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Friday, July 1, 2016

THE REMAINS OF A CONNECTICUT GRASSLAND: A FORTY YEAR HISTORY



The switchgrass-sedge grassland of Great Meadow is now largely invaded by cattails and reeds.

The birds were actually better this time around.  In June of 1976, pickings at Great Meadows in Essex, Connecticut were a bit slim, with gulls being among the most abundant species present.  Aside from the ubiquitous Common Yellowthroats, Swamp Sparrows, Marsh Wrens and lone Bobwhite, there was not much of interest present.  In contrast, during this June of 2016, gulls were uncommon and Bobwhites had disappeared, but multiple Ospreys were nesting and several Purple Martins flew overhead.  Both were all but absent in earlier years.  Great Egrets, confined to the river mouth in the 1970s, were also now conspicuously present, as were Rough-winged Swallows, which had replaced formerly common Bank Swallows.  To round things out, a Spotted Sandpiper fed along the banks of the adjacent Connecticut River and a Common Tern explored the river and adjacent tidal creeks.

Forty years have now passed since my first investigation of this extensive lowland bordering the lower Connecticut River.  I had initially gone there to study the extended ecotone between the site’s weakly brackish marsh and adjacent upland.  I thought the wet, grassy meadow that developed there was about as close as southern New England could come to having an extensive natural grassland, and I wanted to document its nature so that I might determine its persistence over time.  Toward that end, I inventoried the entire site and also established a study plot to quantify the presence of key community members.  My plot, chosen to be representative of the site as a whole (although I noted that there was a gradient in species composition from the north to south end), demonstrated that the predominant species were switchgrass (Panicum virgatum), a short species of bulrush- Scirpus americanus, and a sedge- Eleocharis palustris.  In all, I found 11 herbaceous species occupying the 100 m2 plot. 

In 1983, I re-visited the meadow and observed that the community was much as it had been seven years before.  However, during this 2016 survey, I found that the ecotone had changed dramatically, with cattails and reeds invading much of it.  Furthermore, S.  americanus now appeared to be present primarily along the edge of the Connecticut River.  This observation left me perplexed enough that I began to doubt my initial identification, but upon later examining specimens I had collected both in 1976 and 1983, I found that my initial determination had been correct.  In the place of this species, I found that the sedges S. fluviatilis, S. atrovirens and the forb Peltandra virginica had become widespread.  I had recorded these species on my 1976 surveys, but none had occurred in the study plot, indicating that they were less common than now.  Switchgrass, although still present, was also not nearly as common as it had once been.  Even into 1983, I was still describing the site as a Panicum meadow, but this characterization no longer held.  Moreover, the entire meadow itself had shrunk from about 6 ha in 1976 to about two ha at present.  All these changes suggested that the site had become wetter over time, with the new dominant species t.ypical of emergent marsh rather than upland ecotone.  Human manipulation in the form of expanded mowing further assisted with reducing the meadow’s extent and, indeed, portions of the meadow have in the past been mowed for hay.

So what is to be gleaned from such long-term observations?  Well, first of all, I’ve concluded that my initial characterization of the meadow as a wet, albeit upland grassland was a bit generous.  With the benefit of now having examined all of the major herbaceous wetlands of the lower Connecticut River for decades, I think that it is more reasonable to characterize such meadows as simply vegetation zones within larger marsh ecosystems.  Furthermore, it now is clear that such communities are not static entities, but are rather dynamic associations that change over time in response to changing physical and competitive environment as as well as to human manipulation.

Alas, the notion of naturally persistent grasslands in southern New England is for me one that has become progressively harder to believe in.  We might still hold out some hope for the reed-canary grass (Phalaris arundinacea) ecotones of more completely freshwater marshes further inland, as Phalaris appears to be aggressively competitive with other species.  However, here again, it seems more reasonable to characterize such habitats as simply marsh vegetation zones rather than upland systems.  I suppose dune grass communities of the coast, nominal though they are, hold the only real claim for being naturally persistent southern New England grasslands.

2 comments:

  1. This is interesting but it's written in the first-person. So I'm wondering who the author is.

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  2. In the mid-1980's Ken Metzler and I were invited to survey this marsh and make recommendations to the Essex Conservation Commission. What we found was an oligohaline marsh dominated by the tall Typha X glauca and the co-dominant was a diffuse short form of Phragmites - we suspected it was the native Phragmites - and this was confirmed back in the 00's. In fact the native Phragmites is present throughout this marsh and is probably the largest natural history museum in the northeast for this species. Local farmers were known to burn the marsh periodically to remove the invasive Phragmites from the backside of the levee to make it easier to harvest the 'salt marsh grasses'. Turns out there are no salt marsh grasses - farmers call anything they harvest on a tidal marsh as salt marsh grasses. They were largely harvesting Panicum virgatum. It may be that burning created the condition described in the article above. It is hard to believe that this marsh was not a Reed dominated marsh in the 1970's.

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