11 - Forest Microclimates

Summary

Forest microclimates are the climate within a forest in contrast to a nearby open area created by a clearing or pasture. A robust observation is that less sunlight reaches the ground in a forest than in open areas, but this depends on the size of the clearing, the height of trees surrounding the clearing, and the location in the clearing (relative to the edge) where measurements are obtained. Daytime temperature is generally lower in forest than in open areas, with greatest differences during the growing season; but this, too, is subject to edge effects and whether the canopy is sparse or dense. Wind near the ground is less than in exposed areas or above the canopy. Another point is that there are various microclimates within a forest canopy. The environment of the forest overstory differs from that of the understory, and this has important consequences for species conservation and protection from climate change. Forest microclimates are now recognized as an indispensable ecological service of forests. The forest canopy moderates under-canopy air temperature and buffers the understory from extreme temperatures, possibly lessening the ecological impacts of a warmer world.