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Home → Publications → Tree Planters' Notes → Tree Planters' Notes Volume 23, Number 3 (1972) → Air Humidity, Ground Water Extend Growing Season in Wisconsin

Air Humidity, Ground Water Extend Growing Season in Wisconsin

The length o f the growing season is usually associated with the temperature. Actually the active growth period o f forest stands is determined as much by the available water supply as by temperature. This article describes a more than 100 percent extension o f the growing sea son o f forest plantations in Lake Superior's fog belt under the influences o f "intersylvan rain" and naturally subirrigated soils. Foresters often associate the length of the growing season with temperature range and the period of time between the last and first killing frosts. This emphasis on the temperature factor has been expressed particularly in the classification of H. Mayr (1909), who subdivided the world's forests into units delineated by ranges of temperature in the growing season such as "castanetum," "fagetum," and "picetum." But the period of active growth of forest stands is actually determined as much by the supply of available water provided by precipitation, condensation of vapor, or natural subirrigation as by temperature. This is especially true with coarse sandy soils of field moisture capacities below 8 percent by volume and clay soils of high hygroscopic and inner-capillary retention. The relationship is illustrated by the following example.


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Author(s): G. Chesters, S. A. Wilde

Publication: Tree Planters' Notes - Volume 23, Number 3 (1972)

Volume: 23

Number: 3