Last modified 08/24/2007
Pipestem is a model of carbon allocation and growth that applies to even-aged, mono-specific stands of trees. A detailed description of Version 2 of the model can be found in Canadian Journal of Forest Research, 27:817-830 (1997). Pipestem has been calibrated for loblolly pine in Virginia and North Carolina.
Pipestem projects the growth and development of a model stand over time. The rate of growth of the model stand is defined as the difference between the rates of production and loss of dry matter. Dry matter is measured in units of carbon (C) and the rate of growth per unit land area is measured in units of C/ha/year. The rate of production of dry matter is defined as the difference between the rate of production of C substrate and the rate of consumption of C substrate through maintenance and constructive respiration. These metabolic rates also have dimensions of units of C/ha/year. Version 2.2 affords yearly adjustment of the rate of production of C substrate to account for the increasing concentration of atmospheric carbon dioxide.
Dry matter is divided into foliar, fine-root, and woody components. Carbon-allocation rules based on pipe-model theory are used to divide the dry-matter production into new foliar, fine-root, woody-root, and woody-stem tissue in proper proportions for functional balance. Losses of dry matter result from the turnover of foliage and fine roots, the death and self-pruning of branches associated with crown rise, and the death of trees associated with self-thinning. The latter two processes are driven by the production of dry matter. Version 2.2 affords the removal of dry matter through silvicultural thinning and pruning.
In addition to information about the carbon balance and the production of loss of dry matter, Pipestem also furnishes total basal area (m^2/ha), average tree height (m), average height to the base of a crown (m), and tree density (1/ha) on an annual basis. Estimates or measurements of these four variables (ordinarily obtained from a real stand of age one or older) suffice to initialize the model. Version 2.2 furnishes dominant tree height in addition to the other variables. Version 2.2 of Pipestem runs under Windows 95, NT, or later. The kernel of the model also is available as a Fortran subroutine for incorporation into other programs. The source code is in the download. Download Pipestem model (4,065 KB).
This is a self extracting zip file containing the folder "source code" and "program" and a readme.txt file. The "program" folder contains the program and the help file.
For related publications by the same author, please see: Harry T. Valentine