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The Mighty Oak is Falling

Pitt professor tries to avert a growing crisis in the nation’s forests

Walk through the forests of the Eastern United States today, and nature seems comfortably familiar. Babbling brooks still babble. Trees grow and reach for the sky. Dried leaves and acorns still litter the forest floor. Chipmunks scamper as they always have through scrub brush and woody saplings. A deer stands frozen, then darts majestically away with a wave of white tail.

Take another look. Behind that reassuring sameness lurk ecological changes that will make the familiar strange indeed. The neighborhood is changing, and not for the better. The population of America’s Eastern deciduous forests is undergoing a slow, catastrophic change, hard to see, but real. And the stakes are high—the forest itself, as we know it.

It takes a trained eye to see it and a brave voice to say it. In the corridors of learning, amid floors and shelves strewn with papers, texts, field guides, and yard tools, Pitt Associate Professor of Biological Sciences Walter P. Carson, an ecologist and evolutionary biologist, can see the forest for the trees. He’ll tell you that American oaks—red, white, and scarlet—are in serious decline, along with the food they generate, acorns. And if something isn’t done to stop this process, the loss of oak trees will ripple through the food chain, bringing declines in the size and diversity of American wildlife.

Carson is researching the phenomenon of “failed oak regeneration.” Oaks, which have been the dominant tree species in Eastern woodlands for as long as 10,000 years, are losing ground to competitor maples and beech. Vital as food producers for small mammals, birds, deer, and black bears, as well as suppliers of hardwood for tools, furniture, and interior construction, oaks are a keystone plant resource. The shape of the forest without them is unknown.

To a casual observer hiking the Eastern forests, the tree canopy appears to be dominated by the furrowed limbs and toothed leaves of 100-year-old oaks. With old growth woodlands gone to the logger’s saw, mature oaks still dominate in our second- and third-growth forests. But walk the forests of Pennsylvania, West Virginia, North Carolina, or New Jersey, and step on forest floors dominated by red and sugar maple saplings where oak once ruled. The next generation of oaks is not surviving.

The evidence shows in the underlying layer of vegetation, known as the understory.

It’s here where seedlings are generated. Here is where Carson and his research team, including soil scientist Mary Beth Adams, are looking and experimenting. Here, a different story is showing itself in a population of oak offspring that never reaches maturity.

At two sites in West Virginia—the Fernow Experimental Forest in the Monongahela National Forest and the MeadWestvaco Wildlife and Ecosystem Research Forest—Carson and his colleagues have devised on-the-ground experiments, isolating hypotheses that have been proposed since failed oak tree regeneration was first observed 50 years ago.

Their comprehensive, long-term methods, involving thousands of trees, mimic natural and man-made forces that have shaped forests over time. Preliminary findings show the Eastern forests beset to varying degrees by three factors: fire suppression, decreased gaps in the forest canopy, and over-browsing by deer.

A century of fire suppression has led to shifts in the composition of trees in the forest understory. Periodic forest fires, caused naturally by lightning or artificially by indigenous people clearing land for habitat, favored the fire-tolerance of oaks and hickory. In the absence of fire, maple and beech have overshadowed oak on the forest floor.

Competition for space is aggravated by other factors. Massive tree falls in old growth forests opened larger gaps in the canopy than occur today. Maples, more shade-tolerant than oak, thrive and crowd out sun-worshipping oak tree seedlings.

Carson’s research indicates that deer are perhaps the worst threat to oak regeneration. In presettlement times, 10 or fewer deer populated a square mile. Present-day hunting restrictions and a lack of natural predators have increased deer populations three- to five-fold. The problem is that deer love oak—for dinner—more than they do maple or beech. Research conducted since 1998 by Carson’s team shows that deer are decimating oak seedlings before they can reach the sapling stage for survival.

As research continues, Carson’s findings point to an already full-blown crisis in America’s Eastern forests. Immediate action aimed at reducing the deer population and the institution of controlled burns seems necessary, though politically unpopular. Selective cutting and limited clear-cutting also appear necessary but are equally unpopular in many quarters.

A pastoral hike through the Eastern woodland amid birdcalls and chattering squirrels, towering oaks above and acorns underfoot, seems much the same as always. But for how long? According to Carson, tough decisions in forest management need to be made before it’s too late—if it isn’t already too late.
—Alan Gintzler

Breakthroughs in the Making

Imagine that you are in your 60s, retired, and enjoying life. Lately, though, things aren’t looking the way they used to. It has been getting harder to read and to spot familiar faces. You go to the doctor expecting nothing more than a stronger prescription for your glasses but are shocked when you hear the diagnosis—macular degeneration, a condition that causes permanent vision loss.

Macular degeneration is essentially the wearing out of the retina, and it is one of the most common causes of vision loss among the elderly in the United States. Statistically, one out of four people between the ages of 64 and 74 will become afflicted, and the odds increase with age. At the moment, treatment options are minimal.

If there were a way to diagnose the disease before it manifested itself, it could allow for better treatment. For 16 years, Pitt’s Michael B. Gorin has devoted himself to understanding the condition. For his efforts in the ongoing battle against genetic retinal diseases, Gorin, professor of ophthalmology and human genetics, recently received the Senior Scientific Investigator Award. The $65,000 grant from the Research to Prevent Blindness organization will help fund Gorin’s macular degeneration work, which he believes could lead to new treatments in the next year or so.

His plan of action is not to find the gene that causes the disorder itself, but to identify the genes that modify its severity. Early on, this purely genetics-based approach was met with skepticism, but once Gorin and his team proved it could be done, similar studies around the world began popping up.

Gorin is constantly reminded of the importance of his research. “When most of your patients tend to go blind, you learn the most powerful thing you can offer them is hope and knowledge, and both of those take time and talking. You can’t just sit them down for tests, pat them on the back, and send them out of the room, because there’s more to life than that.”
—Rob Markowski

 

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