Effect of the span length of Granier-type thermal dissipation probes on sap flux density measurements |
| |
Authors: | Shin’ichi Iida Tadashi Tanaka |
| |
Affiliation: | 1. Department of Soil and Water Conservation, Forestry and Forest Products Research Institute, 305-8687, Ibaraki, Japan 2. Graduate School of Life and Environmental Sciences, University of Tsukuba, 305-8572, Ibaraki, Japan
|
| |
Abstract: | ? Granier-type thermal dissipation sensors measure sap flux density (u) by using the temperature difference between the heater and the reference probe. To detect u correctly, heat must not be transferred to the reference probe by thermal conduction. The distance across which heat can be transferred by conduction is important for the span length of a sensor and spacing of a number of sensors. ? To validate span lengths and spacing of sensors, we used numerical simulations to calculate the potential distance across which heat can be transferred by conduction. We compared measurements with an original and a modified sensor for a Japanese red pine (Pinus densiflora) from December 2004 to May 2005. The span length of the original and the modified sensor is 15 and 4 cm, respectively. ? Numerical simulations showed that span length and spacing of Granier sensors should be more than 10 cm for trees in which u ceases for a few hours before the predawn period. The modified sensor underestimated u by 18–46% in winter (December–March) because its reference temperature was increased by heat transferred by conduction. The modified sensor measured u correctly in warm seasons, and only underestimated the annual amount of transpiration by 6%. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|