MEASUREMENT OF SAP FLOW IN AGATHIS BORNEENSIS (ARAUCARIACEAE) WITH DEEP SAPWOOD

Abstract

A quarter section of trunk was removed to enable implanting of probes along the full stemwood radius of Agathis borneensis, which does not form dark wood. Sap flow measured by the heat pulse velocity technique was found to occur at depths of at least 120 mm into the stemwood. Mean daily daytime sap flow in this species exceeded 500 kg d^-1 m^-2 (stem cross-sectional area) and was substantially greater than typical rates measured on four emergent trees in dipterocarp forest. High water use by A. borneensis necessitates deep rooting in this species and may negatively affect other tree species during drought.