Comparing and evaluating ∆Tmax determination approaches for Granier-based sapflow estimations on different time scales (Inken Rabbel)

The water status of trees can be estimated using Granier-type thermal dissipation probes. However, the method requires determining the maximum temperature gradient (∆Tmax) between the heated probe and the reference probe below. By analyzing the effects of different ∆Tmax determination approaches on sapflow density estimations, the uncertainty of sapflow calculations, which is related to the raw signal processing, was quantified. In particular, empirical ∆Tmax approaches figure synthetic flows that (1) significantly raise absolute sapflow density estimations on all scales, (2) affect sub-daily and daily sapflow density dynamics, and (3) reduce data plausibility in terms of climate feedbacks on the daily scale.
Consequently, the choice of the ∆Tmax determination approach may be a significant source of uncertainty in Granier-based sapflow estimations.

Inken Rabbel won an ISHS student award for the best poster at the International Symposium on Sensing Plant Water Status – Methods and Applications in Horticultural Science in Germany in October 2016. The award encouraged her to continue her work on the comparison of ∆Tmax approaches, which resulted in a publication in the journal Sensors (Sensors 2016, 16 (12), 2042; doi: 10.3390/s16122042).

Contact
Inken Rabbel, Department of Geography, University of Bonn, Meckenheimer Allee 166, 53115 Bonn, Germany, e-mail: irabbel@uni-bonn.de