June 09, 2009.  Carl Harting and I (Ed Frank) visited three sites in western Pennsylvania on Tuesday.  These were Wolf Creek Narrows Natural Area, Hogg Woods, and Plain Grove Fen.  I will post each portion of the trip separately   to better organize the information.

Wolf Creek Narrows Natural Area is located in Butler County in western Pennsylvania a couple miles from the town of Slippery Rock.  This 100 acre site was purchased by the Western Pennsylvania Conservancy in 1979.  http://www.paconserve.org/75th/wolf.htm  Wolf Creek is a modest sized stream that flows through a narrow valley.  In portions of the site are located steep slopes to cliffs as high as fifty feet overlooking the stream. 

 

Wolf Creek from bridge - photo by Edward Frank

Portions of the site along the floodplain, hilltop, and shallower slopes were logged 80 to 100 years ago and have since regrown into a secondary forest of yellow birch, hemlock, beech, tuliptree, sugar maple, and red oak.  The forest on the steep slopes of the main valley and tributary stream are reported  to be a remnant of virgin forest that has never been logged.  http://www.naturalheritage.state.pa.us/CNAI_PDFs/Butler%20County%20NHI%201991%20WEB.pdf  This forest is classified as a northern hardwood forest, with most of the species listed above and dominated by eastern hemlock (Tsuga canadensis).  In addition to this remnant virgin forest patch the site is known for its spectacular spring wildflower displays. http://www.pittsburghlive.com/x/pittsburghtrib/s_187294.html  This article by Paul Wegman gives an excellent overview of the site, although the suggested reason of why there is an abrupt change in the stream valley orientation seems questionable to me.

The first posting about this site was by Carl Harting in August 2004 of a trip taken the previous winter. http://www.nativetreesociety.org/fieldtrips/penna/wolf_creek_narrows.htm  He reported measurements of several species:

Species	CBH	Height
Tuliptree	n/a	124
Tuliptree	4.2	103.5
Tuliptree	6.8	109.4
Red Maple	8.4	105.7
Sycamore	8.9	118.3
Sycamore	7.4	117.3
N Red Oak	7.4	108
Beech	7	109.3

Carl and I met at the parking area just across the bridge from the trailhead.  At the trailhead is a kiosk that has a map of the site and some information about the flowers found on the site.  The mile long trail is essentially balloon shaped.  The trail runs across the floodplain along Wolf Creek to just past the point of the large bend in the creek.  From here it climbs up the valley wall and runs along the top of the valley rim until it cuts back across the hilltop, just north of the open square on the air photo, to rejoin the original trail section a few hundred yards from the starting kiosk.  The Western Pennsylvania Conservancy property also includes areas on the other side of the creek that can be reached when the water is low enough for wading.

Air photo including Wolf Creek Narrows Natural Area

It was a warm humid morning and the mosquitoes were quite thick.  The trail was well marked with blue blazes and easy to follow.  Walking along the floodplain we came across some relatively large sycamores.  Some of these were the ones measured by Carl on his first trip.  It is a beautiful little stream.  We did not encounter many flowers as it was past peak bloom season.  Carl said that in the spring the ground was covered by trilliums.  The canopy was very thick and it would have been next to I possible to get good height readings of the trees through the tiny openings available to us. 

Carl Harting at Wolf Creek Narrows Natural Area - photo by Edward Frank

So rather than measure today, we explored a bit and determined to return after leaf fall this autumn.  Some of the trees we passed on the slope did appear to have some age to them, but none were of any great size.  Scattered shots showed heights for most trees being 100 feet or less.  I think it is certainly worth revisiting and getting more measurements, but again I have some concerns about how the site will be represented by a Rucker Height Index.  Many of the trees appear to be old, but they are not of great size.  Using just simple size parameters for these types of forests make them indistinguishable from a common secondary growth forest.  I guess that is what descriptions and photographs are for, but I wish there was some better way to quantify the values of these forest in a way that would distinguish them from younger, post-logging, secondary stands.  Aside from massive amounts of tree coring, I don’t know what else to do.  There were some vernal pools near where the loop connected back into itself that are of importance to amphibian populations. 

Edward Frank