Title: FIA's volume-to-biomass conversion method (CRM) generally underestimates biomass in comparison to published equations
Author: Chojnacky, David. C.;
Source: In: Morin, Randall S.; Liknes, Greg C., comps. Moving from status to trends: Forest Inventory and Analysis (FIA) symposium 2012; 2012 December 4-6; Baltimore, MD. Gen. Tech. Rep. NRS-P-105. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. [CD-ROM]: 396-402.
Publication Series: Paper (invited, offered, keynote)
Description: An update of the Jenkins et al. (2003) biomass estimation equations for North American tree species resulted in 35 generalized equations developed from published equations. These 35 equations, which predict aboveground biomass of individual species grouped according to a taxa classification (based on genus or family and sometimes specific gravity), generally predicted higher biomass than estimates from the U.S. Department of Agriculture, Forest Service Forest Inventory and Analysis Program (FIA). FIA uses a conversion approach called the component ratio method (CRM) (Woodall et al. 2011) to generate biomass estimates. This method converts cubic volume estimates to biomass using constant specific gravity values and auxiliary information for branches, bark, and stumps. FIA tree biomass data were grouped by the same taxa as used for the 35 equations, biomass for the same trees was also predicted with the equations, and then diameter-class averaged values were compared. FIA estimates excluded foliage, but the amount of biomass by which the equation predictions exceeded FIA’s estimates generally suggested more than a foliage discrepancy. The equations predicted 2 to 28 percent higher biomass (at 30-cm d.b.h.) for most conifer and hardwood taxa. Exceptions were Larix and western Tsuga genera which predicted 10 to 12 percent lower for trees at 30-cm d.b.h. Equations for woodland taxa predicted biomass 45 to 53 percent higher than FIA estimates (at 30-cm d.r.c.) but FIA’s woodland biomass definition may have confounded comparison. In a similar study, Zhou et al. (2011) found that a volume-to-biomass conversion method (resembling FIA’s approach) underestimated biomass by 6.3 to16.6 percent--supporting the idea that CRM may inherently underestimate biomass.
Keywords: statistics, estimation, sampling, modeling, remote sensing, forest health, data integrity, environmental monitoring, cover estimation, international forest monitoring
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Chojnacky, David. C. 2012. FIA's volume-to-biomass conversion method (CRM) generally underestimates biomass in comparison to published equations. In: Morin, Randall S.; Liknes, Greg C., comps. Moving from status to trends: Forest Inventory and Analysis (FIA) symposium 2012; 2012 December 4-6; Baltimore, MD. Gen. Tech. Rep. NRS-P-105. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. [CD-ROM]: 396-402.
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