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Responses of Northern U.S. Forests to Environmental Change
ISBN 0-387-98900-5

Chapter 2: Geologic and Edaphic Factors Influencing Susceptibility of Forest Soils to Environmental Change

Scott.W. Bailey
Soil may be the most important factor that determines health and productivity of forests. Nutrient depletion as a consequence of decades of acid deposition is of particular interest in the North, and the subject of much research over the last two decades. In order to compile complete nutrient budgets for forest ecosystems, researchers have begun to study the influence of bedrock on nutrient and water cycling, which may be minimal where thick surficial deposits cover the bedrock, and great where surficial deposits are shallow.

Soil taxonomic units provide a convenient framework to examine effects of environmental change on soil and forest resources. Taxonomic units reflect differences in age of parent material, texture, and composition, which interact with climate, topography, and vegetation to determine how water and nutrients move through the soil profile, how water and nutrients are affected by deposition, and how nutrient content and flux rates are different.

Depletion of base cations is a critical issue for northern forest soils. If weathering of parent material is not sufficient to replace base cations lost to forest growth and leaching, then depletion is likely. Mass balance studies show that depletion of base cations is a problem at some specific sites, but accurate extrapolation of these observations to landscape and regional areas has not yet been achieved. Improved models of susceptibility to nutrient depletion will likely follow better understanding of spatial patterns of the mineralogic composition of soil parent materials, and better knowledge of the mechanisms and locations of weathering patterns at the landscape scale.

Below: Dominant soil orders of the Northern forest region (after Quandt and Wallman, 1997).

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