A STAND-LEVEL MODES OF CARBON ALLOCATION AND GROWTH, CALIBRATED FOR LOBLOLLY-PINE

A stand-level model of carbon allocation and growth (Pipestem) is form ulated as a set of differential equations that contain explicit parame trizations of annual rates of (i) production of photosynthate, (ii) dr y-matter production, constructive respiration, and maintenance respira tion of foliage, feeder roots, and live wood, (iii) foliage and feeder -root turnover, and (iv) loss of woody tissue to crown rise and self-t hinning. The allocation of carbon is consistent with pipe-model theory . The model describes temporal changes in the carbon balance, the prod uction, loss, and standing crop of dry matter, the stem density, and s tand summary variables including stand basal area, average height, and average crown length. Pipestem is linked to a steady-state, carbon-fl ux model in order to gauge the effects, on stand growth, of weather an d other environmental factors that operate on short temporal scales. A nalyses of the linked model, with parameter values set for loblolly pi ne (Pinus taeda L.), indicate that rates of production and loss of dry matter become more sensitive to environmental influences as a stand a ges and the consumption of carbon substrate for maintenance respiratio n increases.