By Dave Houston
A field-use trail guide for the Greenbank’s Hollow Nature Trail is available at the Historical Park. However, the following description contains added detail and photos (click on photos and figures to enlarge). Even so, this is a work in progress as more information will be included as it becomes available.
Examples of things to come:
- Lists, descriptions and photos where appropriate, of plants and animals found here along the trail or surrounding area, including birds, mammals, amphibians and reptiles, and insects, as well as other biota such as fungi and archaea.
- Detailed descriptions and location (map) of the soils present here, including their suitability for supporting plants, etc.
- Information related to Joe’s Brook including seasonal flow data, water chemistry, suitability for fish habitat, and historical use of water power.
- Additional geological details concerning the origin, formation and characteristics of the bedrock beneath the Park.
- The influence of the bedrock and the last glaciation on the shape of our landscape and the soils that blanket it.
The bedrock underlying this area consists primarily of the Waits River Formation,
a metamorphic rock complex formed during the Devonian Period (410 to 360 million years ago). This was a very active period geologically. Land masses in the lapetan Marine Basin (precursor to the Atlantic Ocean) gathered into supercontinents, squeezing sediments from the ocean floor between them and metamorphosing those sediments from the pressure as the landmasses collided.
Before this collision, highlands along the shorelines eroded, yielding huge volumes of sediments that were deposited in vast nearby lowlands and shallow seas. Some of these sediments, together with deposits of lime-rich sea organisms, became the metamorphic rocks of the Waits River Formation when they were subjected to repeated deformation and metamorphism during closure of the lapetan basin and collision of the landmasses that would someday be known as Europe and America.
Our complex bedrock, therefore, has a complex history: Seabed deposits, comprised of both volcanic and carbonate sediments, most likely fine quartz sand with clay partings, silts and clay-rich muds, became sedimentary rock beds of limestone and shale. These rocks, in turn, were metamorphosed to become the dark marbles, phyllite, and mica schists characteristic of the Waits River Formation. These rock types interbed and intergrade and may contain other minerals depending on the degree of metamorphism.
This rock complex, examples of which can be seen exposed as the bottom and south shore of Joe’s Brook near the sawmill and gristmill sites, is the basis of the fertile, non-acidic agricultural soils of eastern Vermont.
Glacial activity and time have blanketed this little park with a relatively complex mosaic of soils. These range from poorly- drained Cabot, to moderately well-drained Buckland, to well-drained Dummerston. The soils appear relatively deep, with pH (acidity) levels ranging from 5.1 to 7.3 (7.0 is neutral), ideal for northern hardwoods (birch, beech, maple) in the drier areas (Buckland, and Dummerston) and cedar where soils are wetter (Cabot). These soils are all highly erodible.
Land Use History
In the early- to mid- 1800’s most of the park and surrounding area was cleared. Areas too wet, steep, or stony for agricultural uses were retained as woodlots. Later, as lands surrounding residences and mills were abandoned from active agriculture, the inexorable natural process of plant succession began and, eventually, much of the parkland earlier cleared for farms and residences became occupied, once again, by forest shrubs and trees. This Nature Trail passes through such early stage forest and “old” woodlot areas.
THE NATURE TRAIL
The trail is described below as it descends down a steep slope to brook level. It is moderate in difficulty (many steps and switchbacks), and one can choose to descend or ascend -–it is delightful either way. For a printable hard copy of the map click this link: map and legend.
Beginning at the School House (Site 8), the trail passes east through large white pines, Pinus strobus L., (1) that seeded in on the formerly open land around the school and the adjacent “Adams residence” (Site 9). Some of these trees are now declining (note their thin, small crowns). It is very likely that parts of this site are a bit too wet to support mature white pine. Indeed, the little “sedge meadow” (2) between the school and the Adams residence denotes a site quite wet for parts of the year and probably delineates where the Cabot soils begin to appear. Near the edge of the steep slope, where soils are better- drained, the pines are bigger and in good health.
Near where the trail turns to start down the steep, south-facing slope some large black cherry, Prunus serotina Ehrh., (3) trees also bear witness that the land here was once open. Like white pine, this “shade-intolerant” species needed full sunlight to become established. Before turning and heading down, note where, just ahead, the land drops sharply to a ravine (4) being created by an intermittent stream cutting down through this highly erodible soil on its way to Joe’s Brook.
The trail descends through a dense stand of northern white cedar, Thuja occidentalis L., (5).
A blow-down here has created a jackstraw tangle of cedar trees. This species characteristically occurs on organic soils in “moist, cool, nutrient–rich sites near streams or other drainage ways” and on “calcareous mineral soils”—a perfect description of this site. In the blow-down area, where light now reaches the ground, saplings of black cherry, white ash, Fraxinus americana L., and sugar maple, Acer saccharum Marsh., are making their way up through the tangle.
Further downslope, light-loving species become more abundant where an opening (6), created by an earlier tree harvest, allows sunlight to penetrate the understory of the slope- side. Along the edge of this opening black cherry, paper birch, Betula papyrifera Marsh., and mountain ash, Sorbus americana Marsh., become more numerous. Clumps of alder, Alnus spp., and an occasional willow, Salix spp., occur in the lower, wetter areas along with dense ground covers of ferns, milkweed, goldenrods and grape. Large remnant ash, cedar, and cherry trees are scattered in and around the opening.
After a short swing back onto the cedar slope, the trail descends through an arch created by a storm-broken cherry. Note the “new” trees that have arisen following the “accident” as well as the storm-bent older cherry nearby.
Just beyond, the first of a series of boardwalk bridges (7) span small “ravines-in-the-making” where water floods downhill in times of heavy rains. Here, moss-covered cedar logs and abundant ash and mountain maple, Acer spicatum Lam., attest to the moistness of this cool bottomland. Large cedar stumps and downed logs still present here, long after trees were cut, testify to the high decay resistance of this species.
Just beyond the bridge, a spur trail turns left (south) and then up and along a narrow knob to its end. Cool and moist, this site is ideal for balsam fir, Abies balsamea L., sugar maple, cedar and, especially, for yellow birch, Betula alleghaniensis Britton, that makes its first trail appearance here (8). This side spur, kept “more natural” than the main trail, affords a wonderful opportunity for solitude and enjoyment of the sight and sounds of the brook below.
A sitting bench at trail’s end (9) rests within a ground cover patch of Canada yew, Taxus canadensis Marsh., surrounded by tall cedars and old birch. While not especially common, the patch of yew here is quite extensive as it spills down over the edges of the knob. This unique knob most likely exists because of its underlying bedrock—a bit of which can be seen from the main trail below.
The main trail continues over the next boardwalk bridges. Note the huge trunks of old trees that have fallen downhill on the right (10). Big trees become targets for wind and ice storms and are especially vulnerable on steep slopes when soils become saturated.
Continue through the “fallen tree zone” to the sawmill (Site 11) where a short side trail leads down to the north shore of Joe’s Brook.
Here, excellent examples of the Waits River Formation rocks are exposed as ledges of both the stream bottom and banks of the south shoreside (11). The brown, weathered, crustose surfaces and the inclusions of quartzite and schists are characteristics of these rocks.
In times of low water, radiating patterns of varying sizes can be seen on some worn surfaces. These are crystals of minerals that were formed during metamorphism. Note that some of these minerals are more resistant to erosion and weathering and stand out in relief from the softer, more calcareous country rock.
The trail ends as it enters the meadow just past the gristmill (Site 10). Here, the forceful, flowing water, long freed from the task of turning millstones, works relentlessly to remove the mill’s foundations and reclaim its stream banks.