Response of estuarine marsh vegetation to interannual variations in precipitation |
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| Authors: | Kenneth H Dunton Beau Hardegree Terry E Whitledge |
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| Institution: | (1) Department of Biology and Biochemistry, University of Houston, Houston, TX 77204, USA; |
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| Abstract: | The response of deltaic emergent marsh vegetation to increases in precipitation was examined over a 14-mo period at three
sites in the lower Nueces Estuary in south Texas. At all three sites, significant changes in plant biomass, percent cover,
and allocation of aboveground and belowground tissues were associated with more than double the rainfall in late winter and
early spring 1992 compared to the previous year and the 50-yr average for this region. Water column salinities, which ranged
from 10‰ to 35‰ at all three sites in 1991, remained below 10‰ through August 1992. Significant changes in marsh vegetative
structure included decreases in bare space, increases in the percent cover and aboveground biomass of a relatively less salt
tolerant halophytes (Borrichia frutescens), and significant increases in root:shoot ratios inB. frutescens, Batis maritima andSuaeda linearis (inSalicornia virginica root:shoot ratios decreased significantly). Higher precipitation generally led to an overall increase in the biomass of most
marsh perennials, but these increases were not statistically significant. For one species,Lycium carolinianum, additional rainfall extended its growing season through August 1992, 2 mo longer than in the previous year. The expansion
(+58%) ofB. frutescens at one site was also coincident with the significant loss ofB. maritima, whose cover decreased nearly 20%. In an ecological context, these responses suggest that precipitation events in arid environments
may be considered a major physical disturbance that can result in large changes in the composition and relative abundance
of emergent vascular plants over a relatively short period. The long-term significance of these changes is unknown and demonstrates
the value of ecological studies that are conducted over several years for a more complete understanding of the dynamic processes
that regulate marsh productivity. |
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