Environment: Northern hardwood forests poised to take big hit from global warming

Groffman concludes,

Forest response to climate change based on complex set of factors

By Summit Voice

SUMMIT COUNTY — Global warming plays out on a stage that’s much more complex than just a rising graph line in a climate model.

In the northern hardwood forests of New England, for example, the models don’t account for factors critical to understanding forest response, such as hydrology, soil conditions, and plant-animal interactions, according to Dr. Peter Groffman, a microbial ecologist at the Cary Institute of Ecosystem Studies.

Those and other factors combined mean that climate change is poised to reduce the viability of the maple syrup industry, spread wildlife diseases and tree pests, and change timber resources. And without long-term studies at the local scale, resource managers will be ill-prepared to predict and manage these effects, Groffman and co-authors wrote in a new BioScience paper.

The study looked at more than 50 years of long term data on environmental conditions at the Hubbard Brook Experimental Forest, located in the White Mountains of New Hampshire.

One thing is clear: at Hubbard Brook Forest spring is advancing and fall is retreating. Over the past half century, the climate has warmed and there has been a rise in rainfall and a decrease in snowfall. Winters are getting shorter and milder, with snowpack melting some two weeks earlier. But soil thaw is no longer tightly coupled with spring plant growth, creating a transitional period that results in the loss of important soil nutrients.

In the absence of insulating snow pack, exposed soils are more susceptible to freezing, which damages tree roots. Sugar maples are suffering a one-two punch: soil frost is linked to tree mortality and warmer winters reduce sap yield. Mild winters are also encouraging the spread of pests and pathogens, including the destructive hemlock woolly adelgid—which was once held in check by cold winter temperatures.

As snow depth decreases, deer are better able to forage in the forest. Their browsing damages young trees and spreads a parasite that is lethal to moose. Reduced snow pack is also a challenge for logging operations, which use snow-packed roads to move trees, and ski resorts, which already rely heavily on manmade snow.

“Managing the forests of the future will require moving beyond climate models based on temperature and precipitation, and embracing coordinated long-term studies that account for real-world complexities,” Groffman said. “These studies can be scaled up, to give a more accurate big picture of climate change challenges—while also providing more realistic approaches for tackling problems at the regional scale.”


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