© 2001 Heron Publishing—Victoria, Canada
An improved heat pulse method to measure low and reverse rates of sap flow in woody plants
Stephen S. O. Burgess (1, 5), Mark A. Adams (1), Neil C. Turner (2), Craig R. Beverly (3), Chin K. Ong (4), Ahmed A. H. Khan (4) and Tim M. Bleby (1)
1. Department of Botany, University of Western Australia, Nedlands, WA, 6907, Australia / 2. CSIRO Plant Industry, Private Bag No. 5, Wembley, WA 6913, Australia / 3. Agriculture Victoria, DNRE Chiltern Valley Road, Rutherglen, VIC, 3685, Australia / 4. International Centre for Research in Agroforestry (ICRAF), PO Box 30677, Nairobi, Kenya / 5. Department of Integrative Biology, University of California, Berkeley, CA, 94720-3140, USA / Received May 26, 2000
Summary
The compensation heat pulse method (CHPM) is of limited value for measuring low rates of sap flow in woody plants. Recent
application of the CHPM to woody roots has further illustrated some of the constraints of this technique. Here we present
an improved heat pulse method, termed the heat ratio method (HRM), to measure low and reverse rates of sap flow in woody plants.
The HRM has several important advantages over the CHPM, including improved measurement range and resolution, protocols to
correct for physical and thermal errors in sensor deployment, and a simple linear function to describe wound effects. We describe
the theory and methodological protocols of the HRM, provide wound correction coefficients, and validate the reliability and
accuracy of the technique against gravimetric measurements of transpiration.
Keywords:
compensation method, heat pulse velocity, reverse flow, transpiration, water transport, water use, woody roots.
