across the horizon. From our usual perspective in the Rec Centre at the old schoolhouse, this channel shows as only a faint groove in the uninterrupted green of vast marshes.
|photo by Neil Galbraith|
The channel would be even less visible if Common Reed were here. Taller than a person, this giant plume-headed grass has taken over the salt marshes of the eastern United States since the 1950s and the roadsides of Ontario and Quebec superhighways since the 1970s. Phragmites australis subspecies australis, the Common Reed of Europe, is a threat to biodiversity, as it grows so thickly that it excludes all other wetland plants.
The Musquash Estuary is considered a "fully functional estuary", complete with a thriving and diverse community of salt marsh plants and invertebrates, a rich source of food for fish and fowl. Fred, who has studied both native and invasive Phragmites says that the message to New Brunswickers is “Be scared, be very scared!” If this marsh were in southern New England, or along the Gulf of Saint Lawrence in Quebec, 3-4 metre tall invasive Reeds would dominate the scene.
You can see my painting of invasive Phragmites near home in eastern Ontario. Like many other invasive plants, the frightening thing about invasive Phragmites is the way it spreads from places disturbed by people into a wide diversity of habitats: fresh & saline tidal marshes, beaches, wet and dry roadsides, disturbance-opened forests, and oldfields as well as its traditional wetlands habitat. This invader arrived on the United States mid-Atlantic coast by 1910. By 1960 it had spread inland to New York, along the southern shores of Lake Ontario, and to Pennsylvania and Ohio, along Lake Erie’s shoreline, and then into southern Michigan and then southwestern Ontario. In December 2009 we drove Highway 1 from Saint John to the Saint Andrews turnoff and found Phragmites represented only by three tall, close-growing stands (and another along Highway 7, 9.8 km NW Westfield), which we took for natives, but which Paul Catling of the DAO herbarium in Ottawa has since identified as the invader.
Fred has been trying to alert New Brunswickers to this threat to their tidal marshes since 2001, when, soon after we learned about the difference between the kinds, he found the invader along Highway 11, in Chatham. In August 2010 we collected specimens that confirmed the identity of the Chatham stand and specimens of ambiguous identity from the beach at Cap Lumiere, 1.4 km NNW Richibucto Light. On 30 September 2010, we found both subspecies among the stands along Highway 2 through the Tantramar Marshes across the Isthmus of Chignecto "The first thing we noticed was that the stands were very distinctly divided into native-like and invasive-like kinds: we counted 11 alien and 7 native stands, and only one that we called ambiguous, though the natives graded out into little whisps, and we doubtless missed some of these which an observer on foot could have waypointed. The most striking feature of this difference was the persistent green foliage of the aliens, in contrast to the shrivelled get-ready-for-winter brown of the natives.”
It's thought that Phragmites spreads by germination of the tiny seeds in mineral soil disturbed by earth-moving or along streams or beaches, or more usually, from sprouting fragments of rhizomes or stolons carried by currents or equipment. Once it's established it spreads steadily by underground rhizomes or may leap across the ground with surface stolons which are often 10 metres long. These tall stands profoundly modify their environment. Nothing else grows in the dense stands, the fallen leaves blanket the soil, the matted growth fills small streams and channels, and the roots extract more nitrogen from the soil than anyone has been able to explain. The wind blowing across broken stems pumps air into the huge twisted rhizomes, to oxygenate and change pH and nutrient availability deep into the ground. When Phragmites spreads into acidic or other hostile soils, its pioneering plants are subsidized through rhizomes until they have neutralized the acidity, or otherwise ameliorated conditions, so that they can grow on their own.
As Phragmites was spreading across wetlands throughout the United States in the 1990s, Kristin Saltonstall analysed the chloroplast DNA of living plants and herbarium specimens, finding that the invading stands were genetically related to European Reeds. Recently, the natives have been described as Phragmites australis subspecies americanus, and since only a few hybrids have been identified, they may, in fact, be separate species that rarely interbreed. Once the DNA had shown the way, visible characteristics of the two kinds have been found: stands of natives are less dense, with other plants growing among them. Natives have narrower rhizomes (less than 15mm diameter) and a red or purplish colour on the upper portions of the sections (internodes) of their lower stems, which are smooth or even polished, in contrast to the rough texture and yellowish colour of the lower stems of the invaders. The seedhead parts, especially the “lower glume” of the wispy plumes of the natives are larger (more than 4.2 mm) than the parts that make up the fuller plumes of the invaders. Kristin Saltonstall worked at Yale, and she wasn't able to find any surviving native Phragmites in Connecticut, where the coasts are blanketed with the invaders.
Even in 1954, Fred's walk to Grade One classes in Stratford, Connecticut, included a 100m shortcut along a narrow path through a metres-high invasive Phragmites stand. There's little enough one can do to conserve the natives in landscapes dominated by the invaders. Sadly, the shining red stems of showy natives in a roadside ditch are unlikely to soon replace Bluebird houses as the public sign of a conservationist household. We've known of the difference between the kinds for only 15 years - the natives are decorative, their open stands do benefit wildlife, and they'd be just as useful as the invaders in waste treatment lagoons. Dispersal seems to be the only limiting step in their spread. Since there's still only a small number of invasive stands in New Brunswick, it may be possible to take them out, and protect the Bay of Fundy marshes from “the Grass that ate New Jersey.”
For more on identification, see Cornell University's invasive plants website, and Paul Catling of Agriculture and AgriFood Canada, reports on identification and the Canadian situation in Botanical Electronic News, most recently at Botanical Electronic News. The New Brunswick Invasive Species Council takes what seems to us an excessively relaxed attitude towards this invader.