Recipient Organization
UNIV OF MASSACHUSETTS
(N/A)
AMHERST,MA 01003
Performing Department
Environmental Conservation
Non Technical Summary
As Massachusetts faces increasing pressure from population expansion, along with increasing challenges due to climate change, we seek a solution to the growing demand in housing that supports the local timber industry and rural economies and also creates an opportunity to store more carbon both in our buildings and across our regional forested landscape. Recent advances in timber technology have produced promising new methods for meeting some of the demand for building materials, as well as the need to store carbon. One of the most promising new technologies for small to mid-sized buildings is cross laminated timber (CLT). CLT is a massive timber panel used in floor, wall and roof applications. Its physical structure is that of a multi-layer composite (3 to 9 layers) comprised of dimensional lumber arranged cross-wise to the next layer for bi-directional strength and stability. Pairing new CLT technologies with management practices that prioritize carbon storage and long-term resilience of forest ecosystems have the potential to both be a local source of building material and increase carbon storage from harvested timber as compared with more traditional harvesting. Simultaneously, the Northeastern United States is one of regions with the highest number of exotic forest pests. One of the pests currently impacting tree species in Massachusetts is the hemlock woolly adelgid (HWA; Adelges tsugae), a sap-sucking aphid-like insect that weakens and then eventually causes mortality in eastern hemlock (Tsuga canadensis). As these trees die, they slow their sequestering of carbon and thier ability to store more carbon is truncated. However, recent research at the University of Massachusetts-Amherst has indicated that eastern hemlock and eastern white pine (Pinus strobus) are suitable timber species as feedstock for three-layer CLT, a product typically suited to light-frame and multi-family residential construction, which could be used to meet some of the demand for housing in the region. With this potential new market for eastern hemlock as an alternative building material, it is imperative we understand the carbon dynamics at play as we think about the benefits and drawbacks of CLT and its impacts on the landscape and climate. We will investigate the carbon impacts, in terms of both storage and emissions, of harvesting eastern hemlock for use as CLT to meet some of our upcoming housing demand. We will update current methods of carbon accounting for harvestd timber, as well as model scenarios of harvesting in response to HWA with and without a CLT market and assess the impacts on forest carbon and resilience. We hope that some of these findings and/or methods will be applicable across a wider array of species affected by forest pests, as we expect increasing numbers of these pests due to climate change.
Animal Health Component
25%
Research Effort Categories
Basic
75%
Applied
25%
Developmental
(N/A)
Goals / Objectives
This project encompasses three major goals to address the overarching question: what are the carbon impacts, in terms of both storage and emissions, of harvesting eastern hemlock for use as CLT to meet some of our upcoming housing demand?Goal #1: Determine landscape potential for hemlock as a source for CLT and the carbon impacts of different harvest regimes to meet an increasing demandObjective 1.1: Quantify the aboveground carbon storage and emissions of eastern hemlocks stands for the next 30 years in Massachusetts without the removal of hemlocks for CLT (carbon potential of the landscape), but with the impacts of HWAObjective 1.2: Understand the potential range of harvest types that could be applied within eastern hemlock stands if they were targeted for CLT, and the impacts of those harvests on aboveground carbon and species composition for 30 yearsObjective 1.3: Update current estimates of carbon allocation of harvesting aboveground carbon to different storage and emissions pools based on more recent trends in milling and timber useGoal #2: Quantify the carbon implications for replacing traditional building materials with CLT for specific construction market segments (e.g., Housing, Multi-family dwellings, Schools, Offices)Objective 2.1: Quantify the carbon storage and emission potential of using eastern hemlock as a source for CLTObjective 2.2: Estimate the production potential, demand, and impacts of one CLT mill in Massachusetts (e.g., with capacity for 1% of the market share), including efficiencies of carbon allocation into product and wasteObjective 2.3: Determine the replacement values of using CLT from local sources in the identified construction market segments vs. traditional building methods (e.g., concrete, steel, and light-frame construction)Goal #3: Identify levels of harvest and CLT use that maximize the carbon and ecological benefits of stands impacted by forest pestsObjective 3.1: Determine the harvest rates and intensities that balance the demand for increased hemlock as a local source of timber for CLT, carbon storage from the use of hemlock in CLT, and carbon loss on the landscape from harvestObjective 3.2: Find methods for generalizing findings of the carbon balance across more species to understand the potential impacts of future forest pests
Project Methods
Goal #1:The first phase of the project will be quantifying the carbon impacts of the potential harvesting initiated by HWA and the use of eastern hemlock in CLT. We will estimate differences in landscape stored carbon using a mechanistic forest growth and succession model (e.g., LANDIS-II with PnET-Succession) coupled with scenarios of harvest responses to HWA to quantify the potential carbon losses due to harvest and the duration of those carbon deficits. Much of the legwork for parameterizing these mechanistic forest models has been done by MacLean for previous studies looking at the carbon impacts of harvesting trends in New England, though we will ensure forest growth model estimates of carbon simulate true forest carbon by comparing estimates to FIA. Harvest in response to HWA scenarios will be informed by previous work completed by MacLean using family forest owner surveys to model harvest response to HWA in the Connecticut River Watershed, as well as outreach to local foresters and loggers on the range of their management responses to invasive insects. These harvest scenarios will also be updated to include scenarios where hemlock of a certain size and grade are preferred for harvest to be used in CLT.Simultaneously, we will work with regional partners (e.g., New England Forestry Foundation, Harvard Forest, MA Department of Conservation and Recreation, MA Executive Office of Energy and Environmental Affairs) to update the carbon allocation process to match the current timber industry in Massachusetts, including updating mill efficiencies and product outputs. Recent Forest Service timber product output records of regional shifts in products and efficiencies will be used to corroborate expert reports of these amounts. Following harvested timber carbon through its full life cycle may present unique challenges - in the event the full life cycle analysis for current timber production is unobtainable, many of the current assumptions for carbon allocation can be applied and the deviation from the current predictions of carbon pools can be used to estimate the impacts of CLT and HWA rather than absolute values of carbon, though we would prefer to report absolute values of the carbon emissions and storage potentials of CLT and HWA.Goal #2:We will use our current knowledge of the construction of CLT with eastern hemlock to create carbon densities for the manufactured boards, as well as estimate carbon emissions from the process. With the results from Goal #1, we will pair the landscape carbon dynamics of harvesting for hemlock for CLT with an updated life cycle analysis, based on previously used carbon allocation methods (Smith et al. 2006). Updates will include: completing a review of current CLT mill capacities and efficiencies to estimate demand and carbon emissions from the manufacturing process; updating carbon emissions and storage proportions and decay rates from species other than hemlock harvested (removed alongside the hemlock); estimating replacement and any potential leakage associated with harvesting hemlock for CLT. We will do a thorough literature search of the carbon impacts of both traditional and CLT construction (though limited) to quantify carbon storage and emission differences between the two methods for different building types. If we are unable to attain exact values for replacement from building plans for CLT buildings, we will use our expertise and collaborators to design the CLT equivalent building to standard buildings in our market segments (e.g., Housing, Multi-family dwellings, Schools, Offices).Goal #3:Finally, we will use our findings from Goal #1 and Goal #2 to determine the optimal levels of harvest and CLT production that produce the most carbon benefits and analyze the ecological and social implications in terms of forest resilience and housing innovation and access. We will weigh different scenarios of hemlock harvesting with their impacts on forest resilience with impacts on carbon, as well as the rate of CLT production associated with those scenarios. Similar analysis will be conducted on test landscapes for additional example pest and target host tree species. We will then determine if our results are generalizable to a larger number of species that could be affected by invasive insects (e.g., ash is currently being invaded by the emerald ash borer).