Wissahickon Part 2: Forbidden Drive

Bell's Mill Road Bridge, viewed upstream

After Kali and I finished exploring Houston Meadows (previous post), which is located on a high, flat bluff above Wissahickon Creek, we descended the steep valley slope to the stream.  An old carriage road parallels the western bank of the creek for seven miles.  Because vehicles are prohibited from using the old road, it is called Forbidden Drive.  Forbidden Drive is one of the most heavily used recreational amenities in the city, with walkers, runners, equestrians, and bicyclists all mixed together in a generally congenial stew. 

Wissahickon Creek downstream of Bell's Mill Bridge

The land that is now Wissahickon Valley Park was a colonial industrial valley with mills and roads throughout.  The city bought the land in the late 19th century because Wissahickon Creek empties into the Schuylkill River just upstream of the city's drinking water intake, so the city wanted to try to preserve water quality in the Wissahickon and the receiving stream.  Nearly all vestiges of the industrial heritage are gone, but many of the stone ruins and the bridges that bore roads over the creek remain.

Blue wood aster (Aster cordifolius) and Wreath goldenrod (Solidago caesia) on the wooded streambank

Forested slope with denuded understory

White-tailed deer have been very abundant in the park.  As a result, nearly all of the forest understory is gone, and few sapling tress are growing to replace the old trees when they die.  For the last decade, the city has hired sharpshooters from the U.S. Department of Agriculture to cull the herd.  The sharpshooters hunt at night over bait, and the venison is donated to local food banks.  Nevertheless, animal rights group protests are a constant thorn in the city's side over this issue.  The culling has significantly reduced the number of deer, and the forest has begun to recover in places.

Parasitic beech-drops (Epifagus virginiana) in a patch of sunlight

One of the reasons that the Wissahickon is so popular is because it is very scenic.  The creek has cut a deep gorge though very hard rock, so the valley slopes are steep with lots of scenic boulders and bedrock exposed.  Because of the steepness, only one old road crosses the valley directly (Bell's Mill Road, the picture at the head of this post), and few roads penetrate down to Forbidden Drive.  Rex Avenue (image below) is one of those roads that descends from the eastern side of the valley and terminates at Forbidden Drive.

Rex Avenue Bridge

Old park guardhouse along Forbidden Drive

Covered bridge, the only one in Philadelphia

Invasive Japanese angelica-tree (Aralia elata), left, and Japanese knotweed (Fallopia japonica)

Wissahickon Creek rapid

Forbidden Drive

Forbidden Drive is not one of Kali's favorite walks because it is dark and claustrophobic; she much prefers the sun and openness of Houston Meadows.  However, I like the views of the creek and the general sense of community among the users.

Wissahickon Part 1: Houston Meadows

Bumblebee on goldenrod

Last Saturday (October 15) was an absolutely perfect early autumn day, with temperatures in the upper 60s, crystal clear blue skies, and very low humidity.  I packed Kali into the car and we drove over to the north-westernmost neighborhood in Philadelphia called Roxborough for a hike in the 1,800-acre Wissahickon Valley Park, Philadelphia's largest and best-known park.  Our goal that day, in addition to just getting some exercise, was to inspect Houston Meadows, a restoration project undertaken by the city's Department of Parks and Recreation as part of an ongoing series of natural lands restorations throughout the city's larger parks.

Trail through goldenrod and little bluestem

A few aspens; there are others growing nearby at the edge of the meadow

Native little bluestem (Schizachyrium scoparium)

To my mind, the Houston Meadows project was not a straightforward "winner."  During the early part of the 20th century, the meadows had been an active farm before urbanization expanded outward to the very edges of the city limits.  When the farm was incorporated into the park, the land became fallow and quickly reverted to herbaceous old-field habitat - a "wildflower meadow" in common parlance.  This habitat was extraordinarily attractive to birds and butterflies that needed such habitat, and Houston Meadows became a birders paradise maintained by fires set periodically by neighborhood hoodlums.

Bluebird box on meadow slope

All was well until houses were built up to the very edge of the park, and then the field fires had to be suppressed.  This fire suppression allowed natural succession to kick in and trees and woody vegetation, formerly killed by the fires, began to creep into the meadows, changing the land first to a thicket and then to a young woodland.  The birds and lepidopterans could no longer find appropriate habitat and abandoned Houston "Meadows."

Goldenrod (Solidago spp.), boneset (Eupatroium perfoliatum) and native grasses

With support from a philanthropic foundation, the city decided to try to restore the meadow habitat and attract the birds back.  So, they brought in heavy equipment to clear the trees in the young woodlands, and they seeded the land with early concessional meadow species and native grasses.    

The result has been mixed in my opinion.  First, I have to admit that I don't know if the "target" birds have returned to the meadows.  If they have, they've "voted with their wings" and given the restoration their approval.  But, if the birds haven't returned, the project cannot automatically be dubbed a failure because (1) they birds may not have "found" the meadows yet, (2) the habitat may not have developed enough to interest the birds, or (3) the restored field really might not be suitable habitat.

This section of the meadows almost looks "western," with a big rock and conifers

Where the herbaceous vegetation has gotten established, the meadows are lush, productive and beautiful.  But Parks and Recreation seems (to me, anyway) to have left too many trees in the midst of the fields.  Hawks and other raptors perch in these trees and prey on the meadow-nesting birds.

In addition, the meadows are small and fragmented.  Some meadow-nesting birds seem to need 160 acres of grassland habitat to breed successfully, and these fields are nowhere near that large.  Other species, especially species that like brushy habitat, may be the first ones to recolonize the site.  To my eye, the habitat looks perfect for birds that like scrubby, brushy habitat.

Deer exclosure fencing

Parks and Recreation also included a deer exclosure as part of the project, but it is in a wooded corner of the meadows.  I don't know the motivation for excluding deer from a meadow project, but perhaps they were trying to expand a section of woodland and not develop meadow here.

Just Shed

Kali and I took a walk in my preserve on Wednesday evening after she got home from work.  As we walked along the trail that parallels the creek running through the preserve, I noticed a long snake skin on the ground.

The owner must have shed the skin very recently because it was still soft and supple.

I decided to bring it back to our Visitor Center to put it on display.  However, it drew a lot of attention from other folks walking the trail that evening  I was glad to be an ambassador for the natural world and for our organization.  Maybe I should walk around with it draped around my neck all the time--sorta' like the puppies guys are advised to use to attract the attention of women.

By the way, the owner more than likely was a Northern Water Snake (Neroida sipedon sipedon), which are very common in the preserve.  When I stretched it out to its full length, the skin measured 3' 11".