Estimation of the net primary productivity of even-aged stands with a carbon-allocation model

The estimation of the time-course of net primary productivity (NPP) is of general ecological interest. Solutions of Pipestem, a model of carbon allocation and growth, show a waxing and waning of NPP in even-aged stands of Pinus taeda between establishment and maturity. Peak productivity occurs at the time of stand closure. Estimation of NPP is inextricably linked with estimation of the production and loss of components of dry matter (foliage, feeder roots, and woody tissues). The fraction of available carbon allocated to the production of each of these components varies considerably over the course of stand development. Analyses also indicate that the increasing concentration of atmospheric CO2 is elevating the NPP of stands of P. taeda.