ABSTRACT
Physiological growth analyses can make significant contributions to sustainable forestry by mechanistically investigating the controls over net primary production in forest ecosystems (Landsberg and Gower, 1997). The success of these analyses relies on accurate measurement of physiological processes. Respiration in the woody tissue of forest trees can consume up to 33% of annual net daytime carbon assimilation (Ryan et al., 1994). Woody-tissue respiration can be measured in situ using removable cuvettes (Ryan, 1990; Sprugel, 1990; Sprugel and Benecke, 1991). However, questions regarding the use of such cuvettes have arisen. For example, it is important that the amount 108of woody-tissue contributing to a measurement is correctly determined, especially when one considers that stand level estimates of woody-tissue respiration are often based on measurements made over just a few square decimeters. The difficulty arises from the gasket material used to seal the cuvettes to tissue sections. Is the respiring tissue volume: (a) the portion between the interior edges of the gaskets, or (b) the portion between the gasket midpoints? The latter volume may exceed the former by more than 15%.
