This is a new file opened on March 19, 2009, for an article for the Summer 2009 issue of Kaatskill Life
NOT ALL ABANDONED PASTURES BECOME FOREST by Michael Kudish
When I was in college, we were taught in ecology classes that when old fields and pastures were abandoned, trees soon moved in and the land became forested. The doctrine was called succession and climax. More recently, ecologists in other parts of the United States have found that this doctrine does not always work. In the Catskills, I also find that this doctrine is not necessarily true. Natural reforestation does happen some of the time but not all the time.
My suspicions of exceptions to the doctrine began in 1970 while I was exploring the Catskills for my dissertation on the history of the region’s forests. I found rough-stemmed goldenrod (Solidago rugosa) at an elevation of 3185 feet on the east slope of Sugarloaf Mountain along the Devil’s Path. “What is this doing way up here?” I wondered. This species of goldenrod typically grows at much lower elevations – along roadsides, in fencerows between pastures, and in abandoned fields. How did the plants get up here on the mountain, at least a mile from the nearest old field?
As I explored the Catskills further, I found more and more such remote, high-elevation (3000 to 3800 feet) populations of rough-stemmed goldenrod, sometimes mixed in with its cousins, the lance-leaved goldenrod (Euthamia graminifolia) and the flat-topped white aster (Aster umbellatus, now Doellingeria umbellata). On a few occasions, Canada goldenrod (Solidago canadensis) and joe pye weed (Eupatorium maculatum) were present. I have almost twenty such small, naturally-open sites on my list now.
As my more recent studies focus more on the middle and lower elevations of the Catskills, I find these same plants in great abundance in old beaver meadows. When beaver ponds had flooded the forest, the trees drowned and died. Later, after the beavers left, the dams gave way and the waters drained. These plants then invaded the sunny meadows. They occur abundantly as well on portions of floodplains where forested areas were also destroyed by excessive volumes of water.
Whether it be a high-elevation site, a beaver meadow, or a flood plain, these native, shade-intolerant plants always grow in open sunny areas. All of these sites are naturally-occuring, many in first-growth forests (see Kaatskill Life, Winter 2008-2009, pp. 14-19); none was ever cleared for pasture or crop land.
Yet, these places have the same plants as many abandoned fields and pastures. Native Americans created very few open fields in the interior of the Catskills; forest was first cleared for crop and pasture land with the advent of settlers of European origin mainly after the Revolutionary War.
How did these plants migrate from the old fields and pastures into the beaver meadows, flood plains, and up to small openings nearly at the tops of the mountains? It finally occurred to me that I was thinking backwards. They didn’t. They originated up on the mountainsides, in the beaver meadows, and on the flood plains and migrated into many abandoned fields! Each seed of these plants is inside a small fruit equipped with a parachute (much like dandelion, a non-native, European cousin). Travel by wind is quick and easy.
How can such places high up on the mountains, beaver meadows, portions of flood plains, as well as many abandoned fields and pastures, remain nearly free of trees even after periods from as long as a half-century to a century or more? The best examples are old fields which became part of the New York State Forest Preserve. If we know when they were acquired, then we have a record of at least how many years these lands have not been planted with crops, mowed, grazed, or burned. I am compiling lists of these old fields for future historians who wish to see how long these sites stay open. One old field in Lot 13 along and near the west end of the Huckleberry Brook Trail, on the south side of Cold Spring Hollow, had been purchased by the state between 1924 and 1938 and is still open.
The Devil’s Acre, in the col between Hunter and Southwest Hunter Mountains, was a clearing made by the Fenwick Lumber Company during the first two decades of the twentieth century. It became Forest Preserve about 1921 and parts of it are still open. An old field near the headwaters of the Batavia Kill, on Lot 62 at the junction of the trails which descend from the Batavia Kill Lean-to and from the Black Head-Black Dome col, was acquired in 1913 and is still open.
How do these places stay open for so long? Have you ever tried to push your way through a thicket of rough-stemmed goldenrod, lance-leaved goldenrod, Canada goldenrod, flat-topped white aster, and/or joe pye weed in late summer or early fall when the plants are at least as tall as you are? Look at your feet when you do so. How many tree seedlings do you see under the thicket, or young plants of any other species for that matter? These five species of the Composite Family are perennial herbs – that is, the roots and underground portions of stems live for many years – decades to centuries. Each spring they send up, from buds on underground stems, above-ground stems bearing leaves, flowers, and later fruits. They spread rapidly by these underground stems as well as by seed.
Blackberries and raspberries (Rubus spp.) are in the Rose Family and unrelated to the Composites. Their life cycle is different: they are biennials (they live two years), rather than perennials, with overwintering buds on above-ground stems called canes. Yet they grow with such density that they have the same effect of inhibiting tree reproduction as the composites.
Once established in an old field, open floodplain, or open beaver meadow, all these plants spread rapidly and produce huge numbers of above-ground stems in great density, thousands and thousands per acre. They can shade out and choke out tree seedlings and other plants; they can absorb nearly all of the available water and mineral nutrients from the soil.
Some ecologists believe that goldenrods and asters are also allelopathic, i.e., they produce biochemicals that retard or prevent the growth of other competing plants. But even if no allelopathic chemicals are produced, the sheer intense physical competition is enough to crowd out almost all other plants including tree seedlings.
Why do some old fields and pastures become forested and others not? The future of the field or pasture depends on what plants seed in first after mowing, grazing, or crop planting ceases. If trees seed in first, the old field will become a forest. In a half-century to a century or so, the young forest will consist typically of aspens, birches, red maple, black cherry, white ash, shadbush, hawthorns, pines, and sometimes oaks. In about 150 years, the old field will begin to resemble the forest which preceded the agricultural clearing – a northern hardwoods beech-sugar maple forest often with hemlock. If goldenrods, flat-topped white aster, joe pye weed (in the wetter places), blackberries and raspberries seed in first, trees watch out! These plants can maintain that old field, pasture, beaver meadow, flood plain, and high-elevation opening treeless for centuries.