Tuesday, February 2, 2010


The snow offered some good examples of the differences that occur because of the way the landscape lays in relation to certain environmental forces. This positioning so as to face a particular direction is referred to as aspect. Sometimes the term exposure is used to describe the same condition. Here we see a photo of two hillsides with opposite aspects. The hillside on the left faces the south, so it is described as having a south aspect. The hillside on the right has a north aspect.

A south aspect presents a broad surface that efficiently collects the energy of the sun’s rays as they angle in from a southerly direction. This causes the ground to warm quickly as evidenced by the lack of snow cover on the hillside to the left of the creek. South facing slopes are generally warmer and drier than any other area. The sun’s rays just give the north aspect a glancing blow, so energy absorption is limited.

Aspect plays a role in defining the conditions available for plant growth on a particular site. The same events that occur on the slopes of a large hill influence small areas, such as the opposite banks of this shallow drain. The effects of prevailing wind also play a large role in defining the characteristics of certain hillside aspects.

This ant mound is an excellent model of how aspect influences microclimate development. To the south we have warm and dry. The north side is cold and snow covered. This is also a good model to illustrate our seasonal changes. When the sun is positioned south of the equator, the southern hemisphere has summer and we get winter. I think I see Ohio on the north side of the mound.

Any object can produce the effect of creating varying microclimates due to aspect. Most people have experienced foundation plantings on the south side of their house that developed weeks ahead of the same species growing on the north side. The knowledge of how aspect influences growing conditions is important if you are going to do any physical manipulation of the landscape. Seemingly minor events can result in serious changes in growing conditions. A well intended act can easily result in the loss of the plants you are trying to benefit.

No comments:

Post a Comment