Living Lighter on the Land
Invasive species are a major threat to biodiversity worldwide, second only to habitat loss. In this enlightening summit in Ross Hall, five experts share their hard-won insights about best practices to manage and restore ecosystems, and engage in audience conversation about how to establish goals, prioritize, take action to implement projects, and overcome challenges to achieve long-term success in both small- and large-scale sites.
Topics and Speakers:
Removal is Not (Usually) Enough!
Paddy Woodworth, award-winning Irish journalist and author of Our Once and Future Planet
Restoration Success in a Densely Urban Environment
Kristy King, Director of Natural Areas Restoration and Management for NYC Parks
So Many Weeds, So Little Time
Art Gover, Research Support Associate for the Penn State
Lessons from Urban to Suburban Environments
Tate Bushell, Director of Stewardship with the Westchester Land Trust
Jessica A. Schuler, Director of the Thain Family Forest at NYBG
Co-presented with Lower Hudson Partnership for Regional Invasive Species Management:
In this latest installment of the Pound Ridge Land Conservancy (PRLC) blog, I invite you to explore the vast history of time written in the rocks of Pound Ridge with a focus on the Armstrong Preserve, located in the northwestern corner of town at 1361 Old Post Road. Trails at this preserve are open to hikers every day of the year from dawn to dusk.
To begin, please imagine that your arm represents geologic time, with your shoulder joint being the Big Bang and the tip of your middle finger representing today. Rocks began to form near your elbow and the dawn of life occurred just before your wrist. Between your wrist and the middle of your palm, the prominent bedrock types of Pound Ridge were created by successive waves of mountain-building events. They were then covered and contorted repeatedly, over millions of years, and eventually stripped bare by the glaciers that receded only 20,000 years ago, near the tip of your middle finger on our imaginary time scale. We must look to the wider region and even the other side of the world to piece together this vast history, much of it obliterated by time.
The oldest rock in Pound Ridge is the Fordham gneiss underlying Armstrong Preserve. It was produced 1.1 billion years ago during a Precambrian period called the Grenville Orogeny, when this part of the world was located in the Southern Hemisphere and was turned 90 degree on its side from our current orientation. This collision between then-continents Laurentia and Amazonia caused the rise of a massive mountain range that compressed and deformed existing rock into a Gneiss basement layer that is called the Grenville Province and underlies much of New York.
Gneiss is a high-grade metamorphic rock, formed from either granite or sedimentary layers under intense heat and pressure. It is resistant to weathering and can be seen in the many exposed outcrops of Armstrong as well as in the nearby Ward Pound Ridge Reservation. While variable in color, gneiss displays distinct foliation, or grain, created by alternating layers of its component minerals: quartz, plagioclase, biotite mica, garnet, hornblende and others. The alternating light and dark colors that are so characteristic of gneiss do not represent fossilized sedimentary layers but rather a restructuring and realignment of minerals into layers that are called “gneissic banding.”
The basement layer we now see visible before us was increasingly buried by the sediments of the eroding Grenville Mountains over the next 400 million years, which depressed the land with their great weight and at times were inundated by shallow seas. Then, in the late Ordovician Period, a volcanic island arc approached and slammed into this part of the continent. Called the Taconic Orogeny, it’s pressure created our local Manhattan Schist and Inwood Marble and severely folded the existing bedrock into large ENE-WSW trending ridges and valleys. This or a subsequent episode caused some intrusions of granitic pegmatite in Armstrong’s bedrock as well, which were subsequently folded too.
Life was difficult in New York for the next few million years as continents collided and mountains rose and fell. The Fordham gneiss of Armstrong experienced a third wave of compression and metamorphosis in the Acadian Orogeny followed by another long period of erosion of highlands and sedimentation of lowlands. Folding caused by this event runs in a NNE direction and is difficult to discern from the preceding episode.
The last of the great mountain-building events was the Alleghanian Orogeny, 300 million years ago in the late Carboniferous Period. This fourth collision resulted in the formation of Pangaea and was strongly felt in southeastern New York, where it produced tight folds that reoriented earlier land formations.
The supercontinent Pangaea did not last long before it began to rift apart, resulting in volcanoes and allowing inundation of previously dry land. Evidence from that period is visible in the Hudson River Valley and in the Palisades, but was largely swept clear from Pound Ridge in the Pleistocene: the age of glacial advance and retreat. An ice sheet measuring one-half mile thick ground back and forth across this landscape for nearly 100,000 years, freezing and thawing, cracking rocks and transporting them from mountaintops to the sea. During four long periods of retreat, the glaciers dropped stone inland and created dams and flooding, and a rise in sea levels that brought the sea to our door.
The last glacial ice disappeared from Pound Ridge about 12,000 years ago, leaving behind a roughened and stony landscape that has been little changed by the thin mantle of forest now covering it. We can readily see the glacier’s action in the exposed stony faces of east-facing hills and the till and boulder-strewn west-facing slopes. Glacial erratics are common: there is a huge boulder perched atop a forty foot cliff at Armstrong’s Crow Ledge, tumbled for some distance but now at a high point in the Preserve. There are also several lesser cliffs, some with wonderful gneissic banding and folding, and talus at their bases. The vast majority of rock seen will be Fordham gneiss but there is the possibility of finding any mineral from higher elevations carried here by force of wind or water, or even human.
Keep an eye out for history on the landscape. It has quite a tale to tell, if only we read the clues.
Thank you to Ted Dowey for photographs and assistance with this exploration. I have also relied heavily upon the following published resources:
Robert Titus of Hartwick College, frequent contributor to regional media and author of The Catskills: A Geological Guide. Third edition 2004. (link)
Chet and Maureen Raymo’s invaluable book Written in Stone: A Geological History of the Northeastern United States. Third edition in 2001. (link)
Mehdi Alavi’s 1975 Thesis: Geology of the Bedford Complex and Surrounding Rocks, Southeastern New York. University of Massachusetts, Amherst. (link)
This collection of photographs depicts mushrooms found in Halle Ravine in the last few fall seasons and is a good primer for what we can expect to see on our guided walk on September 24. Registration for that event is filling quickly so please contact Krista by email or by phone (914-205-3533) to register or to cancel and make room for another person to join us.
We have encountered dry weather conditions in most years and therefore find mainly bracket fungi, which are supported by the moisture held in wood. For the difficult to distinguish species, I include several instructive photos from Richard Nadon and others from MushroomExpert.com.
Halle Ravine is a nature preserve protected by the Pound Ridge Land Conservancy and is open for hiking every day from dawn to dusk. Foraging or collection of any form of wildlife is generally prohibited in the Preserve. Trail maps and more information are available at www.prlc.net/preserves.
Please join us for wildflower planting at Halle Ravine on Saturday, June 3rd, 10am to noon (link to directions). Families and non-gardeners are welcome to participate and to learn more about the value of our native plants and what they can do to bring in more birds and butterflies at home. Volunteers can assist with planting, watering, or removing non-native invasive species. We will have more than 200 plants on hand, all grown from locally collected seed and raised at the Armstrong Preserve and Education Center’s native plant nursery. Please bring a shovel or garden trowel if you have one. We will have some to share.
Our goal is to establish a native plant community in place of the thick stand of invasives that formerly dominated the entrance and pond edges. Wildflowers will help to fill space between the 200 young tree and shrub saplings that were planted during our Arbor Day Celebration last month, anchoring and shielding the soil while providing food for insects and birds. We hope to see these native plants become established and to begin to spread outside of their protective deer cages next year. Please email Krista if you would like to volunteer your gardening, photography, or other skills to this project on another date (firstname.lastname@example.org).
This volunteer event is part of our larger restoration efforts at Halle Ravine and is supported with funding from neighbors like you and by the New York State Conservation Partnership Program (NYSCPP) and New York’s Environmental Protection Fund. The NYSCPP in administered by the Land Trust Alliance, in coordination with the state Department of Environmental Conservation.
Native Plant-Insect Associations of Species Selected for Halle Ravine Restoration Planting
|Common name||Latin name||Bees||Butterflies||Moths||Other||Notable species|
|Blue-stem goldenrod||Solidago caesia||x||x|
|Cardinal Flower||Lobelia cardinalis||x||Ruby-throated hummingbird, Swallowtail butterflies|
|Climbing boneset||Mikania scandens||x||x||x|
|Columbine||Aquilegia canadensis||x||x||Ruby-throated hummingbird|
|Common boneset||Eupatorium perfoliatum||x||x||Baltimore checkerspot butterfly|
|Common heartleaf aster||Symphyotrichum cordifolium||x||American lady, Pearl crescent, Saddleback caterpillar|
|Flat topped aster||Doellingeria umbellate||x||American lady, Pearl crescent|
|Gray goldenrod||Solidago nemoralis||x||x||x|
|Great blue lobelia||Lobelia siphilitica||x|
|Horse mint||Monarda punctata||x|
|Tall meadow rue||Thalictrum pubescens||x|
|White wood aster||Eurybea divaricatus||x||American lady, Pearl crescent|
|Wild bergamot||Monarda fistulosa||x||x||x|
Pound Ridge’s Arbor Day Tree Planting and Celebration at Halle Ravine on April 28, 2017 was a grand success! Twenty-five people planted two hundred trees and shrubs in designated areas around the northern-most pond, which is visible from Trinity Pass near the Preserve entrance. We are grateful for their service in helping us to achieve our goal to enhance native understory forest in a 1.5 acre area that we just cleared of invasive Winged euonymus (aka Burningbush), with the long term plan of supporting native songbirds and other wildlife through habitat management.
We received funding for this work from the New York State Conservation Partnership Program (NYSCPP) and New York’s Environmental Protection Fund. The NYSCPP in administered by the Land Trust Alliance, in coordination with the state Department of Environmental Conservation. We also partnered with the Town of Pound Ridge Conservation Board, the Henry Morgenthau Nature Preserve, The Invasives Project-Pound Ridge, and our local troop of Girl Scouts for this event. Members of the Pound Ridge Garden Club generously donated a shuttle service to and from the Town Park, to alleviate the limited parking situation at Halle, and they helped to plant as well. Special guest Brad Gurr of Bartlett Tree Experts donated 100 oak and sycamore saplings and taught volunteers how to properly plant them. New York State Electric and Gas donated Eastern redbud saplings, and PRLC’s Prop Lab grew many others like Elderberry, Swamp rose, and Buttonbush.
Plantings were flagged temporarily for identification and watering, and most will be fenced from deer with either individual cages or perimeter fencing. We plan to add flowering herbaceous plants to these sites at our June 3 Volunteer Work Session to support pollinator insects and nectarivores. Please join us in supporting the restoration of Halle Ravine’s native forests by pitching in as a volunteer or making a donation to our Spring Fundraiser. This is a wonderful way to meet your neighbors and enjoy the woodlands we hold dear.
More pics coming soon!
Have you driven past Carolin’s Grove recently and noticed the work we have done to clear out some of treefall from Hurricane Sandy? Well, it’s time to stop in and take a few minutes to see the change. With funding from the family of the original donors of this Preserve and support from the Land Trust Alliance, we hired a tree crew, Emerald Organic, to remove dead and downed trees that prevented us from accessing the area for management of invasive species and native plant protection. This part of the forest is now safe for visitors to explore.
While there are large gaps among the towering spruce trees in the Grove, there are also many young saplings, some already above the height of deer browse. We aim to influence the regeneration of this forest to include a mix of deciduous trees and conifers, with berry and nut producing shrubs in the understory to support birds and other wildlife. This month and next, volunteers and students including the entire third grade at Pound Ridge Elementary School will help to plant in the largest forest gaps. More volunteers are always welcome, including those who can stop by and water during dry periods in summer.
We have White pine, Pitch pine, Eastern red cedar, American hazelnut and Northern bayberry saplings to plant, some of which were donated by the New York State School Seedling Program. We are also going to plant wildflowers that are important for pollinating insects, such as Grey goldenrod, Milkweed, and Wild bergamot, grown in our own native plant nursery at the Armstrong Preserve and Education Center. Please see this blog post for more information on the PRLC Prop Lab.
Do you put seed out for birds in winter? Millions of Americans enjoy this hobby, even those who might not otherwise be nature-lovers. We string up suet for woodpeckers and scatter sunflower seed, millet, or corn to attract our personal favorites, perhaps the cardinal, or goldfinches. Some birds are finicky about visiting feeders, and we delight in adding another species to our list – mine is currently at eleven for 2017, but should reach fifteen or so before winter is over. I like to watch the Red-bellied woodpeckers, which are much more numerous this year than last. They are expanding their range further north as our winters grow more mild.
When I visit my mother in Vermont in a few days, I look forward to seeing her regular birds, so different from mine: crossbills and snow buntings, and red-breasted nuthatch. I might see a Cooper’s hawk in either location as they too have expanded their range, to prey on the birds that we attract to our feeders!
Some of you may wonder, is it necessary to feed birds, and can it be harmful? There are no conclusive data showing its benefit or harm to bird populations, although centralized feeding areas can be reservoirs for the spread of disease. It is a good idea to scrub down your feeder periodically, and to offer fresh water if you are providing any. The availability of water is a limiting factor for bird distribution, especially during freezes in winter, when I find dense concentrations of birds near flowing streams. Will the birds starve if you stop feeding them or miss a few days? Unlikely. Their numbers are determined by many factors in addition to food, and birds are adapted to move and forage over a wide area.
It is more important to support birds with a healthy habitat of native trees and plants than it is to provide supplementary foods in any season. Trees moderate our climate, provide shade and shelter and seed, and most critically, harbor vast numbers of insects. Some birds are almost entirely insectivorous, like the Eastern bluebird, while others depend upon insects for short periods of growth and transition. According to entomologist Doug Tallamy, ninety-six percent of terrestrial birds rear their young on insects, especially caterpillars. Many non-native plants do not support the kind or number of caterpillars that birds need, and when those plants become numerous enough to compete with native plants for space and light, the number of birds on the landscape will be diminished. Even non-native plants that appear to feed birds, like Asiatic bittersweet, can be low-quality food sources that provide less nutrition than native plants. We have seen a tremendous increase in the number and diversity of birds at the Armstrong Preserve and Education Center after we replaced our invasive non-native plants with native species.
Here is a list of things you can do to attract songbirds to your property, including suggested native plants for food sources, taken in part from bird habitat specialist Dr. Stephen Kress:
- Maintain a border of native trees and shrubs around lawns, and minimize the area of lawn.
- Create a brush pile.
- Remove invasive plants.
- Rake leaves under shrubs to create feeding areas.
- Clean out bird nesting boxes in early spring.
- Create a water source for bathing and drinking.
- Clean feeders with a 10% non-chlorine bleach solution.
- Keep cats indoors.
Spring and Summer Seed Producers = Red maple, American elm
Early Summer Fruit Producers = Black raspberry, High and Lowbush blueberry, Pokeweed, Shadbush
Autumn Seed Producers = Sugar maple, Eastern hophornbeam, the ashes
Autumn Fruit Producers = viburnums, dogwoods, Common elderberry, Spicebush
Winter Fruit Producers = Bayberry, Eastern red-cedar, Highbush cranberry, American holly, Inkberry, chokeberry, Wild grape, Virginia creeper, Winterberry, Staghorn sumac
Herbaceous plants = asters, Black-eyed susan, thistles, phloxes, sunflowers, goldenrods
Nectar Plants for Hummingbirds = Jewelweed, Cardinal flower, Trumpet honeysuckle, Indian paintbrush, Tulip tree
The stony ground and prominent rock formations of Pound Ridge in Westchester County, New York elicit curiosity in many people, some of whom attended our recent guided hike focused on geology. I will summarize our tour of the geologic history that can be seen at the Bye Preserve, owned by the Pound Ridge Land Conservancy (link to map and directions). Trails at the Preserve are open everyday from dawn until dusk.
Imagine that your arm represents geologic time, with your armpit being the Big Bang and the tip of your middle finger representing today. The dawn of life occurs just above your wrist. Between your wrist and the middle of your palm, all of the bedrock that shapes this land was formed by a process known as the tectonic cycle: erosion of mountains, deposition of materials in layers, subduction (movement of the earth’s crust), and volcanism. There was something on the earth’s crust prior to the formation of our bedrock, of course, but we cannot see evidence of that now. Geologists have discerned that an ancient Acadian Mountain Range once rose east of us, to the height of the Himalayas, and then eroded into particles that were later metamorphosed into our bedrock. Add folding from the movement of tectonic plates, deformation by glaciers, and erosion, and you have a punctuated record of history etched on the landscape.
In its western half, the Bye Preserve is underlain by Fordham gneiss, which formed in the Precambrian era, 1.1 billion years ago. This layer measures up to 500 feet thick and is extremely resistant to weathering. There are many kinds of gneiss, and it is variable in color from brown to buff and can be pink or green. Fordham gneiss contains quartz, biotite mica, silicates, garnet, and other minerals. Bedrock along the eastern side of Bye belongs to the Hartland Formation, which is half as old and is a mixture of gneisses, schists, and amphibolites. It formed when shales and sandstones from a deep ocean metamorphosed and retains its layers of alternating color. Many of these rocks were inverted when the Hartland Boundary Fault displaced older layers and brought in new rocks.
Subsequent to the last great tectonic shifts in the Paleozoic era, the bedrock at Bye has endured at least four episodes of folding and associated metamorphism, which is visible in many rocks where layers are curved rather than straight. The first stage of folding produced large ENE-WSW trending ridges and valleys, while the second stage trended NNE. Later stages produced tight folds that reoriented earlier folds. Where rock is resistant to bending, brittle faulting may occur, which produced the Mill River Gorge just northeast of Bye Preserve and the Mianus River Gorge as well. In the midst of these changes, magma intruded the bedrock at Bye and produced a very pretty white-to-pink granite that is rich in quartz and mica.
More recently in geologic time, between your furthest knuckle and fingertip on our imaginary time scale, the glaciers of the Ice Age left their mark. An ice sheet more than one mile thick ground back and forth across this landscape for nearly 100,000 years in freeze/thaw cycles. Each advance brought in new rock from afar. Each period of retreat caused mass deposition, flooding, and a rise in sea levels. Bye Preserve is now only ten miles from the Long Island Sound and was at times submerged by ocean, although fresh water has played a greater role in carving this landscape. We can see evidence that great torrents once ran in the boulder fields that line two now-intermittent streams, scouring away soil such that even today, only ferns and moss grow there.
The last glacial ice disappeared from Pound Ridge about 12,0000 years ago, leaving behind piles of sand, rock, and even huge boulders on the surface of our scoured bedrock. These are the clues from which we can piece together millions of years of history on the land. To end our story, I invite you to sit with a favorite rock and to ponder what it has endured to bring you both to this moment in time.
Forests in Pound Ridge and surrounding areas are under siege by one of the gentlest of animals, the white-tailed deer. Deer are keystone herbivores and eat from five to seven pounds of vegetation per day. In summer, deer dine richly on the buffet of tender plants provided by home landscaping. In winter, our subsidized deer herds turn to the forest to browse buds, tender saplings, and even tree bark. At ideal densities of 10-15 per square mile, deer browse checks the growth of plant life without hindering forest regeneration. At higher densities, they can strip the understory bare. With deer density in Pound Ridge as high as 65 per square mile, we face the loss of wildflower species first, and then the pollinators that depended upon them, and then the birds that can’t find shelter or food, and finally, the forests themselves as trees are not replaced.
Is the situation really so dire? Scientists and natural historians have documented all of these effects, including our friends at Mianus River Gorge who found that tree sapling diversity in a local protected forest decreased from 15 species to 4 over the last thirty years, due to overbrowse by deer. Local land managers seek solutions, but first we must know our problem. I will describe here a simple method for assessing the level of deer browse in virtually any patch of forest in Pound Ridge. Rather than counting deer or deer density, we are going to measure the effect of deer browse on each plot and use that as a baseline that guides future management. This methodology was developed by Thomas Rawinski of the United States Forest Service, who shared his knowledge and skill with us in a training session this summer.
We begin by choosing a site for our study plot(s). The circular plot covers 100 square meters and must include at least ten measurable saplings of one of the indicator species. Measurable means that the sapling is still below the average browse line and therefore vulnerable. Indicator species include any browsed species with beech and sassafras preferred followed by the shrubs; maple-leaf viburnum, sweet pepperbush, alternate-leaf dogwood, red elderberry, choke-cherry, and even the invasive burning bush. I do not mean to imply that deer prefer these plants – rather, they avoid them – so that browse levels reliably indicate the severity of deer pressure on forest growth.
Once the indicator plant has been selected and the plot margins delineated, we set out to find the ten tallest measurable saplings of our chosen species. Then we average those ten measurements to find the definitive “tallest” for that plot. In itself, this doesn’t tell us much. Over time though, we can discern trends and hope to associate those with management actions. We can also make comparisons among plots to measure relative levels of browse across landscapes. For example, Sugar maples at Armstrong were browsed down to 8.9 inches, while those at Halle measured 8.1 inches. Deer pressure may be more severe at Halle than it is at Armstrong.
We can avoid the costly and time-consuming task of measuring deer density by using this simple approach to assess deer impact on our preserves. We will measure again next year and compare our findings both within PRLC holdings and with a larger community of land managers and report back to you then.
For more information, please see http://www.na.fs.fed.us/pubs/2014/NA-IN-02-14_WhitetailedDeerNEForestsWEB.pdf
We had a great turnout for the mushroom hike at Armstrong Preserve on October 23, 2016 and turned up some interesting finds. The most distinctive was a single specimen of the Dog stinkhorn, Mutinus ravenii, so-named for its shape and strong odor. We also found a few edibles, noted in the captions below. Please use caution when foraging for wild mushrooms and refrain from eating any that are not verified by an expert. Please also note that collection of mushrooms, along with plants and animals, is not permitted on Pound Ridge Land Conservancy preserves except during our guided hikes. If you would like to join our email list to be notified of future mushroom forays, email PRLC’s land steward or call our office at 914-205-3533.
Thank you to our event participants for the photographs, and happy hunting!