Sunday, April 12, 2015

Pool Party

     Ephemeral. Such a lovely, bittersweet word. Beauty paying a brief visit, the essence of spring.
Vernal pools are one of the more intriguing of the seasons ephemeral phenomena. Small ponds of water that collect in topographic hollows, they fill up in wetter times of the year from rain and snowmelt and are usually dry by summer. Here today, gone tomorrow. Beauty, but not forever.
     When I think of vernal pools Denton Preserve comes to mind. The Eastern New York Chapter of the Nature Conservancy owns Denton, which is located in the Town of Greenwich. The 350 acres of land border the Hudson River on the west and stretch a mile east to high bluffs. Access is at a small parking area on Rt. 4 about a half mile north of the green bridge.

     Here is the beginning of a small trail system that winds thru the preserve on the east side of the highway. After just a few steps you will notice a water filled ditch flanked by large abutments. This is a section of the old Champlain Canal that functioned as a major travel corridor for nearly 100 years from 1822 to 1917. Today boat traffic uses the river with locks downstream at Northumberland and upstream at Fort Miller. You can still trace the route of the old canal up thru Fort Edward and beyond all the way to Whitehall.

     Beyond the canal is an open area that was previously mined for shale and used as a dump. Back in the 1980's I spent countless hours as a Conservancy volunteer cleaning the area. Today you can see natural succession at work as mosses, lichens and shrubs slowly reclaim the barren ground. Later in the season look for the unusual fungi called earthstars seemingly growing out of the shale.

     Bordering the opening are woods and several color-coded trail loops. A unique feature of Denton are the shale ridges you will soon encounter. They strike about 30º northeast and dip in an easterly to nearly vertical direction. Deposited horizontally, they have somehow been tilted almost 90º. These ridges create a corrugated washboard landscape with relief maybe 50 feet between ridge top and intervening valley. It's a place quite different from any other and its origin intrigues me.

     I've never found an explanation for the ridges so until a real geologist comes along I'll venture an interpretation. Because the orientation of the ridges matches the Taconic hills just a few miles east it seems there might be a connection. Perhaps blocks of shale were pushed and tipped by tectonic thrusting into a trench in front of the advancing Taconic slices. These blocks could have emplaced in an upright position and if the shale had harder, resistant layers of chert in it that might account for the differential erosion and roller coaster terrain we see today. Glacial scouring could have played a role and the Hudson's flow may have further sculpted the rock. I love a good landscape mystery, especially one that has a satisfying resolution. I'll keep you posted if I find out more.
     In the troughs of this rumpled surface are the vernal pools. During a walk earlier this week I visited at least a dozen of them. Some had opened up, others were still iced over. Any night now they will be busy places, as amphibians use the pools to lay their eggs. Wood frogs, spring peepers and several types of salamanders are known to frequent such pools.

     They are attractive to amphibians for several reasons. Because they dry up later in the season they don't have fish. This eliminates a major predator of amphibian eggs, larvae and tadpoles. Also, being shaded slows down evaporation so they don't dry up too quickly. Plus, the surrounding forest provides ideal habitat for the amphibians once they reach adult stage.
     Naturalists will enjoy checking Denton's pools for eggs and juveniles over the next few months. But remember, this is a dawn to dusk preserve and the big event happens at night. Try to find vernal pools where you have access after dark and go out with a flashlight on a warm, rainy spring evening. Unleash your inner voyeur and enjoy the party. It's the best time to see a variety of frogs and salamanders that are mostly hidden the rest of the year.

     Take note of the forest geography while walking Denton's trails. White pine are the biggest trees and pitch pine and scrub oak hint at past fire. I've also seen traces of fencing indicating a history of grazing. The soils are thin over bedrock and you'll see tipped over trees with their roots pulling up shale. It's a good place to apply some of the principles found in Tom Wessels's Reading the Forested Landscape.

     To the north and east you'll encounter wetlands associated with Van Antwerp Creek and for a short distance the trails use the bed of the old Hudson Valley Trolley Line that once took people from Troy to Lake George. I believe it stopped rolling sometime in the 1920's.

     I'm not aware of any trails on the west side of Rt. 4 but a tour of River Road gives access to both the Hudson and this part of the preserve. The quiet dirt lane starts at the end of the green bridge where Rt. 4 enters Washington County. It's great for walking, running and biking and a favorite spot for birding. You can launch your canoe on the river or explore a small pond. Mrs. Denton lived on River Road, a perfect place for a nature lover. I believe she wanted her homestead to be used as an Audubon Education Center and her land to be preserved for wildlife. I don't think the Education Center ever happened but she got her wishes in the Denton Preserve where both animals and people benefit from her vision.

     After my hike I paused by the side of Rt. 4 for a moment of reflection. Traffic was whizzing by and with errands to run I'ld soon join it. But I was happy I'ld taken an hour to slow down, to experience the brief and the hidden. People have always been on the move here. Indian trails followed the river, Burgoyne's army passed this way enroute to Saratoga. There was the busy canal and the crowded trolley cars taking people to a day at the lake. They're just history now, fading memories, ephemeral. Forests evolve, glaciers melt and rock erodes. The amphibians of spring have some ancient knowledge that tells them "Do it now. This is the time." There's a lesson for us all.

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