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Harvard Forest Symposium Abstract 2019

  • Title: Ribbonized Sap Flux: A new integrated sap flow sensor platform
  • Primary Author: Joy Winbourne (Boston University)
  • Additional Authors: Lucy Hutyra (Boston University); Taylor Jones (Not specified)
  • Abstract:

    Sap flux sensors that are accurate, inexpensive, robust, and easy to calibrate are essential to the development of large-scale experiments that quantify transpiration and carbon exchange, and scale tree-level responses to the regional and landscape. The rate of sap flow in plants is strongly coupled to rates of transpiration, photosynthesis and carbon flux in ecosystems. Quantifying sap flux is therefore key to understanding the mechanistic drivers on water and carbon flux of trees, helping to inform landscape management decisions and predict ecosystem responses to global change. Here we present a new sap flow sensor design where all sensor components are on a single circuit board, or ribbon, thereby eliminating misalignment errors while also providing several advancements in the quantification of sap flux. We tested our ribbon sap flow (RSF) probe design with three experiments. First, we tested the reliability of the system over time. Second, the performance across four tree species each with different wood anatomy and radial sapwood velocity profiles. Lastly, we simultaneously compared the RSF with the commonly used thermal dissipation method to assess relative accuracy and the tree's wound response.Collectively, our experiments demonstrated the new RSF sensor produced reliable temporal data, capturing changes with wood anatomy and sapwood depth. The RSF showed good correspondence with the TD sensor (R2=0.82) with a high signal-to-noise ratio (>10). Our assessment of the wounding response suggests a systematic effect similar to that of other systems. The novel construction and installation method for the RSF sensor addresses major issues associated with common sensor designs. The RSF is a calibratable sensor that eliminates errors due to misalignment common to previous designs using a heat pulse method, while also being easily mass produced and installed. The overall design is compact, robust, and versatile. RSF sensors allows for a dense network of observations facilitating the study of forest ecosystem function and response to global change. In addition to its ability to measure sap velocities, the RSF sensor also represents a new 2-dimensional platform for the deployment of other types of electronic, electromechanical, and electrochemical sensors at various depths in the sapwood of trees.

  • Research Category: Forest-Atmosphere Exchange