Eleven University of Vermont researchers and students spent five days in late May planting 7000 tree seedlings in the wilderness of northern New Hampshire. The work, part of a national series of field experiments intended to run for decades, will test ways to help forest ecosystems adapt to impacts of changing climate and disturbances.
In addition to increasing temperatures in the Northeast, scientists project shorter winters, changing precipitation patterns, more destructive wind and ice events, and greater damage from forest insects and diseases.
“Some dominant tree species, such as sugar maple, are predicted to decline on certain sites under future climate scenarios, while for other species, such as northern red oak, habitat suitability is expected to increase,” said Tony D’Amato, a silviculturist and professor in the UVM Rubenstein School of Environment and Natural Resources and primary lead on the project.
D’Amato and his UVM team, along with the USDA Forest Service and other partners, are using silviculture, or tactics to grow and regenerate trees and maintain the health and ecological conditions of forests. The silvicultural experiment at the Second College Grant in New Hampshire includes strategic harvesting of trees and creation of openings, or gaps, for growth of planted seedlings — all based on ecological science — to help the future forest adapt.
“Given the unprecedented number of stressors our future forests will face, such as climate change, invasive species, heavy deer browse, and fluctuating timber markets, developing science to meet these challenges is paramount to the sustainability of future forests,” said Christopher Woodall, a scientist with the Forest Service Northern Research Station and co-lead on the New Hampshire project.
“We are focusing on three adaptation strategies: resistance, resilience, and transition,” said D’Amato who has practiced forest research for close to twenty years. “We are trying to increase forest ecosystem resistance and resilience to projected climate change scenarios using silvicultural techniques that carefully select trees to harvest and retain so that we increase the complexity of this northern hardwood forest with trees of all ages, sizes, and species.”
Map shows location and layout of experimental plots at the Second College Grant in northern New Hampshire. The study covers 400 acres with each silvicultural treatment repeated on four 25-acre blocks. (Map created by Jennifer Santoro)
Planting for change
The researchers are also encouraging forest ecosystem transition by planting future adapted tree species from warmer climates.
“Climate is changing at a pace that far exceeds the ability for tree species to migrate and adapt,” said Peter Clark, a Rubenstein School PhD student working with D’Amato. “One aspect of the project examines the response and challenges of artificially regenerating tree species from southerly ranges that might be better adapted to future environments.”
The planting event at the Second College Grant, a 27,000-acre northern hardwood forest owned and managed by Dartmouth College, took place in a 400-acre experiment installed in 2017 as the largest silvicutural study in the northeastern United States. This collaborative effort also includes scientists and land managers from Dartmouth College, University of New Hampshire, University of Maine, and the U.S. Department of Interior Northeast Climate Adaptation Science Center.
A planting site at the Second College Grant in northern New Hampshire.
The experimental installation in New Hampshire is one of five sites located in different forest ecosystem types across the United States that are included in a long-term study of forest ecosystem responses to climate adaptation actions. This national, collaborative project, called Adaptive Silviculture for Climate Change (ASCC) and led by Linda Nagel, a professor at Colorado State University, builds off the Northern Institute of Applied Climate Science Climate Change Response Framework. The four other ASCC sites include the J.W. Jones Ecological Research Center in Georgia, Chippewa National Forest in Minnesota, Flathead National Forest in Montana, and San Juan National Forest in Colorado.
At the New Hampshire site, researchers co-developed silvicultural treatments with regional forest managers and fisheries and wildlife biologists to ensure the experiment reflected current and future management needs and addressed a range of forest stakeholder perspectives. In quarter- and one-acre harvest gaps, researchers planted eight carefully chosen, native tree species: northern red oak, bitternut hickory, black birch, eastern white pine, eastern hemlock, basswood, bigtooth aspen, and blight resistant varieties of American chestnut.
From left, Rubenstein School PhD student Peter Clark, PhD student Jennifer Santoro, and undergraduate student Jack Goldman assist with planting. Clark is investigating survival and growth of future-adapted tree species, and Santoro is modeling future landscape-level forest conditions across northern New Hampshire and Vermont.
“We used several criteria for choosing species to plant, including potential performance in warmer climates, susceptibility to wind and ice damage and current non-native pests, and similarity in traits, like leaf and growth characteristics to species currently found in these forests,” said D’Amato, who conducted forest research at the University of Minnesota prior to coming to Vermont and also co-leads the Minnesota ASCC project (headed by Brian Palik, a scientist with the USDA Forest Service). “Many tree species projected to do well under future climates in the Northeast are not tolerant of shade, and to become established, they need light created by gaps left from harvesting mature trees.”
Keeping working forests working
Because of its remote, wilderness setting and 210-year history of stewardship by Dartmouth College, D"Amato said, "Second College Grant is an ideal location for long-term research on the silviculture and ecology of northern forests."
“We manage this property for education, recreation, and timber which provides important revenue to the College,” said Kevin Evans, director of Dartmouth College Woodlands Operations. “Research is a critical component of our educational efforts here. The ASCC project has allowed us to incorporate critical climate change research into our continuous sustainable timber management program; this research may guide how our management and harvesting will need to adapt to the changing climate in the coming years.”
“The working forests on this site allow us to examine long-term options for maintaining characteristic northern forest species, including sugar maple, yellow birch, and red spruce,” said D’Amato, “while also evaluating their interactions with species projected to fare better in these areas over the next century.”
D’Amato and his students and colleagues will monitor how the new trees, as well as those naturally regenerating on the site, do as climate change and other stressors, such as invasive species, develop in the region. Their work will help Evans and other forest managers to develop silvicultural strategies for maintaining healthy northern hardwood forests in light of projected future changes.
Other measurements collected by collaborators across the experiment involve small mammal, bird, and insect communities, and soil, water, carbon, and deadwood dynamics. These data will allow for overall assessments of how adaptive silvicultural strategies affect biodiversity and delivery of key ecosystem services such as clean water, timber, and wildlife habitat.
“Adaptive silviculture research in New England provides a rare opportunity to bring together scientists and practitioners from across a spectrum of state, federal, and private entities to develop science that is operational,” said Woodall. “People that work in the woods and whose livelihood depends on thriving future forests are helping develop science that ensures New England’s forests remain productive for future generations.”
Vermont studies
At UVM’s research forests, D’Amato and his students are conducting a small-scale application of this larger study to evaluate similar tree species and techniques in three different forest ecosystems in Vermont. Sites range from a northern mixed wood forest in Wolcott, a low-quality northern hardwood site in Jericho, to a high-quality northern hardwood site in the town of Washington.
Clark, who works at both the New Hampshire and Vermont sites, is running an experiment at the Jericho site to evaluate the influence of changing moisture conditions on the germination and establishment of seeds from the tree species being planted across these experiments.
“Building off of the ASCC work, at UVM, we have designed a silviculture experiment in university research forests that will allow us to manipulate precipitation to examine the response of northern tree species along with potential replacement species better adapted to a shifting climate,” said Clark. “By testing a range of climate projections, this work aims to better understand the regeneration patterns that will shape future forests of the Northeast during a time of uncertainty.”
"It has been an incredible experience working for and alongside a diverse group of scientists studying the effects of climate change on northern hardwood forests,” said Jack Goldman, an undergraduate student in the Rubenstein School. “I have learned so much over the past two summers ranging from field methods to the ecological rational behind large-scale experiments like ASCC. It has certainly made me a better scientist. I'm excited to see the results of all of our hard work!"