Forests Feel Impact of Late-Season Freeze

By Robin Hartman

Aerial photograph of trees in Estill County. Photo courtesy of the Division of Forestry.

Even in the midst of the COVID-19 pandemic, there’s a new and concerning malady that has thrown Kentucky’s Forest Health a double-punch: the impact of late-season hard freeze on trees and vegetation. The Kentucky Energy and Environment Cabinet’s Division of Forestry has been monitoring the damage, and it appears to be statewide in scope.

“The impacts are startling when you see them,” said Brandon Howard, division environmental control manager whose team inspected the damage. “We’ve had a number of inquiries asking what the phenomenon is. There’s a distinct difference you can see in many of the tree lines.”

With early spring-like temperatures this year, many forest trees had begun to leaf out. Then, as unseasonably cold temperatures arrived in mid-April, and a heavy freeze struck the state in early May, many of those trees unfortunately experienced leaf loss; some were hit twice.

The division was actively surveying damage in eastern Kentucky when a local graduate student noticed definitive changes in the tree line near the Land Between the Lakes in western Kentucky. Photos were sent to the U.S. Forest Service in Atlanta which contacted Kentucky’s Division of Forestry. Local foresters in Madisonville were deployed on site.

“We have a really good working relationship with the U.S. Forest Service, Forest Health Protection Program,” said Abe Nielsen, an environmental control supervisor with boots on the ground. “The initial concern was an influx of damaging insects or disease, but we were all relieved to confirm it was due to the unusual weather conditions.”

Photo courtesy of John B. Hewlett, Graduate Research & Teaching Assistant, Murray State University.

Division crews then realized the damage was statewide. “Most of the state has been impacted,” Nielsen confirmed, “but because the growing season tends to be about two weeks further along in western Kentucky than in the eastern part of the state, different trees have been affected.”

Trees that escaped damage had developed early due to the warm March weather Kentucky experienced, and were already well-established. Others had not yet begun budding, and as a result were also safe. Those most susceptible were trees in the process of establishing new leaves. In eastern Kentucky for example, yellow poplar and sycamore, and understory species like spice bush, were hit hard. In western Kentucky, bottomland oaks took the brunt as cold temperatures stayed in the lower elevations.

Private land owners may have also seen damage to trees or ornamentals. Those that were in the process of flowering may produce less fruit and may not grow as much this year. Stress over time, like last season’s drought, added to this year’s freeze, could also affect some species. These added stressors could result in minor decline in some localized areas, but overall the trees should be fine.

“This event put things on pause. But trees are very resilient and they should bounce back pretty quickly,” Nielsen said. The US Forest Service’s near-real-time satellite imagery currently shows a 10-15 percent reduction in the greenness of tree canopies in much of Kentucky compared to this time last year. “This will likely just put us a few weeks behind. With warmer, more seasonable temperatures expected in the weeks ahead, we shouldn’t see any lasting effects.”

This is just one of many influences on Kentucky’s forest health the division will monitor. Invasive species and insects like the emerald ash borer and hemlock wooly adelgid have and will prove much more damaging, Nielsen said. “This is definitely unusual to see, and we’ll monitor the impact over time. But it’s one of many components. Seems like every year gets a little more interesting!”

The Kentucky Division of Forestry works to protect, conserve and enhance Kentucky’s forest resources through stewardship and forest protection programs. Read more about KDF here.

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