3-Point Derivation of Dominant Tree Height Equations

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#1)  3-Point Derivation of Dominant Tree Height Equations

Postby DonCBragg » Sat Mar 31, 2012 3:54 pm

               
                       
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A 3-Point Derivation of Dominant Tree Height Equations
by Don C. Bragg, In: Fei, Songlin; Lhotka, John M.; Stringer, Jeffrey W.; Gottschalk, Kurt W.; Miller, Gary W., eds. 2011. Proceedings, 17th Central Hardwood Forest Conference; 2010 April 5-7; Lexington, KY; Gen. Tech. Rep. NRS-P-78. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 678 p. CD-ROM. pp. 41-50.

http://www.nativetreesociety.org/specialreports/bragg/Bragg2011A.pdf

               
                       
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Abstract.—Th is paper describes a new approach for deriving height-diameter (H-D) equations from limited information and a few assumptions about tree height. Only three data points are required to fi t this model, which can be based on virtually any nonlinear function. These points are the height of a tree at diameter at breast height (d.b.h.), the predicted height of a 10-inch d.b.h. tree from an existing H-D model, and the height at species maximum d.b.h., estimated from a linear regression of big trees. Dominant sweetgum (Liquidambar styraciflua L.) from the Arkansas region and yellow-poplar (Liriodendron tulipifera L.) from across the southeastern United States were used to estimate height at species maximum d.b.h. A composite of these field-measured heights and site index trees from the U.S. Forest Service’s Forest Inventory and Analysis (FIA) database were used to compare the 3-point equations (fi t to the Chapman-Richards model) with the Forest Vegetation Simulator (FVS) default H-D models. Because of the limited range of diameters in the FIA site trees, the Chapman-Richards equations developed from site trees underpredicted large tree heights for both species. For the sweetgum, the 3-point equation was virtually identical to the FVS default model. However, the 3-point equation noticeably improved dominant height predictions for yellow-poplar.

Available for download as part of the Native Tree Society Special Publication Series: NTS SP #21

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#2)  Re: 3-Point Derivation of Dominant Tree Height Equations

Postby gjschmidt » Thu Oct 22, 2015 6:55 pm

I have just seen this paper. Do you think that your new equations will change how forest growth is simulated by the Forest Service? Will there be an update to the site index curves?   I also wonder whether there shouldn't be two parameters for "site index" rather than one (one for initial growth rate - based on productivity, the other for maximum height potential - based on exposure to dry air as well as structural limits of the species).
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#3)  Re: 3-Point Derivation of Dominant Tree Height Equations

Postby DonCBragg » Wed Nov 04, 2015 7:25 pm

I'm not sure this will have much impact on how forest growth is simulated by the Forest Service...This paper was more intended as a alternative way to derive height curves using information from a range of tree sizes.  Site index curves are generally derived for simplicity of use, rather than to describe the complexity of the process of height growth over time...
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