Signs of Winter #2: Spruce Flats Bog

Photo by D. Sillman

Photo by D. Sillman

The visual image and history of the Spruce Flats Bog are important (to the left is a summer picture of the bog). First, like the top of most of Laurel Hill, the overall topography of this site is remarkably flat. Also, like most of the top of Laurel Hill, the rock underlying this site is a thick, hard, water impermeable layer of sandstone that is covered by only a very thin layer of soil. This underlying sandstone spreads out under the Spruce Flat Bog area in a broad, shallow, saucer-shaped pan that tends to accumulate rain water and snow melt. The formation of this depression may have been caused by the weight and movement of a ridge top glacier that formed during the last Ice Age tens of thousands of years ago. The great continental ice sheets of this Ice Age terminated many miles to the north of here, but the locally cold climate they generated and the high altitude of this ridge (2720 feet) may have combined to support an isolated mass of ice. Retreat of the continental ice sheets and the warming of the climate would have melted the ridge glacier leaving behind a broad, shallow lake that then began the slow process of pond succession and transition into increasingly solid land. Simply visualized, the pond slowly filled with vegetation and sediment, and its water tolerant plants were slowly replaced by more truly terrestrial plants that began an incremental march in from the edges into the slowly solidifying center. So, this area of open water became a bog, and then a peaty-soiled wet forest, and then, as larger and larger, more rapidly transpiring trees became established, it eventually became a dry soiled forest in which the rates of water accumulation into the saucer were balanced by the outward (and upward) transpirational loss of water by the standing trees. To have looked at this site in its forest form, the potential for a bog would have been very difficult to see!

In 1908, the virgin hemlock forest on this site (and “hemlocks” were frequently mislabeled as “spruces.” Hence, the very odd name for this bog!) was cut. Following this logging, a fire burned away the slash, the re-grown shrubs and sprouts, and also much of the humus-rich upper soil layers. The site now lacked both the sponge-like organic soil materials and also its ecological “pumps” (the transpiring hemlocks). So, rainfall and snow melt once again began to accumulate as free water in the saucer shaped depression. A shallow pond formed followed by a repeat of sediment and vegetation accumulation to form a bog. The inability of trees to grow on the site and the uninformed opinion of the worthlessness of wetlands led to attempts to drain the bog. Dynamite allegedly was used to try to fracture the underlying sandstone and allow downward flow of the bog water into ground water, but the pond/bog persisted. The donation of the land to the state and the creation of the state park protected this bog (although in other state park areas other bogs have not been so fortunate).

Photo by D. Sillman

Photo by D. Sillman

In the 1950’s pitcher plants (a summer photo of these pitcher plants is to the left) were transplanted into the bog by members of the Botanical Society of Westmoreland County, and other wetland plants (like sundews) were also, undoubtedly, introduced into the site at this time. The bog contains cotton grass, cranberry, blueberry, white cedar, pitcher plants, and round-leaved sundews. Sedges grow profusely across many areas of the bog and Juneberry shrubs line the edges of the boardwalk that connects to the observation platform that was built by the Pennsylvania Conservation Corps and Youth Conservation Corps in 1995 and 1996. Conifers (including white pine, pitch pine, Norway spruce, black pine, and eastern hemlock) have been planted around the circumference of the bog forming a tall, green, wall-like palisade on the high edges of the great depressional saucer. Some of the white pines are extremely sculpted by the strong west to east prevailing winds and have grown into fantastic, “action-shaped” morphologies.

We walk down the flat, level, and evenly graveled path and in ten or fifteen minutes are standing on the boardwalk that extends out over the shallow water and wet soil. Even in the cold air of the fading afternoon I can smell the richness of the bog. The scent, a combination of rich organic muck, water, and hydrogen sulfide, pours over me and triggers a cascade of old (and very good!) memories of coastal wetlands and hours spent mucking and kayaking through them. We have the two golden retrievers on leash so that they don’t go off splashing in the bog muck. Izzy is tired and sticking with us, so we leave her off her leash. She takes a short walk into the edge of the bog but comes back to dry land quickly.

Photo by D. Sillman

Photo by D. Sillman

The brown, dry tops of cotton grass spread out over the surface of the thick, black water. Scattered cedars of various sizes and ages stand like islands in the sea of dry grass. You can picture these little cedar islands slowly expanding as the vegetative debris steadily builds up a peat layer into which more and more rooted plants can grow. We also see sphagnum moss growing in from the edges of the bog. Its slow growth and steady accumulation will be another major player in the inevitable re-transformation of this wetland into a solid, richly organic saucer of soil. Scattered in clumps of cotton grass and sphagnum are the red “pitchers” of last season’s pitcher plants. The chambers of the pitchers are designed to lure and trap insects in an enzyme rich fluid where they will be slowly digested to harvest their body nutrients.

Insectivorous plants of the bog (like the pitcher plants) are evolutionary solutions to one of the fundamental nutrient problems of wetlands specifically and wet soils in general: the lack of nitrogen. Nitrogen is a vital nutrient needed for plant growth. Nitrogen in soil is available to plants either as ammonium ions (NH4+) or as nitrate (NO3-). In very wet soils, oxygen levels are often very low due to the inability of air to penetrate into the water filled soil profile. Anaerobic bacteria in the soil then use nitrates as the final electron acceptor in their energy metabolism instead of oxygen. This bacterial generated reduction of nitrate (which is called “denitrification”) generates nitrogen gas (N2) which then leaves the soil and joins the incredibly abundant nitrogen gas reservoir in the atmosphere. So, when a soil is very wet and anaerobic, it is also almost always deficient in nitrogen. The pitcher plants and also the sundews (which we have seen here in the summer but which are not visible here on the cusp of winter) harvest nitrogen from their ensnared insects to help fuel their growth and reproductive metabolisms

After a long hike in the confines of the woods, standing on the edge of the open expanse of the bog is peaceful and welcoming. The wind, though, is picking up and the temperature is continuing to fall. The dogs lie down on the planks of the boardwalk and leave behind perfect, muddy outlines of their legs and bodies. We are going to have to find somewhere to clean these guys up before we go back to Rob and Michele’s condo in Hidden Valley! We leave the observation platform reluctantly but with even more pace to our walking speed. It is getting dark when we get back to the cars. The soft car seats and the quickly warming heater feel unbelievably good! Definitely a sign of winter!

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Signs of Winter #1: Hiking Wolf Rocks Trail

Photo by D. Sillman

Photo by D. Sillman

Wolf Rocks Trail is in Laurel Summit State Park about five miles east from the Grove Run Trail that we hiked last month. This area, like that around Grove Run, was extensively logged in the late nineteenth and early twentieth centuries. Most of the park roads, in fact, have been built on the rail beds of the logging railroad spurs that connected into the main line of the Pittsburgh, Westmoreland, and Somerset Railroad which ran along the present day Linn Run Road. Remnants of these old rail beds (old rail ties, gravel, etc.) can still be found along some of trails.

It is difficult to visualize the activity and human and mechanical energy that filled this area just over 100 years ago. The primal forests of hemlock, white pine, and mixed hardwoods were cut acre by acre, the downed trees were dragged to the rail sidings by horses and then hauled away to the saw mills in Ligonier. There were piles of logs everywhere. The finished lumber was shipped to Philadelphia to build houses, props were cut and sent deep into the booming coal mines, and the mining companies bought entire towns-worth of lumber. Great piles of tannin rich hemlock bark were stacked along the sidings waiting for loading and shipping to leather tanning factories. Fires from the locomotives and from the boilers in the mills were common. Much of the land was cut, then burned, and then burned again. Only a few plant species could survive the incredible ecological “filter” of this destruction and stress.

Deborah and I met Rob, Michele, Nancy and Deb down on Route 30 and then drove up the rough, dirt and gravel road to the Laurel Summit State Park picnic area. We brought Izzy for another woods adventure and Nancy and Deb brought their golden retrievers, Ripley and Maizey. The three dogs handled each other well and added a great sense of the unexpected to the hike (it is amazing what dogs find when they are in the woods and what they think to do!).

Photo by D. Sillman

Photo by D. Sillman

The first section of the Wolf Rocks Trail is a young forest dominated by red maples, sugar maples, black cherries, yellow birches and red oaks. In the summer the understory is lush and green with ferns. Today, though only a few scattered evergreen wood ferns are still green and standing. All of the other species have succumbed to the seasonal changes and are brown and dry. Witch hazel trees and saplings of the over-story trees form a middle vegetative layer along with sometimes very dense stands of the still green and vibrant mountain laurel. In the deep shade under the laurel there are small patches of snow (now THAT’s a sign of winter!).

The trees on this section of the trail are very uniform in diameter (about 12 inches) and height. This homogeneity in size is characteristic of a re-growth site that was uniformly affected by a large disturbance. The abundance of northern red oak and red maple is also consistent with a forest site that has been massively disturbed. Red oak’s ability to stump sprout and withstand fire, and red maple’s ability to rapidly reproduce and, via their abundant winged seeds (“samara”), colonize newly disturbed sites fit the site history of clear cutting and extensive ecosystem fires. The secondary trees (yellow birch, pin cherry, and black cherry) among the red oaks and red maples are also all very common “early colonizers” of sites after widespread logging and fires.

Photo by D. Sillman

Photo by D. Sillman

As we move along the trail the trees become more widely spaced. The understory between them gets a great deal of sunshine and in the summer is full of a tall and lush undergrowth. Today, great circular expanses of the frost killed ferns open up along the side of the trail. White pines (from very large trees with twenty inch trunk diameters, to saplings, to tiny seedlings) “suddenly” are growing among the maples, yellow birch, and black cherry trees. Have the pines “replaced” the red oaks? Possibly the greater distances between the individual trees in this trail section favors the sun loving pines over the more shade tolerant oaks. The pines are reproducing vigorously here. Pine needles cover the trail surface in a smooth, thick, orange carpet. The scent of the pines is incredibly pleasant.

The trail surface is wet and very broken up by rocks and roots. Its irregularity demands careful attention to each step. The trail has been very heavily used. Its surface is compacted several inches below the surrounding soil levels. Surface water from rainfall probably is directed into this lowered hollow of the trail generating an on-going erosion problem. The extensive root exposure on the trail is a direct reflection of this erosive flow of surface water. Sections of the trail have moss growing directly on the soil surface and on the exposed rocks and roots. A bare, well walked step line winds its way around and through these glowingly green surfaces

Photo by D. Sillman

Photo by D. Sillman

Catbrier (also called “greenbrier”) grows very thickly among the surrounding ferns and out into the edges of the trail. The sharp thorns cut at our pant legs as we walk past. We quickly come to the juncture of the Loop Trail, the Spruce Flats Trail and the Hobblebush Trail. The Hobblebush Trail is labeled “Expert Biking Only.” Can that trail somehow be even rougher and rockier than the trail we have been walking on?

We turn onto the Wolf Rocks Loop trail which runs first to the west and then toward the northwest along the edge of the ridge that overlooks the Linn Run Valley. Through the bare trees we get glimpses of the valley. Wolf Rocks at the end of the trail will give us an unobstructed panorama over the Linn Run and Fish Run valleys and their surrounding hillsides.

American beech dominates the first section of the Loop trail. Under the beech trees are patches of a lycopodium called “ground pine.” Over three million years ago, ancestors of these fern relatives grew as massive, tree-sized plants in the wet, coastal, swamp forests of what would become western Pennsylvania. As these behemoths died, they fell into the poorly oxygenated waters of the swamps and partially decomposed into peat. These peat layers were then sealed away from atmosphere by sediment layers laid down by the rising and falling oceans. These fossilized remains became, over time, the “fossil fuels” of coal, natural gas, and petroleum that have been and continue to be so important in Pennsylvania’s economy.

The three dogs race back and forth between their scattered people walking the trail. Maizey and Izzy come back to check on Rob and I (at the back of the group again!) and then speed on up ahead to see what Ripley might have found (often deep puddles of water and mud that are perfect spots to lie down in!). All three dogs have mud-blackened legs and feet to complement their gorgeous, golden coats. They are also having a great time!
There are more wind-thrown trees on this section of the trail. We are close to the western edge of the ridge and undoubtedly the wind exposure here is greater than at the more sheltered trailhead. The power and consistency of the wind blowing in from the west all across the Laurel Highlands represents a potential energy resource. A number of “wind farms” have been built along the ridges to try to tap into this renewable resource. But, nothing is ever free or completely harmless, and the potential impacts of these wind turbines especially on birds need to be clearly understood before we rush into their widespread construction.

The Loop rejoins the main Wolf Rocks Trail at a junction we name “Jameson’s Point.” We stop and have a quick snack and break. The trail then follows a broad, flat, well walked path out to the rocky overlook. The rocks themselves are great blocks of sandstone that have begun to crack and shift away from the mass of the ridge. Ice wedging, root intrusion, and the slow, steady pull of gravity (not to mention the weights and vibrations of quite a few hiking boots) will slowly power the separation of these rocks from the ridge top. Someday, the rocks will break away and tumble down the slope to make a “rock city” on some level section of the hillside.

Photo by D. Sillman

Photo by D. Sillman

We put the dogs on their leashes as we approached the rocks and promontory. We don’t want them stumbling off of the rocks or sliding down the steep cliff face. On past visits to these rocks we have seen large rattlesnakes among the shrubby vegetation. In fact, in 2006 we saw the biggest timber rattlesnake I have ever seen in Pennsylvania coiled up under a mountain laurel bush. His warning rattle was deep and loud! It was difficult to determine his exact length but he was in a foot diameter coiled mass, repeatedly wound around himself, and his body was the diameter of my forearm. Even allowing for adrenaline induced visual exaggerations, he was impressive! But today, in early November, there are no active rattlesnakes so we climb about and put our hands and feet into crevices that we would surely avoid in warmer weather.

The sun is starting to drop down in the western sky and the temperatures are steadily falling. We zip up our coats more tightly and speed up our pace a bit as we walk the main trail back to the parking area. Red and sugar maples, red oak, black cherry, and sassafras dominate the forest. Cat brier and mountain laurel fill in the understory along with an impressive number of mostly red maple seedlings. There is a park-like feeling to the forest: widely spread trees surrounded by a uniform understory. Could the rocky soil be one of the causes of the great spaces between the trees? Along one long section of the trail the path was elevated on packed up soil and crossed several covered cross-logs that spanned sections of boggy soil that was loaded with sphagnum moss. Possibly this was an extension of the nearby Spruce Flats Bog.

We get back to the cars after a little more than three hours of hiking. We are tired, a bit footsore, and cold but decide that we need to keep going so that we can see the Spruce Flats Bog before the sun completely sets.
(continued next week!)

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Signs of Fall 11: Robins and Ring-necked Snakes

Photo by D. Sillman

Photo by D. Sillman

I hadn’t seen (or heard) a robin (good old Turdus migratorius) in several weeks. Over the early weeks of the Fall small flocks had passed over our hilltop on their south and west trajectories. Every once and a while one or two had dropped down from their flight paths and paused here in Apollo to snack on some local earthworms or grab some wild grapes, but there had been no robins for quite a while. It was exciting, then, last Saturday morning when I went out early to fill the front yard bird feeders and was greeted by a loud, unmistakably “robin” extended cackle. It took me several minutes to find the singer: it was a dark black robin with a bright red breast perched up on the almost leafless branches of my red maple tree. A Newfoundland robin!!

Robins spend their springs and summers as mated pairs with very loose flock connections. In the fall and winter, though, they form large flocks that travel locally from one feeding area to another. Many of these flocks even migrate long distances to spend the winter in milder, southern climes. The driving force that moves these flocks is food. In the late summer robins “disappear” from many places here in Western Pennsylvania much to the concern of local bird watchers. These “gone robins,” though, have just vacated one spot to concentrate themselves in some other locale that has more abundant food supplies. People living in these robin-blessed sites wonder at the population explosion going on around them and are concerned by the out-of-control expressions of nature. Deborah and I were driving out in Burrell Township (Armstrong County, PA) late one July a few years ago and were stunned by the thousands and thousands of robins that were hopping around on the ground and perching on almost every free tree branch. The noise they made and the mess they created on every surface with their droppings (is this where their genus name comes from?) were astounding!

It is interesting that although the American robin is one of the most common, most abundant, and most recognized birds in North America its migration patterns are not at all well described. I think that the lack of patterns in their year to year migrations at the onset of winter and then at the advent of spring is due to their dependence not on temperature or weather patterns or geomagnetic sensory systems (things that would be predictable and generate fairly hardwired responses) but instead it is because they follow their food supplies wherever the vagaries of the previous season generate scattered spots of abundance.

American robins are found all over North America. They summer and breed in Canada and Alaska, spend the entire year and breed all across the continental United States, and winter down to southern Mexico and even just a little further south into Central America. The mid-February “arrival” of the robins here in Western Pennsylvania is major sign of spring but probably represents just the ebb and flow of locally overwintering populations transiently leaving their sheltered (and probably fruit filled!) hollows and valleys on short forays out into suburban landscapes to look for earthworms in thawing acres of yard grasses.

I am familiar with three of the seven subspecies of T. migratorius. The subspecies here in Western Pennsylvania is the classic (or “nominative”) form of the American robin. It is widely distributed across the northern United States and Canada all the way north to the very edge of the tundra. The “Newfoundland” subspecies (whom I think that I saw up in my tree last Saturday) has darker black back feathers and redder breast feathers than its nominative subspecies. It may also be (in my opinion anyway, although I could find no reference that agrees with this!) slightly larger than our “usual,” nominative robin. These “Newfoundland” robins may simply represent a color form that is out on one extreme of the species normal color distribution. “Black backed” robins can be seen almost any time of year through the bird’s North American distribution. But this dark, intense coloration does seem to predominate in the robins from Canada’s northeastern coast. The third subspecies is the “Oklahoma” robin. This robin’s back feathers are more gray than black, and it has a pale, reddish orange breast. They look dusty and dry (as is fitting the dust-bowl center of their distribution). When I visited my parents in Tulsa these are the robins I would watch ranging across the suburban lawn-scape as they searched in the coarse grasses for worms.

Photo by David Hoffman (Flickr)

Photo by David Hoffman (Flickr)

Changing the subject to snakes! My good friend Carl Meyerhuber called me last weekend to report a sighting down on the Roaring Run Trail. Near the Canal Street parking lot Carl spotted an immature ring-necked snake crawling slowly across the trail. It seems very late (and it has been very cold!) for these delicate snakes to be out and about. It was a good thing that Carl was there to make sure that this slowly crawling, well chilled young snake made it all the way across the trail!  Last summer I wrote about ring-necked snakes and said that in spite of the DER’s declaration that they are one of the five most common snakes in Pennsylvania I had never seen one. They are shy and nocturnal and hard to find. I hope that this little immature ring-neck found a suitable place to hibernate down in the vegetation beside the Kiski River. I will look around for him next summer!

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Signs of Fall #10: Where do the frogs go in winter?

Northern green frog (photo by Contrbaroness. Wikimedia Commons)

Northern green frog (photo by Contrbaroness. Wikimedia Commons)

A few weeks ago Jane Viti, one of my teaching colleagues, asked me what was going to happen to the two frogs that had been living in her small, backyard pond all summer. As we talked about her frogs’ appearance, behavior, and songs I decided that they must be Northern green frogs (Lithobates clamitans melanota), and since her pond is quite shallow and expected to freeze solid over the winter, and also because it is surrounded by a very dense growth of myrtle, I speculated that the green frogs (which can either hibernate underwater or underground) would leave the soon-to-be-solid pond and dig a hibernaculum in the soil under the protective cover of the myrtle. But where these frogs sit out the winter was just the beginning of this story. Frogs are ectothermic (they rely on the heat of their environment for their body heat) and would seem quite vulnerable to freezing solid in the very cold winters of Western Pennsylvania even if they were underground or underwater. How could they survive this extreme thermal trauma?

In my Cell Biology class I talk about changes that can be seen in cell membranes in both amphibians (like the green frog) and reptiles (like turtles and snakes) as seasonal temperatures begin to fall. An enzyme is stimulated that begins to add double bonds to the fatty acids of the cell membrane phospholipids. This “desaturase” enzyme makes the altered fatty acids more crooked and thus less able to stick together. This reduces the freezing point (which usually referred to as the “melting point” for some reason) of the cellular membrane and keeps the membrane “fluid” and functional at lower and lower temperatures. Also, amphibians add cholesterol to their cell membranes, and these steroids further keep the fatty acids from clumping together even at decreasing temperatures.

These changes help to keep our frog active at temperatures that are lower than optimal, but eventually temperatures start to approach the freezing point of water, and the frog is at risk of cell and tissue damage from the freezing of the water in its blood and cytoplasm.

Frostbite on human toes (Photo by Dr. S Falz-Colleque Wikimedia Commons)

Frostbite on human toes (Photo by Dr. S Falz-Colleque Wikimedia Commons)

Let’s take a second and think about people. When skin is exposed too long to freezing temperatures cells are destroyed and “frostbite” occurs. Why do the cells die? First, the blood flow into the cold body part is curtailed in order to prevent excessive body heat loss (humans are endothermic organisms who use the heat from their metabolic activities to generate their body heat and there is only so much heat energy to go around!). The lack of blood flow into the tissue means that oxygen is no longer being delivered and cell death from lack of oxygen may occur. Also, and maybe of a more immediate concern, the lack of warm blood entering the tissue means that the fluids in the tissue and in its cells may start to freeze. Usually the interstitial fluid around the cells freezes first and these ice crystals actually start pulling water out of the inside of the cells. For a while this dehydration event may actually hold off cytoplasmic freezing, but eventually the cell will be irreversibly damaged (i.e. “killed”) by either excessive dehydration or by the inevitable freezing of its cytoplasm.

But, let’s get back to our frogs: before the frogs are exposed to freezing temperatures they undergo many physiological changes in addition to the cell membrane changes I listed above. Their livers start synthesizing and releasing large quantities of glucose (“sugar”) into their blood streams. These sugars are absorbed by the cells of the body causing the cytoplasm to become thick and syrupy and increasingly hypertonic to the surrouding interstitial fluids. Also the frog releases special proteins called Protein Ice Nucleases (or “PIN’s”) into their blood stream. These proteins will stimulate freezing of the water in the blood stream which will then inhibit the potentially lethal freezing of the water of the cytoplasm inside the cells! When the frogs are finally exposed to truly freezing temperatures the skin and then the rest of the body freezes solid (they are like little rock statues of frogs!), but the freezing is primarily confined to the blood and to fluids around the cells! The forming ice crystals in the interstitial fluid draw water out of the cells (just like in human frostbite) but the high levels of sugar inside the cells not only act as a natural antifreeze for the cell but also hang onto enough water so that the cells don’t dehydrate to the point of death!

Gray tree frog (photo by L.A.Dawson. Wikimedia Commons)

Gray tree frog (photo by L.A.Dawson. Wikimedia Commons)

Terrestrial frogs (like the American toad (Bufo americanus), the wood frog (Rana sylvatica), the spring peeper (Hyla crucifer), the gray tree frog (Hyla versicolor) and the northern green frog when it decides to hibernate on land) basically let themselves freeze solid in their soil hideouts. Wood frogs and tree frogs don’t even go down into the soil but just bury themselves in piles of leaves and ride out the months of freezing temperatures. During warm spells these terrestrial hibernators may even thaw out and move around, but they will typically then re-freeze and settle back into their winter slumbers. I noted in several spring and summer blogs this year the very large number of gray wood frogs in the trees around my field and yard. I wonder if all of the leaves that I have been letting pile up under my trees (because of my selective leaf-raking policies) provided these great creatures with sufficient winter habitat to favor the growth of their population?

Aquatic frogs (like the leopard frog (Rana pipens) and the American bullfrog (Lithobates catesbeianus) and the northern green frog when it decides to overwinter in a body of water) spend the winter if not frozen then nearly so in the still liquid environment of their ponds or pools. They do not bury themselves in the muds of these systems because they must continue to pick up oxygen from the surrounding water through their skin. Sometimes they sink to the bottom of their pools or ponds (they are quite solid and have no air in their lungs) but they must keep contact with the oxygen-rich water in order to survive. They also may swim about a bit when they warm up during lulls in the winter cold. Aquatic frogs can survive freezing solid in ice, but I don’t know how long they can live that way. The lack of oxygen would surely be fatal if the ice-encasement persisted for too many weeks.

So, on the next cold Fall night as you sit in your warm house wrapped in an afghan or a sweater, give a thought to the little frozen frogs outside who are waiting for their personal Spring thaws to come.

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Signs of Fall #9: Grove Run Trail (part 2), Striped Maples and More Rocks

Photo by D. Sillman

Photo by D. Sillman

(Portions of this blog posting are taken from my hiking essay about Grove Run Trail (on the “Between Stones and Trees” web site))  (Continued from last week)

We crossed the narrow wooden bridge over Grove Run. The stream bed was filled with rocks and fallen trees. Some of the rocks had been deeply grooved by the water flows, but there was no flowing water today.

Across the bridge we climbed steadily up the slope on the opposite side of the deep hollow and headed, in general, to the east. The trail followed a small tributary of Grove Run back up the ridge. This side of the hollow faced the northern sky. In this more shaded environment, American beech saplings and pole trees became increasingly abundant. Beeches should grow especially well in this ravine. The cool, moist conditions are ideal to nurture this slowly growing species, and the near immunity the beech seedlings have against deer browsing will greatly favor its persistence.

Photo by D. Sillman

Photo by D. Sillman

The trail surface was covered with rocks that seem to get larger and larger as we hike up the ridge. We had to pay close attention to each footfall and were forced to stop when we wanted to look around or try to take in the beautiful scenery and day. The walking was hard, and Rob and I agreed that we were glad that we were wearing boots and had hiking sticks. Deborah was in tennis shoes and never uses a stick. She and Michele were also probably a half a mile ahead of Rob and I by now. As I stumbled along looking to my footing I wondered how they were going along so rapidly! Different hiking techniques, I guess.

There were even more downed trees along this section of the trail than in the previous one. There were great stacks of fallen tree trunks piled up on the slopes and scattered down into the deep recesses along the stream. There were extensive areas of open canopy generated by newly fallen trees and abundant zones of sunlight that illuminated the forest floor. The “sun spots” were especially filled with yellow poplar and red maple seedlings.

We turned left and walked due north up a side hollow crossing several small, dry stream beds. We hike up and up on long switchbacks that were edged by briers and nettles. In one section of the switchback trail someone has cleared away most of the path rocks and lined them up neatly along the left side of the trail. Suddenly, it was very easy to walk! The twisting, jarring strain on the ankles, knees, and back with each footfall was gone! Our walking pace picked up. It was possible to look around while walking without fear of missteps. The trail was clear for about a quarter of a mile and then reverted back to its un-managed state. The memory of the cleared trail, though, actually slowed us down as we twisted and stepped up through the continuing rocky footpath.

Photo by D. Sillman

Photo by D. Sillman

The trail surface and most of the surrounding boulders are covered with moss. Everything was green and soft looking and must spend a great deal of its growing season in a wet state. The “up” continued and we passed into an increasingly dry forest dominated by oaks. Chestnut oaks, often very large specimens, fill in the surrounding woods inter-mixed with red, black, and also white oaks.

At the top of one of the switchbacks there was a trail register and a sitting log. We had caught up to Deborah and Michele and stopped to have a water and gorp break. Izzy ate four dog biscuits and drank two Sierra cups of water. A group of teenagers came up the trail from the opposite direction. They were staying in the Linn Run cabins and were out for a stroll. They didn’t look nearly as tired as we felt! They petted Izzy (once she stopped growling at them) and headed on down into the ravine.

Photo by D. Sillman

Photo by D. Sillman

Most of the trees on the ridge top were striped maple. This is a tree species of some poor reputation among foresters. Their idea, of course, of a “poor” tree is heavily influenced by the economics of that tree’s wood. Striped maple is not a tree from which any lumber or wood products could be easily made. Whatever the future potential of this tree is, though, along this ridge it was generating a rich habitat that in the summer at least is full of birds!

Striped maple is also called “moosewood” in places, I assume, that have the luxury of having moose. It is a small tree or large shrub that thrives in cool, moist, but well drained sites. It is found throughout the northeastern United States and across southern Canada. It makes up part of the understory vegetation in a wide variety of forest types.

Striped maple can live in the deep shade of a forest for many decades in a slow growing, suppressed state. Over these decades, in spite of a very high mortality rate in its first year seedlings (9 out of 10 seedling die in their first year of life), very large numbers of individuals can accumulate in the forest system.

Canopy disruption allows increased light to reach this understory triggering a vigorous growth response in these suppressed striped maples often to the great disadvantage of other, less abundant seedlings. Forests that have striped maple making up 30% or more of its total seedlings typically will generate after clear cutting nearly pure striped maple stands. These ridge forests, then, must have had dense undergrowths of striped maple that were released when the larger trees were cut or burned.

Deer browse heavily on striped maple. Rabbits, porcupine, and moose (hence the “moosewood” name!) also readily eat it. Beaver will even take striped maple if their preferred aspens are not available. The very large number of individual trees that build up in a stand, though, and their rapid potential growth rates upon release from shade suppression, enable this species, unlike many of its less abundant or less robust competitors, to thrive in areas even with very high deer populations.

Striped maple flowers in May or June and has a very interesting “gender” story. Most striped maple individuals are either “male” or “female” and, thus, only set either pollen synthesizing flowers or ova synthesizing flowers. But, from year to year, an individual tree can either be male or female. Environmental variables are thought to determine the yearly gender of a particular tree.

In a stand of striped maples there are always many more female trees than male trees, and these female trees, undoubtedly due to the extreme energetic demands of seed production, are much less vigorous than the males. In fact, in one study 65% of the female striped maple on site died by the end of the growing season.

The seeds in winged samaras are wind dispersed in October or November and may germinate the next growing season or, possibly, the season after that. Birds (including ruffed grouse) and many types of small rodents eat striped maple samaras, but, again, overwhelming numbers insures the survival of more than enough seeds to fuel the explosive growth of seedlings in the forest understory.

We crossed the broad, open Quarry Trail (part of the snowmobile trail system that crisscrosses the Laurel Highlands) and continued on the Grove Run Trail. The red blazes were set very far apart and in places the trail was so covered with rock that it was difficult to see the path. We focus on the blazes and keep on the trail.

Years ago, Deborah and I were caught in a large thunderstorm up on this section of the trail. Lightning and thunder, torrential rain, and hale pounded on us for over an hour. Today, thankfully, the skies stayed clear and blue. It was hard enough walking on these rock paths without having them coated with water and ice!

Photo by D. Sillman

Photo by D. Sillman

The remaining trail was all side-hill cuts into a very steep slope. The pull to the downside of the slope really strained our knees and ankles. You felt like you could go tumbling down the slope with even a tiny stumble. To our right was the valley of Linn Run and all around us were stands of beautiful oaks and red maples and great expanses of ferns.

We had been hiking for two and a half hours. The end of the trail should be close but everything seemed to stretch out to longer distances that we expected. At one point the trail even turned back uphill! That didn’t seem right (or fair) but we stuck to the red blazes and pushed on. Deborah and Michele were far ahead of Rob and me and even told other hikers heading up toward us to say “hello” and ask if we “needed a rescue party?” (what great sense of humor, eh?). One woman with a young, bouncing golden retriever asked me “are you Izzy’s owner? She’s so cute!” They must have had a pleasant encounter.

We stretched out the last mile and finally got a glimpse of the Grove Run parking area. Deborah and Michele were sitting with Izzy around the blister beetle fire ring. Deborah has used her scarf for an Izzy leash (the actual leash was in my pocket). Rob and I had the car keys, too. We were also carrying the extra water and all of the trail snacks. We sat down and, eventually, agree to share (we have a sense of humor, too!).

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

Photo by D. Sillman

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

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

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

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

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!)

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Signs of Fall #7: Falling Leaves and Compost

Photo by D. Sillman

Photo by D. Sillman

I am waiting for the leaves to start to fall from my trees. It is an event that occurs at the same time each year (sometime after Columbus Day and before Halloween) but it always seems to be late in coming. I am not sure why I am always so eager to get on with the Fall, it just means that winter is closing in on us and that the color green is going away for five months!

There are so many “truths” and “myths” about tree leaves and what you need to do with them after they fall. One lawn product company stated on their web site that you need to rake up and dispose of these leaves or else “you will get rats in your yard.” Yeah, right. One of my neighbors piles his leaves in a great mass on top of his cleaned out garden and sets them on fire (or tries to set them on fire, anyway). The resulting smudgy, smoky mess smolders for hours and hours and triggers asthma in everyone for blocks around. One of my other neighbors runs her riding mower over and over her yard to scoop any stray leaves. I am not sure what she does with the mower bag’s contents. Another neighbor runs his leaf blower from August to November pushing his leaves to somewhere out of sight. His hearing must be destroyed by the din of that blower!

Photo by D. Sillman

Photo by D. Sillman

I usually rake up my leaves into several large, strategically located piles around my yard and leave them to nourish the worms and beetles and other invertebrates that will shred and grind them up into food for fungi and bacteria. In the old days my kids and I would jump in the leaves and further accelerate their fragmentation. Now I just rely on the worms to do the job with less noise and vigor (and much less fun, too!). Through the next spring and summer birds (especially the robins and the cardinals) peck at and dig around in the leaf piles looking for insect larvae and earthworms. These leaf piles are a great source of nutrition for these hunters and gleaners. By the time the next fall rolls around, the piles are remarkably reduced in size and are ready to be renewed by the freshly raked up leaves. One pile down in my orchard was kept in this yearly equilibrium for over twenty years. The rich, humus that accumulated at the bottom of the pile eventually was raked up and added to the soil of my tomato patch.

In a forest, the fallen leaves spread out in a thin layer over a broad area. Often earthworms start working on these leaves right away, pulling them into their middens and burrows, grinding them up with their muscular mouth-parts and gizzards, mixing them up with ingested soil, and defecating them out in nutrient rich, erosion resistant pellets. In soils without earthworms, numerous arthropods of many sizes begin to slowly chew away the leaf materials making a fine powder of organic residues enriched with bacteria. Both the worms and the arthropods are setting the table for the bacterial and fungi that then steadily work away at the less resistant molecules in the leaves. Like in my leaf piles, by the time the next fall comes around what’s left of the old leaves serves as the base for the new and the decomposition process grinds on.

Photo by D. Sillman

Photo by D. Sillman

Another fate of some of the leaves that fall in my yard is my household compost bin and pile. I collect a couple of trashcans of dry, freshly fallen red maple and apple leaves each fall and store them over the winter in my garage. When I charge up my composting bin in the spring, I throw in a good amount of the dry leaves to serve as a carbon source for the brewing compost and to give the dense, wet kitchen materials (usually dominated by coffee grounds!) some structure and air spaces. After some weeks in the bin (with regular turning and weekly additions of fresh kitchen materials) I shovel out some of the compost and transfer it to my nearby compost pile. Then I add some more leaves to the bin. By the end of the summer I have a rich pile of compost ready to be used in my garden or Deborah’s flower beds.

My leaf piles decompose more slowly than the managed compost piles primarily because of an innate nutrient imbalance in systems made up simply of leaves. There is too much carbon on these piles and not enough nitrogen. In the compost bin and pile the kitchen materials (especially all of those coffee grounds!) need the extra carbon of the leaves to balance out their decomposition. On the forest floor the richness of the chewing and shredding and burying organisms add nitrogen to the leaf materials via their feces and accelerate and balance the decomposition of leaves.

Natural decomposition is best thought of as an ensemble effort of an entire community of organisms where the products of one group of species becomes foods of another group of species until the food energy in the decomposing leaves is exhausted and only humus is left.

An old friend and mentor of mine, Daniel Dindal, summarized this community concept of composting into a very visual diagram that he called the “Food Web of a Compost Pile.” Please look over this marvelous work of art and science!

Drawing by D.L.Dindal

Drawing by D.L.Dindal

Up on campus we have started a composting system for the materials generated in the Café. We have three fence-sided compost bins into which we are putting kitchen and post-use “waste” materials. We are monitoring the rates and directions of the composting process, and I have three students who are conducting experiments on various stages of the composting system. Hopefully, in the spring we will have some rich compost to add to the flower beds and tree plantings around campus.

 

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Signs of Spring 6: Return of the Stink Bugs!

Photo by D.Sillman

Photo by D.Sillman

When I sit at my writing desk I spend as much time as possible looking out the window at the ongoing events in my backyard. A few days ago my view of a blue jay digging around in my compost pile (he was looking for, finding and eating fragments of egg shells!) was interrupted by the arrival of an organism that I haven’t seen since the end of June: the brown marmorated stink bug (which is frequently referred to as “BSMB”)!
One of these exotic invasive stink bugs attached itself onto the outside of my window screen and was walking around in a tight circle. When I looked back up a minute or so later, there were seven of them slow dancing around each other. They have been increasing in numbers ever since.

These stink bugs have spent the summer out in the surrounding vegetation (especially in my grape vines and apple trees, I am sure). They are the progeny of those stink bugs that survived their winter hibernations and managed to mate this past spring. Each mated female could have laid three hundred eggs which would have quickly hatched into the first of five immature, instar stages. These growing immature stink bugs spent the next two months feeding and growing and hiding out in the vegetation until they molted into their adult forms. They then started to look for a safe place to spend the upcoming winter.

Bill O’Hara (Dee’s husband) caught thousands of adult BMSB’s last fall. He used one liter, plastic, screw-top bottles with some soap solution in the bottom and took advantage of the typical escape behavior of the stink bug (they drop straight down when disturbed!) to induce them to fall into the bottle and the killing soap. Deborah and I had tried to be tolerant of the BMSB’s but their numbers finally overwhelmed even our ecological sensibilities. We used the “O’Hara method” this past spring as thousands of stink bugs emerged from their winter hibernaculae inside and around our house. We filled up several bottles a week with dead and dying stink bugs. When we had house guests we gave everyone their own stink bug bottle so that they could contribute to the correction of this exotic species invasion! We were the perfect hosts!

D. Lance Wikimedia Commons

D. Lance Wikimedia Commons

As I mentioned last year, the brown, marmorated stink bug (scientific name: Halyomorpha halys) is a relatively new sign of fall here in Western Pennsylvania. It is a native of northeast Asia (Japan, Korea, and China) and, apparently, is just as annoying there as it is here! Its use of human habitations as hibernation refuges, and its ability to communicate via pheromones and then aggregate in great numbers in some selected house, barn, porch, garage, or any other stink-bug-determined-suitable building makes their presence both in their native and also in their invasive regions impossible to ignore.

It is thought that this insect was first released into the United States in Allentown, PA in 1996. It apparently traveled from northeast Asia in a shipping container that was delivered either to the port of Philadelphia or Elizabeth, New Jersey and then trucked to Allentown. Five years later this new, alien, invasive species was recognized and identified by entomologists at Cornell University, but by then large populations were established throughout eastern Pennsylvania, New Jersey and New York. This insect has now spread to thirty-five states primarily in the eastern United States. It has very large populations in Pennsylvania, Maryland, Virginia, New York, New Jersey, Massachusetts, Delaware, Ohio, and North and South Carolina. It has also spread to California and Oregon allegedly in a car driven by a person traveling from Pennsylvania to California in 2005.

Here in Western Pennsylvania our first, massive fall outbreak of brown marmorated stink bugs was in 2010. Two of my students since then have gotten interested in the species and have done some research into their biology and ecology and even conducted some experiments to determine the species’ habitat selection preferences. I had hoped that their research would result in an effective stink bug trap, but we’re still working on that!

There is a consortium of university and government researchers who are looking into the basic ecology and biology of the brown marmorated stink bug. Their goal is to come up with effective control measures to stem this growing biological invasion. The group (called “Stop BMSB”) is funded by the US Dept. of Agriculture and includes fifty researchers from ten universities (including Penn State!). They are even conducting a “citizen’s science” survey this fall to try to determine some of the ecological and behavioral features of this bug. Their “2014 Great Stink Bug Count” asks homeowners to go out around their houses every day to determine the numbers and locations of any stink bugs that are present. If you are interested in participating, the URL for the group is www.stopbmsb.org. Maybe they can figure out what that better stink bug trap should be!

So far, the stink bugs are only on the outside of the house, but they will start to slip in soon. We are saving up screw top bottles. Drop by anytime for a lesson in the O’Hara technique!

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Signs of Fall #4: Leaf Changes

Photo by D. Sillman

Photo by D. Sillman

During most summers we hit a dry spell and several types of trees respond to the lack of water with leaf loss. The two, tall, skinny black locusts out on the back edge of my field lose half of their leaves in a typical July. Sudden breezes send swirling clouds of yellow leaflets down onto the lush, green grass, and the black locusts, which are typically one of the last trees to leaf out in the spring, stand mostly denuded but increasingly watertight against the summer drought. Cherry trees (black and sweet cherries) have the same response to drought but don’t shed their leaves quite as extensively as the locusts. I do remember, though, back in 2010 that the cherry trees along the Baker Trail lost at least thirty percent of their canopies in the dry summer. The trail surface was littered with bright, yellow leaflets all through July and August.

This summer both the locusts and the cherries have kept their leaves and are only just now starting to show any color changes or leaf losses. The abundant and remarkably steady rainfall this year (May through August we were three and half inches above average) is probably the reason: no water stress, no leaf changes or leaf losses until the seasonal cues kick in that push the deciduous trees into their winter physiologies.

Leaf loss is a purely “economic” decision for a tree. Leaves are the organs for photosynthesis and energy acquisition, but they also lose incredible quantities of water via transpiration. In the summer the black locusts and the cherries balance their needs for energy (for growth, reproduction, repair etc.) with the necessity of maintaining an acceptable water balance in their tissues and cells. In wet summers these trees can keep all of their leaves, fix abundant energy, and transpire water without damage. In dry summers, the limiting factor of water availability makes the tree give up some of its photosynthetic potential in order to maintain its water balance.

Photo by D. Sillman

Photo by D. Sillman

With the approaching winter the leaves for all deciduous trees are shed primarily to help the trees withstand the dry conditions of winter (also, the freezing of the water in the leaves would destroy their cellular structures and render the leaves useless as photosynthetic organs!). The types of trees that keep their leaves (the coniferous, or “evergreen” trees) do so by making a tougher, more water tight “leaf” (often very tightly pored needles that are wrapped in layers of waxes) and by some elegant physiological adaptations that go on inside the cells of the needles. This winter acclimation adaptation includes altering the chemical nature of the lipid molecules inside the cells (making the lipids more “unsaturated” and, therefore, more twisted and bent and thus less able to join together in a solid form (this significantly reduces the freezing temperature of the cells!). The cells also increase the cytoplasmic concentrations of these freeze-resistant lipids to amplify this antifreeze effect. The cells also add other solutes to their cytoplasm and break up some of their intracellular proteins into many smaller pieces. Both of these responses act to further decrease their freezing points.

The cells in these conifer needles also alter their plasma membranes to allow water to move across the membrane more freely. Then, as ice begins to form in the spaces around the cells, the water of cytoplasm is drawn out into the surrounding ice crystals and away from triggering possible freeze events inside the cell itself! An interesting side note is that the freezing of this surrounding liquid water to form ice releases a small amount of heat energy (the “heat of fusion”) and the cells of the leaf take advantage of this added heat to help maintain their internal liquidity!

Photo by D. Sillman

Photo by D. Sillman

When the deciduous trees get ready to shed their leaves in the fall, they undergo several well defined stages of change. First, in response to the duration of the dark period of the day reaching a critical length, the leaves begin to generate large numbers of cells right at the junction of the leaf’s stem and its branch. These cells greatly increase in number but not, at first, in their individual sizes. This layer of cells (the “abscission layer”) slowly starts to interfere with the flows of sugars out of the leaf and nutrients into the leaf. The lack of nutrients entering the leaf stops the synthesis of new chlorophyll molecules that are needed to replace the ones that wear out in the ongoing process of photosynthesis. Chlorophylls are, of course, the pigments that give plants their characteristic green colors. Initial cessation of chlorophyll production makes the leaves appear a bit paler and less intensely green than they were during the height of summer. Continued breakdown of the chlorophylls then starts to unmask the other pigments (the “accessory” pigments of photosynthesis: the carotinoids and xanthophylls) that had been present in the leaves all summer long). As these pigments are “revealed” the leaves then “turn” orange (from the carotinoids) or yellow (from the xanthophylls) before they finally fall. The accumulation of the sugars in the leaves also has an effect on eventual leaf color. These sugars stimulate the synthesis of anthocyanin pigments in the leaf. These pigments generate purple or bright red colors in the leaf and are thought (by W. D. Hamilton, the famous “Bill Hamilton” of biology!) to possibly protect the leaf (and particularly next year’s delicate leaf buds) from insect damage.

The deciduous trees in our area will be turning their autumnal colors very soon. The breakdown of the chlorophyll and the revealing of the accessory pigments is inevitable in our climate zone. In some years, though, the intensity of the reveled colors is much more extreme than in other years. The weather patterns of the fall and of the preceding spring and summer all contribute to the magnitude of the final color response.

Good, healthy abundant leaves are favored if the previous spring had adequate rainfall. A normal to wet summer will then insure that these leaves persisted intact through their active photosynthetic seasons. Warm, sunny autumn days combined with cool but not freezing autumn nights will maximize sugar production and anthocyanin synthesis in the leaves. These accumulating anthocyanins then give the leaves their brilliant red and crimson colors that seem to define a “good” color year in the forest!

The way this year is working out, we should have some very spectacular colors around us, and that is almost everyone’s favorite Sign of Fall!

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Signs of Fall #3: Feral Cats

Photo by Stavrolo, Wikimedia Commons

Photo by Stavrolo, Wikimedia Commons

A couple of weeks ago I received an email from my friend and fellow environmental enthusiast Patrick Kopnicky asking me for my opinion about feral cats and their impacts on their environments. Patrick and his wife Mardelle, as I have mentioned in several previous postings, head up the Environmental Learning Center and the Friends of Harrison Hills organization at Harrison Hills Park (Allegheny County). The feral cat discussion that he was involved in centered on not only the maintenance of some area feral cat colonies but the proposed establishment (and support) of new colonies in some of the county’s other public parks.

So let’s get some facts lined up about feral cats. A feral cat is defined as a domesticated cat (Felis catus (or Felis sylvestris catus , if you prefer)) that has returned to the wild. A feral cat is not the same as a “stray” cat. Stray cats are domesticated cats that are lost or abandoned although the kittens of stray cats can, indeed, grow up to be feral cats. Feral cats typically live in colonies of three to twenty-five individuals. They are wild animals that live by consuming human refuse or by hunting small mammals, reptiles and birds (and it is the magnitude of this hunting that is the crux of the problem concerning feral cat populations!). It is estimated that there may be up to ninety million feral cats in the United States alone!

Photo by S. Golemon, Wikimedia Commons

Photo by S. Golemon, Wikimedia Commons

Some feral cat colonies are tended by human caretakers. These volunteers provide food, shelter and a degree of protection for the colony. Attention to disease and parasite prevention is also a part of this colony maintenance. These tended feral cat colonies are made up of animals that have very similar levels of health, vigor, and expected life spans that are seen in populations of domesticated (“house pet”) cats. A notable exception to this concerns rates of disease and mortality in kittens which are much higher in feral cat colonies than in “housecat” cohorts.

Cats are not native to North America. Feral cats, then, by definition, are alien, exotic species in our ecosystems, and they can have impacts on small mammal, reptile and bird populations that are, potentially, quite significant. The Smithsonian Institution and U.S. Fish and Wildlife Service released a study recently in which they estimated that up to 3.7 billion birds and 20.7 billion mammals are killed by cats in the United States each year. “Un-owned” cats (strays, feral cats, and barn cats) kill three quarters of these small animals while “owned” housecats are responsible for the remainder of kills.

Photo by Brisbane City Council, Wikimedia Commons

Photo by Brisbane City Council, Wikimedia Commons

Cats of all definitions are marvelously efficient hunters. It is this ability to hunt and kill that led the World Conservation Union to list the cat as one of the world’s one hundred worst invasive species. I have found a number of specific studies that correlate the presence of cats to the decline in the populations of many types of birds. One of the most compelling papers that I read described a seabird chick survival study set on two of the smaller islands in the Hawaiian chain. The island that had established populations of cats had a sea bird chick survival rate of 13%, while the island that had no cats had a sea bird chick survival rate of 83%. Cats are very active hunters!

An observation closer to home concerning the impacts of feral cats comes from a conversation I had a few years ago with John and Marilou McNavage. They told me (and recently confirmed that this is still the situation) that no longer had any chipmunks around their house. They correlated the lack of chipmunks to the presence of a near-by feral cat colony.

Now I have written about my two cats in this blog on a number of occasions. Two years ago I proposed “Housecat Day” as a logical (and ecologically sound) February alternative to Groundhog Day, and, as I write this, one of my cats is laying half across my computer key board and is purring so loudly that is hard to keep a train of thought going.
In short, I love cats very much! I also acknowledge, though, that they are incredibly efficient predators!

The Audubon Society endorses the American Bird Conservancy’s “cats indoors” campaign. The Audubon web site states that “worldwide cats may have been involved in the extinction of more bird species than any other cause except habitat destruction.” The American Association for the Prevention of Cruelty to Animals (“ASPCA”) states on their web site that feral cats mostly hunt and kill rodents not birds. The Smithsonian data listed above agrees with that: a cat will on average kill 5.6 small mammals for every bird. But, although the kill ratio seems to favor rodent control, the numbers of birds killed each year is still staggeringly high!

The ASPCA estimates that a feral cat without human intervention has an expected life span of about two years if it survives its time as a kitten. With human intervention and management of a feral cat colony the expected life span of the cats is ten years. The ASPCA also states that if a feral cat colony is eradicated (i.e. the cats are killed) a “vacuum effect” occurs and cats from outside the colony come into the area and rapidly re-establish the colony. Killing feral cats, then, only opens up resources for other feral cats.

The ASPCA and many other animal welfare groups advocate programs of Trapping…Neutering…and Releasing (“TNR”) as the most effective way to deal with feral cat populations (a variation on the TNR is “TVHR” (Trap-Vasectomy-Hysterectomy-Release) and there are studies that compare the relative effectiveness of each type of population control program). These types of programs have been used extensively in the United States and also in Europe. How effective are they? Studies in North Carolina and Florida showed 36% declines in colony populations in TNR treated feral cat colonies after two years and an 85% decline after eleven years. In Rome (the feral cats of the Coliseum!) there was a 32% decline in treated feral cat populations after six years.

TNR (or TVHR) works. The treated feral cat colony slowly declines in numbers and should, if there are no additional cats added to its population via stray or abandoned animals, result in the eventual extinction of the colony.

So what do I think about feral cats? Having some of these small predators in our ecosystems actually might be a benefit (we have far too many white-footed mice out there for, example, and these mice are important intermediate hosts for the bacterium that causes Lyme disease. Increasing predator control of these mice might be a way to get our local Lyme epidemic under control!), but having ninety million of these small predators out in our ecosystems is excessive. I personally could not go out and trap and kill a cat, but we need to control their numbers (via TNR and TVHR?) and also deal with the source of the feral animals, irresponsible pet owners who do not spay or neuter their cats and allow them to reproduce so excessively that the numbers of abandoned pet cats that head off into feral existences explosively increases each year.

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