Wednesday, October 30, 2013

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

Tuesday, October 29, 2013

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

Tuesday, October 1, 2013

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