A Walk in Penn’s Woods

Last autumn, on a hot, humid Sunday afternoon in early October, my son Dave and I led a Walk in Penn’s Woods on our property. This program, begun in 2017 by the Center for Private Forests at Penn State, has attracted support from both private and public land owners eager to share their forests and the trees, shrubs, wild flowers and wild creatures that inhabit them.

Black birches in Plummer’s Hollow

Black birches in Plummer’s Hollow (Photo by Dave Bonta on Flickr)

Our walk was the only one scheduled in Blair County, and we did not advertise it ahead of time. Still, we had one man from Centre County, another from our county, and a couple from Indiana County.

From our 10 miles of trails, Dave and I had chosen the walk up our mile-and-a-half entrance road paralleling our Plummer’s Hollow stream, through a mostly diverse hardwood forest that also has a stand of hemlocks affected by hemlock woolly adelgids. Many of the trees in the hollow date from the 1840s when it was last clearcut to feed the iron furnace at the base of our road known as Upper Tyrone Forge.

Since visitors to our property first drive across an old couty bridge over the Little Juniata River and then bump across the main railroad line from New York to California, we are able to point out the remnants of the watering tank near the bottom of our stream which was used by the steam locomotives beginning in 1850. It was first overseen by the original William Plummer who came here in 1832 to work as a forge man and ended his life working on the railroad.

Beech trees below the driveway

Beech trees below the driveway (Photo by Dave Bonta on Flickr)

Human history that impacted our forest was important, but so was learning about our forest today and the plants and animals that live in it. Because the trees are old and the understory on the steep slopes of Laurel and Sapsucker ridges fairly diverse, we were able to show our visitors a wide variety of native tree species and their fruits from cucumber-tree and American basswood to American beech, red, black, white, chestnut and scarlet oaks, white pine, sugar and red maples. All of these species and more provided dense shade that made the walk pleasant.

A Sunday afternoon in early October was not the best time to see or hear the many songbirds that live in this forest, but we could at least mention the red-eyed and blue-headed vireos, ovenbirds, scarlet tanagers, Acadian flycatchers, Louisiana waterthrushes, wood thrushes, black-throated green, hooded and worm-eating warblers and other birds nesting here in spring and summer, and the year round species such as black-capped chickadees, white-breasted nuthatches, and downy, hairy, red-bellied, and pileated woodpeckers, for instance.

Beechdrops in Plummer’s Hollow

Beechdrops in Plummer’s Hollow (Photo by Dave Bonta on Flickr)

The wildflower season was also waning, but I did show them blooming beechdrops, wavy-leaved asters, and blue-stemmed goldenrod. In addition, I identified native shrubs—maple-leaf viburnum, red-berried elder, wild hydrangea, spicebush, mountain laurel, and my favorite rhododendron–while Dave pointed out the various tree species.

Halfway up the road we were able to feature a large white oak growing atop the flat remains of a charcoal hearth as well as the chunks of charcoal beneath the thin layer of topsoil.

Since our goal is to let our forest mature into old growth, when trees die, we let them fall and rot to provide more soil and have so many dead snags that birds, bats, gray, fox and flying squirrels and other mammals have no trouble finding nesting holes. We also told our bear, fisher, and coyote stories and mentioned the success of the Game Commission’s program to bring back the extirpated fishers. In addition, the Commission’s efforts to increase bald eagle numbers has led to nesting bald eagles on game lands at the other end of our mountain. This was a gift we had never expected to see in our lifetimes.

We led our visitors to the base of Guesthouse Trail to point out the small rhododendron exclosure Dave had built to keep the deer away from this shrub that is a favorite of theirs especially during the winter months.

One of our deer exclosure fences showing the abundance of vegetation inside it

One of our deer exclosure fences showing the abundance of vegetation inside it (Photo by Dave Bonta on Flickr)

And finally we went on to our three-acre exclosure in a part of our forest with a white oak and several red oak trees that date to 1812. Despite our successful hunter program with excellent hunters on our land from the beginning of archery season in October to the end of flintlock in mid-January, our visitors could still see the difference between the open forest outside the exclosure and the dense understory inside including the numerous oak, white pine, black gum, and maple saplings.

In the heavily forested portion of our property, primarily on Laurel Ridge, we have little trouble with invasives, but our 37-acre meadow and the 125 acres we purchased on Sapsucker Ridge after it had been high-graded back in 1991 are infested with barberry, mile-a-minute, stiltgrass, multiflora rose and other pernicious non-native plants, most of which provide little or no nourishing food for birds and mammals, unlike our native trees and shrubs.

Invasive plants and diseases, tree, shrub, and wildflower identification, wildlife, including birds, mammals, reptiles and amphibians, and forest management seemed to be the dominant themes in the 68 walks in 48 counties attended by 1,136 people last autumn.

For instance, at the 50-acre Laura Olsen Memorial Sanctuary walk in Crawford County, hosted by Presque Isle Audubon Society and the Foundation for Sustainable Forests, they entitled their walk “Exploring Forest Bird Habitat” where as many as 51 species have been documented in this forested wetland.

The Musser Gap walk in Centre County, which attracted 66 participants, had 10 stations leading into Rothrock State Forest. There were handouts at the parking lot and leaders at every station that covered forest management, natural or cultural topics.

The Pennypack Ecological Restoration Trust in Montgomery County led a walk around the wooded areas of Pennypack Creek that featured a native persimmon tree with fruit and the fruit of a black walnut tree. Visitors saw an American kestrel and sharp-shinned hawk and identified bird and animal calls. The leaders explained why they had wrapped trees in preparation of the deer rut. At a pond everyone heard frogs and saw a beaver lodge.

A Walk in the Woods in 2018 on the Jackson’s property, Bedford County

A Walk in the Woods in 2018 on the Jackson’s property, Bedford County (Photo by Laura Jackson, supplied by the Center for Private Forests)

In Bedford County, Mike and Laura Jackson led 22 people over their mostly wooded property. They walked through part of their woods that was high-graded back in the 1980s and talked about how that type of logging creates an unhealthy forest. They pointed out invasive species and the impact of too many deer on the forest even though Mike does his best during hunting season.

They also have a shelterwood cut that was done in the autumn of 2014 and enclosed by an eight-foot-high fence. On a trail through the exclosure, they identified the native trees and shrubs that have appeared such as sassafras, both hornbeam species, and quaking aspen in addition to stump sprouts of tulip poplar, black cherry, oak, elm and red maple that are already almost 20 feet tall.

The large seed trees that were left after the shelterwood cut included shagbark and pignut hickory, black cherry, sugar maple, tulip poplar, white and red oaks, butternut and American basswood, all of which provide excellent wildlife food.

Another view of the 2018 walk on the Jackson property

Another view of the 2018 walk on the Jackson property (Photo by Laura Jackson, supplied by the Center for Private Forests)

That was the second Walk in Penn’s Woods the Jacksons’ hosted. On each walk, like most folks on these walks throughout the state, walkers were interested in learning how the Jacksons have managed their woods for wildlife and what birds and animals live there.

In Lancaster County the Game Commission’s Middle Creek Wildlife Management Area sponsored a walk on a nature trail with 10 stations featuring wildlife and forest management techniques and tree identifications.

State Game Lands #37 in Tioga County, hosted by the Tioga County Group Effort, attracted 27 people who learned about game food plots, timber harvesting, wildlife and general forest management principles.

Young and old enjoying a walk in the woods at the Montour Preserve, Montour County

Young and old enjoying a walk in the woods at the Montour Preserve, Montour County (Photo by Henry Williams, supplied by the Center for Private Forests)

A few of the walks were stroller and wheelchair accessible and, as such, attracted over 30 people. One was in Montour County at the Montour Preserve where they were led on the Goose Woods Trail by Jon Beam who has been associated with this preserve for decades and once showed me the signs of American woodcock during a visit.

At Tuscarora State Park in Schuylkill County 33 people walked on a wheelchair-accessible paved path around Tuscarora Lake where they learned to identify the trees and shrubs of this forest and were told about the forest benefits to humans and wildlife.

Two young people participating in a Walk in the Woods at the Wolf Creek Narrows Natural Area in Butler County

Two young people participating in a Walk in the Woods at the Wolf Creek Narrows Natural Area in Butler County (Photo by Andrew Zadnik, supplied by the Center for Private Forests)

Because of the popularity of wheelchair and stroller accessible walks, this year’s organizers of the Walk in Penn’s Woods on October 6 hope to have more such walks in what they are calling Walk and Roll in Penn’s Woods. But many of the same walks as last year plus new walks are featured on their website.

For most walks there is no reason to sign up ahead of time. Just pick your walk anywhere in the commonwealth and go. You are bound to learn something new about Penn’s Woods and meet knowledgeable people both leading and attending the walks.

 

 

Food for Wildlife

After three lean years, our oak trees finally produced a bumper crop of acorns last September. Forewarned by hordes of blue jays screaming from the treetops as they plucked ripe acorns from the oaks, I had to be careful on our steep trails not to slide on the fallen nuts that were more hazardous than marbles.

grey squirrel

Grey squirrel eating an acorn (Juraj Patekar image on Flickr, Creative Commons license)

Still, not every section of forested Pennsylvania had a good acorn crop, despite predictions from folks that should know better. Dr. Marc Abrams, a forestry professor at Penn State says there’s “no way to predict it,” calling a heavy mast year “one of the amazing mysteries in nature that we still do not have a handle on.”

Dr. Warren G. Abrahamson, a Bucknell University professor who conducted a long term study of acorn production from 1969 to 1996 with Jim Layne of the Archbald Biological Station in Florida, agrees, although he says that “the production of acorns definitely is not forecasting but hind casting the weather.” In their September 2003 report of their work they claimed that the size of the acorn crop each year is partly controlled by precipitation which affects acorns during different stages of development in prior years.

Other experts think that the group behavior of masting trees called synchrony most likely depends in part on the temperature during pollination in late April or May. Since oaks are wind-pollinated, meaning the wind must transfer pollen from staminate (male) to pistillate (female) flowers, a period of rain might disrupt the process.

For instance, a cold, wet spring in 2012 affected red oak production in 2013 because all the oaks in the black oak group (those with pointed lobes on their leaves) take two years to mature. Those in the white oak group (those with smooth lobes on their leaves) take only a year and would be affected by a late spring frost during pollination.

Still others believe that synchrony occurs as a way to outsmart nut predators by producing more nuts than the predators can eat, ensuring that at least some nuts will grow into trees. But whatever the causes, it is cyclic and occurs every three to five years.

On our dry mountaintop we have mostly chestnut oaks with an occasional white oak in the white oak group. Deer prefer these tastier acorns and squirrels eat them almost immediately because they spoil more quickly than those in the black oak group, which include scrub, black, northern red, and scarlet oaks here. Those acorns the squirrels store.

hickory nut

Hickory nuts form 10 to 25 percent of a squirrel’s diet in a good year (image by Peppysis on Flickr, Creative Commons license)

Acorns are not the only hard mast fruit. Others include the squirrels’ favorite—hickories, especially pignut, mockernut, and shagbark—which consists of 10 to 25 % of their diets in a good year and ripen before acorns. But like oaks, as well as the other hard mast producers—American beeches and black walnuts—they are also wind-pollinated.

Hard mast is high in fat, carbohydrates, and protein and is important to at least 180 species of birds and animals in fall and winter, but since it is highly variable in production from year to year, wildlife must depend also on a wide variety of soft mast throughout spring, summer, and fall. These fleshy, perishable fruits high in sugar, vitamins, and carbohydrates include a wide variety of native trees, shrubs, and woody vine species.

Foresters and wildlife biologists, in fact, consider mast to be the woody plant fruits and browse of native trees, shrubs and vines even though the word mast comes from the Old English “maest” which meant the forest tree nuts on the ground that fattened domestic pigs and other animals.

A wide variety of soft mast allows many mammals and birds to survive the lean years of hard mast. Of course, there are always some nuts every year, but ever since the extinction of American chestnut trees which, because they were insect-pollinated and didn’t bloom until summer, reliably produced an excellent crop of nuts, wildlife has had to adjust to a feast or near famine hard mast situation.

Consequently, encouraging biologically diverse meadows and forests, stocked with native trees, shrubs, and woody vine species produces food for wildlife throughout the year. And diverse food leads to diverse wildlife, as we’ve discovered on our property.

Other examples of trees that are insect-pollinated and produce a huge number of seeds every year as well as foliage, twigs and bark are red and striped maples. Striped maple, also called moosewood or goosefoot, has fruit that matures in early fall and is eaten by ruffed grouse, rodents, and songbirds. In addition, it produces browse for deer and bark for rabbits and beaver.

Elk eat the buds, foliate, twigs and bark of red maple, songbirds gorge on the seeds, and squirrels and mice store them for winter.

Basswood is another insect-pollinated tree, producing seeds squirrels and chipmunks consume while deer and rabbits browse its foliage.

The best of the soft mass fruit is that of wild black cherry trees. It fruits abundantly every third or fourth year in August and is pollinated by solitary bees. Seventy bird species feed on the fruit including grouse and wild turkeys. Black bears, raccoons, foxes, rabbits, squirrels, chipmunks and mice relish the dark cherries.

witch-hazel fruit and flowers

Witch-hazel fruit and flowers (Image by Rodger Evans on Flickr, Creative Commons license)

The fruit of sassafras trees, which is high in fat, is eaten by turkeys, bobwhite quail, black bears, pileated woodpeckers and gray catbirds. Rabbits and deer browse its twigs, black bears like its stems and deer its leaves. Despite its popularity, we have many sassafras trees in our forest.

Common witch-hazel, which flowers in late fall, develops woody capsules the following spring and summer. Those capsules contain a pair of shiny, black hard-coated seeds that shoot out in autumn before the next flowering. But squirrels, turkeys, quail, and grouse go after them, especially if the acorn crop fails. Deer browse heavily on witch-hazel, but it persists in growing above the deer line here.

Common spicebush (my personal favorite) produces brilliant spicy red fruits eaten by grouse, pheasants, and quail. It also provides shoots for rabbits and browse for deer, but it too survives and thrives, especially in wet areas along our stream. Our son Dave has planted it as an attractive shrub in our yard and his.

Both red-berried elder, which blooms the same time as the invasive barberry, has red berries available for birds in June or early July, although it only lives on steep slopes here because deer are fond of its browse. Deer also like common elderberry. It blooms in late June or early July and hangs heavy with clusters of dark purple berries favored by birds and humans in late August.

White-throated sparrow with staghorn sumac fruit

White-throated sparrow with staghorn sumac fruit (Kelly Colgan Azar photo on Flickr, Creative Commons license)

Staghorn sumac is making a recovery on our property, living on the sunny edges of meadows and forests. Blooming in late June and early July, its greenish-yellow, fragrant flowers morph into bright red, cone-shaped clusters of fruit that last through the winter, providing food for squirrels, songbirds, grouse, pheasants, turkeys and quail. Deer and rabbits browse on this shrub as well.

Wild berries are a popular summer food. First come the lowbush blueberries as early as mid-June on our powerline right-of-way, followed by the huckleberries. Black bears are particularly fond of them, but so are songbirds, grouse, chipmunks, pheasants, and mice.

Black raspberries ripen in early July and blackberries in early August. Both are incredibly important fruit for songbirds, skunks, opossums, foxes, squirrels, chipmunks, and black bears, while rabbits like their cover and rabbits and deer browse on their stems. Of course, the wildlife must also compete with me, especially in the blackberry patches.

Opossum eating wild grapes

Opossum eating wild grapes (photo by pverdonk on Flickr, Creative Commons license)

Greenbrier of several species has bluish-black berries eaten by songbirds and gamebirds and deer browse them. They browse wild grapevines too, but wild grapes are among the most important and valuable food for wildlife including songbirds, gamebirds, foxes, skunks, raccoons, opossums, squirrels and deer. The vines provide winter shelter for animals and birds too. I remember one winter when the hard mast failed and deer spent the season among the grapevines of the Far Field thicket, yarding up like they do in northern New England.

My list of native trees, shrubs and vines could be greatly expanded. In other parts of Pennsylvania, particularly south of us, still other wildlife food, such as common papaws, are important. But diversity remains the key to providing abundant wildlife food, even in years when hard mast is scarce.

White-footed Mice

White-footed mouse from Squirrels and Other Fur-Bearers

Illustration from Squirrels and Other Fur-Bearers by John Burroughs (1909)

“I think mice are rather nice.” So began the children’s poem by Rose Amy Fyleman that I read to my three sons when they were young.

Fyleman was an English writer who lived in earlier times (1877-1957) and her mice were not the primary hosts for the larvae and nymphs of black-legged (Lyme disease) ticks or the possible carriers of hantavirus. Unfortunately, our winsome, large-eyed, big-eared white-footed mice are. They can be covered with the larvae and nymphs of black-legged ticks and build up huge concentrations of the Lyme disease bacteria Borrelia burgdorferi, which doesn’t sicken them, and thus remain the principal reservoir for the disease.

They also enjoy life in our old farmhouse, and we are compelled to keep traps laced with peanut butter especially in early autumn when they are seeking warm winter homes. Live-trapping and moving them are not an option even if we wanted to. The late, great mammalogist William J. Hamilton, Jr. once live-trapped and marked white-footed mice and released them a mile away from their home territory. A few days later they were back, exhibiting an amazing homing ability.

In addition, they know their home ranges of approximately one-fifth of an acre so well that they can quickly find hiding places whenever they are needed.

White-footed mice in an old bluebird box by Mark Lethaby

White-footed mice in an old bluebird box by Mark Lethaby (license)

But as Hamilton once wrote about the white-footed mouse, “It often takes up residence in houses; the first evidence of its presence may be a boot half filled with cherry pits or hickory nuts.” In our house, I find sunflower seed stashes not only in old boots but stuffed under the cushions of our sofas and chairs. And occasionally I’ve uncovered shredded sweaters or shirts balled up into nests on some forgotten closet shelf or in an old bureau drawer.

However, most white-footed mice find homes outdoors in abandoned squirrel, woodchuck, or bird nests, bird nest boxes, tree cavities, half-rotten stumps, rock piles or even in a ball of leaves underground. Recently, researchers have noted that they especially like the humid conditions under the rapidly expanding invasive shrub Japanese barberry, which is also favored by black-legged ticks, still another connection with Lyme disease and white-footed mice.

White-footed mice use their long tails as props and balancing organs, to climb trees, although they are not as adept as their longer tailed congener’s deer mice. White-footed mice (Peromyscus leucopus) and woodland deer mice (P. maniculatus) look alike, and often live in the same habitat in our Appalachian forests. The length of their tails can sometimes be their distinguishing characteristic because the tails of white-footed mice are slightly less than half the total length of their bodies while the eastern woodland deer mice have tails more than half their total length. But the best way to tell them apart is by comparing their skulls. Since I’m not inclined to measure their tails or study their skulls, perhaps some of the mice in our home are deer mice because they too can create havoc inside homes and camps and are carriers of hantavirus, although so far they’ve not been indicted as primary hosts for black-legged ticks.

Both species of mice are abundant over a wide range of North America, but white-footed mice have drastically increased their distribution over the last few decades and now are found in the eastern two-thirds of the United States except for Florida, as far west as portions of Wyoming, Colorado, and eastern Arizona, south through eastern Central America and north in Ontario, Quebec, southern Nova Scotia, and even Labrador.

White-footed mouse by Patrick Coin

White-footed mouse by Patrick Coin (license)

Back in the 1980s, J.O. Wolff did extensive studies of both white-footed mice and deer mice in the Appalachians of southern Virginia and found that female white-footed mice lived in separate home ranges while males had ranges overlapping one or more females with which they mated. It seems as if white-footed mice are usually polygamous, but can also be monogamous, and even in at least one known case polyandrous. These choices may protect their mothers and their young because males can recognize their mates and children and will not kill them. They even often help raise their offspring, although females do most of the work.

Mating begins in early March and continues through late October in Pennsylvania. Their gestation period is usually 23 days unless a female is still nursing a previous litter. Then gestation can be anywhere from five to 14 more days. Most litters contain four or five young but can be from two to eight.

Born tiny and naked, they develop rapidly, and at three weeks of age they are able to leave their nest, although if they are threatened they can leave at 16 days. Previously, if their mother is disturbed while nursing, she runs from the nest with her young clinging to her teats and sometimes falling off as she heads for the nearest hiding place.

These young can breed as early as 46 days of age, but most are two months or 60 days old before they do. Still, it is easy to see how many would survive if they did not have many predators such as skunks, mink, weasels, raccoons, foxes, coyotes, bobcats, black bears, and black rat snakes.

These “most abundant and ubiquitous rodents in Pennsylvania,” according to mammalogist Joseph F. Merritt, also have catholic food tastes, eating whatever fruits, seeds, and small creatures are available. A short list includes various grass seeds, raspberry seeds, shadberries, the fruits of viburnum species, hickory nuts, basswood seeds, and conifer seeds, and in the summer they add meat to their diets in the form of caterpillars, ground beetles, snails, centipedes, occasional small birds, and even other small mammals including young white-footed mice. But their favorite foods appear to be pitted wild black cherry seeds, acorns, and the seeds of jewelweed. The latter taste like walnuts and have turquoise-blue endosperms that turn their stomach contents turquoise-colored in late summer.

northern red oak (Quercus rubra) acorns by free photos & art

northern red oak (Quercus rubra) acorns by free photos & art (license)

On a study of the impact of small mammals on northern red oak regeneration by Colleen A. DeLong and Richard H.Yahner from October 1989 until December 1990 in Huntingdon County, Pennsylvania, they attributed most red oak acorn loss to white-footed mice from 67% to 88% in autumn and 94% to 100% in spring in a section of mature forest where they had planted 400 red oak acorns. Certainly, we’ve had fewer mice in our traps lately, and it may be because we haven’t had a good acorn crop in three years. In fact, many wild fruit and nut crops were sparse or nonexistent in 2013, including wild black cherries.

But by mid-autumn white-footed mice have collected caches of food to get them through the winter. Hamilton discovered that they are also fond of storing clover seed and beech seeds, and once found almost a peck of beechnuts they had stashed in a beech tree cavity in New York State.

Here in Pennsylvania, some white-footed mice have periods of torpor from late December until early February, but most remain active. They stay warm by nesting with other white-footed mice and/or deer mice huddled in tree cavities or by nesting underground.

During all seasons of the year, though, in our home, “they run about the house at night; they nibble things they shouldn’t touch, and no one seems to like them much,” as the poet Fyleman wrote. She may have thought mice were nice, but despite their beguiling appearance, I think they are an attractive nuisance.

The Value of Aging Trees

A big red oak on top of Sapsucker Ridge

A big red oak on top of Sapsucker Ridge

On a hot July day, I sit beneath a large red oak, nestled into a deep buttress, one of several that flare out from this 200-year-old tree. The ground beneath the tree is littered with old acorn remnants as are the bases of the other elders in this stand of deciduous trees.

Protected as a picnic spot by the previous owners, the trees were allowed to prosper even as other portions of our property were cut over in the nineteenth and even twentieth centuries. Instead of fencing a young forest, such as that last 120-acre cutover piece we acquired back in the 1990s, we put up our three-acre deer exclosure in March 2001 around these mature trees.

Now, as I gaze around, I see dozens of oak seedlings and saplings filling in the forest floor. Most are red oaks, but some are offspring of the enormous white oak beside the exclosure gate.

Technically, this is not an old-growth forest but one that is becoming old-growth. Still, it and much of the rest of our property consists of an aging forest. Not long ago, old trees were seen as useless and were harvested so that young trees would grow in their place. But in the last few decades scientists have been discovering that old trees in an old forest are incredible absorbers of carbon dioxide. And red oaks, with their dense wood, are particularly good at absorbing impressive amounts of carbon.

One study, in Massachusetts’s Harvard Forest, found that at 50 years of age, their trees, both oak and maple, were absorbing 0.8 tons of carbon per acre every year. After 15 years, the rate of carbon uptake had doubled. Researchers studying old-growth forests in the West discovered that those forests too absorbed more carbon as they aged.

One of those researchers, Bev Law, of Oregon State University, told a journalist that, “Across forest types, globally, we find that the amount of carbon stored is high in older forests, and that live carbon continues to accumulate for centuries.” This carbon is held not only in the trees themselves but in their fallen leaves and branches as well as in the fertile soil of old forests.

Law is director of the AmeriFlux Network, an international collaborative project founded in 1996 to measure the carbon dioxide, water vapor, and energy in all kinds of major ecological community types or biomes in North, Central, and South America. Using a variety of sophisticated tools, scientists are able to track carbon in any ecosystem. Here in our eastern forests, studies have been done in several states including the aforementioned Massachusetts.

Old trees in an old forest have other uses too. They provide large hollow trees for a variety of birds and animals that use them for nesting, food, and shelter. For instance, sycamore trees are the most massive trees in the eastern United States. They can grow over 100 feet tall and 10 feet wide and live up to 500 years. When they are very old, they have a cavity at ground level large enough, in one recent case, to house a maternity colony of 100 Indiana bats, researchers discovered back in 1993.

A giant eastern hemlock tree in Central Pennsylvania

A giant eastern hemlock tree in Central Pennsylvania

Large, hollow trees also appeal to children of a certain age. I was reminded of Jean Craighead George’s book My Side of the Mountain which my husband Bruce read aloud to all of us when our three sons were young. They were all entranced by the 12-year-old hero of the story, Sam Gribley’s large, hollow tree home in the wilds of the Catskill Mountains. In his case it was a hemlock tree. Remembering the many old-growth hemlocks we have (or had, before the hemlock woolly adelgids killed so many of them in our Pennsylvania old-growth forests), I knew that such trees might have been large enough to house one young boy.

Because our old-growth hemlock trees are mostly in Pennsylvania’s state natural areas, the trees attacked by adelgids have been allowed to die and be reclaimed by the earth as our son, Dave discovered during a recent visit to Snyder-Middleswarth Natural Area. Many people find this wasteful, believing that such trees should be harvested. But Dr. Joan Maloof, who has been writing and speaking about the value of old-growth forests, maintains that “old-growth forests are one of the few land uses where topsoil is created instead of destroyed.”

We like to think that our own younger but mature forest is also creating soil as we allow our trees to fall over and rot, creating, as our young nephew Patrick once cried over and over, “Dirt, dirt, dirt” while sifting the powdery, reddish-brown remains of red oak branches through his fingers. Those powdery remains of the heartwood and sapwood appear to be a nursery for the downy rattlesnake plantains I’ve discovered inside and outside our exclosure. When we first put up the exclosure, I found a large colony of this orchid growing on a slope where several trees had rotted down to heartwood and sapwood. Another plant that we found outside the exclosure and fenced had germinated beneath a stump that was seeping rotted wood at its base.

Then, a couple years ago, I found still another downy rattlesnake plantain plant that had germinated on the decaying remains of a fallen red oak limb. At the same time, I noticed that the fenced plant outside the exclosure was looking poorly. I gathered up more of the “natural” fertilizer from the trunk and sprinkled it over the plant, and once again it is thriving. I haven’t seen any studies that indicate that downy rattlesnake plantain needs this material, but I wonder.

Photographing downy rattlesnake plantain in our deer exclosure

Photographing downy rattlesnake plantain in our deer exclosure

As our forest has aged over the last 41 years we’ve lived here and now nearing one hundred years of age in our hollow area, our forest bird diversity has increased. Fallen trees across our first-order, headwater stream, attract several breeding Louisiana waterthrushes and winter wrens. Barred owls court and nest in our larger, hollow trees. Scarlet tanagers, worm-eating warblers, and red-eyed vireos, among others, are more common than ever. Once we had no nesting black-throated green warblers, cerulean warblers, blue-headed vireos, winter wrens, or Acadian flycatchers, but our aging forest has attracted them. All of these bird species and several more, such as blackburnian warblers — depending on whether species need coniferous, deciduous or mixed deciduous forests — use older, mature forests. And the larger these forests are, the better the chances are for the birds to fledge nestlings.

The same is true for many mammal species. Bears, raccoons, and porcupines, for example, like to den in large, hollow trees. One study of black bear den trees found that in order for red and white oak trees to be big enough, they had to be between 175 and 280 years old, which reminds me of the huge oaks our boys found more than 30 years ago at the steep base of our mountain on a property line with a neighbor. They took some box camera photos of themselves standing in front of them and they looked as if they were as large as California redwood trees. I was amazed and delighted, but before I had a chance to see those trees, our neighbor’s logging operation had cut them down. The boys went to check on them and said that they were all hollow inside, so excellent habitat had been destroyed and not a dollar earned on those trees.

The same den tree study found that raccoons liked tree hollows in trees from 90 to 164 years old, and gray squirrels 65 to 130 years in age. Many bat species, too, like old trees with cavities and loose bark. Other opportunities for denning in older forests include in soil pits created by large root masses of wind-tilted trees, in the root masses themselves, and in stumps, logs, large, horizontal limbs and cavities in standing trees, all of which we have in abundance in our aging forest..

One special kind of older forest that has diminished greatly is that of mixed red spruce and hemlock in the northern tier of Pennsylvania. Such a forest especially appeals to red-backed voles, water shrews, and state-endangered northern flying squirrels. According to researcher Dr. Carolyn Mahan of Penn State, this type of coniferous forest creates a moist microclimate that supports a diversity of fungi, which both the voles and the northern flying squirrels thrive on. They also spread the fungi spores, thereby enriching the soil. Water shrews also seem to prefer such forests, but they like them to be in swampy ravines.

Megalodacne heros beetles feed and mate on varnish shelf fungi, found on an ancient hemlock logs

Megalodacne heros beetles feed and mate on varnish shelf fungi, found on ancient hemlock logs

We also have red-backed voles in our deciduous forest, and Mahan explains that they are not specific to old red spruce/hemlock forests, but more of them are found there than in forests such as ours. Northern flying squirrels are much rarer in our state because they are habitat specialists and their red spruce/hemlock forests have been lost to habitat fragmentation from development of all kinds and to hemlock woolly adelgids. The remaining smaller, patchier coniferous groves next to deciduous forests also attract the more generalist and numerous southern flying squirrels. They are sharing nest sites and even hybridizing with northern flying squirrels, and in the process, passing on a roundworm species, Strongyloides robustus, to which they seem to be immune but which is killing the northern flying squirrels.

Mahan has 600 nest boxes in 21 study sites for the northern flying squirrel, and this year not one northern flying squirrel has been found in any of those boxes. Last year she and other researchers planted an experimental 2500 native red spruce seedlings among the dying hemlocks of a site and others in a recent Game Commission clearcut which was fenced to see if they will grow and thrive and someday produce more red spruce forests. If they do well, they will plant more red spruce seedlings. But think how long it will be before there will be another red spruce forest as magnificent of those we had in Pennsylvania. How much better it would have been if we had saved larger pieces of our older spruce forests.

After talking to Mahan and other researchers, I am more determined than ever to keep growing an older forest. But on this hot summer day, I most appreciate our mature forest for its deep shade that cools not only me but all the creatures large and small that live here.

All photos by Dave Bonta ~ click on images to view larger versions at Flickr