Signs of Fall #8: Grove Run Trail (part 1), Blister Beetles and Rocks

Photo by D. Sillman

(To read more about the Grove Run Trail check out my “Between Stones and Trees” hiking web site))

A couple of weeks ago on a beautiful Saturday morning Deborah and I met Rob and Michele Bridges down in Lynn Run Sate Park for a hike. The woods around Linn Run are a second (or, maybe, even a third or a fourth!) growth forest that date back to the first decade of the Twentieth Century. This was one of the first tracts of land purchased by the State of Pennsylvania (in 1909) in its efforts to reclaim and protect potential forest lands in the Ohio River watershed. When the state bought the land (much to the derision of the local inhabitants), it was a scrubby, tree-less tract dominated by ferns and briars and was almost completely devoid of wildlife or beauty. Not only had the woods been clear-cut by logging companies, but extensive fires (often caused by sparks thrown by the logging railroads) had repeatedly burned off the early successional recovery stages. It was a pretty miserable place!

The passage of time, though, has been kind to this area. With our region’s abundant rainfall and diverse seed reservoirs, a century of robust re-growth of the forest ecosystem followed in spite of the thin, rocky soils and continued sequences of insults and stresses.

Linn Run is shallow, rocky stream. It has a fast pace and lots of splash and foam and now has an abundance of trout and other fish. The forest that fills in the spaces around the narrow road that follows the run is lush and moist with the spray from the creek. Ferns and mosses grow in great abundance along the streamside. Hemlocks, yellow birches, and red maples crowd the edges of the creek and hang their dense branches over the water frequently generating a continuous tree tunnel over the path of the creek. It is a shady, cool place even on the hottest summer day. The hills and ridges around Linn Run through which our hiking trail will pass vary in elevation from 1300 to 2800 feet above sea level. Many of the trails climb up steep slopes in long switchbacks that are carved directly into the hillsides. All of these trails are covered in by layers of cobble-sized rocks that are a great challenge for a hiker’s feet and ankles!

Deborah and I parked in the picnic area of Grove Run (a small tributary of Linn Run) and sat beside a large fire ring to wait for Rob and Michele. Our dog, Izzy, was with us and was very excited to be away from home (or maybe she was terrified at being away from her familiar territory, it’s hard to tell with her sometimes!). She ran from scent to scent in the picnic area adding her scent to the olfactory symphony until she ran dry. She also growled at every large dog (and they were all larger than her!) that walked by. She was full of energy that amazingly did not flag throughout the long, rocky hike that we are about to start.

Photo by D. Sillman

Deborah and I watched a male and a female blister beetle walking around in the cleared area around the fire ring. The blue coloration of these beetles announces their presence and also their potential toxicity to any potential predator. This type of warning coloration is called “aposematism,” and it benefits both the beetles (who are able to avoid being eaten) and predators (who avoid getting blasted with the caustic cantharidin secretions produced by the beetle). The physiological steps by which the cantharidin is synthesized and violently released make blister beetles great biological curiosities. They are often used as examples of the unexpected outcomes of evolutionary selection.

The two beetles were mating. The much larger female dragged the attached male around the fire ring. A second male blister beetle showed up but was out of luck for this encounter. This was late in the year for these beetles to be mating. July is usually the peak time for reproduction because the beetle’s eggs and larvae have to have several months to go through all the required developmental changes needed to get them ready to overwinter. The female blister beetle can produce up to six clusters of fifty to three hundred eggs and will deposit these egg masses in the ground or under rocks. A week and half to three weeks later the eggs hatch into first instar larvae which then seek out grasshopper egg cases. The larvae voraciously feed on the grasshopper eggs and go through increasingly larger and more sessile stages until they reach their fifth larval instar. The fat, almost legless fifth instar “grubs” then dig down into the soil where they molt into the sixth instar stage. The sixth instars overwinter and sometimes actually stay in their subterranean hideouts for up to two years! Usually, though, these sixth instars pupate in the spring and then emerge as adults in the late spring or early summer.

Photo by D. Sillman

Rob and Michele arrived so we tore ourselves away from the dancing blister beetles and headed off on the old logging road that makes the start of the Grove Run Trail. The lushness of both the undergrowth and the canopy trees is striking. Many tall yellow poplars, red oaks, black oaks, sugar maples, red maples, black cherries, and scattered basswoods, cottonwoods, and American beeches fill up the spaces in the forest.

In 2008 (when I wrote the hiking essay about this trail) there were abundant American chestnut seedlings in the understory of this first section of the woods. I took that as a hopeful sign that some individuals of this formerly abundant tree might be eking out an existence in these ecosystems. I looked carefully to see if the seedlings have survived and grown, but they were no longer here. They must have succumbed to the lethal fungus that causes chestnut blight. The yellow poplars that were growing with them, though, were flourishing.

Photo by D. Sillman

On the trail, there is a grace and spacing of the trees that seems almost managed and park-like. This openness is the dominant feature of the trail for many hundreds of yards. As a consequence of this spacing abundant sunlight reaches the forest floor and a rich growth of plants is seen in between the trees. Stinging nettle, cat briar, hay-scented fern, interrupted fern, sensitive fern, Christmas fern, jewelweed, partridgeberry, and extensive patches of blue cohosh grow densely along the trail and out into the surrounding forest. Seedlings of yellow poplar, American beech, red maple, and striped maple grow in clusters among the ground plants and form a dense, green “sea” in between the rich mixture of mature trees. Witch hazel, spice bush, and dogwood generate a scattered understory layer, and near several of the oaks are odd, brown, pine-cone-like patches of squawroot.

The trees are very uniform in diameter (and, therefore, I infer, they are very uniform in age). At the start of the trail trunk diameters of over a foot were common, but soon diameters of significantly less than a foot became the norm. These younger trees generate a “pole forest” that runs up the surrounding hillsides and down the short slopes to the stream. Along the way, there are a few very large, widely dispersed red oaks. These trees might have either survived the early logging or, at the very least, the initial rounds of fire that leveled the recovering forest.

Photo by D. Sillman

There are many downed trees and fallen branches along the trail. Large trees, often wind-thrown with huge, still attached root balls lay in regular lines mostly perpendicular to the path. Some of these fallen trees are old and are covered with mosses, lichens, fungi, and even stands of robustly growing tree seedlings. Others of the fallen trees have bare, intact bark and look like they might have come down quite recently. Most of the fallen trees are yellow poplars with a much smaller number of oaks. Most of the seedlings, though, growing on and around these fallen trees are yellow poplars. The shallow, rocky soil of this ridge undoubtedly was the cause these very numerous wind throws. The cycle of canopy disruption, light influx, and the consequential growth of seedlings favors the very rapidly growing, sun-loving yellow poplars over the oaks. It is possible that this “dynamic equilibrium” of wind throw disturbance and re-growth will result in a persisting, yellow poplar “climax community.”

On past hikes of the Grove Run Trail we have seen abundant birds. In particular many species of warblers were active in the dense forest understory vegetation. Today, though, there are no birds. We are far too late in the season for them. We heard what might have been a grouse chucking in the distance, but no warblers, no woodpeckers, and no towhees sang us along the trail. There were not even any crows raising commotions up in the trees!

The trail followed the curve of the hollow back into deeper and deeper forest. As we hiked up away from Grove Run, the trees grew closer and closer together. The forest and the trail got darker and quieter. The breeze faded away and the undergrowth supported more and more ferns. There are some very large yellow poplars here and increasingly abundant basswoods and red maples. There are also more downed trees that are surrounded by dense growths of yellow poplar and striped maple seedlings. We climbed along the slope on a laboriously carved side-slope trail that was cut all the way down into the underlying rock. There were many rocks and fallen trees all up the sides of the ravine. The uneven trail surface and the necessity of climbing over fallen tree trunks became more and more exaggerated as we go along! THIS was a hard 4 miles!

Michele and Deborah and Izzy walked out ahead of Rob and I. Soon we no longer could see or even hear them. The forest was dense and quiet and surprisingly dry. The surrounding creeks and rills were quiet and have hardly any trickles of water flowing in them. The trail was marked with red blazes. There were older, blue blazes, too, often on downed trees and sometimes painted over with a slap of red

Downed logs have been sawed and pushed off the path, and, very significantly, the stinging nettle and greenbrier has been cut back from the narrow path to make a three or four foot wide swath through the woods. Warm weather, to me, demands hiking shorts (and it was seventy degrees at the peak of our hike!), but the abundance of greenbrier and nettle on this trail might make one consider wearing long pants.

(continued next week!)