Evaluating the influence of wood water content under no flow conditions for trees among isohydric and anisohydric species.

Abstract:

The hydraulic performance of woody species plays an important role for productivity and survival of trees. Sap flux (SF) measurements are the most common individual-scale measurements used as a proxy for transpiration (T) through the conservation of mass. While multiple thermotracer sensor types exist, the most broadly used are Granier-style thermal dissipation sensors. Beginning in 2014, work at University of Michigan Biological Station (UMBS) pioneered the use of capacitance sensors to monitor wood water content (WWC) continuously in mature trees. This unique data set has been used to demonstrate the key role that stem-stored water, or the trees’ hydraulic capacitance, plays in buffering T against water stress. These studies proved an existing relationship for Acer rubrum and Quercus rubra stem water storage and water use consistent with their wood densities and respective isohydric and anisohydric hydraulic strategies. Moreover, there is mounting evidence that variation in wood water content influences the nocturnal maximum temperature (T_max) baseline of thermal dissipation probes affecting SF readings in thermal dissipation sensors. We pair measurements of WWC with SF observations made using traditional thermal dissipation probes in a mixed forest at UMBS. Our study aims to (i) evaluate the difference in the dynamics of the response of T_max to WWC for the canopy dominant species at the site (ii) demonstrate the species-specific influence of wood moisture content on the T_max baseline and suggest its applicability as a correction factor for long-term sap flux datasets.