Effects of regular salt marsh haying on marsh plants, algae, invertebrates and birds at Plum Island Sound, Massachusetts |
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Authors: | Robert N Buchsbaum Linda A Deegan Julie Horowitz Robert H Garritt Anne E Giblin John P Ludlam David H Shull |
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Institution: | (1) Massachusetts Audubon Society, 346 Grapevine Rd, Wenham, MA 01984, USA;(2) The Ecosystems Center, Woods Hole, MA 02543, USA;(3) Arkansas Cooperative Fish and Wildlife Research Unit, Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA;(4) Department of Environmental Sciences, Western Washington University, Bellingham, WA 98225, USA |
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Abstract: | The haying of salt marshes, a traditional activity since colonial times in New England, still occurs in about 400 ha of marsh
in the Plum Island Sound estuary in northeastern Massachusetts. We took advantage of this haying activity to investigate how
the periodic large-scale removal of aboveground biomass affects a number of marsh processes. Hayed marshes were no different
from adjacent reference marshes in plant species density (species per area) and end-of-year aboveground biomass, but did differ
in vegetation composition. Spartina patens was more abundant in hayed marshes than S. alterniflora, and the reverse was true in reference marshes. The differences in relative covers of these plant species were not associated
with any differences between hayed and reference marshes in the elevations of the marsh platform. Instead it suggested that
S. patens was more tolerant of haying than S. alterniflora. Spartina patens had higher stem densities in hayed marshes than it did in reference marshes, suggesting that periodic cutting stimulated
tillering of this species. Although we predicted that haying would stimulate benthic chlorophyll production by opening up
the canopy, we found differences to be inconsistent, possibly due to the relatively rapid regrowth of S. patens and to grazing by invertebrates on the algae. The pulmonate snail, Melampus bidendatus was depleted in its δ13C content in the hayed marsh compared to the reference, suggesting a diet shift to benthic algae in hayed marshes. The stable
isotope ratios of a number of other consumer species were not affected by haying activity. Migratory shorebirds cue in to
recently hayed marshes and may contribute to short term declines in some invertebrate species, however, the number of taxa
per unit area of marsh surface invertebrates and their overall abundances were unaffected by haying over the long term. Haying
had no impact on nutrient concentrations in creeks just downstream from hayed plots, but the sediments of hayed marshes were
lower in total N and P compared to references. In sum, haying appeared to affect plant species composition but had only short-term
affects on consumer organisms. This contrasts with many grassland ecosystems, where an intermediate level of disturbance,
such as by grazing, increases species diversity and may stimulate productivity. From a management perspective, periodic mowing
could be a way to maintain S. patens habitats and the suite of species with which they are associated. |
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