Forest understories have lower light intensities. The wavelengths of light that are available are only a subset of those that are available in full sunlight. Understory plants must therefore be shade tolerant—they must be able to photosynthesize successfully with the limited amount of light that is available. They are often able to use wavelengths not available to canopy trees. In temperate deciduous forests understory seedlings "leaf out" before the canopy trees do. This is important because it allows the understory plants a window in which to photosynthesize without the canopy present. This brief period (usually 1–2 weeks) is often a crucial period which allows the plant to maintain a net positive carbon balance over the course of the year.
Forest understories also have higher humidity than exposed areas. The forest canopy reduces solar radiation, so the ground does not heat up as rapidly. Consequently, the understory dries out more slowly than does more exposed areas. The greater humidity allows fungi and other decomposers to flourish. This drives nutrient cycling, and provides favorable microclimates for many animals and plants.
PLANT DIVERSITY IN MANAGED FORESTS: UNDERSTORY RESPONSES TO THINNING AND FERTILIZATION.(Statistical Data Included)
Aug 01, 1999; Abstract. Although most temperate forests are actively managed for timber production, few data exist regarding the long-term...
Overstory influences on light attenuation patterns and understory plant community diversity and composition in southern boreal forests of Quebec.
Sep 01, 2006; Abstract: We have characterized overstory light transmission, understory light levels, and plant communities in mixedwood...