Nov 11, 2010

The Sky Is Falling

[This is the first article in my new syndicated nature column "Wild Ideas," published in October 2010. One way to see the articles earlier is to go to the online edition of my local paper, Rappahannock News. Just search on my name. —Pam Owen]

Except for poison ivy, thorny vines, and the occasional venomous rattlesnake, the Virginia Piedmont forest is usually not too hazardous. This autumn, however, danger has been raining down from above.
The instigators are trees, releasing acorns and nuts—a bumper “hard mast” crop, by early estimates. Mast is the fruit (with seed inside) produced by trees and shrubs that is eaten by wildlife. Because of their hard shells, acorns and nuts are considered “hard mast,” while berries, cherries and other soft fruit make up “soft mast.”

After a lean year in 2009, Virginia has a bumper mast crop.
All but a small area of the 11-acre property where I live on Aaron Mountain, in Castleton, is covered by an oak–hickory forest “community.” Growing conditions (for example, soil, water, and elevation) mostly dictate which trees make up a particular community. As the name implies, this one is dominated by various species of oaks and hickories. The most abundant on this dry ridge are chestnut oak (Quercus prinus), which has long leaves with serrated edges similar to our native chestnut, and pignut hickory (Carya glabra), so named because its nuts are a favorite with pigs. 

Like much in nature, mast crop production is cyclical, with some years better than others, and varying from place to place and among species. Last year the Virginia Department of Game and Inland Fisheries (VDGIF), which tracks data on mast because of its importance to wildlife, reported a “generally poor” crop. 

This was not true just in Virginia. The online conservation community was a-buzz with similar reports, with even a "No Acorns this Year" discussion group popping up.  Low yields were reported as far north as Nova Scotia and out to the Midwest, although some areas were reporting good crops of some oak species.

This fall, it’s a different story. While official estimates are not yet in, anecdotal evidence abounds. VDGIF develops its mast estimates mostly from reports from the Virginia Department of Forestry, whose foresters are out in the woods regularly and take note of the crop to factor it into forest management. Those foresters are reporting seeing abundant mast, according to VDOF Conservation Specialist Mike Santucci. Although the crop varies from region to region, he says, overall “this is the largest mast crop I’ve seen.”

During my walks in the forest behind my house during the last few weeks, I sometimes have felt under siege, even considered taking an umbrella along for protection. I’ve also done a few awkward dances when treading on the carpet of little round tree spawn that covers the forest floor.

Why was mast so scarce last year and so abundant this year? Noting the early rains this year, Santucci suggests that “conditions were absolutely perfect for producing a bumper crop. Everything has mast on it.” This includes soft-mast crops, he says.

VDGIF Watchable Wildlife Biologist Louis Verner suggests there could be an additional factor at play, referring to the “predator satiation hypothesis.” The idea is that mast-eating wildlife—including Virginia’s native bears, turkeys, roughed grouse, squirrels and deer—get used to eating a certain amount of it each year, and their reproductive strategies are geared to this. To keep these predators from devouring all their seeds and leaving none to sprout, every few years trees “fake out the seedeaters,” as Verner puts it, by producing a really big crop—more than wildlife will consume. Plants and animals that evolve together often develop such survival strategies.

Deer hunters may not be happy with the bounty. With so much good chow scattered throughout the forest, deer are less likely to congregate in search of food, especially in open areas.

Fueled by high-protein food, deer are also likely to produce more offspring. This in turn means more destruction of our native and cultivated plants in future years—and more of us playing “Dodge the Deer” on the roads.

The upside is that the other, less abundant mast eaters are also likely to have a boost in reproduction. For the first time since I moved onto the property last February, a flock of turkeys has been foraging regularly in the woods behind the house. Bears will also benefit, likely waiting longer to den up this year because of the abundant food.

And then there are the squirrels. From the back deck, where I like to start the day’s challenges quietly over a cup of coffee while enjoying a bird’s-eye view of the forest, I can hear the squirrels noisily burying acorns. Since squirrels don’t eat a lot of what they bury, they’re basically little foresters, planting the seeds that will become future mast producers. 

Mighty oaks from little acorns grow...
When the shower of mast began in early September, many acorns were green or beige, and pignuts were securely wrapped in their shells. This week, walking through the forest, the acorns have mostly turned to a mosaic of brown or black. Many have sprouted and are on their way to becoming oaks. The pignut shells have opened up to release the nuts inside.

The footing out back will be tricky for some time, but it’s worth it to see wildlife enjoying the bounty. Next year, who knows?

No comments:

Post a Comment