Nature Notes: Seeds of Change

Hints of global warming
Non-native grasses like broomsedge and purple love grass, which normally thrive in slightly warmer climates, are taking over in open meadows where the native little bluestem once thrived. Larry Penny PhotosNon-native grasses like broomsedge and purple love grass, which normally thrive in slightly warmer climates, are taking over in open meadows where the native little bluestem once thrived. Larry Penny Photo

   Monday morning, the yard covered with a thick blanket of snow, but hints of global warming — six male robins and some starlings visited the privet and sniped the dark berries one by one. They were at it yesterday as well. The berries looked black, but when digested and defecated, they left deep purple stains in the snow. Privet berries must be emergency rations for berry-eating robins, which never feed on seed or suet.
    Each year more and more robins show up in local midwinter bird counts. They are invariably males. The females with less colorful breasts must all go south. It has not been determined if these winter robins breed locally, as cardinals, titmice, red-bellied woodpeckers, and mockingbirds do, or if they arrived from farther north.
    Having both migrating bird species in the wrong place in the wrong season speaks to climate change. But so, too, does certain changes in plants. In the last few years some remarkable changes have occurred among the Long Island grass species. The weather must have something to do with it, but there may be other causes working behind the scenes.
    Up until a few years ago when you rode along roads with open fields or shoulders on both sides, especially on the Sunrise Highway and Long Island Expressway, you were bound to see little bluestem grass among the non-native grasses. A two-foot high native that is tawny to mauve, slender and flexible in stature, and standing up proudly well into winter, it is one of the original grasses of the Long Island prairies, those where the Long Island Coliseum and airports now stand in western Suffolk County and Nassau County, as well as at the Shinnecock Hills and in Montauk, where extensive grasslands at one time covered more than 50 percent of the hamlet of Montauk.
    Lately however, the little bluestems have been replaced by two other grasses, broomsedge (Andropogon virginicus) and purple love grass (Eragrostis spectabilis). The first is straw-colored to tawny and taller than little bluestem, the latter is less than eight inches tall and is purple. It has a special mechanism for expanding its range not seen in many grasses.
    It turns out that little bluestem (Schizachyrium scoparium) is in a group called cold-weather grasses. On the eastern seaboard it ranges far north, throughout New England and into Canada. Apparently, it was one of the first grasses to colonize Long Island after the glacier melted and retreated to the north about 10,000 years ago, before which Long Island’s surface was like a tundra. Dune bluestem (Schi­zachyrium littorale), a much rarer and much taller sibling cold-weather grass species found along the duny edges of salt marshes, also ranges north to Maine along our coast.
    Little bluestem likes cold winters, moist weather, and soils that are not sparing of nutrients. When many Long Island agricultural fields went out of cultivation, little bluestem gladly stepped in and became one of the dominant “old field” species. Things are changing rapidly, however. Broomsedge has been taking over its former territory, forming pure stands and outcompeting little bluestem. In Brookhaven Town, Southampton Town, and large areas of East Hampton Town, broomsedge is now the dominant grass. Little bluestem is making its last stand in Montauk where broomsedge is still uncommon.
    It turns out that broomsedge and purple love grass are warm-weather grasses. They get as far north as Cape Cod in Massachusetts but not to Vermont, New Hampshire, and Maine. These two can handle poor sandy soils well, and eschew long periods of freezing weather and droughty conditions. Last summer was droughty and broomsedge thrived as never before. After Irene, with its highly desiccating gale force winds passed by in late August 2011, purple love grass became dominant along many of the major highways, forming a pleasing purple haze for miles on end.
    It’s not just global warming that is abetting the spread of these two grasses. They both bloom in late summer, and don’t shed their seeds readily, sometimes not until the following spring when germination time comes around. The love grass has a special attribute for spreading. It dries up into a loose ball about six inches in diameter after fruiting and becomes a tumbleweed, rolling over flat unimpeded surfaces as fast as the wind will take it. In the early fall when the winds are still warm and westerly, it travels east. I was standing on Cranberry Hole Road on Napeague in October of 2011 and watched one roll past me at more than five miles an hour. It traveled east some 100 yards before it passed out of sight.
    The seeds of broomsedge are held tightly within the inflorescence and it takes a lot of work to separate them out. Victoria Bustamante who specializes in gathering seeds and fruit from native Long Island species has spent many an hour extracting a few handfuls of seeds to germinate in her greenhouse. But once extracted, she says, “all you have to do is sprinkle them on bare earth slightly moist and they germinate overnight.” Highway mowers that begin mowing major Long Island roads as early as May can easily pick up and spread stalks with seeds attached and move them along before dropping them.
    Deer feed on little bluestem, but have yet to take to purple love grass, which is scratchy, and broomsedge, which is dry and stiff. That may be another reason for the recent success of these two newish grasses in our area.
    One thing is certain, whether it be climate change, storms, wildfires, foraging competition, or some other chain of events, species both animal and vegetable will continue to change in range and population numbers. Some common ones will become scarce, the way deer were in the mid-20th century, some will flourish, as broomsedge and phragmites are doing now. Each species has different needs, and as we humans rapidly change the landscape, water, and the air around us, some will take advantage of it and some will fall by the wayside.