Keeping Forests Healthy
By Randy Weckman
Kentucky's forests are a vast treasure, extending from the far reaches of Eastern Kentucky to the tip of Western Kentucky.
All totaled, just shy of 12 million acres of Kentucky is forested, down by half of what was here when the first Europeans arrived. And this, Kentucky's forest
treasure, is being jeopardized by a variety of threats, including insects, fungus-like bearers of disease, and even the suppression of fire.
And while the old adage about money not growing on trees is technically true, it would be wrong to trivialize the economic nature of forests. Pure and simple, Kentucky's economy depends in some large measure on the well-being of its forests.
All in all, Kentucky's forests generate about $4.6 billion in revenue each year, with a big part of that figure coming from the harvesting and processing of oak lumber, said Jeff Stringer, extension forester with the UK College of Agriculture.
College researchers are taking a hard look at the well-being of forests, asking questions about why they have changed during the last 60 years and looking for solutions for maintaining the forests as the economic and ecological treasure they are.
Using Fire for Forest Management
Every spring UK forest ecologist Mary Arthur heads eastward toward the forest. Her purpose is to study the effects of prescribed fires set by the U.S. Forest Service as a tool for managing the composition of tree species in the forest. When the Forest Service personnel start fires in the forest-sometimes they start them from helicopters and other times by hand torch-Arthur measures the immediate impact of the fire while it still smolders. She studies the temperature of the fire and the amount of fuel (mostly leaf litter) that's burned.
That's the easy part. The hard part comes later, when she carefully monitors the regrowth of species on the forest floor to see what types of plants are thwarted and what types are invigorated by the fire.
Oaks have not been regenerating well in our forests for the past 40 to 60 years, Arthur said. One hypothesis for their lack of regeneration is that fire suppression has led to the proliferation of more fire-sensitive species, such as red maple, that shade out oak seedlings.
Upland forests, Arthur said, have developed for the past few thousands of years within the context of human influences. It is widely believed that Native Americans used fire throughout the region, which probably contributed to the maintenance of vigorous stands of oaks.
My research into the use of fire suggests that fire kills more red maples than oaks, Arthur said. My research also shows, however, that the maples that do survive fire grow faster than oak seedlings of the same size. It may turn out, she said, that fire will be a good maintenance tool for removing fire-sensitive species.
Arthur also said that there is something of a myth that our forests have a problem with fuel accumulation-leaf litter and woody debris on the ground. Her research will test this assertion by measuring the amount of fuels, such as leaf litter and woody debris, before and after fires to see whether prescribed fires significantly reduce fuels that could increase the threat of unplanned fire.
A Fungus (-Like Creature) Among Us
The Sudden Oak Death pathogen has been found in 21 states, mostly in diseased plants in nurseries. As yet, only California and Oregon have experienced the disease in the forest.
While Arthur works toward finding whether fire can help regenerate oak stands, other UK College of Agriculture researchers are examining ways to thwart a potential attack by a tiny fungus-like pathogen that could have devastating consequences for Kentucky's oak trees.
Sudden Oak Death was first identified in California in 1995 and has since invaded 20 other states. It could jeopardize Kentucky's oak stands in a huge way-perhaps as seriously as chestnut blight did in the 1930s, when virtually all American chestnuts were killed by a fungus that invaded North America.
And while in Kentucky no cases of Sudden Oak Death have yet have been identified (through major investigations of plant material at nurseries and inspections at 11 state parks), that could change quickly, said UK plant pathologist John Hartman (picture).
The southeastern corner of Kentucky is at high risk, and both western and northeastern Kentucky are at moderate risk for Sudden Oak Death disease outbreaks, Hartman said.
The disease is caused by a fungus-like organism, Phytophthora
ramorum, that infects rhododendrons in Germany and the Netherlands and is closely related to the fungus that caused potato blight in Ireland in the 1840s. The disease is lethal to many oaks, including, potentially, Kentucky's red oaks, but infections also occur, and the pathogen can build up on other native species such as rhododendron, mountain laurel, and vibernum, further promoting its spread to oaks.
Gypsy Moths: Looking for a New Home
And it isn't just pathogens that threaten Kentucky forests.
Another pest, this one an insect, has been menacing other states' forests for 100 years and may be viewing Kentucky's forests as its next feeding ground. The gypsy moth may be coming to a forest here soon.
Gypsy moth caterpillars are voracious eaters, feeding on nearly 500 plant species.
The European gypsy moth was introduced into the United States near Boston just after the Civil War, when it was imported by E. Leopold Trouvelot to evaluate its potential for silk production. However, a few of the moths escaped, and by 1889, they were in sufficient numbers to defoliate some neighborhoods around Boston.
Since then, gypsy moths have continued to increase their range, and the pest is now found in many states. The caterpillars are voracious eaters, and they're not particularly picky, either, feeding on nearly 500 plant species.
In Kentucky, the moths have yet to set up residence, but surveys conducted annually-using traps to monitor their presence-find a few male moths. Although no breeding populations have been found in Kentucky, it may be just a matter of time.
UK entomologist Lynne Rieske-Kinney is researching how the pest behaves in the forest, including which oak species are most susceptible to defoliation. Her research has shown that black oak is the most preferred of Kentucky's common forest oak species, but caterpillars consumed the most of northern red oak. Her research also shows that pin oak is the most preferred of our urban oak species and is likely to suffer high levels of defoliation.
Because many oaks are used as landscape trees and in urban forests, we could reduce the gypsy moth's impact by planting fewer preferred oak species in urban areas, she said.
Rieske-Kinney also is studying how management techniques, such as controlled burning, affect caterpillar growth and development. Fire provides additional nutrients for plant growth, which can change the nutrient content of the leaves, influence the plants' production of defensive compounds, and alter plant susceptibility to insects.
So far, Rieske-Kinney's research into fire as a management technique has shown that the gypsy moth growth rate was enhanced when gypsy moths were fed foliage from burned forests, but the development rate of caterpillars (the stage at which the moth does the real damage) isn't affected by fire.
Some oaks in Kentucky may be lost to the gypsy moth, but if we can maintain a variety of healthy trees through good management, then we'll have fewer stressed oak trees that are susceptible to defoliation, Rieske-Kinney said.
Come this fall the University of Kentucky Department of Forestry, in conjunction with the U.S. Forest Service, will start studying methods of timber harvest to see which methods help improve the health of the forest, especially the forest's ability to withstand gypsy moth defoliation.
With the dedication of University of Kentucky scientists to the task of protecting Kentucky's forests from diseases and insects as well as humans, the rich treasure of trees will stand the state's economy in good stead for years to come.