Estimating tree canopy water use via xylem sapflow in an old Norway spruce forest and a comparison with simulation-based canopy transpiration estimates Barbara Köstner, Eva M. Falge, Martina Alsheimer, Ralf Geyer and John D. TenhunenAnn. For. Sci., 55 1-2 (1998) 125-139DOI: https://doi.org/10.1051/forest:19980108