Carbon Storage Calculations and Species Map

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Carbon Storage Calculations and Species Map

Post by Erika.Teach » Wed Jan 24, 2018 10:17 am

Carbon storage calculations and species map for i-Tree tools can be found at this link [ ... esMap.xlsx]. The spread sheet at that link contains carbon storage calculations and variables used in the underlying modeling code of the i-Tree tools, and shows which tree species there are equations for. The equations come from literature on various tree species. Background information and methods can be found for the various i-Tree tools on the Resources – Archives pages [].
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Re: Carbon Storage Calculations and Species Map

Post by aaronkingsley » Tue Jul 16, 2019 12:54 pm

I'd like to know more about the carbon storage calculations (I'm running Davey Treekeeper 8), but the link says the page no longer exists. Specifically, I'd like to know more about the methodology for the carbon storage calculations.


Aaron Sawatsky Kingsley
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Joined: Fri Feb 12, 2016 2:59 pm

Re: Carbon Storage Calculations and Species Map

Post by Erika.Teach » Tue Jul 16, 2019 6:35 pm

Hi Aaron,

We recently redid the i-Tree website, some of the docs may not of made the crossover. The documents with the carbon calculations are attached. Additional information about methods can be found here: ... -resources

A document titled, Understanding i-Tree is in draft phase. Below is the excerpt concerning carbon storage and sequestration:

This section relates to estimating total carbon storage in trees, annual carbon sequestration and emission of carbon via tree decomposition.
Required user inputs:
Tree species
Tree height
Crown dieback
Crown light exposure
Location (city)

Methods Overview
Tree biomass (see above) is converted to carbon storage by multiplying biomass by 0.5 (Chow and Rolfe 1989). To estimate annual carbon sequestration, the tree dbh is increased based on an estimated annual growth rate. The carbon storage in the current year (year 0) is then contrasted with carbon storage in the next year (year 1) to estimate the annual sequestration. Annual growth rates vary by: a) location depending upon frost free period, b) tree condition with trees in poor health growing slower than healthy trees, and c) crown competition with trees in highly competed sites (e.g., forest stands) growing slower than open grown trees.
An estimation of the amount of carbon lost due to more rapid carbon release (e.g., mulching, burning) and delayed release (e.g., decomposition) is calculated and contributes to net sequestration. Estimated carbon lost annually is subtracted from gross sequestration to produce net sequestration estimates. To estimate carbon release, various assumption were made related to probability of mortality, probability of recording a dead trees, and decomposition rates. More detailed information on storage, gross and net sequestration, and tree growth can be found in Nowak et al. (2002b, 2008).
Economic Valuation
Carbon valuation is based on the social cost of carbon as reported by the Interagency Working Group on Social Cost of Carbon (2015). Social cost associated with a pollutant (e.g. CO2) refers to an estimate of total (global) economic damage attributable to incremental increase in the level of that particular pollutant in a given year. The current value (in 2015) is $39 per metric ton of CO2 based on a three percent discount rate (Interagency Working Group 2015). Users can adjust this value to other values, if they so desire, by taking a ratio of the desired value (DR) per tonne CO2 to the $39/tonne CO2 (updated value = i-Tree reported value x DR/39).

Advantages, Uncertainties and Limitations
The advantages and limitations associated with carbon storage estimates are the same as with tree biomass estimates (provided earlier) as carbon storage is
directly related to biomass. Overall the storage estimates are reasonable and the standardized values per unit tree cover are comparable to estimates for US forests and from other cities around the world (Nowak et al. 2013b). National estimates of urban forest carbon storage and sequestration have been through the years using this procedure (Nowak 1993; Nowak and Crane 2002; Nowak et al. 2013b). Estimates of storage could be improved with additional biomass equations (see planned future improvements below), specifically biomass equations developed for urban conditions.
Estimates of gross carbon sequestration are dependent upon good biomass and tree growth equations. Growth rates for urban trees will range between 0 in/yr (dead trees) to 0.79 in/yr for open-grown healthy trees in areas with no frost. Estimated growth rates are average rates where rates of individual trees may be higher or lower than the estimated class average. These average growth rates are within range for measured urban and forest tree growth (e.g., Smith and Shifley 1984; Fleming 1988; Frelich 1992; deVries 1987; Nowak 1994a; Wood 2010). There is currently no differentiation of growth among species. That is, trees with the same dbh, condition and competition factors in the same location will have the same growth rates. Differentiation by species is to be added to help separate out slow vs. fast growing species (see planned future improvements below).
Net sequestration is based on gross sequestration minus losses due to decomposition. The decomposition estimate are quite rudimentary and are based on various assumptions of mortality and decomposition rates. Improved research on decomposition rates, how wood is decomposed (e.g., burn, mulch, natural decomposition) and mortality rates for urban trees would greatly enhance the net sequestration estimates.

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