Day of Service to the Forest

 

For the second year in a row, the Pennypack Trust sponsored a Day of Service on the Martin Luther King, Jr. holiday.  Like they did last year, the 15 volunteers who came out to work readied an area for reforestation in the spring by gathering large woody debris into a central location.  The volunteers concentrated their efforts in the wooded 5-acre tract immediately adjacent to the Trust's headquarters on Edge Hill Road.

Woody debris is important in the forest ecosystem, but our degraded woodlands are under siege by invasive plants, and the branches, limbs and logs on the forest floor prevent the land stewardship staff from gaining access to new planting sites.  New plantings need to be kept clear of non-native plants - especially vines.

The former owner of this land planted non-native pachysandra; it's visible in the background as a green "blanket"

So, we've weighed our management options and have made the decision to remove the maintenance obstacles.

Besides, there's always more wood falling from the canopy as the mature trees shed limbs and topple over during storms.  The forest floor won't remain "clear" for long.

Submitted by David Robertson
Executive  Director

At the Edge

Mary and I are having our 25-year-old couches reupholstered and have been working with a fabric and upholstery store located near the mouth of Pennypack Creek.  On Saturday, we went to pick up the finished upholstery, and took a walk along the creek while we were there.

The Pennypack flows south out of the Pennypack Preserve, enters Montgomery County's Lorimer Park, then crosses the line into the city of Philadelphia where it flows within Pennypack Park all the way to its mouth at the Delaware River.  About two miles upstream of its mouth, the creek falls off the hard edge of North America and flows onto sediments deposited on the shallow continental shelf - the Coastal Plain.  The transition from the hard, ancient Piedmont rock so familiar to visitors to the Pennypack Preserve to the sandy Coastal Plain - the fall line - is dramatic.

Pennypack Creek at the fall line

The creek rushes over resistant bedrock and creates a series of rapids at the fall line.  Early European colonists took full advantage of the transition by building a dam on top of the rapids and harnessing the water power for a mill - the most southerly (downstream) of the 28 mills that at one time operated along the creek.  In the image above, the rocky ruins of the massive dam are still in place on the opposite side of the creek, and some of the ruins of the mill are visible as a stone wall in the background.

The Piedmont bedrock at the fall line displays graphic evidence of the repeated stresses experienced by the rock at the edge of the continent.  North America and Africa have collided with one another on at least two occasions, and the bedrock, composed  mostly of dull, gray metamorphic gneiss, is twisted and bent like taffy.  In addition, other types of rock have gotten caught-up in the collisions and been incorporated into the cooled "taffy" like the quartzite in the image above, and the granite in the image below.

A stone studded with mica

Silvery flakes of mica are abundant in some of the rocks.  In the sunlight, the rock above glistened hypnotically.  If I'd been much younger and in an acquisitive (rather than de-acquisitive stage in my life), I would have brought the rock back with me.  The image hardly does it justice.

Fish ladder

A few hundred feet upstream of the fall line, state agencies have constructed a fish ladder in the creek.  Pennypack Creek once was spawning ground for anadromous shad that returned from the ocean to spawn, just like salmon.  With the construction of colonial dams for water power, the shad were excluded from their historic spawning streams and their populations plummeted.  There's an effort to remove dams and restore shad runs in some of their historic streams, including the Pennypack.  This fish ladder was created to allow the shad to swim over a sanitary sewer line partially buried in the streambed; the sewer pipes formed enough of a barrier that the fish could not ascend beyond them, so the Pennsylvania Fish and Boat Commission built this series of riffles and pools.  In addition, they released many thousand hatchery-raised fingerling Hickory Shad into the creek in the hopes that some will return to spawn.

The pools created by this fish ladder have become very popular swimming holes with members of the Hispanic community in the neighborhood.  Although swimming is prohibited, and the creek is far too "impaired" for safe contact, that doesn't stop the kids from cooling off.  Fortunately, if the shad begin to use the creek for spawning again, they would return in March and not have to contend with crowds of kids.

Requisite sycamore-against-blue sky image

Just a few hundred feet downstream of the fall line, the creek is spanned by the oldest extant bridge in the United States: the Frankford Avenue (King's Highway) Bridge, built in 1797.  The King's Highway, constructed during the English colonial period, connected Philadelphia and New York City, and ran approximately along the fall line.  The highway replaced a Native American pathway that traced the same route.  The bridge is a National Engineering Landmark.

The fall line's a pretty "happening" place!

Submitted by David Robertson
Executive Director

Frosty November Morn

 

I awoke on Saturday morning (November 9) to the beautifully frosted native grasslands on Raytharn Farm.  I did my best to capture the crispness before the rapidly rising sun dispelled the magic.

Weedy, non-native foxtail (Setaria spp.) in front of tawny Indian-grass (Sorghastrum nutans)

Rimed thistle rosette and oak leaf

Submitted by David Robertson
Executive Director

Discouraging Forest Restoration Setback

In 2003, the Pennypack Trust expanded a forest restoration project originally begun in 1990.  In the expanded planting of 200 trees, we included a dozen pure American chestnuts (Castanea dentata) that we obtained from a nursery in Oregon.  The Oregon nursery said it believed its seedlings were resistant to the chestnut blight fungus (Cryphonectria parasitica), a pathogen introduced into the United States in the 1920s via imported Chinese chestnut trees.

For those who don't know the story of chestnut blight, the fungus quickly spread from the point of introduction (New York City) throughout the eastern United States.  By the time the pandemic had subsided, one quarter of all trees in the eastern deciduous forest had died, and what had been a major component of the forest became, for all intents and purposes, ecologically extinct in only a few decades.  (Not all chestnut trees died outright; the roots of some of the trees remain alive and continue to produce sprouts.  Once the sprouts reach about 20 feet in height, they are attacked by the fungus again [the fungus remains in the environment] and die back to the ground.  Some saplings even survive long enough to flower and set seed.)

With regard to Pennypack's planting, the chestnuts have grown tall and beautiful over the last decade; perhaps, I hoped, they really were resistant to the fungus as the nursery suggested.  Then, two weeks ago while on a walk, I noticed that one of the trees had a wound located right a the top of the tree shelter we use to protect all trees from deer damage.  Maybe the tree shelter had rubbed the bark and caused the wound...  But, you probably already know where this is going.  On closer inspection and upon comparison with references, the wound turned out to be a canker caused by the blight fungus.  In fact, there are tiny tell-tale red fungal fruiting bodies on the bark surrounding the canker as well, visible above the canker if you look closely at the image accompanying this post.

I contacted the American Chestnut Foundation (which is trying to develop a resistant chestnut strain) to determine if I should destroy the tree to prevent or delay the fungus from spreading to the other chestnuts.  The Foundation's representative told me that my story was all too familiar and that destroying the tree would only delay spreading the fungus by a very short time.  Better, the person said, would be to let nature takes it course and, hopefully, the roots will re-sprout once the above-ground portion of the tree dies back.

By the way, the Trust has also planted about a dozen American-Chinese hybrid chestnut seedlings we obtained from the American Chestnut Foundation in a different reforestation planting.  (The Foundation hopes that crossing American chestnuts with the closely related and fungus-resistant Chinese chestnuts will make the hybrids resistant.)  Those hybrid trees are still too young to show signs of resistance, one way or the other. 

Submitted by David Robertson
Executive Director

Hayrides and More on a Perfect Autumn Sunday

 

Because of rain two weekends ago, we postponed Pennypack's annual autumn festival until Sunday afternoon, October 27.  Though it didn't end up raining on the date the event was originally scheduled, the sky that day was still mostly overcast and the Raytharn Farm trails were muddy; in contrast, last Sunday offered a perfect fall weekend, so I'm glad we waited.

The hayrides are popular with children, their parents, and their grandparents.  Our wagon will accommodate about 25 people for a 45-minute ride.  The first two rides weren't full, but the third ride was "sold out" and wouldn't hold another person.

You can see from the images that the native grasses are at their peak right now - tawny and beautiful - but the trees in the background remain dull green or muted shades of tan and brown.  Pennypack's forests are never as vibrant as the New England forests on October calendars because we don't have many maples in our woods, but this year's colors are not be among the best regardless.

There's a 10-acre private in-holding in our grasslands: a gentleman's horse farm.  While the in-holding breaks up the sweep of the grasslands, it nonetheless adds an  accent to the landscape.

Following the hayrides, children had an opportunity to decorate pumpkins and have their faces painted with Halloween themes in the Visitor Center.  A few kids took advantage of early leaf-fall to dive into a pile and have a great time.

Submitted by David Robertson
Executive Director

Surrounded, but No Surrender!

Porcelain-berry, the "kudzu of the North," on the periphery of the Pennypack Preserve

For some reason (perfect temperatures, soil moisture, carbon dioxide concentrations, or a synergistic interaction of all three), the invasive Asian vine porcelain-berry (Ampelopsis brevipedunculata) "exploded" in the Pennypack Preserve this summer.  The perennial vine is ever present, and always the biggest threat in the natural area.  When I began my job here 25 years ago, one of the first tasks I set for myself was to bring the plant under control in the most heavily infested areas, and I was really able to knock it back with several years' intensive mechanical and chemical control efforts.  But, as I said, this year it has re-surged with a vengeance. 

Porcelain-berry fruits in varying stages of ripeness

Porcelain-berry was introduced to the united States from eastern Asia, probably as a garden ornamental.  It's fruits are attractive for about two weeks in the fall, but the rest of the year the plant just looks like a sprawling grapevine - to which it is very closely related.

Once the plant escaped the bounds of gardens (undoubtedly aided by birds that eat its fruit and then defecate the seeds elsewhere), it found a perfect home in the Mid-Atlantic.  It grows up into the canopy, spreads out to capture sunlight, and blankets the trees supporting it, eventually shading the trees to death or ripping off their limbs when the weight of the vines becomes too much for the tree to bear, especially when covered in snow and ice in the winter.

Porcelain-berry flowers attracting a honeybee

Porcelain-berry is served by generalized pollinators, so it is not dependent on a specialized bee, wasp or bat to spread its pollen.  And, while it's an introduced species, our native North American songbirds (and white-tailed deer) consume it readily, helping to spread the plant across the landscape, probably because it is so closely related to the grapes that are already familiar to our native species.

The only insects I have ever observed damaging porcelain-berry leaves are invasive, non-native Japanese beetles, but they never become numerous enough to inflict real harm to the plant.  I suspect that even if the plant has a specific disease or insect pest that keeps it in check in its East Asian homeland, such a disease or insect could never be imported into the United States as a biocontrol agent because it likely would also attack commercial grapes.

A porcelain-berry rhizome

Porcelain-berry develops an extensive, thick underground stem or rhizome.  The rhizome grows through the soil and sends up shoots ever few feet or so.  An infestation of porcelain-berry may actually consist of only a few plants all growing from the same underground stems.  Cutting off a few of the above-ground vines hardly fazes the plant, which has plenty of resources stored underground.  The only feasible method of control is to poison the plant with a broad-leaf herbicide applied either to the foliage or directly onto the rhizome after an above-ground stem is severed.

One of Pennypack's board members asked me to do a photographic inventory of land parcels on the periphery of the preserve that we might be able to acquire to add to the natural area.  I completed the inventory and prepared a PowerPoint program that I presented at the last board meeting.  In my remarks prefacing the presentation, I alerted the board members to note that every single one of the parcels I had photographed that was not maintained as a meadow or as lawn was completely overwhelmed by porcelain-berry.  Even if we got the plant under control within the preserve, the Vandals are at the gates on private properties we can't touch.


But we do have a chance to maintain the natural diversity inside the preserve, and we will redouble our efforts to try to bring porcelain-berry under control or the winter and during the next growing season.

Submitted by
David Robertson, Executive Director

Of Birds and Men

Pennypack Executive Director David Robertson (left) with Pennsylvania Game Commission grassland bird expert Dan Mummert

For the last thirteen years, Pennypack's land stewardship staff has been working to convert the 160-acre Raytharn Farm into native warm-season grasslands.  Our goal has been to create habitat that will support breeding populations of "grassland obligate" birds - birds that nest in grasslands and in no other habitat.  Good examples in our area include Bobolinks; Eastern Meadowlarks; Savannah, Grasshopper and Vesper Sparrows; and Upland Sandpipers (the last one being, admittedly, a real long shot).

When we bought the property in 1997, the land was used to grow non-native cool-season grasses that were harvested for hay.  We started small with our conversion; each year, we would herbicide a 10- or 25-acre patch of the pasture grasses, and then reseed the area with native grass seed.  In 2008 we finally finished the conversion by reseeding the final 50-acre patch.

The grasses have performed well, and our farm now looks much like a tallgrass prairie in the Midwest.  Though the grassland conversion has been very successful, none of the grassland obligate birds has chosen to nest in the fields yet (with the notable exception of one very rare species that occurs in only a few very scattered locations in Pennsylvania - our resounding success to date).  We routinely observe Bobolinks and Eastern Meadowlarks stopping for a few days in the fields during spring and autumn migration, and each year we hope they'll linger to raise a brood, but inevitably they move on.

We have our suspicions about why they don't nest here.  The largest contributor to their decision may be that the fields are just too dense with grasses, and they can't find suitable small open patches in which to build their nests.  We know this is an issue, but there's a good reason why there aren't many openings in the fields:  we have an absolutely horrendous problem with non-native invasive plants. Any openings in the dense grass cover are quickly colonized by invasive plants, which then begin to spread and take over the grasslands.  So, we use herbicides to control the broad-leaved invasive weeds, which reduces competition for the grasses, and the grasses grow in to fill the openings.  Result: few nesting sites.

Grasslands with desirable diversity

Furthermore, the grasslands are not diverse and don't contain many meadow plants that would attract insects and pollinators on which the birds could feed.  Again, most of the good native wildflowers that we could seed into the grasslands would be killed by the broad-leaf herbicides we use to control the pernicious invasive plants, so we can't create a diverse meadow with a mixture of grasses and broad-leaved native wildflowers.  A 60:40 grass:wildflower mix is ideal; we probably have 90:10.      

Oh, and another thing.  The Pennypack Preserve is in the middle of the suburbs.  We're largely surrounded by houses, roads, and businesses.  So our grassland is an island in a suburban sea, and it simply may not appeal to these grassland obligates that are used to wide open expanses of grassland in an agricultural matrix.

So, long and short, we may never be successful in getting grassland obligate birds to nest in our grasslands, but it doesn't stop us from trying.  One of our premier birders, Harris Brown, called the Pennsylvania Game Commission when he learned that the commission employs a consulting grassland expert who would be willing to visit and share his knowledge and recommendations with us.  The expert, Dan Mummert, visited the Pennypack Preserve on Tuesday, August 27 and Harris and the staff escorted Dan on a tour through the fields.

From left:  Staff members Brad Nyholm, Christopher Dartley, and David Robertson; volunteer Harris Brown; and Dan Mummert

Dan commended us for our success in establishing our grasslands in light of the nearly overwhelming pressure of invasive plants, and considering that we cannot use the two tools best suited to managing grasslands: prescribed burning and disking.  (We can't burn because of air pollution regulations and because the local fire marshals are terrified that we'll burn down houses on our periphery.  We can't disk the fields because we'd open up bare ground that would be colonized by invasives.)  

He did note that some of the grasslands contained wildflowers and that not all of the fields were grass monocultures; he encouraged us to try to create similar diversity in fields that were dominated solely by grasses.  He also recommended that we remove trees that had become established in fence-rows; the trees serve as perches from which raptors can survey the fields for prey, and the trees interrupt the "flow" of the broad grassy expanses the birds are seeking.  And last, but not least, he recommended that we consider closing some of our trails through the center of the grasslands during the birds' breeding season (May to mid-July) to limit disturbance by human activity.

None of these recommendations was new.  We'd had other wildlife biologists make similar suggestions in the past, but it's good to hear that everyone is "singing from the same hymnal."  We'll have to give all of these suggestions some thought since we have to weigh aesthetics, land management, and public use in the preserve.

Submitted by
David Robertson, Executive Director