"My research focuses on understanding the structural characteristics of and functions performed by forest ecosystems and how those are affected by natural and human-caused change," explains Bill Keeton, professor of forestry and forest ecology at the University of Vermont (UVM). "I then apply that knowledge to managed forests to develop sustainable management and conservation approaches. These days, a particularly important objective is maintaining and possibly enhancing carbon storage in forests and thus, reducing greenhouse gas emissions."
For more than 15 years, Bill has studied the dynamics of primary forest landscapes, including carbon dynamics, old-growth forests, ecosystem recovery from natural disturbances, and forest-stream interactions. As interest in "disturbance-based" forestry has emerged internationally, nationally, and in the Northern Forest region specifically, the question for Bill became "how can we design sustainable forestry practices that interact with forest development and ecosystem functions the way natural disturbances do?"
Bill was awarded Northeastern States Research Cooperative (NSRC) funding in 2004 to augment his long-term Vermont Forest Ecosystem Management Demonstration Project principally supported by the Vermont Monitoring Cooperative and USDA National Research Initiative. Bill worked with U.S. Forest Service and UVM colleagues and graduate students to design and test disturbance-based forest practices in managed forest stands. Their goal was to develop late-successional, or old-growth, forest characteristics, a type of habitat and carbon storage condition that is vastly under-represented on the Northern Forest landscape due to our land use history.
"Architecturally complex forests develop over time if left to their own devices or managed lightly," explains Bill. "Old-growth hardwood forests have complex canopies with multiple layers of trees and shrubs, a patchwork of varying tree densities and gaps, an assortment of tree ages and sizes, and plenty of coarse woody debris or downed logs and standing dead trees."
In study plots on the UVM Jericho Research Forest and on the west side of Mount Mansfield in Vermont, Bill, his colleagues, and local loggers experimented with techniques to mimic processes and characteristics of old-growth forests, called structural complexity enhancement (SCE). They pushed trees over to add tip-up mounds and organic matter to the soil and provide habitat for wildlife and herbaceous plants, girdled trees to develop standing dead snags for cavity-nesting birds, and harvested deteriorating, small- and medium-sized trees to give large, healthy trees more growing space. To create small gaps and horizontal variation in stand structure, they used variable density marking, now widely practiced in the western U.S., to mark trees to be cut.
In several plots, Bill's team harvested commercial timber with a modest profit and improved wildlife habitat for several indicator species, such as red-backed salamanders, ground beetles, and sensitive herbaceous plants, such as wild ginger and starflower. Bill stresses that his team is experimenting with additional tools for forest managers and landowners who can "mix and match" these new tools with other sustainable management approaches and more traditional silvicultural methods depending on owner objectives and economic constraints.
Across North America, researchers like Bill are finding that old-growth forests sequester, or store, much more carbon than do young forests. Younger forests absorb carbon at a faster rate, "but older, higher biomass forests act like big carbon reservoirs, holding carbon that, if cut, would be released to the atmosphere, even accounting for new growth and the portion of carbon transferred to wood products," Bill acknowledges. Researchers suggest that managing for high biomass forests and improving the forest’s ability to store carbon will help address excess carbon dioxide in our atmosphere.
In 2013, Bill received NSRC support to evaluate carbon responses one decade after harvest treatments on the Vermont Ecosystem Management Demonstration Project. He and his graduate students found that SCE treatments in northern hardwood-conifer forests resulted in carbon storage only slightly less than simulated no-harvest baselines and substantially greater than in conventional selection harvests. Total aboveground carbon storage in SCE plots was 15.90% less than that projected for no-treatment, compared to 44.94% less in conventionally treated areas.
The researchers recommend SCE treatments as an effective approach for northeastern landowners to increase carbon storage in managed northern hardwood forests and as an option for capturing supplemental revenue from rapidly developing compliance and voluntary carbon markets.
To explore how to better sequester carbon over time in the Northern Forest, Bill received NSRC funding in 2006. He and graduate student Jared Nunnery used Forest Service Forest Inventory and Analysis (FIA) data from across the northeastern U.S. and subjected the data to nine simulated management scenarios, representing a range of harvest intensity and frequency. A computer model then projected forest development forward in time over more than a century, simulated carbon fluxes between different pools in the forest and wood products, and estimated the net average carbon storage for each scenario.
"Modeling showed that switching from higher to lower intensity harvesting practices can sequester up to 57% more carbon," reveals Bill, "allowing a landowner to achieve a margin of enhanced storage, called 'additionality.' This can earn revenue in a carbon market while keeping open the option to harvest timber."
Bill is quick to acknowledge that their findings do not take into account "substitution effects" or increases in carbon emissions related to production and use of steel or concrete in place of wood; nor do they account for possible displacement of harvesting to other properties or regions. "This is the next step in the accounting we need to do," he says, "but carbon markets are rapidly developing mechanisms that track these effects. This ensures that lower intensity cutting practices actually achieve real emissions reductions."
His 2009 NSRC project coincided with the exploding interest in forest biomass as an alternative to fossil fuels in the Northern Forest region and elsewhere. Bill and his colleagues, including two graduate students, assessed the ecological outcomes and tradeoffs involved in managing northern hardwood forests for biomass fuel production. "Low intensity biomass harvests conducted carefully might actually improve forest condition and carbon sequestration, providing economic and environmental incentives for sustainable forest stewardship," proposes Bill, "but at the same time there is uncertainty regarding net carbon cycling effects and impacts on wildlife habitats."
Bill's more recent NSRC-funded projects include Evaluating Supply and Demand of Northern Forest Branded Carbon Credits and Effects of Forest Recovery from Agricultural Land Use on Carbon Storage and Ecological Benefits.
Using forest inventory data from 25 non-industrial, privately owned properties, combined with intensive interviews with potential buyers (universities and businesses), Bill and co-researchers found high potential for both supply of and demand for Northern Forest carbon credits but with important limitations. Carbon projects conducted on medium- to larger-sized properties (>1,000 acres) and/or with initial carbon stocking (i.e. timber volume) higher than regional averages have the greatest likely rate of return on investment. The researchers suggest that as carbon markets continue to develop, opportunities for smaller landowners may improve.
Bill and graduate student Andrea Urbano observed high carbon storage in mature, planted, and naturally regenerated secondary forests at the Marsh-Billings-Rockefeller National Historical Park in Vermont. This supports previous reports that aboveground biomass can accumulate late into stand development in secondary forests. Forest recovery to 2003 reveals high potential for carbon accumulation on sustainably managed landscapes, particularly where high stocking is maintained. Findings suggest that New England’s secondary forests have potential to re-achieve high levels of carbon storage.
The recipient of a 2016 NSRC Special Topics project award, Bill and colleagues Jim Duncan and Jennifer Pontius of the Forest Ecosystem Monitoring Cooperative (formerly Vermont Monitoring Cooperative) are conducting a regional geospatial synthesis designed to leverage the relative strengths of NSRC projects and forest health aerial surveys in an interactive mapping tool. Researchers will be able to identify the most widespread and severe disturbances across the region. By combining aerial survey and NSRC databases, they will improve interpretation of geospatial data while making NSRC studies accessible to a much broader audience.
Bill's expertise in sustainable forest management, carbon sequestration, and biomass fuels is sought by local, national, and international government and non-profit groups. As a member of the Vermont Forest Roundtable convened by the Vermont Natural Resources Council (VNRC), he contributed his expertise to a final report released in 2007 that outlined recommendations for reducing forest fragmentation in Vermont. Bill is currently a participant on the Vermont State Legislature's Biomass Energy Development Working Group charged with developing ways to enhance Vermont's biomass industry while maintaining forest health.
"Bill has positively influenced the Forest Roundtable by bringing scientific information and research to our discussions," says Jamey Fidel, forest and biodiversity program director for VNRC. "Through the Biomass Energy Development Working Group and the Forest Roundtable meetings, I have come to rely on Bill's insight and ability to condense complex research and scientific principles into workable suggestions for policy at the state level."
As a member of the Forest Guild, a national organization of forest stewards and natural resource professionals, Bill contributes to development of carbon policy and carbon markets. He advised the Obama administration on climate change mitigation options for the National Forest system. International connections take him to Belgium, where he helps to assess carbon across large landscapes and to the Carpathian Mountains of Eastern Europe where he helps to develop incentives for sustainable forestry through carbon market participation.
Back home, Bill conducts his research, leads his students, and spends his free time hiking, cross country skiing, and paddling as deep into the Northern Forest as he can.