A paper about the comparison of several sap flow sensors, co-authored by Dirk De Pauw (Phyto-IT), was published in Agriculture and Forest Meteorology. A laboratory test and field evaluation were conducted to determine the accuracy of the three commonly used techniques for measuring sap flux density in trees: heat pulse velocity, thermal dissipation and heat field deformation. In the laboratory test a constant flow rate of water was maintained through freshly cut stem segments of diffuse-porous Fagus grandifolia trees. The three sensor types were measured simultaneously and compared against gravimetric measurements. All three techniques substantially underestimated sap flux density. It is concluded that a species-specific calibration is necessary when using any of these techniques to insure that accurate estimates of sap flux density are obtained, at least until a physical basis for an error correction can be proposed.

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A paper on the use of Phyto-IT’s Sap Flow Tool, co-authored by Dirk De Pauw (Phyto-IT), has been published. This work was presented at the 7th International Workshop on Sap Flow which which was held in Seville, Spain from October 21th-24th 2008. The paper deals with the measurement, calculation and analysis of radial sap flow profiles.

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A paper dealing with hydraulic redistribution in trees, co-authored by Dirk De Pauw (Phyto-IT), was published in New Phytologist. During a dry period, a 53-year-old Douglas-fir tree was subjected to localized irrigation on one side of the tree. This created heterogeneous soil water conditions which resulted in a stem-mediated hydraulic redistribution of the water to the other (non-irrigated) side of the tree. In addition, bidirectional flow in the dry root was also observed. This illustrates that water can simultaneously flow in opposite directions in the same part of a tree.

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A paper dealing with on-line plant stress monitoring, co-authored by Dirk De Pauw (Phyto-IT), was published today. Continuous monitoring of stem diameter variations combined with Unfold Principal Component Analysis (UPCA) allowed for successful on-line stress detection, days before the appearance of visible symptoms. The technique was applied successfully to two plant species: young apple trees and truss tomato plants.

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