North American Forest Health | NRM Science & Forest2Market

This is a brief overview from the most recent issue of Natural Resources Management Today, which covers scientific findings and silviculture-related topics impacting forests across North America.

Earthworms May Be a Threat to Canada’s Boreal Forest

According to a recent study, earthworms in Canada’s forests could be accelerating climate change. Earthworms feed on organic matter, releasing the stored carbon.

“Most earthworms disappeared from North America during the last ice age more than ten thousand years ago,” said Dr. Jérôme Laganière, a research scientist at the Laurentian Forestry Centre (LFC) of Natural Resources Canada. “They reappeared in the 18th century with the settlement of European colonists, probably transported with the soil from tomato plants.”

The study, conducted in 2018 and 2019 in Alberta and Quebec, compared the impact of earthworms in two different soil types. In Alberta, the soils are richer and less acidic, but in many regions of Quebec, the soils are more acidic, so, in theory, Quebec soils should be less hospitable to earthworms. However, the researchers were surprised to see how abundant and active they were—even to the extent of expanding their range.

“Our study shows that earthworms are spreading north into the boreal forest,” says Jérôme. “Currently, they are present in 10 percent of the boreal forest. But by 2050, they will likely have invaded most of the boreal forest, which will have direct consequences on its ability to store carbon.”

Southern Pine Beetle Moving North

Researchers at the University of New Hampshire recently found the southern pine beetle, one of the most damaging tree-dwelling insects in the Southeast, in forests in Maine and New Hampshire. The southern pine beetle has never been seen this far north and has forestry experts concerned, specifically about the pitch pine barren found throughout New England.

“Warmer winter temperatures make it easier for beetles to survive further north,” said Jeff Garnas, associate professor of forest ecosystem health, whose research team made the discovery. “While not exactly surprising, this finding is a stark reminder of how species, including those of significant ecological and economic importance, are already responding to the changing climate.”

The southern pine beetle (SPB) was found in research traps set by Garnas’ research team in both Ossipee, New Hampshire, and in southern Maine, near Waterboro. Prior to its discovery on Long Island in 2014, the SPB had never been detected further north than New Jersey.

Relative Density of US forests Increasing

Researchers at the US Forest Service’s Northern Research Station have found that the area of forestland in the US is static, but has fewer trees and greatly increased timber volume and tree biomass. The study is described in Scientific Reports. The researchers found that “the area of high RD [relative density] stands (RD > 0.6) has quintupled over the past 20 years, while the least stocked stands (RD < 0.3) have decreased 3%. The evidence from the coterminous US forest RD distribution suggest opportunities to increase live tree stocking in understocked stands while using density management to address tree mortality and resilience to disturbances in increasingly dense forests.”

This piece was originally published in the February 2022 edition of Natural Resources Management Today (NRM Today). Steve Wilent is Editor of NRM Today, a monthly digital newsletter for North American natural resources professionals who manage fish, forests, range, water, wildlife, and other resources, as well as for the people who depend on or enjoy these resources.