Predicting and managing light in the understory of boreal forests

This paper reviews current information relating to the dynamics of light in northern and boreal forests and discusses factors affecting overstory ligh t transmission, seasonality of light, sunflecks, canopy gaps, and understor y development, particularly with regard to tree regeneration. Techniques fo r measurement of light in forests such as radiometers, photosensitive paper or chemicals, hemispherical canopy photographs, the plant canopy analyzer, or visual estimators of canopy density are each discussed in terms of thei r accuracy, costs, ease of use, and conditions required during measurement. Predictive models of light transmission based on canopy architecture are a lso described in terms of their assumptions, accuracy, and input data costs . Lastly the paper discusses the relationship among overstory and understor y densities, ground-level light, and "windows;of opportunity" for regenerat ion of trees in the understory following management interventions.