatal conductance）与光合作用（photosynthesis）这类对光照截获（light interception）等环境变量存在非线性响应的过程时，平均尺度的选择至关重要。本次存档的模型结果，旨在量化因平均尺度选择差异所引发的冠层通量模拟误差。研究采用叶片解析模型（leaf-resolving model），对一系列具有不同冠层结构的均质冠层（homogeneous canopies）的光照截获过程开展模拟，同时还对辐射模型参数与光响应的非线性程度进行了调整。本研究将单叶片平均与多种亚叶片分辨率下的平均方案，与多层冠层模型（multi-layer canopy models）及双叶片冠层模型（two-leaf canopy models）所采用的平均方法进行了对比。