[Insert Fig. 9 here]
4.3 Misalignment correction
Misalignment of probes is a major source of uncertainty for heat-pulse techniques. It affects all methods and can bias inferred sap velocity either positively or negatively. Burgess et al. (2001) suggested three options to correct for misalignment in the HRM: forcing the calculated sap velocity to equal zero under conditions when the true sap velocity is known to be zero (e.g., after an extended period at 100% RH), by correcting either the upstream (x 1) or downstream (x 2) probe locations, or by averaging both of the resulting corrected values, assuming misalignment for either probe is equally likely (∆x 1=∆x 2, where ∆xi is the misalignment correction for Probe # i ). While all three methods result in matched calculated and measured sap velocities under ”zero-flow” conditions, they do not yield consistent day-time sap velocities (Fig. 10 ).