Seasonal Fluctuations In Tree Water Sourcing At H.J. Andrews Experimental Forest
Jarvis, Stephanie K 1 ; Barnard, Holly 2 ; Singah, Kamini 3
1 INSTAAR
2 INSTAAR
3 Colorado School of Mines
The model of ecohydrological separation suggests that trees source water from a different subsurface pool than what is contributing to stream flow during dry periods, however diel fluctuations in stream flow and transpiration are tightly coupled. To better understand the mechanism of this coupling, this study examines seasonal patterns in water isotopic relationships between tree, soil, and stream water in a watershed where ecohydrologic separation has been shown to exist. Stream, soil, and tree water samples were collected for isotopic analysis from H.J. Andrews Experimental Forest in Oregon in 2016, an exceptionally wet year, and 2017, a very dry year. A mixing model is used to analyze source water for trees, which is found to change seasonally with drying conditions.