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Book: Field Soil Water Regime
Published by: Soil Science Society of America

 

This chapter in FIELD SOIL WATER REGIME

  1.  p. 195-212
    SSSA Special Publication 5.
    Field Soil Water Regime

    R.R. Bruce (ed.)

    ISBN: 978-0-89118-900-8

     

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doi:10.2136/sssaspecpub5.c11

Development of Soil Temperature and Soil Water Criteria for Characterizing Soil Climates in Canada1

  1. Wolfgang Baier and
  2. Alex R. Mack2

Abstract

Criteria were established for describing the climatic characteristics of a soil using thermal and water parameters. Indices defining these parameters were based on standard climatological data and on soil temperature measurements, but for areas without adequate measurements, they were based on estimates derived from atmospheric data. Soil temperature at the 50-cm depth was selected to provide basic data on the thermal conditions of the site in terms of daily mean temperature and accumulated heat units. Seasons and periods of the year were established to describe the thermal condition of the site for different intensities of biological activity. Cardinal values to represent seasons and periods of different biological activities were established at mean soil temperatures of OC (32F), 5C (41F), and 15C (59F). The moisture conditions were characterized in terms of rainfall in relation to the water requirement for potential evapotranspiration (PE) over the growing season. A storage capacity of 5 cm (2 inches) of available water was used for the major regions, but other storage capacities could be used to characterize variations in soil textures (sands, loams, clays) and topography that occur within a broad region. Eight moisture subclasses subdivided the spectrum of moisture properties during the growing season (i.e., when soil temperatures were ≥5C) to cover the range in conditions from dominantly saturated for long periods (prehumid) to severe water deficits (subarid). Provision was made for two additional classes which do not occur in Canada. A Soil Climate Map of Canada was prepared from these characterizations showing the thermal classes and moisture subclasses (scale 1:5 million). Known physiographic features of soil types, distribution of natural vegetation, and landscape were used to define the boundaries in greater detail. Some adjustments in the criteria were made to coordinate them with the FAO/UNESCO classification system for North America.

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