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Acorns: Science & Mysteries

Penn State Forest Stewards series article – written by Jim Finley, Professor Emeritus, Forest Resources Management, Center for Private Forests at Penn State.

Oaks are economically important tree species in Pennsylvania and across the East. Acorns, or mast – a word derived from old English which means “forest food,” are important to wildlife. Oak-borne mast production varies from year to year. Much research has sought to predict masting years, when big acorn crops occur, and shed light on what leads to poor years – or early acorn abscission (detachment) – like you may have seen this season.

Science and Mysteries of Acorns - Pennsylvania Forest Stewards article

Oaks separate into two groups, popularly referred to as red and white, and learning to identify the difference between the two groups is easy.

Red oaks – e.g. Northern red oak, pin oak, scarlet oak, and black oak – have small “bristles” on the lobes and tips of their leaves. White oaks – e.g. white oak and rock, or chestnut, oak – lack these bristles, and have rounded leaf lobes.  (CFC note: the image above is of a white oak.)  There are other differences that are more difficult to recognize, such as acorn structure and wood anatomy.

The Process of Creating an Acorn –
and the Trials of 2020

Both red and white oaks produce female and male flowers on the same tree, unlike ash which has male and female trees. The process of producing an acorn starts late in the growing year when the male flowers form as the tree’s growth slows toward the end of summer. That is the end of the first year (year 1) in the process. Then, in the second year (year 2), as the tree comes out of dormancy, female flowers form in the axil of the leaf stem and the twig and remain dormant. As the spring leaves begin to unfold, the male flowers emerge and are very apparent as rather-long, drooping, greenish-yellow catkins. These appear about two weeks before the much smaller female flowers emerge.

White Oak Acorn Production

For the white oaks, as the male and female flowers emerge in year 2 as described above, pollination and fertilization should happen. The pollen from the male flower, which is wind-disseminated, lands on the style, which is part of the female flower. When this happens, the pollen initiates the development of a pollen tube that transfers male cells into the ovule to complete fertilization and the process of acorn formation should start in earnest. For this to happen, it is ideal to have warm days and cool nights. 

If temperatures are not right, fertilization may fail, and the female flowers will abort, which results in low acorn initiation. Alternatively, if temperatures become too hot or drought conditions occur, white oak acorns may abort, which is likely apparent in mid-June to mid- to late-July; perhaps that is the reason for reported early acorn drop this year. The other big threat to white oak acorns is late spring frosts, which also happened this year, and would again remove the fertilized flowers.

Trees and Dry Conditions

Penn State Forest Stewards series article – written by Allyson Muth, Interim Director, Center for Private Forests at Penn State.

Many areas across the northeastern US are experiencing dry and drought conditions, Pennsylvania included. As of July 28, two-thirds of Pennsylvania was in an abnormally dry to moderate drought condition. Yet, tallied across the state, we are very close to the total predicted rainfall for an average year to date. Depending on where you look in Pennsylvania, the regions are somewhere between 25% below, to as much as 26% above annual precipitation. These numbers don’t sound like they would result in two-thirds of the state be in abnormally dry conditions. So, how does that work?

PAFS article tree health during drought

Climate Change

Climate change models for Pennsylvania have consistently predicted the pattern that we’re seeing this summer. Less frequent, but more intense rainstorms, with extended drought periods occurring between those large rain events. The result is highly variable and uneven conditions across the state. Conversations with landowners in the south central region have shared their recent 4-inch rain storm events and subsequent flooding. In many other Pennsylvania regions, rains came early, and we’ve entered a dry summer period with rather infrequent rain events.

Pennsylvania is known for its waterways – over 86,000 miles of streams, creeks, and rivers. We usually have ample water during the growing season. We rarely have the water conservation requirements that the US West and Midwest implement to conserve water for human consumption. But when it’s this dry, do we need to worry about the trees?

Contributing Factors

Healthy, established trees can normally withstand relatively long periods of drought, so long as there are intervening months or years that are more favorable. However, recently planted trees, or trees with small soil footprints (rootprints?) are more susceptible to decline under these dry conditions. 

Forest Resilience in a Changing Climate

Penn State Forest Stewards series article – written by Jim Finley, Professor Emeritus, Forest Resources Management, Center for Private Forests at Penn State.

So far for most Pennsylvanians, Winter 2020 has been a non-event. Depending on where you live, temperatures are considerably above normal and snowfall below normal. Individual perspectives might lead to interpreting these two statistics as either positive or negative. No snow equals no shoveling. Warm temperatures equal more time outside. Or, no snow equals no sledding or skiing. Warm temperatures equal more ticks.

Thinking more broadly than personal values or needs; Is this winter’s weather a harbinger of a future driven by climate change? If so, how will Pennsylvania’s forests respond?

PA Forest Stewards - Jim Finley on Climate Change 2020

For sure, weather is fickle. Mark Twain purportedly said, “Climate is what we expect, weather is what we get.” It seems something is happening to the climate and, whether you attribute it to human activities or just unexplainable variation, Pennsylvania’s forests are facing challenges.

Forest Resilience in a Changing Climate

Aldo Leopold, a 20th century mid-western conservationist, and author of The Sand County Almanac and many other writings about our relationships to the land and natural systems, was a keen observer of change that others seemed to miss. He wrote, “One of the penalties of an ecological education is that one lives alone in a world of wounds. Much of the damage inflicted on the land is quite invisible to laymen . . . in a community that believes itself well and does not want to be told otherwise.” Simply, he was saying that the more one knows about ecology, the more apparent change is and that many will neither see nor believe that it matters. Many resource professionals as well as laypeople are seeing change in many areas of our environment. As Leopold suggests though, many of these changes and linkages may not be obvious to less than “keen observers.”

Disturbance and change are part of natural systems. Resilience is the ability of a system to recover after disturbance, which determines its ability to persist and function over time. The degree and extent of a disturbance logically affects the capacity of a natural system to recover. For example, in a typical winter, forests often experience damage from wind and ice. Most commonly this is local damage and a few trees experience broken limbs and some trees tip over. The ability of the forest to function across a larger landscape continues unabated – some trees benefit from increased light and growing space from the loss of their neighbors – the forest almost ignores the event.

Woods not Lawns for Water Quality

Penn State Forest Stewards series article – written by Jim Finley, Professor Emeritus, Forest Resources Management, Center for Private Forests at Penn State.

It’s January and perhaps your thoughts are already turning toward summer activities. For many Pennsylvanians, mowing and maintaining lawns is either a larger or small part of their summer routine. Lawns, as we know them, are part of American culture and history(1). An Internet search on lawn maintenance suggests creating the perfect lawn is a major industry very dependent on labor and chemical inputs.

Annually we spread millions of tons of insecticides, herbicides, fungicides, and fertilizer around our homes to have the envy of the neighborhood – a perfectly green lawn(2). Interestingly, as interest in organic foods increases, there is a disconnect about using despised chemicals where our children and pets spend quality time. At the same time, water quality suffers as excess nutrients from lawns and agricultural fields are one of the largest sources of non-point pollutants impacting water quality in our streams, rivers, lakes, and the Chesapeake Bay.

Penn State’s Center for Turfgrass Science estimates that Pennsylvanians maintain about 2 million acres of grass (about 7% of the state’s surface area), and 1.4 million acres of this are home lawns (about 5% of the state). About two-thirds of Pennsylvania is in the Chesapeake Bay watershed and contains an estimated one million acres of lawns. 

Pennsylvania has set a goal of converting 10,000 acres of these lawns to woodlands or meadows. This seems like a small target and maybe you can help by learning how to convert lawns to woodlands and meadows by participating in a Penn State Extension Winter Workshop series entitled “The Woods in Your Backyard: Learning to Create and Enhance Natural Areas Around Your Home.” This webinar-based education program will use a full-color, 108-page publication by the same title to guide you through the process of developing and implementing projects to enhance your land’s natural resources. Register by Saturday, 18 January 2020 via the link above, or call 877-345-0691.

A principle focus of the workshop series is to learn about what happens to the rain and snow that falls on your land. There is a very strong link between land use and our water resources. Buildings, pavement, lawns, fields – human changes to the landscape – have affected natural water movement and water cycles Water now moves across the land and into streams in different ways and carries with it nutrients and pollutants.

Interestingly, most lawns are very poor at absorbing water – in fact, they are only a little better than pavement! Your lawn, because of grass root structure and soil compaction, can only absorb about 2 inches of water per hour compared to a forest that can handle 14 inches or more in the same time frame. In the ideal scenario, water does not move across the land – instead, it should move into the soil.

Some Litter Is Necessary

Penn State Forest Stewards series article – written by Jim Finley, Professor Emeritus, Forest Resources Management, Center for Private Forests at Penn State.

Well once again, Pennsylvania’s forests are a mess – full of litter. Following the annual spectacular display of colors, fallen leaves, twigs, and branches “litter-ly” despoil our forest floors with layers of brown discarded leaves. What a mess!

2019-11 PAFS article Jim Finley on leaf litter

Depending on your awareness of litter’s value and your aesthetic sensibilities it can result in different appreciation levels. If you are a gardener, you would welcome, collect, compost, and hoard tree leaves. If your taste leans toward green grass lawns, you may abhor fallen leaves. Either way, you will likely gather them up; however, there are some who want to leave them in situ and mow them into increasingly smaller pieces to foster quicker decay hoping they will benefit that lawn.

Forests full of fallen leaves are a gift trees give to themselves. No one rakes or mulches them; nonetheless, they do slowly disappear. Estimates are that a mature hardwood forests produce an estimated 2,000 and 3,000 pounds per acre of litter annually. While most of this (about 70%) is leaves, it also contains twigs and branches, which may be partially decomposed prior to falling. It is amazing that through natural decomposition processes, tons of leaves contribute to forest vitality and health in so many ways.

 

Funding Shortfalls in Cook Forest State Park

the first bridge to close in CFSP

While visitation is increasing, state funding of the park system continues to dwindle, and the impacts are being felt here in Cook Forest State Park.

One of the busiest of our steel bridges over Tom’s Run closed earlier this year, with five more slated to follow – which requires trail re-routing away from some of the forest’s most lovely locations. Playgrounds are being removed, and picnic tables are turning into nurse logs. 

This article printed in the Oil City Derrick details the issues affecting our park, which hosts nearly 500,000 visitors annually, which produces $11 million dollars in economic activity in the area.  Please read the full account here – and then urge your legislators to support our beloved state parks, and restore the funding to them:  https://www.thederrick.com/free/cook-forest-facilities-are-being-closed/article_76a74e40-d173-11e9-98fc-d75dcc79ddd4.html

If the webpage link ever doesn’t work, a PDF version is available here:

2019-09-06 Cook Forest facilities are being closed _ thederrick

Scouting for deer browse

Penn State Forest Stewards series article – written by Dave Jackson, Forest Resources Educator, Penn State Extension and Matt Russell, Associate Professor/Extension Specialist, University of Minnesota

Many woodland owners take to their woods in October to begin scouting for deer season. A good way to learn more about where white-tailed deer might be found is by understanding what they’re eating. A deer’s diet consists of a variety of crops, herbaceous and woody vegetation, fruits, and nuts. A healthy diet will consist of a variety of different foods. A deer requires an estimated 6 to 8 percent of their body weight daily in forage to stay healthy. For a 150-pound deer, that’s up to 12 pounds of food every day!

PAFS series - Dave Jackson on Deer Browse

Too much browsing pressure, eating twigs and young shoots, from deer can kill or limit the growth of tree seedlings, a fact that foresters and woodland owners know very well. Over decades, deer populations can greatly impact the look of woodlands. Knowing which tree seedlings are growing in your woods and which ones are browsed can give you more details on a deer’s diet.

In Pennsylvania, tree species that rank high on a deer’s list include a number of hardwood trees. Red and white oaks are two of the primary hardwood species that deer prefer to browse, while blackgum, hickory, and yellow poplar are also very high on the preference list. As you move north, species like maple (red and sugar), white ash, and basswood become more preferred species where they are more abundant.

While deer prefer these tree species, they also avoid certain plants. Deer will start by browsing the most preferred or palatable trees first. If there are high populations of deer in an area, preferred plants will see more browsing which can lead to other plants, that deer don’t prefer, taking over.

So what does it mean if deer are browsing beech seedlings/sprouts? Likely that deer are getting desperate and other food sources are limited. Evidence of high deer populations can be seen in a woodland that is dominated by beech brush, striped maple, black birch, black cherry, mountain laurel, ferns (primarily hayscented and New York) and invasive exotic plants. Deer avoid browsing these plants because they are not as digestible compared to other vegetation.

More evidence of deer browse impacts is the presence of a browse line on all understory trees, where there are no green branches until about five or six feet up. Another sign may include the presence of seedlings that are severely hedged and not able to grow above 1-foot in height, as well as understories dominated by species that deer avoid. Deer do not readily eat species like ferns, striped maple, beech, ironwood, mountain laurel, blueberry, and spicebush. As a result, we see these species dominating the forest understory in many areas.

To have a healthy woodland, tree seedlings need to develop into healthy, mature trees. As an example, consider a browse-sensitive species like oak. First, it can take over thirty years for an oak tree to produce acorns. Second, acorn crops only occur every two to five years and truly “bumper” crops much less often. In these good crop years, acorns can make up the majority of a deer’s diet in the late fall. If oaks can never make it from acorn, to seedling, to sapling, to healthy mature tree, the habitat quality for deer can suffer in the long term as oaks are replaced by other, potentially less desirable, species.

Knowing which species are being browsed can also give you insight into which methods can be used to protect seedlings. Although costly, fencing can be constructed around individual trees or larger areas several acres in size. Protecting tree seedlings ensures that you have healthy trees for the future while steering deer towards other food sources.

You may also consider harvesting additional antlerless deer. The Pennsylvania Game Commission’s Deer Management Assistance Program (DMAP) helps landowners meet their forest management goals by allowing hunters to harvest additional antlerless deer from a property during the regular hunting seasons.

Areas with low deer browsing pressure provide diverse wildlife habitats. They support healthy understories, preparing the forest for future replacement following natural tree mortality or planned timber harvests. Habitat repeatedly damaged by over-browsing continues to decline, losing its ability to support additional deer and other wildlife. It is important to reach a proper balance between desired habitat conditions and deer populations.

What is Forest Fragmentation & Why is it a Problem?

by Michael Snyder, forester & Commissioner of the Vermont Department of Forests, Parks, and Recreation. 
Generously permitted for re-publication by Northern Woodlands magazine – original article here

forest fragmentation photo by Pok Rie from Pexels

Forest fragmentation is the breaking of large, contiguous, forested areas into smaller pieces of forest; typically these pieces are separated by roads, agriculture, utility corridors, subdivisions, or other human development. It usually occurs incrementally, beginning with cleared patches here and there – think Swiss cheese – within an otherwise unbroken expanse of tree cover.

Over time, those non-forest patches tend to multiply and expand until eventually the forest is reduced to scattered, disconnected forest islands. The surrounding non-forest lands and land uses seriously threaten the health, function, and value of the remaining forest.

Any large-scale canopy disturbance affects a forest, but it is important to distinguish between a forest fragmented by human infrastructure development and a forest of mixed ages and varied canopy closure that results from good forest management. The former is typically much more damaging to forest health and habitat quality, usually with permanent negative effects, whereas the latter may cause only temporary change in the forest.

The effects of fragmentation are well documented in all forested regions of the planet. In general, by reducing forest health and degrading habitat, fragmentation leads to loss of biodiversity, increases in invasive plants, pests, and pathogens, and reduction in water quality. These wide-ranging effects all stem from two basic problems: fragmentation increases isolation between forest communities and it increases so-called edge effects.

When a forest becomes isolated, the movement of plants and animals is inhibited. This restricts breeding and gene flow and results in long-term population decline. Fragmentation is a threat to natural resilience, and connectivity of forest habitats may be a key component of forest adaptation and response to climate change.

Edge effects are even more complicated. They alter growing conditions within the interior of forests through drastic changes in temperature, moisture, light, and wind. Put simply, the environment of the adjacent non-forest land determines the environment of the forest fragment, particularly on its edges. This triggers a cascade of ill effects on the health, growth, and survivability of trees, flowers, ferns, and lichens and an array of secondary effects on the animals that depend on them. Ecologists suggest that true interior forest conditions – you know, where it’s hard to hear cars and lawnmowers and it remains cool, shady, and downright damp even during a three-week drought – only occur at least 200-300 feet inside the non-forest edge.

And so a circular forest island in a sea of non-forest would have to be more than 14 acres in size to include just one acre of such interior forest condition. Put differently, reports indicate that the negative habitat effects of each residential building pocket within a forest radiate outward, affecting up to 30 additional acres with increased disturbance, predation, and competition from edge-dwellers. This may not matter to generalist species like deer, raccoons, and blue jays, which may actually benefit from fragmentation, but it is hell on interior-dependent species like salamanders, goshawks, bats, and flying squirrels. The smaller the remnant the greater the influence of external factors and edge effects. A wise person once likened it to ice cubes: the smaller ones melt faster.

Moreover, as forest fragments become ever smaller, practicing forestry in them becomes operationally impractical, economically nonviable, and culturally unacceptable. In turn, we lose the corresponding and important contributions that forestry makes to our economy and culture. The result is a rapid acceleration of further fragmentation and then permanent loss.

Here is the tricky part: when fragmentation occurs in a heavily forested region like ours, at least in the early going we are still left with a largely pleasant condition. We sense that we still have lots of woods where we can work, hunt, ski, and walk the dogs. And to most of us, this seems good enough, even when the perforations expand and those woods are the scattered remains of a fragmented forest.

But is it enough? At some point when the larger forest is highly fragmented, the size, integrity, and connectivity of those wooded remnants deteriorate beyond recovery and they are no longer adequate for native forest plants and wildlife. After all, when the Swiss cheese has more holes than cheese, the whole sandwich suffers.

aerial forest fragmentation - Tom Fisk on Pexels

Air rescue: Saving Pennsylvania’s northern flying squirrel

By Kathy Hackleman, Senior Editor/Writer, Penn Lines
Reprinted with permission from Penn Lines / Pennsylvania Rural Electric Association

adult flying squirrel in Texas - photo by akire-tanzt

It is almost impossible to distinguish between a northern flying squirrel and a southern flying squirrel without close observation of the hairs on their chest (if the hairs are white from tip to base, it’s a southern flying squirrel; if they are white at the tip, but darker at the base, it’s a northern flying squirrel). While to the average Pennsylvanian, it appears as if one could easily be substituted for the other, they are very different.

The southern flying squirrel, with its disproportionately large eyes, conspicuous skin flaps and a flattened tail to assist in gliding, is prevalent in much of the state. However, these nocturnal creatures go about their lives seldom noticed — unless they inadvertently end up in a chimney with no way out. When they are seen gliding from treetop to treetop to rooftop in the darkness, they are often mistaken for a bat or a bird. Once found only in the southern United States, they have slowly but steadily crept northward until they have taken over much of Pennsylvania.

The northern flying squirrel, on the other hand, is in trouble despite its almost-identical appearance.

APPEARANCES CAN BE DECEIVING 

“The northern flying squirrel, which is listed as endangered in Pennsylvania, is a part of the state’s historic population of wildlife,” says William M. Williams, information and education supervisor for the Pennsylvania Game Commission (PGC). “It is a native Pennsylvania species that was here prior to the European colonization. Because of human behavior in destroying their habitat, the conifer forest, they have been wiped out in Pennsylvania almost entirely.”

However, there is a group of people determined to halt the decline in the northern flying squirrel numbers and, if possible, increase their population in the state through forest management.

Greg Turner, the PGC state mammologist, is one of those people. He has been studying northern flying squirrels since 1995 when he was a part of a study team at Wilkes University in Wilkes-Barre, Pa. He and his university colleagues wrote a grant to obtain funding specifically to determine the distribution of the northern flying squirrel in Pennsylvania.

“The northern flying squirrel is very rare and very difficult to find,” Turner reports. “It is a mammal that is very secretive and rare, so they get ignored by a lot of people because it takes a lot of time and work to figure them out, but I like the challenge.”

Fewer than 50 northern flying squirrels have been located in Pennsylvania since 1995.

“That gives you a good idea of how rare they are,” Turner says. “I have personally handled around 30 of those. In an effort to locate where they are, we have placed over 700 nest boxes across the state, and we have also done some live-trapping. Live-trapping is a very labor-intensive process as we bait the traps in the evening and check them at first light daily because our primary goal is not to harm any of the species.”

Interview with Wild Excellence Films by Allegheny Front

Listen to “Filmmakers Highlight Plight of Cook Forest’s Iconic Hemlocks,” an interview with Dave & Melissa Rohm, the team behind Wild Excellence Films‘ documentary on Cook Forest, Cathedral: The Fight to Save the Ancient Hemlocks of Cook Forest. Here’s an excerpt:

Interviewer Kara Holsopple: What would it mean to lose the hemlocks in Cook Forest, to the ecosystem there and also to people?

David Rohm: Cook Forest would be a much different place. If you’ve been to Cook Forest, there’s a sheltering ability that these hemlock trees provide. 120-foot trees, you take away even half of them, and you’re going to see a huge difference. There’s a lot of wildlife. Migrating birds love the forest –way up in the canopies, they’re safe there. They reintroduced fishers there not too long ago. It’s like a mink but a little bigger. To people, Cook Forest means a tremendous amount. They get 500,000 visitors a year who aren’t going to visit if it’s not the same forest.

Please visit the Allegheny Front, via this link, for the full interview and audio.