Analyzing Transpiration in Replacement Trees Following Emerald Ash Borer Infestation

Abstract

The invasive emerald ash borer (Agrilus planipennis) poses an immediate threat to black ash (Fraxinus nigra) wetland forests across the U.S. Black ash is an important mediator of hydrological dynamics in such systems – they serve to lower the water table and prevent transition to cattail-dominated wetlands. Given their unique ecohydrological niche, black ash mortality via emerald ash borer stands to disrupt the hydrologic processes of these wetlands. This study aims to provide transpiration data on tree species that may potentially replace black ash to mitigate changes in the hydrology of these sites. This study employs Granier (1985) style thermal dissipation probes to measure sap flux density as it relates to transpiration. Transpiration was measured on black ash and several co-occurring tree species during the growing season. We found that black ash had sap flux rates similar to several other trees but, depending on the method used to calculate sap flux from raw data, the black ash transpiration may actually be much higher. The results from this study demonstrate the potential impact on hydrology from the loss of black ash but also the need for more intensive comparisons between black ash and potential replacement trees.