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A generalized sigmoid growth function was used in this study to model site index (SI) for unmanaged or lowintensity managed loblolly pine (Pinus taeda, L.) and slash pine (Pinus elliottii, Engelm.) plantations in east Texas. Schnute's growth function was fit to 11 ,367 and 5,040 height-age observations of loblolly and slash pine, respectively. These data were collected over a 20-year period from unmanaged pine plantations located across the east Texas region as a part of the East Texas Pine Plantation Research Project (ETPPRP). The fit model was used to derive Sl equations (25-year index age). The Sl equations apply to unmanaged or low-intensity managed loblolly and slash pine plantations in east Texas ranging in age from 5 to 40 years. They can also serve as a baseline for Sl estimation of intensely managed pine plantations.


Coble, D. W., and Y. J. Lee. 2006. Use of a generalized sigmoid growth function to predict site index for unmanaged loblolly and slash pine plantations in east Texas. P. 291-295 .IN: Conner, K.F., ed. Proceedings of 13th Biennial Southern Silvicultural Research Conference. General Technical Rep. SRS-92. Ashville, NC: US Department of Agriculture, Forest Service, Southern Research Station. 640p.



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