Academic journal article The American Midland Naturalist

Heavy Metal Accumulation by Old-Field Plant Species during Recovery of Sludge-Treated Ecosystems

Academic journal article The American Midland Naturalist

Heavy Metal Accumulation by Old-Field Plant Species during Recovery of Sludge-Treated Ecosystems

Article excerpt

JOHN D. PELES

Institute of Ecology, University of Georgia, Athens 30602

SUSAN R. BREWER

Department of Zoology, Miami University, Oxford, Ohio 45056

GARY W. BARRETT1

Institute of Ecology, University of Georgia, Athens 30602

ABSTRACT.-Concentrations of heavy metals in old-field plant species were compared among untreated reference subplots, unlimed sludge-treated subplots and limed sludge-treated subplots during the 4th yr of ecosystem recovery following long-term (Il-yr) nutrient enrichment. Although results varied on a metal-specific and species-specific basis, liming was overall successful in reducing metal concentrations in old-field plant species. For example, concentrations of Cd in leaves and roots and concentrations of Pb and Zn in roots of Ambrosia trifida were significantly lower in plants collected from limed compared to unlimed sludge-treated subplots. Liming significantly reduced concentrations of Cd in leaves and roots of Solidago canadensis, and in the leaves, roots, and seeds of Setaria faber to levels found in untreated reference subplots. Liming also significantly reduced concentrations of Cu in the roots of Solidago canadensis, Pb in the roots and seeds of Setaria faberii, and Zn in the roots and leaves of S. faberii to reference levels. Changes in plant species composition during secondary succession may also indirectly reduce metal uptake since the annual Ambrosia trifida accumulated Cd and Zn in leaves, roots and seeds at levels two to three times greater than did the perennial Solidago canadensis.

INTRODUCTION

Long-term application of municipal sewage sludge or fertilizer to old-field communities alters plant community composition and the trajectory of secondary succession (Hyder and Barrett, 1986; Carson and Barrett, 1988; Brewer et al., 1994). For example, following 11 yr of sludge or fertilizer application at a study site in the midwestern United States, nutrientenriched plots (i.e., sludge- or fertilizer-treated plots) were dominated by summer annual plant species whereas untreated reference plots were dominated by perennial species (Carson and Barrett, 1988; Brewer et al., 1994). In addition, soil pH was significantly reduced in sludge- and fertilizer-treated plots compared to reference plots (Benninger-Truax and Taylor, 1993; Brewer et al., 1994). Long-term sludge application also significantly increased levels of heavy metals in soil and within species representative of the producer, primary consumer, secondary consumer, and detritivore trophic levels at this study site (Anderson et al., 1982; Kruse and Barrett, 1985; Levine et al., 1989; Brueske and Barrett, 1991; Benninger-Truax and Taylor, 1993; Larsen et al., 1994).

Following long-term nutrient enrichment, mechanical (tilling to disturb the plant seed bank) and chemical (liming to restore soil pH to reference values) manipulations were done to examine the potential for recovery of old-field ecosystems. Recovery is defined here as when values for structural and functional parameters no longer differ significantly from values in untreated reference plots. Although tilling had little effect on old-field community or ecosystem parameters, liming restored soil pH in sludge- and fertilizer-treated plots to reference values by the 3rd yr of the recovery period. In addition, total annual net primary productivity (ANPP) of the perennial Solidago canadensis-the dominant species in untreated reference plots-had greatly increased in former nutrient-enriched plots by the 3rd yr of liming (Brewer et al., 1994).

Although it appears that the recovery of old-field ecosystems is possible following longterm sludge application, there is a paucity of information regarding metal uptake by oldfield plant species during the recovery process. The present investigation focused on the accumulation of heavy metals within the producer trophic level of an old-field community during the 4th yr of recovery in sludge-amended ecosystems. …

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