Carbon
footprints of alternative transportation and land use scenarios
PhD
Assistantship available to begin Fall 2008: please contact
Dr. Jenkins for details
Because transportation sources are proportionally large contributors to greenhouse gas (GHG) emissions, transportation is one of the sectors in which policy changes are likely to have the greatest impact. While mobile sources are significant contributors to GHG emissions, the GHG impacts of transportation infrastructure are also important. Specifically, new highway infrastructure can have significant environmental consequences by redistributing the spatial pattern of development, as previously inaccessible, yet potentially environmentally significant lands become subject to development pressures. Land converted to a developed use often represents foregone sequestration potential in the forest or agricultural sector. Yet despite the importance of transportation in GHG emissions, and the key role that changing land uses can play in mitigating or enhancing the atmospheric GHG burden, the interrelated impacts of transportation and land use change decisions on atmospheric GHG stocks are rarely considered in projections of alternative development scenarios.
This project brings together estimates of GHG emissions in the transportation and land use sector in a modeling framework to consider the impacts of land use change on GHG emissions under a series of alternative futures. It is one component of a larger project entitled "Integrated Land-use, Transportation and Environmental Modeling: Complex Systems Approaches and Advanced Policy Applications" (link), and is funded by the US Department of Transportation through UVM's University Transportation Center (http://www.uvm.edu/~jcjenkin).
A Land-Use-Based County-Level Carbon
Budget for Chittenden County, Vermont
MS Student, Erin Quigley
As concern grows over the possible effects of increased atmospheric carbon (C), there is substantial interest in understanding both natural and anthropogenic C dynamics. This project aims to quantify the sources and sinks of atmospheric carbon dioxide (CO2) on a county scale. With support from the Hubbard Brook Research Foundation's Sciencelinks Carbon Group, I am creating a net C budget for Chittenden County, Vermont, with key C sinks and emissions categorized in terms of land use. Land use history and its effect on C dynamics is also being examined. The primary goal of the budget is to provide up-to-date and accurate decision-making information to planners and policy-makers in the county, allowing them to get the most tangible benefits out of their mitigation efforts. I also hope to create and refine a methodology that is easily replicable in any county in the United States, making county-level C data readily available beyond Vermont and the Northeast. The budget is part of a larger study by the HBRF, where five counties representing different land uses are working together to create consistent county-level C budgeting methodology.
Greenhouse
gas life cycle assessment of organic versus conventional biofuel crop production
for canola and sunflower crops grown in the Northeast.
MS Student,
Nell Campbell
The purpose of this study is to complete greenhouse gas (GHG) life cycle assessments of two biofuel crops grown in the Northeast (NE). Biofuels can theoretically reduce GHG emissions compared to their petroleum counterparts through the sequestration of carbon during the feedstock growth as well as by the avoidance of GHG emissions from fossil fuel combustion. However, biofuel production requires energy and material inputs that vary according to feedstock type and production methods. This means that some biofuel development choices are likely more successful than others in meeting the goal of reducing overall GHG emissions from fuel use. Comprehensive analyses of GHG emission sources, sinks, and offsets associated with biofuel production, refining, and use, also known as 'GHG life cycle assessments', are necessary to understand the environmental implications of biofuel development for GHG accounting and in order to make informed policy decisions. While a number of life cycle assessments for a variety of biofuel feedstock types have been published, most are focused on the large-scale production of energy crops such as corn and soy, and use national averages for key variables such as fertilizer quantity and harvest yield. These studies do not apply to the NE region because land ownerships tend to be much smaller and because the growing season is much shorter than the national average. Furthermore, the oilseed crops currently in production, for example canola and sunflower in Vermont, differ from those most frequently covered in other life cycle assessments. This study will take place on two on-farm fuel facility demonstration sites in Vermont where ongoing research trials have been conducted to identify the most promising oilseed crops and best management practices for biofuel production. At these two farm facilities, canola and sunflower energy crops will be produced with organic and conventional growing methods, refined into biofuel, and used within the farm system pending the completion of biorefinery facilities by the end of 2008. All aspects of the production, harvest, and refining processes will be recorded and used to complete a thorough assessment of total GHG emissions as well as to determine carbon sequestration and fuel substitution benefits associated with small-scale energy crop production. These data will also be used to generate an analysis of the economic costs and benefits for crop-based biofuel development, particularly in these small-scale operations typical of the Northeast, where transportation costs are minimized and the biofuel and its co-products offset on-farm requirements.
2. Residential Carbon
Residential
Carbon Projects (http://www.residentialcarbon.org)
Dr. Jennifer Jenkins, PhD Candidate Paul Lilly, and MS Student Laura Nagel.
The Residential Carbon Projects seek to quantify the stocks of carbon, and the fluxes of carbon (C), carbon dioxide, and other greenhouse gases, in urban and suburban systems. There are several components to the residential carbon work:
a.
Field work at the parcel level in Baltimore (NSF-DEB-0444919):
In association
with the Baltimore Ecosystem Study (BES), an NSF-funded Long Term Ecological Research
(LTER) site, we are conducting field measurements to quantify the rate at which
C is stored in soils and vegetation in residential landscapes. The study design
is set up to test the influence of various drivers of social and biophysical factors
such as land use history, soil type, management inputs, and residential age on
rates of C cycling. This three-year project is scheduled to conclude in 2009.
b.
Field work at the parcel level in Burlington, VT (McIntire-Stennis):
We are
conducting field measurements to quantify C stocks and fluxes in residential parcels
in Burlington, VT. The study design for this project will compare residential
and native vegetation, to test the influence of prior land use on C cycling rates
(see below).
c. Influence of management on turfgrass dynamics (NSF-DEB-0444919):
At
the University of Maryland-College
Park turfgrass facility, we are testing the influence of various fertilization
and irrigation regimes on rates of C sequestration and greenhouse gas fluxes.
Carbon stocks and fluxes in residential
landscapes of different land use histories in Chittenden County, Vermont
MS Student Laura R. Nagel
In an effort to enhance our understanding of the carbon (C) cycle and the role of suburban lawns in C cycling, my research seeks to quantify annual rates of C storage in suburban soils and turfgrass in Chittenden County. For this study, which I plan to conduct from February to November 2008, I will compare C cycling rates in soils and vegetation in lawns, forests, and grasslands. I am particularly interested in figuring out if, how, and how quickly land use changes (e.g., converting from pasture to lawn)affect the C storage process. Similar residential C research is underway in Baltimore, MD, and looking more closely at the landscapes in Vermont will help us understand how C cycling varies between regions.
Vermont Forest Ecosystem
Management Demonstration Project: Evaluation of Biomass and Carbon Storage Dynamics
Under Alternate Forestry Practices
P.I. William S. Keeton, University
of Vermont
In the northern hardwood region of North America managing for late-successional forest of forest carbon management due to the high levels of biomass accumulations in older forests. This study tests the hypothesis that uneven-aged practices can be modified to accelerate rates of late-successional forest development and associated biomass accumulation. An approach, termed "Structural Complexity Enhancement (SCE), is compared against conventional uneven-aged systems modified to increase post-harvest structural retention. Experimental treatments, including controls, were applied to 2 ha units and replicated at two multi-aged northern hardwood forests in Vermont, U.S.A. Structural objectives include vertically differentiated canopies, elevated large snag and downed log densities, variable horizontal density, including small gaps, and re-allocation of basal area to larger diameter classes. The latter objective is achieved, in part, by cutting to a rotated sigmoid diameter distribution. This is generated from a basal area (34 m2 ha-1) and tree size (90 cm dbh) indicative of old-growth structure.
Forest structure data have been collected over two years pre-treatment and four years post-treatment. Fifty-year simulations of stand development were run in NE-TWIGS and FVS comparing treatment and no treatment scenarios. Simulations also tested the sensitivity of large tree development to prescription parameters. Leaf area index retention was spatially variable but significantly (p < 0.001) greater under SCE (91%) compared to conventional treatments (75%). Post-harvest aboveground biomass (p = 0.041), total basal area (p = 0.010), relative density (p = 0.008), and stem density (p = 0.025) were significantly different among treatments, with SCE generally retaining more structure than conventional treatments. SCE successfully achieved the rotated sigmoid diameter distributions, and sustained these 50 years into the future, resulting in reallocated basal area and biomass. Cumulative basal area increments are projected to increase by 3.7 m2 ha-1and 5.0 m2 ha-1compared to no treatment scenarios for SCE and conventional treatments respectively.
Basal area and aboveground biomass will be significantly (p = 0.025) greater after 50 years in SCE units as compared to conventional treatments. Aboveground biomass is predicted to increase over the next 50 years in all of the experimental units, including controls, based on the FVS simulations and NED-2 biomass calculations. Living biomass increases 70.5, 66.1, and 73.6% on average for SCE, uneven-aged, and control units respectively under a "no treatment" scenario. It increases 90.7 and 105.2% following SCE and uneven-aged treatment, but starts from a post-harvest level that is 18.3 and 35.9% lower than pre-treatment respectively. Consequently, none of the treatments achieve the biomass they would have without treatment. However, after 50 years SCE results in aboveground biomass that is 91.4% of that projected under no treatment, while the conventional treatments result in 79.1% of the no treatment potential. Biomass production annual increment is accelerated 5.1% for SCE and 1.9% for conventional treatments based on normalizing treatment against no treatment scenarios. Enhanced biomass accumulation and carbon storage in northern-hardwood systems can be promoted through a variety of modified uneven-aged silvicultural approaches based on the results. Passive management offers another alternative for maintaining high biomass levels in mature and older forests.
Biomass Accumulations in Mature and Old-Growth
Northern Hardwood-Conifer Forests: Implications for Forest Carbon Sequestration
P.I. William S. Keeton, University of Vermont
Collaborators: Clifford E. Kraft
and Dana R. Warren, Cornell University, Department of Natural Resources
Quantification of biomass in forested ecosystems is important for managing global carbon budgets and dampening the magnitude of climate change. A prerequisite is our ability to predict biomass dynamics in relation to forest stand development. A widely used theoretical model of stand development in the northern hardwood region of eastern North America predicts peaks in biomass accumulation after about two centuries of development, followed by declining biomass in stands roughly 200 to 350 years of age, and "steady-state" biomass dynamics in stands > ca. 350 years of age. However, recent empirical studies have found continued basal area accumulations far later into stand development than the theoretical model would predict. Our study evaluated these competing views, focusing on mixed northern hardwood-conifer forests in the Adirondack Mountains of upstate New York. We sampled 29 sites along 150-300 meter long, 1st and 2nd order stream reaches. Sites were classified as mature forest (9 sites), mature with scattered remnant old-growth trees (5 sites), and old-growth (15 sites). Average age of the largest, dominant trees ranged from approx. 81 to 410 years. At each site forest structure was sampled at varying distances from both stream banks using 6-10 variable radius plots. We used the Northeast Ecosystem Management Decision Model (NED-2) to calculate biomass using species-specific allometric equations. ANOVA and post-hoc multiple comparisons were used to analyze categorical data, whereas continuous variables were evaluated using Classification and Regression Trees and linear regression analysis. Aboveground biomass was significantly (p <0.001) different among mature (165 Mg/ha), mature w/remnants (177 Mg/ha), and old-growth (254 Mg/ha) sites. Of 17 independent structural variables used to predict dominant tree age in an initial model, 5 were included in a final CART model. Of these basal area was the strongest predictor variable overall, but aboveground biomass was an important secondary variable. Both basal area (r2 = 0.60) and aboveground biomass (r2 = 0.65) were strongly (p < 0.001) and positively correlated with dominant tree age based on regression results. There was little or no evidence of an asymptotic relationship with age over the range of values examined.
Our results support the hypothesis that basal area (live and dead) and aboveground biomass can continue to develop and/or accumulate very late into succession in northern hardwood-conifer forests. Consistent agreement between empirical studies (upland and riparian) in the Adirondack region suggests a need to reexamine theoretical models of stand development and biomass dynamics for northern hardwood-conifer systems. If the empirical data represent a trend of continued biomass additions in stands well over 300 years of age, which cannot be inferred directly from chronosequence comparisons, a leveling off or decline in standing biomass would have to occur later in stand development than previously predicted. Emerging research suggests that biomass may seldom actually reach an equilibrium condition, but rather exhibits quasi-equilibrium dynamics, depending on natural disturbance regime. This would have important implications for our understanding of both the quantity and duration of carbon storage in old-growth forests. Old-growth forests may have greater potential for carbon sequestration in the northern forest region than previously recognized.
Climate Change Impacts on Western Forest
Fires
P.I. William S. Keeton, University of Vermont
Collaborators:
Jerry F. Franklin, University of Washington, College of Forest Resources; Philip
W. Mote, University of Washington, Joint Institute for the Study of Atmosphere
and Oceans, Climate Impacts Group
Climatic change during the next century is likely to significantly influence forest ecosystems in the western United States, including indirect effects on forest and shrubland fire regimes. Further exacerbation of fire hazards by the warmer, drier summers projected for much of the western U.S. by climate models would compound already elevated fire risks caused by 20th century fire suppression. This has potentially grave consequences for the urban-wildland interface in drier regions, where residential expansion increasingly places people and property in the midst of fire-prone vegetation. Understanding linkages between climate variability and change, therefore, are central to our ability to forecast future risks and adapt land management, allocation of fire management resources, and suburban planning accordingly. To establish these linkages we review previous research and draw inferences from our own retrospective work focused on 20th century climate-fire relationships in the U.S. Pacific Northwest (PNW). We investigated relationships between the two dominant modes of climate variability affecting the PNW, which are Pacific Decadal Oscillation (PDO) and El Nino/Southern Oscillation (ENSO), and historic fire activity at multiple spatial scales. We used historic fire data spanning most of the 20th century for USDA Forest Service Region 6, individual states (Idaho, Oregon, and Washington), and 20 national forests representative of the region's physiographic diversity.
Forest fires showed significant correlations with warm/dry phases of PDO at regional and state scales; relationships were variable at the scale of individual national forests. Warm/dry phases of PDO were especially influential in terms of the occurrence of very large fire events throughout the PNW. No direct statistical relationships were found between ENSO and forest fires at regional scales, although relationships may exist at smaller spatial scales. However, both ENSO and PDO were correlated with summer drought, as estimated by the Palmer Drought Severity Index (PDSI), and PDSI was correlated with fire activity at all scales. Even moderate ( 0.3 C decadal mean) fluctuations in PNW climate over the twentieth century have influenced wildfire activity based on our analysis. Similar trends have been reported for other regions of the western U.S. Thus, forest fire activity has been sensitive to past climate variability, even in the face of altered dynamics due to fire suppression, as in the case of our analysis. It is likely that fire activity will increase in response to future temperature increases, at the same or greater magnitude as experienced during past climate variability.
If extreme drought conditions become more prevalent we can expect a greater frequency of large, high-intensity forest fires. Increased vulnerability to forest fires may worsen the current fire management problem in the urban-wildland interface. Adaptation of fire management and restoration planning will be essential to address fire hazards in areas of intermingled exurban development and fire-prone vegetation. We recommend: 1) landscape-level strategic planning of fire restoration and containment projects; 2) better use of climatic forecasts, including PDO and ENSO related predictions; and 3) community-based efforts to limit further residential expansion into fire-prone forested and shrubland areas.
Climate
Change Impacts on Pacific Northwest Forests
P.I. William S. Keeton,
University of Vermont
Collaborators: Jerry F. Franklin, University of Washington,
College of Forest Resources; Philip W. Mote, University of Washington, Joint Institute
for the Study of Atmosphere and Oceans, Climate Impacts Group
An analysis of relationships between past climate variability and ecosystem dynamics was used to project the likely responses of PNW forests to anthropogenic climate change. Potential impacts on forest management are assessed in this context. Important drivers affecting PNW forest responses to climate include precipitation (amount, timing, and type) and summer drought (frequency, intensity, and duration). Fluctuations in climate influence the structure, function, and composition of PNW forest ecosystems both directly - by influencing the establishment and growth of individual trees - and indirectly - by influencing the frequency and intensity of natural disturbances. Indirect climate effects are likely to be especially powerful agents of change over the near term in particular. The most common disturbance in the PNW, forest fires, is strongly correlated with summer drought conditions, which tend to be heightened by the warm/dry conditions prevalent during the warm phase of the Pacific Decadal Oscillation.
The consequences of climate variability for tree growth and regeneration vary spatially with forest type, elevation, hydrology, soils, and other site-specific factors. The growth and establishment of trees near lower tree lines in the PNW tend to be limited by summer moisture availability; their response to climatic variations depends on whether summer drought conditions are exacerbated or ameliorated. Trees at high elevations, in contrast, tend to be limited by winter snowpack, exhibiting increased growth when winter snows are below normal and vice versa. Sensitivities to climate variation tend to be greatest near the extremes of species' tolerance and geographic ranges.
Compared to water resources management, forest managers make relatively little use of climate forecasts, due to: (1) limited understanding of the implications of climate variability for forest management, (2) concerns about the reliability of climate forecasts and predictability of climate impacts, (3) the nature of long-term forest management planning that tends to discount climate variability over shorter time scales, and 4) difficulties inherent to dealing with uncertainty.
Climate change will impose multiple stresses, both direct and indirect, on the PNW's forested landscapes. Human-caused changes in the structure and function of PNW forest ecosystems since European settlement have reduced the ability of forest ecosystems to absorb or recover from additional stresses associated with future climate change. We poject a number of such changes based on a review of previous research as well as original analyses. New species assemblages may appear on the landscape as species' distributions shift individualistically. Rates and trajectories of vegetation change at small or local spatial scales will be highly variable. Projected temperature increases related to climate change would produce increases in wildfire activity. Key uncertainties associated with projecting climate change impacts on PNW forests are (1) uncertainty about how temperature and precipitation changes will interact to affect drought stress in trees and otherwise modify annual productivity and (2) whether CO2 enrichment will help trees withstand reduced soil moisture and/or increase productivity.
We suggest that PNW forests are likely to decline in many areas due to the combined effects of increased drought stress in established stands, increased probability of insect and fire disturbance, and reduced seedling survival. Alternative scenarios are also possible based on some of the previous research using simulation models. For instance, a transient, short-term expansion of forests may occur, with forests expanding into low elevation areas in the interior Northwest and high elevation meadows and forest productivity increasing throughout the region. Subsequent, long-term decline at lower elevations is a possibility under this scenario if drought stresses ultimately overwhelm CO2 enrichment effects.
New forest management approaches, as well as a rethinking of how we design and manage the PNW's protected areas, are needed to plan for climate change. It is recommended that forest managers focus on maintaining the adaptability and resilience of the ecosystems they manage. In light of the uncertainty about the specific nature of future climate impacts, this would require - from among a suite of possible adaptive management approaches - maintaining biological diversity and ecological connectivity, adapting protected areas design and management, restoring riparian areas and forest structure associated with historic fire regimes, and developing adaptive planting and silvicultural strategies. These general approaches are currently in use to varying degrees depending on location. The challenge now is to incorporate climate information into planning such that adaptive management explicitly addresses climate variability and change.
Quantifying
forest carbon storage under alternate forest management scenarios in the northeastern
United States: tradeoffs among carbon sinks and implications for forest sector
carbon credits
MS Student, Jared Nunery
This study addresses the growing regional debate regarding how best to manage forests for carbon sequestration and storage. The debate pertains to rapidly developing carbon markets and the potential for landowners to participate by modifying forest management practices to provide "additionality" in storage over baseline levels. A critical question has been whether carbon storage can best be increased through forest management strategies emphasizing intensified harvests coupled with carbon storage in wood products versus strategies stressing low intensity harvest, long rotations, and carbon storage in extant forests. This study employs simulation modeling techniques using existing datasets. Results from this study will inform forest policy and planning in the Northeast by offering a means of quantifying carbon storage associated with a range of management scenarios. In addition, the suite of silvicultural treatments will include tradeoffs of complementary and competing options, such as maximized standing biomass, production of durable wood products, short rotation forestry for fiber production, and reserved based management.
A
Framework for Greenhouse Gas Accounting and Management Concepts
MS
Student. Ryan Salmon
Collaborators: University of Vermont, Alliance for Climate
Action
Individuals and organizations working on climate action projects
face the challenge of balancing the need for action with the need for further
information. Because the subject of climate change mitigation is so complex and
new information is so rapidly emerging, striking this balance is difficult. Recognizing
that people working on these projects face time constraints, the purpose of this
project is to simplify the complexity surrounding climate action with a framework
that organizes pertinent information to increase the effectiveness of climate
action projects. The project deliverable is a document entitled Climate Action
Guide to Greenhouse Gas Accounting and Management, intended for use by members
of the Alliance for Climate Action and other individuals and organizations working
on local-scale climate action projects.
Last modified March 04 2008 01:40 PM
