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Acute salt marsh dieback in the Mississippi River deltaic plain: A drought-induced phenomenon?

Global Ecology and Biogeography

By:
, ,
DOI: 10.1111/j.1466-882X.2004.00075.x

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Abstract

Aims Extensive dieback of salt marsh dominated by the perennial grass Spartina alterniflora occurred throughout the Mississippi River deltaic plain during 2000. More than 100,000 ha were affected, with 43,000 ha severely damaged. The aim of this work was to determine if sudden dieback could have been caused by a coincident drought and to assess the significance of this event with respect to long-term changes in coastal vegetation. Location Multiple dieback sites and reference sites were established along 150 km of shoreline in coastal Louisiana, USA. Methods Aerial and ground surveys were conducted from June 2000 to September 2001 to assess soil conditions and plant mortality and recovery. Results Dieback areas ranged in size from???300 m2-5 km2 in area with 50-100% mortality of plant shoots and rhizomes in affected zones. Co-occurring species such as Avicennia germinans (black mangrove) and Juncus roemerianus (needlegrass rush) were unaffected. Historical records indicate that precipitation, river discharge, and mean sea level were unusually low during the previous year. Although the cause of dieback is currently unknown, plant and soil characteristics were consistent with temporary soil desiccation that may have reduced water availability, increased soil salinity, and/or caused soil acidification (via pyrite oxidation) and increased uptake of toxic metals such as Fe or Al. Plant recovery 15 months after dieback was variable (0-58% live cover), but recovering plants were vigorous and indicated no longlasting effects of the dieback agent. Main conclusions These findings have relevance for global change models of coastal ecosystems that predict vegetation responses based primarily on long-term increases in sea level and submergence of marshes. Our results suggest that large-scale changes in coastal vegetation may occur over a relatively short time span through climatic extremes acting in concert with sea-level fluctuations and pre-existing soil conditions. ?? 2004 Blackwell Publishing Ltd.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Acute salt marsh dieback in the Mississippi River deltaic plain: A drought-induced phenomenon?
Series title:
Global Ecology and Biogeography
DOI:
10.1111/j.1466-882X.2004.00075.x
Volume
13
Issue:
1
Year Published:
2004
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Global Ecology and Biogeography
First page:
65
Last page:
73
Number of Pages:
9