Altitudinal zonation

Altitudinal zonation in mountainous regions describes the natural layering of ecosystems that occurs at distinct altitudes due to varying environmental conditions. Temperature, humidity, soil composition, and solar radiation are important factors in determining altitudinal zones, which consequently support different vegetation and animal species. Altitudinal zonation was first hypothesized by geographer Alexander von Humboldt who noticed that temperature drops with increasing elevation. Zonation also occurs in intertidal and marine environments, as well as on shorelines and in wetlands. Scientist C. Hart Merriam observed that changes in vegetation and animals in altitudinal zones map onto changes expected with increased latitude in his concept of life zones. Today, altitudinal zonation represents a core concept in mountain research.

A variety of environmental factors determines the boundaries of altitudinal zones found on mountains, ranging from direct effects of temperature and precipitation to indirect characteristics of the mountain itself, as well as biological interactions of the species. The cause of zonation is complex, due to many possible interactions and overlapping species ranges. Careful measurements and statistical tests are required prove the existence of discrete communities along an elevation gradient, as opposed to uncorrelated species ranges.

Decreasing air temperature usually coincides with increasing elevation, which directly influences the length the growing season at different altitudes of the mountain. For mountains located in deserts, extreme high temperatures also limit the ability of large deciduous or coniferous trees to grow near the base of mountains. In addition, plants can be especially sensitive to soil temperatures and can have specific elevation ranges that support healthy growth.

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