By Terry Belke
Of the almost 750 million acres of forest in the U.S., only about 3.5 million acres (or 6-percent), are considered old growth.
COOKSBURG PA — Old growth forests in North America are very rare. It’s estimated that of the almost 750 million acres of forest in the U.S., only about 3.5 million acres are considered old growth forests, and scientists have been debating for years on how to define them.
Cook Forest Environmental Education Specialist Dale Luthringer explains, “I think the best definition that I’ve seen so far is you’re trying to get a certain number of trees in the forest that pre-date the lumber history for that area.”
Cook Forest in Northwest P.A. was founded in 1927, and Luthringer says it’s considered one of the finest stands of old growth White Pine and Hemlock in the United States.
“By far, the ancient White Pine and the Hemlock is really what sets Cook Forest apart,” he says. “In terms of tall White Pine, we’ve got three White Pine that are in the hundred and seventy foot class. Our tallest Hemlock is just shy of a hundred and fifty feet, it’s about a hundred and forty eight feet tall.”
But this forest is not special only for the immense height of it’s trees. These towering sentries are truly ancient.
“Our oldest Hemlocks and Pines are around three hundred and fifty years old,” says Luthringer. “We have White Oak and Chestnut Oak that are approaching that, that we’ve got actual ring data, three thirty plus. The oldest known tree in the woods is actually a Cucumber Tree […] it’s on the ground now, but it’s the oldest known Cucumber Tree to science. That tree was about four hundred and forty years old.”
When the park was founded it was an effort to protect this unique environment from the ravages of the timber industry. Now almost a century later, park management must defend the Hemlocks from a new destructive force.
The invasive insect Hemlock Wooly Adelgid was discovered in Cook Forest in 2013. The tiny insect can kill trees within four to 10 years of infestation, and is ravaging forests across North America. Fortunately for the Cook Forest Hemlocks, the park was prepared for the invaders, and have been successful in protecting the cherished trees.
By Margaret Nagle
Land managers in New England and eastern New York state have a new tool to help identify eastern hemlock stands at greatest risk for rapid growth decline by evaluating stresses on the trees, including response to the hemlock woolly adelgid and changes resulting from a warming climate.
Today, an estimated 26 percent of the region’s hemlock stands are at high risk. As winters get warmer, the decline will increase, with 43 percent of stands expected to be at high risk, according to a research team led by University of Maine Associate Professor of Forest Resources William Livingston.
The researchers’ comprehensive landscape model maps the varied response to the invasive Asian insect across the Northeast, and identified the site characteristics of stands with the highest potential for tolerance and recovery in order to prioritize management efforts.
Eastern hemlock is a towering foundational species in eastern North American forests valued from southern Canada to Alabama and as far west as Minnesota. But since the mid-20th century, eastern hemlock that can live more than 500 years have been increasingly threatened by the hemlock woolly adelgid that can kill a tree within four years by feeding on its needles and branches, preventing new growth.
Using changes in tree rings — basal area increment (BAI) measurement — in mature hemlock, the researchers quantified annual growth decline in 41 hemlock stands across New England representing a range of infestation density and duration, and species vigor. The model also was applied to 15 hemlock sites in Massachusetts.
Among the findings of the research team using the growth decline metric: Eastern hemlock sited on steeper slopes with increased exposure to solar radiation and warmer January minimum temperatures have a greater probability of experiencing rapid decline.
The results of the study, which involved researchers from UMaine, the University of Vermont and LandVest Inc., in Portland, Maine, were published in the journal Biological Invasions.