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Northern Research Station
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Madison, WI 53726
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You are here: NRS Home / Research Programs / Clean Air and Water / Estimating and Monitoring Carbon Stocks and Greenhouse Gas Fluxes
Clean Air and Water

Estimating and Monitoring Carbon Stocks and Greenhouse Gas Fluxes

Forests of the United States absorb about 10% of the carbon dioxide emissions from burning fossil fuels for energy. This function of forests is an important part of the solution to reducing the buildup of greenhouse gases in the atmosphere, which is linked to climate change. Scientists at the Northern Research Station conduct research and prepare annual reports on the contribution of U.S. forests to the nation’s greenhouse gas inventory. Our estimates are adopted by the U.S. Government and many states as the official forest greenhouse gas statistics. The Northern Research Station also leads the development of the accounting rules and guidelines for the private sector to voluntarily take action to reduce greenhouse emissions or increase carbon sequestration in forests. These guidelines are used by states in their greenhouse gas action plans, and by the newly revised national greenhouse gas registry, maintained by the Energy Information Administration of DOE.

Selected Research Studies

[map:] The global distribution and number (shown in square brackets) of single-factor and multifactor manipulative experiments (1973–2016).Analysis Synthesizes Global Carbon Research To Refine Future Modeling
An international collaborative of researchers, including a scientist with the Northern Research Station, has recently analyzed more than 1,000 large-scale ecosystem studies in an attempt to inform the next iteration of carbon cycling modeling.


[photo:] Sampling carbon stocks in the forest floor.Carbon and Forest Management
Forests play an important role in the global carbon cycle – forests take up carbon dioxide from the atmosphere as they grow.  This carbon is "sequestered", or temporarily removed from the atmosphere.   Since forest carbon sequestration can help offset emissions, it is important to learn how much carbon our forests are storing, and how management practices affect the rate of carbon sequestration (storage) in the forests of our region. 


[photo:] Precipitation manipulation experiment in a piñon pine - juniper ecosystem at the Sevilleta Long Term Ecological Research (LTER) site at the Sevilleta National Wildlife Refuge in central New Mexico, USA.Increasing the reliability of predictions of the landscape effects of climate change
Climate change is producing new environmental conditions that have not existed for study in the scientific age.  It is quite possible that many of the empirically-derived relationships developed under the conditions of the past for predicting forest dynamics will be rendered obsolete by climate change.  For example, forest growth and yield models are based on empirical relationships measured nearly a century ago when CO2 and temperatures were lower.  Recent research suggests that tree growth in the Midwest may be up to 20% higher in the current century because of CO2 fertilization.


[photo:] WLEF tower, Park Falls WI.Chequamegon Ecosystem-Atmosphere Study (CHEAS)
As part of the cooperative Chequamegon Ecosystem Atmosphere Study (ChEAS), NRS scientists have been studying the energy, water vapor and CO2 exchange between forest ecosystems and the atmosphere to understand the dynamics of forest productivity.


[photo:]  Howland Ameriflux Site - tower viewed from aboveAtmospheric Exchange - AmeriFlux - Howland Site
The goal of this project is to develop a capacity to predict how future climatic change may affect carbon cycle processes and carbon storage in an evergreen, sub-boreal forest located in the northeastern US. 


[photo:] The eddy flux tower at Silas Little Experimental Forest.  Measurements of energy, water vapor and net CO2 exchange started in April 2004.  Annual net CO2 exchange (NEEyr) measured at this site ranges between 187 and -293 g C m-2 yr-1, with the largest C loss value corresponding with complete defoliation by Gypsy moth in 2007.  Monitoring and Understanding Forest/Atmosphere Carbon Dioxide Exchange: the NRS Flux Tower Network
Data from flux sites help test physiological models of C exchange and are critical to relating fluxes and remote sensing data. Companion physiological and ecological measurements enable partitioning carbon fluxes into plant and soil components and reveal mechanisms responsible for these fluxes. At some sites, biomass-based estimates of C storage have validated C budgets from direct flux data, and vice-versa. Data from the flux sites have been applied in ecology, weather forecasting, and climate studies, especially for sites with several years of data to quantify inter-annual flux variations.


[photo:]  Forests surrounding Monocle Lake=Modeling: Optimal Co-allocation
Forest production varies from site to site, depending in part on the availability and uptake of nitrogen. Understanding how nitrogen affects productivity is key to precise forecasting of productivity, but our understanding is incomplete.


[photo:]  Autumn landscape- trees in fall colors=Modeling: Calibration
We have formulated a process-based model of a tree that predicts time-streams of tree diameter, height, crown ratio, and volume.  The tree model is intended for use in spatial forest models that predict time-streams of production, growth, and carbon sequestration. At the present time we are investigating ways to calibrate the tree model and characterize variation among trees.


[image:]  Pond surrounded by treesCarbon Cycling Research at Silas Little Experimental Forest
An understanding of carbon, water, and energy exchanges between forests and the atmosphere at multiple scales in time and space is necessary to better inform decisions that are made concerning forest management, carbon sequestration, fire management, and the climate system.


[image:] Graph shows relation of basal area, umber of trees, and average tree diameter to stocking percentage for upland central hardwoods.Thinning in Mixed Hardwood Forests
Very little was known about managing the growth and quality of hardwood forests in the east as the second- and third-growth forests were developing. Studies of “growth and yield” were established to quantify the growing capacity of these forests.


[image:]  Propagating probability distributions of stand variablesData Assimilation
Data sampling routinely involves some degree of uncertainty in the measurements, often called noise, which is unpredictable. Likewise, models used to estimate system processes also contain uncertainty, which can come in many forms, not the least of which is their imprecise formulation based on incomplete understanding of the phenomenon being modeled. The question is how best to estimate the state of the system under consideration through time, along with any unknown model parameters, from these (possibly nonlinear) noisy model predictions and incoming measurements.


[photo:] Soil respiration measurements in this northern hardwood stand are used to understand the impact of exotic earthworms on forest carbon dynamics.Earthworm Invasion
Populations of exotic European earthworms have been expanding into formerly worm-free forests in the north central and northeastern United States.  These earthworms consume the organic horizons of the forest floor, often removing leaf litter within several years of invasion.  This leads to changes in soil carbon, nutrients (e.g. nitrogen and calcium), soil microclimate, hydrology, soil organisms, and plant community assemblages. 


[image:] Changes in climate, atmospheric components, land use and disturbance regimes affect forest carbon sequestration and biofuel product. It is important to understand these processes and attribute the effects to different causesImpacts of Disturbances and Climate on Carbon Sequestration and Biofuels
Currently, U.S. forests and forest products offset about 20% of the nation’s fossil fuel emissions. However, recent findings cast doubt on the sustainability of this offset. First, the strength of the U.S. forest carbon offset may be weakening due to forest ageing, climate variability, and increasing natural disturbances. Second, climate change is expected to further increase frequencies of insect outbreaks and wildfire, and alter species composition in forest ecosystems, consequently influencing forest carbon pools in a significant way.  These current and projected forest carbon cycle dynamics need to be considered in strategic forest planning and management decisions in coming decades if the nation’s forests are to provide stable or even increasing ecosystem services.


[image:] Fragmented forest landscapeIntegrating Landscape-scale Forest Measurements with Remote Sensing and Ecosystem Models to Improve Carbon Management Decisions
Managing forests to increase carbon stocks and reduce emissions requires knowledge of how management practices and natural disturbances affect carbon pools over time, and cost-effective techniques for monitoring and reporting.


[image:] Carbon calculation toolsTools for Carbon Inventory, Management and Reporting
Much of our science is used to provide information for policymakers and planning.  We have developed tools so that others may apply this information, or work with our tools to further the science.


[photo:] Poplar energy crops recently harvested for evaluation of aboveground carbon storage.Carbon Implications of Poplar Energy Crops Throughout the Energy Supply Chain

Woody production systems and conversion technologies are needed to: maintain healthy forests and ecosystems, create high paying manufacturing jobs, and meet local/regional energy demands. Poplars are dedicated energy crops that can be strategically placed in the landscape to conserve soil and water, recycle nutrients, and sequester carbon. However, key environmental and economic uncertainties preclude broad-scale production of biofuels/bioproducts from poplar wood. Therefore, building on decades of research conducted at our Institute and throughout the region, we are evaluating the fate of carbon in soils and woody biomass, soil greenhouse gas emissions, and conversion efficiency barriers throughout the energy supply chain.


[photo:] Forester using the point relascope method for sampling coarse woody debris.Coarse Woody Debris
A proportion of the carbon in forest ecosystems is contained in coarse woody debris on the forest floor. Estimating the carbon stock and other attributes of coarse woody debris can be time consuming and error-prone. New methods for field sampling of coarse woody debris are needed for efficient estimation of the carbon stock in this forest pool.


[photo:] Ground estimates of insect defoliation are scaled-up to regional scales using multiple remote sensing platforms, including aerial photography, Hyperion, Landsat ETM+, and MODIS.Effects of Insect Defoliation on Regional Carbon Dynamics of Forests
On an annual basis, insects severely defoliate more than 20 million acres of forested land in the conterminous United States, affecting a larger area and incurring higher economic costs than any other disturbance.  However, the long-term costs and ecosystem consequences of insect outbreaks on forest health and productivity are difficult to quantify at the regional scale because of the variety of pests involved, differences in forest types affected, and varying spatial scale and intensity of the impacts.  In particular, the effect of insect activity on carbon cycling and sequestration at the annual and decadal scale is poorly characterized.  


[image:] Map of predicted losses of nitrogen from forested lands of the Chesapeake Bay watershed under no nitrogen deposition, current nitrogen deposition, and doubled nitrogen deposition (Pan et al. 2004).Mid-Atlantic Forests and the Chesapeake Bay Watershed
Forest landscapes are changing as a consequence of climate and environmental change. These changes affect people and the forest ecosystems they depend on for clean water, clean air and forest products, and recreation. How can we best manage our forest resources to sustain this array of ecosystem services under increasing environmental stress and a changing climate?


[image:] Graph indicating Forest Carbon BudgetForest Carbon Models and Budgets
There is increasing interest in accurate estimates of national, regional, state, and local carbon fluxes, and identification of the causes of land / atmosphere / ocean exchange of carbon.  Because forests store large quantities of carbon and these stocks are affected by many factors, accurate monitoring of forest carbon stocks and fluxes is a critical component of strategies to manage greenhouse gas emissions and sequestration. 


PhotoGlobal Change Research
The goal of global change research is to establish a sound scientific basis for making regional, national, and international resource management and policy decisions in the context of global change issues. The Northern Global Change Research Program currently emphasizes scientific inquiry into the effects of multiple air pollutants and climate changes on forest ecosystems. As the program matures, the impacts of prospective changes on interactions between forest ecosystems and social and economic processes will be evaluated, as will policy options for mitigating or adapting to predicted changes.


[photo] The Aspen FACE siteAspen FACE Experiment
The Aspen FACE (Free-Air Carbon Enrichment) Experiment is a multi-disciplinary study to assess the effects of increasing tropospheric ozone and carbon dioxide levels on the structure and function of northern forest ecosystems.


Last Modified: 01/05/2021