It is so important that many botanists classify communities along a moisture gradient. The lay of the land, whether it is flat, hilly, upland or low-lying, further refines the composition of a woodland. Low areas, such as those along rivers or in depressions, support species adapted to wet conditions. High, dry uplands support species tolerant of drought. The direction a slope faces, known as slope aspect, also plays a role.
Plants growing on north-facing slopes encounter cooler temperatures and deeper shade.
Maple forests will grow on a north-facing slope.