This page last reviewed January 4, 2017

Compliance Offset Protocol U.S. Forest Offset Projects

The Assessment Area Data File contains the following: 

The Assessment Area Data File component description is applicable to projects in all eligible states.

Supersections are geographical units that contain from 1-6 Assessment Areas.  Supersections were generated from individual or combined Ecosections established by the U.S. Forest Service based on generalized forest communities1.  Supersections were established to allow for stratification of plots into high and low site class while maintaining or increasing the statistical reliability of the Common Practice estimates derived for each Assessment Area.  Within each Supersection, Assessment Areas were defined based on key drivers that influence forest carbon stocks.  These drivers include common forest vegetation, common jurisdictional and regulatory influences, and common economic influences.

Assessment Area2
Assessment areas are used to provide standardized regional data for offset project development.  An Assessment Area is a forest community within a defined geographical unit, it is a grouping of forest tree species that coexist within an Ecosection3, or combined Ecosections referred to as Supersections.

  • Associated Species: A grouping of native forest tree species that coexist within the Assessment Area. 
  • Common Practice: A Common Practice statistic is used to carry out calculations required in Section 6.2 of the Protocol.  Common Practice is the average carbon stocks in metric tons of the above ground portion of live trees on private lands resulting from a suite of management activities within that Assessment Area.  Used as an input to establish the baseline for IFM projects.
  • Species Diversity Index: The maximum allowable percentage of any one native species within the Project Area (by basal area or stems per acre, depending on project type)4.  Used to determine conformance with the Native Species and Composition of Native Species requirements in Table 3.2.
  • Rotation Length: Standard rotation age for the project’s Assessment Area (e.g. long, short). Used to determine whether a project meets eligibility requirements for a Reforestation Project.
  • Value of Harvest: Classification of the relative value of harvested wood products associated with the Assessment Area (high, low).  Used as an input for the financial test employed to assess the eligibility of Reforestation projects.
  • Harvested Woods Products Generated (HWP tab found behind assessment area Data File). Breakdown of wood products generated within each Supersection by generalized category (e.g. softwood lumber, plywood, non-structural panels, etc.).  Used as an input to determine the average carbon storage in in-use wood products over 100 years.

[1] Forest communities are based on Bailey (1994). Ecosections are based on McNab (2007).  A Forest Service website describing the work and where data can be downloaded is found here:
[2] The U.S. Forest Service Forest Inventory and Analysis Program (FIA) is the basis for development of assessment areas.  The FIA program collects data on U.S. forests using an extensive array of coordinated sample plots throughout the nation.  Together the plots comprise a national inventory system designed to assess the state of U.S. forests on an ongoing basis.  The hierarchical and spatial nature of FIA data make it possible to group sample field plots by geographical location.  FIA plots are assigned an attribute referred to as ‘forest type’ that identifies the dominant vegetation present at the plot.  Forest Types were combined by the Reserve into forest communities.
[4] FIA plots contain a variable referred to as “Forest Type” and it is this variable that indicates the dominant species present on each plot.  The range of Forest Types within an Assessment Area provides the basis for identifying the species diversity present within an Assessment Area.  Some Assessment Areas have many Forest Types within an Assessment Area while others may be limited to two Forest Types.

Bailey, R. G.; Avers, P. E.; King, T.; McNab, W. H., eds. 1994. Ecoregions and subregions of the United States (map). Washington, DC: USDA Forest Service. 1:7,500,000. With supplementary table of map unit descriptions, compiled and edited by W. H. McNab and R. G. Bailey.

Forest Inventory and Analysis.  2009.  Appendix J.  In: DRAFT FIA Database Description and Users Manual for Phase 2, version 4.0, revision 2.  U.S. Department of Agriculture, Forest Service.

Heath, Linda S.; Hansen, Mark; Smith, James E.; Miles, Patrick D.; Smith, Brad W.  2009.  Investigation into calculating tree biomass and carbon in the FIADB using a biomass expansion factor approach.  In: McWilliams, Will; Moisen, Gretchen; Czaplewski, Ray, comps. 2009. 2008 Forest Inventory and Analysis (FIA) Symposium; October 21-23, 2008; Park City, UT. Proc. RMRS-P-56CD. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 26 p.

McNab, W.H.; Cleland, D.T.; Freeouf, J.A.; Keys, Jr., J.E.; Nowacki, G.J.; Carpenter, C.A., comps. 2007. Description of ecological subregions: sections of the conterminous United States [CD-ROM]. Gen. Tech. Report WO-76B. Washington, DC: U.S. Department of Agriculture, Forest Service. 80 p.

For questions or comments regarding the U.S. Forest Protocol please contact

Barbara Bamberger at 916-324-2303 or e-mail