Aspect (geography)

[2] For example, a slope landform on the eastern edge of the Rockies toward the Great Plains is described as having an easterly aspect.

The further north or south you are and closer to winter solstice, the more pronounced the effects of aspect of this are, and on steeper slopes the effect is greater, with no energy received on slopes with an angle greater than 22.5° at 40° north on December 22 (winter solstice).

This can have major effects on altitudinal and polar limits of tree growth and also on the distribution of vegetation that requires large quantities of moisture.

In Australia, for example, remnants of rainforest are almost always found on east-facing slopes which are protected from dry westerly wind.

Particulate laden winds often blow from a prevailing direction near solar early afternoon; the effects combine in a pattern common to both hemispheres.

Slope effect, a vegetational result of aspect, in evidence in the coastal sage scrub community of southern California's Santa Monica Mtns . The slope on the left side is north-facing, thus moister and dominated by Ceanothus sp. The south-facing slope on the right side is much drier (receiving more direct sun), and is more sparsely vegetated with the more drought tolerant Artemisia californica and Yucca whipplei .
Effects of aspect on vegetation can be clearly seen in this photo from Southwest Idaho near Anderson Ranch Reservoir. The north facing slopes receive more snow often because of prevailing winds and are shaded from direct sunlight during the winter, consequently they have more water available to support trees and forests, while the south facing slopes which receive more insolation are much hotter and dryer and support only smaller more desert adapted woody plant species. North facing slopes here are dominated by a Pinus ponderosa, Pseudotsuga menziesii forest while the south facing slopes are mainly dominated by desert shrubs Artemisia tridentata and Purshia tridentata.