15 Mar 2022
15 Mar 2022
Status: this preprint is open for discussion.

Water Use Strategy of Riparian Conifers Varies with Tree Size and Depends on Coordination of Water Uptake Depth and Internal Tree Water Storage

Kevin Li and James Knighton Kevin Li and James Knighton
  • Department of Natural Resources and the Environment, University of Connecticut, Storrs CT, 06269, U.S.A.

Abstract. Trees employ mechanisms to maintain safe xylem water transport including variations in trunk water storage and the depth of root water uptake. We tested the hypotheses that 1) trunk water storage is correlated with root water uptake in Eastern hemlock, 2) and that water use strategy varies with tree size. High spatiotemporal sampling of soil and hemlock xylem (30 trees) water isotopic ratios (2H, 18O) and tree tissue Relative Water Content (RWC) was conducted across seven months. Hemlock accessing more evaporatively enriched water from shallow soils stored less water within their trunks during dry periods, and more during wet periods. Soil and xylem water isotopic compositions revealed older and lower elevation hemlock primarily sourced water uptake from the upper 10 cm of soils, whereas younger and higher elevation trees sourced some water uptake from deeper soil layers. Larger diameter hemlock showed significant temporal changes in trunk RWC. In contrast, smaller diameter trees exhibited more temporally stable RWC. Observed species-level heterogeneity in xylem water isotope composition suggests the need for reporting of tree ages and a standardization of field sampling protocols to support our understanding of tree water use strategies. Our results inform the development of plant hydraulic strategies in ecohydrological- and terrestrial biosphere-models to understand forest responses to external stressors.

Kevin Li and James Knighton

Status: open (until 10 May 2022)

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Kevin Li and James Knighton

Data sets

Fenton Tract Research Forest - Hydrologic Data James Knighton

Kevin Li and James Knighton

Metrics will be available soon.
Latest update: 03 Apr 2022
Short summary
We utilized xylem water isotopic compositions (a non-reactive tracer) to evaluate the possibility of within-species variation in tree water use strategy, which is assumed to be minimal. Results show significant coordination between trunk water storage and depth of root water uptake across riparian conifers, and that these mechanisms vary with tree age and elevation. Species-level variability may be an important consideration for understanding how forests respond to external stressors.