Signs of Summer 1: The Up and Over Hike (Part 1)!

The Up and Over rail. Photo by D. Sillman

(Click on the following link to listen to an audio version of this blog … Up and Over Part 1

This hike narrative was originally published in 2008 on my now defunct “Between Stones and Trees” website.  I think that it describes very clearly the impacts of invasive plants and human use on the ecosystems of Pennsylvania. It also highlights the inherent robustness and vitality of Pennsylvania’s ecosystems. Enjoy this walk in Penn’s woods!

Roaring Run Trail is a wide, crushed limestone, heavily used path that is part of the ‘rails-to-trails’ system in Pennsylvania.   There is, however a side path which branches off the main trail just outside the parking lot in Apollo. This narrow path travels up into the dense woods of the surrounding ridge. Deborah and I call this trail the “Up and Over” and use it regularly for a  conditioning hike. Some members of a local mountain biking group have adopted parts of this trail and have greatly improved its marking and maintenance.

The first part of this hike is all uphill.   After a brief start in the woods, you turn and follow a narrow, dirt truck trail that runs straight up the ridge. The trail passes several gas wells and pipeline access points, and, depending on the time of year and the number of maintenance visits to the wells, the trail may be choked with encroaching knotweed.

Japanese knotweed. Photo by D. Sillman

Knotweed (a.ka. “Japanese” or “Asian” knotweed) (Fallopia japonica (or Polygonum reynoutria, or Reynoutria japonica) is one of the more spectacular exotic/invasive plants not only affecting Western Pennsylvania but also much of the United States and also Europe. Originally from Northeast Asia (Korea and northern China), knotweed is a plant that is a primary colonizers of volcanic lava fields. Its tenacity and ability to grow in the extremely stressful conditions of barren lava is impressive. Its establishment is one of the first steps in the development of a vital, natural ecosystem on these lava sites. In these ecosystems knotweed has a number of natural controls which regulate its growth. These controls will lead to the inevitable replacement of the plant via the steady, ongoing integrated process of succession.

In ecosystems outside of its native range, though, knotweed grows out of control and persists long past the useful time interval for pioneering colonization. In these non-native environments, knotweed forms dense, single species thickets which are unusable by most native animal species for either food or habitat.  These thickets are also intensely inhospitable and destructive to native plant species.

The tiniest fragment of a knotweed plant has the ability to root and form a new plant. Water transport of fragments of the weed is very common, which explains why knotweed is so abundant along rivers. Railroad rights‐of‐way are also frequently clogged with knotweed possibly because the train cars and engines transport cut fragments of the weed all along the tracks.  When knotweed is cut, fragments fly about and have the potential to establish new plants and colonies. Thickets also form from shoots that rise from spreading rhizomes from a single established plant. Knotweed is almost impossible to eradicate once it gets established in a site.

Knotweed “tunnel.” Photo by D. Sillman

Last year, this part of the trail was almost completely closed over with encroaching knotweed. The long, arching stalks knit together to make a low‐headroom tunnel through the mass of interconnecting stalks and leaves. Today, though, the knotweed has been extensively cut back by the passing gas line trucks and crews. The trail feels more like a boulevard than a path through the woods. The sides of the trail, though, are thick with the weed and many of the plants tower over the trail. It has been a wet summer, and these weeds have responded with robust growth.

Multiflora rose (Rosa multiflora) is the main shrub along this next section of the path. This plant is another exotic, Asian, invasive species that has “escaped” from local gardens and hedges to which it was introduced back in the 19^th Century. It has become a very serious pest of woodland and rangeland ecosystems. In the early spring, I remember looking out across the long, systems of ridges that border the nearby Kiskiminetas River and seeing the scattered and, in places, almost continuous masses of the early emerging, light green  leaves of the multiflora rose.

Multiflora rose thicket. Photo by D. Sillman

If left undisturbed (which is a very good idea when you consider the number and sharpness of its thorns!) multiflora rose forms great,  dome‐like masses of intertwined stems. Old, brown  and dry, thorn‐filled stems fill the inner volume of the dome, and green, flowering, but still thorn‐covered stems cover its outer surfaces. Other plants are shaded out under and within the growing mass of the rose. This plant represents a very serious threat to the less aggressive, more slowly growing, native plants of our forest and grassland ecosystems.

Many small animals (birds, rodents, rabbits) use these rose thickets for shelter and for their nesting and denning sites. This beneficial symbiosis, though, does not balance out the potentially calamitous impact that this species is having on our native flora. In some states, it is actually illegal to have a multiflora rose plant growing on your property! All across theses ridges are incredibly large numbers of these plants.  Their abundance and distribution will undoubtedly increase over the coming years.

Garlic mustard. Photo by Sannse. Wikimedia Commons

Another exotic invasive plant also present in great abundance along this ridge‐top trail section is garlic mustard (Allaria petiolata). Garlic mustard is a plant native to Europe. Via vigorous seed production and some serendipitous seed dispersal mechanisms, it has spread to almost every temperate zone ecosystem around the world. A single garlic mustard plant in its second (and final) year of life is capable of producing up to eight thousand tiny seeds that are then dispersed though the soil of their ecosystems. These seeds can cling to the feet of passing animals and can be spread everywhere that animal walks. These seeds also gather on the boots and clothing or equipment of any human moving though the system, and wherever that person goes, so go the seeds!  The rate of these dispersions and the distances that they can cover are incredible. On our campus nature trail, for example, we had no detectable garlic mustard back in 1985 when we did our first flora survey. In 2007, though, the understory flora, especially in the upper part of the trail, was absolutely dominated by it.

Garlic mustard (whose leaves smell fresh and garlicky when crushed) is thick and flourishing all along this ridge trail. It makes a rich green understory layer around the patches of the multiflora rose that are, in turn, bordered by knotweed: a European herb under a spreading Asian shrub surrounded by a tall Asian weed filling up the trailside here in Western Pennsylvania.

Wild grape engulfing tree canopy. Photo by D. Sillman

Wild grape (Vitis spp.) is also growing very abundantly on the  trees along this part of the trail. The grape vines provide a rich, fall food supply for birds and  mammals, but also can do a great deal of damage to  the trees on which they grow.  Not only do  the vines shade out significant portions of the tree canopy but they also make the entire canopy denser and more resistant to wind. On our Campus Nature Trail we have documented that white ash and yellow poplar trees are more likely to be subject to wind-throw if they support significant densities of  wild grape in their upper canopies.

Oak seedling. Photo by D. Sillman

Some good news on this “Up and Over” hike: there are large numbers of oak seedlings under the taller stands of red maple (Acer rubrum) and black cherry (Prunus serotina). This past fall, in fact, the trail was actually littered with acorns (which are now all gone! Only the caps remain). In the fall the abundance of acorns actually made walking on the trail difficult. The large northern red oaks and white oaks growing up on the hillside drop their acorns in the early fall which, with some help from gravity and maybe even some assistance by foraging squirrels, tumble down the slope to this flat space on the ridge. Seedlings of some appreciable size are developing under the cover of the shading, overstory trees. Along this trail, anyway, the possibility of an eventual oak forest looks quite promising.

Red maple. Photo by Kaselow (NPS)

In the early spring it was possible to assess just how many red maples are growing on these ridges. The red maples are among the earliest trees to bud out in the spring. Their swelling red leaf buds and tiny, reddish and pale green leaves make the surrounding slopes and hillsides shimmer with color. The red maples are everywhere! Red maples have become one of the most widespread and abundant trees in the forest ecosystems of the eastern United States.

How and why this tree species which, according to early survey and logging records initially made up only a very small percentage of our original, uncut forest, has become so abundant is a complex question. Many forces and many characteristics have combined to favor this species over its competitors. The fact that red maples can begin to make seed as very young trees (as young as four years of age, in fact) and that a single tree a foot in diameter can make a million seeds in a single year is a significant starting point. That these seeds (the very familiar, winged “samaras”) can then fly and float in the air great distances from the parental tree and can then germinate almost anywhere over a very broad range of site conditions paints a vivid picture of red maples as ecological “generalists” filling up any open “spaces” in the eastern forests.

Photo by D. Sillman

White-tailed deer (Odocoileus virginianus) browsing of seedlings is a major force affecting the persistence and survival of many tree species. Red maples and most other tree seedlings are extensively browsed by deer especially in the winter, but the fact that there are so many red maples especially in comparison with the smaller numbers of individuals of the other tree species has allowed a substantial number of the maples to escape deer predation and become established as the incredibly abundant tree of our forests.     So, the red maple’s high rate of reproduction, rapid dispersion over an area, broad tolerance of site conditions, and sheer numbers have all combined to favor its existence in our human (and deer) impacted ecosystems.