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Patterns of Forest invertebrates Along an Acidic Deposition Gradient in the Midwestern United States

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The Ohio Corridor Study (OCS) was designed to detect possible effects of acidic deposition on oak-hickory (Quercus-Carya) forests in the midwestem United States. There was one study site in Arkansas, and two each in Illinois, Indiana, and Ohio. Estimates of total sulfate deposition have generally increased about two-fold from west (Arkansas) to east (Ohio) during the 1900s. Sites were broadly analogous in forest cover type, stand age, slope, aspect, mean annual temperature and rainfall, soil type (mostly poorly buffered soils derived from sandstone and shale), and disturbance history. The overall hypothesis was that for analogous stand conditions and soil types, differences in various forest response variables along a geographic acidic-deposition gradient would correspond to differences in pollutant dose. Response variables were correlated with the soil Ca:AI molar ratio, as an indicator of soil acidification, for the upper 50 cm of soil. In the OCS insect studies, as the soil Ca:AI ratio decreased, i.e., became more acidified, there tended to be an increase in (1) population densities of early season, canopy-feeding Lepidoptera larvae (P =.19); (2) foliage consumption by gypsy moth larvae, using a standardized feeding choice test with early season (P= .01) and late-season (P =.16) oak foliage; (3) attack densities of non-lethal, trunk-infesting, living oak borers in the families Cerambycidae and Cossidae on white oaks (Quercusalba) and black oaks (Quercus velutina) (P =.003); and (4) the probability of oak mortality being caused by the twolined chestnut borer, Agrilus bilineatus, a lethal cambial-feeding buprestid beetle (P = 057). Data from other OCS investigators indicated strong correlations between lower soil Ca:AI ratios and reduced tree growth, reduced soil pH, reduced soil invertebrate densities, and increased soil carbon levels. These results suggest that acidic inputs can alter forest ecosystem processes in oak-hickory forests growing on poorly buffered soils.


Forest Invertebrates; Acidic Deposition Gradient; Midwestern United States; oak-hickory


Haack, Robert A. 1996. Patterns of Forest invertebrates Along an Acidic Deposition Gradient in the Midwestern United States. null

Last updated on: August 11, 2006