Climate zones used in The Compleat Botanica

Climatology is the study of seasonal weather patterns occurring in a geographic region. The key factors influencing climate are altitude, latitude, and the proximity to large bodies of water. Several simple but useful schemes attempt to capture these factors into well-defined discrete categories. The most useful of these for the United States of America are:

The USDA hardiness zones, published by the United States Department of Agriculture.

The AHS heat zones, a complement to the USDA hardiness zones. There are 12 geographic zones based on the number of days which reach 86 degrees Fahrenheit. This is published by The American Horticultural Society, 7931 East Blvd. Dr., Alexandria VA, 22308 USA. See also �Heat-Zone Gardening: How to choose plants that thrive in your region�s warmest weather", Linda Bellamy & Henry Marc Cathey, Time Life, New York NY USA, 1998.

The Sunset climate zones, published in the �Sunset National Garden Book�, The editors of Sunset Books and Sunset Magazine, Sunset Books Inc., Menlo Park CA USA, 1997.

The first 24 of these zones were previously published in �Sunset Western Garden Book�, The editors of Sunset Books and Sunset Magazine, Sunset Books Inc., Menlo Park CA USA, 1988.

The Plant communities are published in �A California Flora and Supplement�, Philip A. Munz & David D. Keck, University of California Press, 1959, 1968.

The Biotic communities represent the hierarchical classification system published in "A Classification of North American Biotic Communities", David E. Brown, Frank Reichenbacher and Susan E. Franson, University of Utah Press, 1998.  This system defines seven global "realms": Nearctic, Palearctic, Neotropical & Antarctian, Indomalayan, African, Australian, and Oceanic.  Within each realm are defined four "hydrologic regimes":  Natural upland vegetation, Natural wetland vegetation, Aquatic/submerged freshwater, and Marine environment.  These hydrologic regimes are subdivided into six "formation-types":  Tundra, Forest and Woodland, Scrubland-grassland, Desertland, and Non-vegetation.  Further refinement of this hierarchical system extends to four "climactic zones", multiple "biotic communities", "series", "associations", and "strands".