Distance-independent models for predicting photosynthetically active radiation transmission through young forest plant canopies

Abstract

We developed two distance-independent models for predicting photosynthetically active radiation (PAR) transmission through young forest plant canopies. The two models (model 2, using individual-plant crown area, and model 3, using species cover) were derived from a more complex individual-plant, distance-dependent model (model 1) described in an earlier study. Models 2 and 3 require fewer data inputs and can be used when detailed data on individual plants are not available and (or) spatially explicit predictions of PAR transmission are not of interest. We found close agreement between PAR transmission values between model 1 and models 2 and 3 using data from a plant density study. Mean prediction errors between models 1 and 2 were 0.34% and 1.09% for two plant species studied. Mean prediction errors between models 1 and 3 were 0.77% and 2.58% for the two plant species studied. The extinction coefficients estimated from model 1 were used successfully in models 2 and 3 without additional calibration.