SREL Reprint #3691

Interspecific variation in the timing and magnitude of hydraulic redistribution in a forest with distinct water sources

Michael Belovitch1,2,3,4, Steven Brantley3, and Doug P. Aubrey1,2

1Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA
2Savannah River Ecology Laboratory, University of Georgia, Aiken, SC 29802, USA
3The Jones Center at Ichauway, Newton, GA 39870, USA
4Odum School of Ecology, 140 East Green Street, Athens, GA 30602, USA

Abstract:
Aims: Trees regulate water availability among their rooting strata through a nocturnal, passive transference of water known as hydraulic redistribution (HR). This study investigates differences in HR and groundwater use among common canopy species in longleaf pine (Pinus palustris Mill., Pinaceae) woodlands and explores environmental factors influencing HR.
Methods: HR was estimated by sap flux of lateral roots and main stems of three mature canopy species (P. palustris, Quercus laevis Walter., Fagaceae and Quercus margarettae Ashe., Fagaceae). We used δ18O and δD of xylem water, soil water, and groundwater to determine water source. Finally, we related HR to environmental factors (Temperature, VWC, VPD) to better understand controls of HR dynamics.
Results: Pinus palustris had higher water use than either Quercus species, and also redistributed significantly more water as a nocturnal subsidy. HR fluxes were inversely related with mean nightly temperature and independent of shallow soil moisture. Stable isotope mixing models, based on δ18O and δD, indicated that all species have access to groundwater, but utilized shallow soil water in differing amounts when available.
Conclusions: In systems with strong water potential gradients among soil strata, any species with access to a groundwater source is likely capable of HR; however, the magnitude of HR varies significantly by species, even among closely related taxa.

Keywords: Hydraulic lift; δ18O; δD; Drought resistance; Root profile; Soil water content; Hydrologic niche; Groundwater use

SREL Reprint #3691

Belovitch, M., S. Brantley, and D. P. Aubrey. 2022. Interspecific variation in the timing and magnitude of hydraulic redistribution in a forest with distinct water sources. Plant and Soil 472(1-2): 451-464.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).