Comparing Sapflow Methods Granier vs Heat Ratio Clarissa

Comparing Sapflow Methods: Granier vs. Heat Ratio Clarissa Lyons (Smith College 2013) Kate Bussell (Transylvania University 2012)

Motivation Slide courtesy of Matt Green

Forest Water Balance

Intro, cont. Two different methods are being employed in the MELNHE plots: the Granier method and the heat ratio method (HRM) Heat-based sapflow techniques are the most widely used methods for sapflow measurement

Heat Ratio Method An improvement of the compensation heat pulse method by Burgess et al. (2001) Method being used by researchers at UNH, led by Heidi Asbjornsen Measures the ratio of the increase in temperature at points equidistant from the line heater following the release of a heat pulse

Below: Thermocouple placement within sensor Sapflow tree in Bartlett Experimental Forest (C 8)

Granier Method Developed by André Granier in 1985 Method used by Dr. Michele Pruyn and team from PSU Constant heat source Sapflow calculated from difference in temperature between two thermocouples

Comparison Results Sugar Maple 1 40 35 Sapflow (g/m 2/s) 30 25 20 Heat Ratio Method 15 Granier Method 10 5 0 228 230 232 234 236 Ordinal Date and Time 238 240

Results, cont. Sugar Maple 2 120 Sapflow (g/m 2/s) 100 80 60 Heat Ratio Method 40 Granier Method 20 0 228 230 232 234 236 Ordinal Date and Time 238 240

Special Thanks to Our Contributors Dr. Michele Pruyn, Assistant Professor of Plant Biology, Plymouth State University Adan Hernandez, Graduate Student, University of New Hampshire Dr. Heidi Asbjornsen, Associate Professor of Ecosystem Ecology, University of New Hampshire Dr. Ruth Yanai, Professor of Forest and Natural Resources Management, SUNY ESF Craig See, Master’s Student, SUNY ESF Mark Green, Assistant Professor of Hydrology, Plymouth State University

References Burgess, S. O. et al. (2001). An improved heat pulse method to measure low and reverse rates of sap flow in woody plants. Tree Physiology, 21, 589 -598. Granier, A. et al. (1996). Transpiration of trees and forest stands: short and long-term monitoring using sapflow methods. Global Change Biology, 2, 265 -274. Granier, A. et al. (1987). Evaluation of transpiration in a Douglas-fir stand by means of sap flow measurements. Tree Physiology, 3, 309 -320. Kostner, B. et al. (1998). Sapflow measurements in forest stands: methods & uncertainties. Annals of Forest Science, 55, 13 -27.