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 (C8)

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

229 230 231 232 233 234 235 236 237 238 2390

5

10

15

20

25

30

35

40Sugar Maple 1

Heat Ratio MethodGranier Method

Ordinal Date and Time

Sap

flow

(g

/m2

/s)

Comparison Results

229 230 231 232 233 234 235 236 237 238 2390

2

4

6

8

10

12 Sugar Maple 2

Heat Ratio MethodGranier Method

Ordinal Date and Time

Sap

flow

(g

/m2

/s)

Results, cont.

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.