Altitudinal zonation

Temperature, humidity, soil composition, and solar radiation are important factors in determining altitudinal zones, which consequently support different vegetation and animal species.

[2][3] Altitudinal zonation was first hypothesized by geographer Alexander von Humboldt who noticed that temperature drops with increasing elevation.

Careful measurements and statistical tests are required to prove the existence of discrete communities along an elevation gradient, as opposed to uncorrelated species ranges.

[8] In addition, plants can be especially sensitive to soil temperatures and can have specific elevation ranges that support healthy growth.

[9] Even though rainfall may not be a significant factor for some mountains, atmospheric humidity or aridity can be more important climatic stresses that affect altitudinal zones.

One of the most important factors that control the lower boundary of the Encinal or forest level is the ratio of evaporation to soil moisture.

For example, for mountains found in the tropical rainforest regions, lower elevations exhibit fewer terrestrial species because of the thick layer of dead fallen leaves covering the forest floor.

[3] In a different example, weathering is hampered by low temperatures at higher elevations in the Rocky Mountain of the western United States, resulting in thin coarse soils.

However, there is an accumulating body of evidence that competitively dominant plants may seize the preferred locations (warmer sites or deeper soils).

Along with the expected arid conditions at higher elevations, shrubs and grasses tend to thrive because of their small leaves and extensive root systems.

These include: frequency of disturbance (such as fire or monsoons), wind velocity, type of rock, topography, nearness to streams or rivers, history of tectonic activity, and latitude.

Elevation, climate, and soil fertility set upper limits on types of crops that can reside in each zone.

Populations residing in the Andes Mountain region of South America have taken advantage of varying altitudinal environments to raise a wide variety of different crops.

The increase in accessibility of mountainous regions allows more people to travel between areas and encourage groups to expand commercial land use.