Criterion 5: Maintenance of Forest Carbon Contributions to Global Carbon Cycles

Indicator 12: Forest ecosystem biomass and forest carbon pools

This indicator describes changes in live tree biomass and carbon pools specifically in relation to forests. Although much of this data only exists for recent years, over time the indicator will show whether forestlands are acting as gains or losses to the carbon pool.

Relation to Sustainability

As a nation and a global population, our technologies emit carbon. Forests play a large role in sequestering and recycling carbon from the atmosphere. During the photosynthesis process, carbon is removed from the atmosphere and becomes part of the plant mass. Managing forests to sequester carbon therefore reduces the net amount of carbon dioxide accumulating in the atmosphere, which in turn helps reduce the extent or severity of human-induced climate change. This indicator provides an estimate of forest carbon sequestration that may be subtracted from gross carbon emissions to estimate net carbon emissions. Tracking the amount of forest carbon may also be useful to develop “green” accounting methods to place economic value on forest carbon sequestration.

In the future, woody biomass may also be tracked as a means of renewable energy production. Currently, soil carbon changes are not included in this indicator; however, forest soils are estimated to sequester carbon at a higher rate than above-ground biomass.

The Statewide Forest Plan (completed in 2004) identified a number of forest trends and issues in Wisconsin that relate to specific indicators presented in this Framework. Trends and issues that relate specifically to Indicator 12 are presented below. As the Framework is used to develop the Statewide Forest Assessment, these trends and issues may be assessed and explored further through the metrics presented in this indicator. Identified trends and issues are:

• Trend 2: Forestland is increasing.
• Trend 15: Warming of the earth may affect forest composition, structure and function.
• Issue 16: Forests affect carbon emissions and sinks.
• Issue 23: "Green" accounting represents a new way of evaluating the benefits of forests.
• Issue 52: Wood biomass for energy production.

12.1 Forest Ecosystem Biomass

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Map 12.1: Carbon in Aboveground Live Tree Biomass in Forests (metric tons/ha)

This metric shows the carbon in above-ground live tree biomass in metric tons/ha by county in 2005. Data for this metric was obtained through a special request to the USFS Northern Research Station Forest Carbon Dynamics and Estimation Research Work Unit. Counties having less than five percent of total land area in forest are excluded from the analysis.

The amount of live tree biomass in a forest is directly related to that forest’s ability to sequester carbon; the more tree biomass, the more carbon a forest may sequester. From Map 1, we see that most counties in Wisconsin have 51-75 metric tons/ha in above-ground live tree mass in forests. Forest managers can combine this data with metric 12.3, forest carbon by forest type, to locate areas with the greatest potential for carbon sequestration.

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12.2 Forest Carbon Pools

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Table 12.2: Forest Carbon Pools in Wisconsin

This table shows the amount of carbon in different types of forest vegetation. Currently, comparisons can be made between 1996 and 2003 data sets. The next data set released will be for the year 2006. (Data will be collected more frequently in the future). Data were obtained through a special request to the USFS Northern Research Station Forest Carbon Dynamics and Estimation Research Work Unit. Within this data, a set of above-ground biomass regression equations (Jenkins et al. 2003) are utilized to estimate carbon from tree-level data.

Growing forests store carbon in vegetation, the forest floor (including down dead wood), and soil. The age and health of a forest affects the rate of carbon sequestration and the overall inventory of stored carbon. Trees represent the most dynamic component of the carbon pool, with soil and forest floor carbon pools remaining largely constant over time. As more yearly data is collected, this metric will give an indication of changes in forest structure and function, as well as how well Wisconsin’s forests are sequestering carbon.

Data on carbon pools in urban forests will come from the USFS FIA Urban Forestry Pilot project for 2002 and 2008, and will be reported separately. Presentation for this data is currently being developed.

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12.3 Forest Carbon by Forest Type

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Table 12.3(a): Current forest carbon by coniferous and broad-leaved forests in Wisconsin, 2004

Data in tables 12.3(a) and 12.3(b) allows us to compare the amount of forest carbon by forest type and species type, as well as the amount stored above-ground and below-ground. Comparing this data with overall species acreage in Wisconsin, we may discover that certain tree species sequester more carbon per acre than others. This information, combined with data on carbon sequestration by age, may allow forest managers to manage for carbon sequestration by planting the appropriate tree species at optimal rotations.

Table 12.3(b): Above-ground tree carbon by forest cover type group in Wisconsin, 2003

It is important to note that Wisconsin’s forests are predominantly hardwood types (generally broad-leaved). The large amount of carbon stored in broadleaf forests does not, therefore, indicate that broadleaf forests necessarily store carbon better or more efficiently than coniferous forests, but merely that there is a larger percentage of broadleaf forests in the state. Amount of carbon stored per species type (Table 12.3(b)) gives a more complete picture of which species store more carbon than others.

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12.4 Change in Forest Carbon

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Map 12.4: Average annual change in Forest Ecosystem Carbon in the Northern United States from 2000 to 2005 (million metric tons)

Data in this metric show the annual average change in forest ecosystem carbon at the state level. Data were obtained through a special request to the USFS Northern Research Station Forest Carbon Dynamics and Estimation Research Work Unit.

Data on change in urban forest carbon will come from the USFS FIA Urban Forestry Pilot project for 2002 and 2008. Presentation of this data is currently being developed.

From map 12.4, we see that about 6.4 million tons of forest ecosystem carbon were released (lost) per year in the years 2000-2005. This data may indicate broader trends, such as the effect of global warming on Wisconsin’s forests. Data may also be compared to other states to give an indication of how well Wisconsin’s forests are sequestering carbon relative to other areas of the country.

Managers could act on these trends to understand how issues like recycling and other wood storage mechanisms may help reduce the loss of forest ecosystem carbon.

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Data Limitations/Considerations

There are some data gaps associated with the metrics in Criterion 5. Biomass by component (stump, bole, tops, and limbs) data is lacking in recent FIA online data. Data on carbon sequestered in forest soils, forest floor, and down woody material is also limited. To augment carbon estimates from the FIA, carbon conversion factors from ecological studies were also incorporated.

Related Indicators

In developing this Framework, several other state and national criteria and indicator-based initiatives were used as a model. Indicators presented in this report therefore relate directly to indicators used in the model reports. Related indicators are listed below.

• Northeastern Area Association of State Foresters and Forest Service State and Private Forestry Base 18 Indicators of Sustainability [exit DNR]: Indicator 11
• Montreal Process Proposed 2010 [exit DNR]: Indicator 22, 23, 24
• Forest Stewardship Council Principles and Criteria for Forest Stewardship [exit DNR]: None
• Sustainable Forestry Initiative [exit DNR]: None
• American Tree Farm SystemStandards of Sustainability for Forest Certification [exit DNR]: None

References

Carbon Calculation Tool [www.nrs.fs.fed.us/pubs/2394 [exit DNR]].

Jenkins, Jennifer C., Chojnacky, David C., Heath, Linda S., and Birdsey, Richard A. 2003. National-scale biomass estimators for United States tree species. Forest Science. 49(1): 12-35.

Nichols, Mike. Nov. 2005. Unpublished data based on FIA data and augmented by carbon conversion factors from ecological studies. Durham, NH: USDA Forest Service, Northeastern Research Station, Forest Carbon Dynamics and Estimation Research Work Unit (NE-4104). For additional information on the state level data, contact Mike Nichols at mnichols@fs.fed.us or 603-868-7682.

Smith, W. B., Miles, P.D., Vissage, J.S. and Pugh, S.A. 2004. Forest Resources of the United States. 2002. A technical document supporting the USDA Forest Service 2005 update of the RPA Assessment. Gen. Tech. Rep. NC-241. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Research Station. 137 p. [http://www.ncrs.fs.fed.us/pubs/viewpub.asp?key=1987 [exit DNR]].