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    Author(s): Dehai Zhao; Michael Kane; Daniel Markewitz; Robert Teskey
    Date: 2015
    Source: In: Stanton, Sharon M.; Christensen, Glenn A., comps. 2015. Pushing boundaries: new directions in inventory techniques and applications: Forest Inventory and Analysis (FIA) symposium 2015. 2015 December 8–10; Portland, Oregon. Gen. Tech. Rep. PNW-GTR-931. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station: 36-38.
    Publication Series: General Technical Report (GTR)
    Station: Pacific Northwest Research Station
    PDF: View PDF  (322.0 KB)

    Description

    The conversion factors (CFs) or expansion factors (EFs) are often used to convert volume to green or dry weight, or from one component biomass to estimate total biomass or other component biomass. These factors might be inferred from the previously developed biomass and volume equations with or without destructive sampling data. However, how the factors are related to tree size such as DBH, height or tree volume had not been examined. Using the tape and biomass measurement data of about 2000 destructively sampled loblolly pine trees, we developed several nonlinear equations to relate ratios between stem green/dry weights and stem volume to DBH and height, or tree volume. We also developed tree fractional biomass component equations with the Dirichlet regression and logratio regression approaches. These two approaches guarantee all component proportions sum to 1, and have almost the same performance. The ratios are functions of tree size and can be better estimated by DBH and HT than by stem volume.
    The conversion factors (CFs) and expansion factors (EFs) are commonly used to convert tree volume to green and dry weights or from one component or total biomass to other components. These factors are usually derived from previously developed biomass and/or volume equations. How the factors are related to tree size had not been formally tested. Traditionally, separate tree fractional biomass component equations were developed, but this approach cannot hold the constraint that all component proportions sum to one. Using loblolly pine expanded datasets and new modeling approaches, in the study we developed a series of ratio equations for: (1) ratio of stem total green weight to total outside volume, (2) ratio of stem-wood dry weight to total outside volume, (3) proportions of stem-wood and bark in stem biomass, and (4) proportions of stem-wood, bark, branch, and foliage components in total tree aboveground biomass. We also compared two new modeling approaches.

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    Citation

    Zhao, Dehai; Kane, Michael; Markewitz, Daniel; Teskey, Robert. 2015. Ratio equations for loblolly pine trees. In: Stanton, Sharon M.; Christensen, Glenn A., comps. 2015. Pushing boundaries: new directions in inventory techniques and applications: Forest Inventory and Analysis (FIA) symposium 2015. 2015 December 8–10; Portland, Oregon. Gen. Tech. Rep. PNW-GTR-931. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station: 36-38.

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