Allometric equations
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Allometric equations
Where i can find the allometric equations that iTree use about the tree growth?

 iTree Team
 Posts: 188
 Joined: Fri Dec 21, 2012 7:45 am
Re: Allometric equations
Hello Giacomo,
This may depend on which of the iTree Tools you are using. If you are using iTree Eco please see the section of this paper, http://www.itreetools.org/eco/resources ... ethods.pdf, titled "UFOREC: Carbon Storage and Annual Sequestration". iTree is not using species specific growth rates but rather general rates for species classified as fast, moderate, or slow growing. These three base rates are then adjusted up or down depending on measurements like the crown light exposure, annual frost free length, and current tree size relative to maximum.
Hope that information is helpful.
Jason
This may depend on which of the iTree Tools you are using. If you are using iTree Eco please see the section of this paper, http://www.itreetools.org/eco/resources ... ethods.pdf, titled "UFOREC: Carbon Storage and Annual Sequestration". iTree is not using species specific growth rates but rather general rates for species classified as fast, moderate, or slow growing. These three base rates are then adjusted up or down depending on measurements like the crown light exposure, annual frost free length, and current tree size relative to maximum.
Hope that information is helpful.
Jason
A member of the iTree Team
Re: Allometric equations
Hi Jason, that was really helpful.Jason.Henning wrote: ↑Thu Oct 24, 2019 1:19 pmHello Giacomo,
This may depend on which of the iTree Tools you are using. If you are using iTree Eco please see the section of this paper, http://www.itreetools.org/eco/resources ... ethods.pdf, titled "UFOREC: Carbon Storage and Annual Sequestration". iTree is not using species specific growth rates but rather general rates for species classified as fast, moderate, or slow growing. These three base rates are then adjusted up or down depending on measurements like the crown light exposure, annual frost free length, and current tree size relative to maximum.
Hope that information is helpful.
Jason
I I would like to ask one more thing, on the paper they talk about this: "The multiple equations used for individual species were combined together to produce one predictive equation for a wide range of diameters for individual species. The process of combining the individual formulas (with limited diameter ranges) into one, more general species formula, produced results that were typically within 2% of the original estimates for total carbon storage of the urban forest (i.e., the estimates using the multiple equations). Formulas were combined to prevent disjointed sequestration estimates that can occur when calculations switch between individual biomass equations"; but there's no reference about where i can find the equations that were created about every species.

 iTree Team
 Posts: 188
 Joined: Fri Dec 21, 2012 7:45 am
Re: Allometric equations
Hello Giacomo,
That paper references this document,
Nowak, D.J. 1994b. Atmospheric carbon dioxide reduction by Chicago’s urban forest. In: McPherson, E.G.; Nowak, D.J.; Rowntree, R.A., eds. Chicago's urban forest ecosystem: results of the Chicago Urban Forest Climate Project. Gen. Tech. Rep. NE186. Radnor, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station: 8394.
Which can be found through the US Forest Service archives, https://www.fs.usda.gov/treesearch/ or directly here, https://www.nrs.fs.fed.us/pubs/gtr/gtr_ne186.pdf. In chapter 6, page 85, please see table 1 which lists the biomass equations and provides references for each one. You will have to track down those references for the actual equations but many of them are also available in the US Forest Service, "Treesearch" archives.
Thanks,
Jason
That paper references this document,
Nowak, D.J. 1994b. Atmospheric carbon dioxide reduction by Chicago’s urban forest. In: McPherson, E.G.; Nowak, D.J.; Rowntree, R.A., eds. Chicago's urban forest ecosystem: results of the Chicago Urban Forest Climate Project. Gen. Tech. Rep. NE186. Radnor, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station: 8394.
Which can be found through the US Forest Service archives, https://www.fs.usda.gov/treesearch/ or directly here, https://www.nrs.fs.fed.us/pubs/gtr/gtr_ne186.pdf. In chapter 6, page 85, please see table 1 which lists the biomass equations and provides references for each one. You will have to track down those references for the actual equations but many of them are also available in the US Forest Service, "Treesearch" archives.
Thanks,
Jason
A member of the iTree Team
Re: Allometric equations
Thank you so much, Jason.Jason.Henning wrote: ↑Mon Oct 28, 2019 8:48 amHello Giacomo,
That paper references this document,
Nowak, D.J. 1994b. Atmospheric carbon dioxide reduction by Chicago’s urban forest. In: McPherson, E.G.; Nowak, D.J.; Rowntree, R.A., eds. Chicago's urban forest ecosystem: results of the Chicago Urban Forest Climate Project. Gen. Tech. Rep. NE186. Radnor, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station: 8394.
Which can be found through the US Forest Service archives, https://www.fs.usda.gov/treesearch/ or directly here, https://www.nrs.fs.fed.us/pubs/gtr/gtr_ne186.pdf. In chapter 6, page 85, please see table 1 which lists the biomass equations and provides references for each one. You will have to track down those references for the actual equations but many of them are also available in the US Forest Service, "Treesearch" archives.
Thanks,
Jason
I have a last question, on my study fild i have a bit of coppice tree, i can't understand how to add it to itreeeco6, because i just have the DBH of the biggest stem but every trees has like 10+ stem more or less of the same dimension; i need to add them alone like a single tree even if they are the same plant? or there's a way to make i treeeco knowing that they are coppice tree?
Thank you again for the help, u are really kind.

 iTree Team
 Posts: 188
 Joined: Fri Dec 21, 2012 7:45 am
Re: Allometric equations
Hello Giacomo,
Copice is not a common practice here in the US so iTree doesn't have a defined way to handle those trees. However, for multistem trees you can enter up to the 6 largest stems as DBH1 to DBH6. Alternatively, you could calculate the dbh of a tree that would have the same basal area as all stems combined. The formula for this is: combined DBH = square root (sum (DBHi^2)). Where DBHi will be your dbh values for each of the stems. This calculation is actually what iTree does when you enter multiple stems. You should get identical results with either approach for trees with up to 6 stems.
Thanks,
Jason
Copice is not a common practice here in the US so iTree doesn't have a defined way to handle those trees. However, for multistem trees you can enter up to the 6 largest stems as DBH1 to DBH6. Alternatively, you could calculate the dbh of a tree that would have the same basal area as all stems combined. The formula for this is: combined DBH = square root (sum (DBHi^2)). Where DBHi will be your dbh values for each of the stems. This calculation is actually what iTree does when you enter multiple stems. You should get identical results with either approach for trees with up to 6 stems.
Thanks,
Jason
A member of the iTree Team
Re: Allometric equations
Tnx a lot
Re: Allometric equations
Hello Jason, i follow your suggestion but i have some problem whit the Corylus avellana, because, in me study case, they have too much stems and is almost impossible to measure their DHB; do you have any advice? or i just exclude them? (the url is a photo similar to my trees).Jason.Henning wrote: ↑Mon Oct 28, 2019 10:31 amHello Giacomo,
Copice is not a common practice here in the US so iTree doesn't have a defined way to handle those trees. However, for multistem trees you can enter up to the 6 largest stems as DBH1 to DBH6. Alternatively, you could calculate the dbh of a tree that would have the same basal area as all stems combined. The formula for this is: combined DBH = square root (sum (DBHi^2)). Where DBHi will be your dbh values for each of the stems. This calculation is actually what iTree does when you enter multiple stems. You should get identical results with either approach for trees with up to 6 stems.
Thanks,
Jason
https://it.wikipedia.org/wiki/Corylus_a ... struik.jpg
Thanks,
Giacomo
Re: Allometric equations
Giacomo,
Given a bunch of stems, you can estimate the combined DBH by performing the following steps:
1. Take several measurements of the total width of all the stems from various sides.
2. Average the measurements from #1 to obtain the Average Width.
3. Compute the combined DBH using DBH = Sqrt[(1  % missing) * (Average Width)^2)] where % missing is your best estimate of the amount of area missing from a circle with a diameter of the Average Width determined in step 2.
Another option would be to compute the average DBH from measuring a few stems and then extrapolate the average based upon the total number of stems via:
1. Compute average stem DBH via avg_dbh = Sqrt[Sum(DBH_{i}^2) / n] where n is the number of stems measured and i is each individual stem from 1 to n.
2. Compute the combined DBH using DBH = sqrt[avg_dbh^2 * m] where m is the total number of stems
Neither of these methods are as accurate as having measured every stem, but they should at least get you close to the desired value.
Given a bunch of stems, you can estimate the combined DBH by performing the following steps:
1. Take several measurements of the total width of all the stems from various sides.
2. Average the measurements from #1 to obtain the Average Width.
3. Compute the combined DBH using DBH = Sqrt[(1  % missing) * (Average Width)^2)] where % missing is your best estimate of the amount of area missing from a circle with a diameter of the Average Width determined in step 2.
Another option would be to compute the average DBH from measuring a few stems and then extrapolate the average based upon the total number of stems via:
1. Compute average stem DBH via avg_dbh = Sqrt[Sum(DBH_{i}^2) / n] where n is the number of stems measured and i is each individual stem from 1 to n.
2. Compute the combined DBH using DBH = sqrt[avg_dbh^2 * m] where m is the total number of stems
Neither of these methods are as accurate as having measured every stem, but they should at least get you close to the desired value.