Water status dynamics and drought tolerance of juvenile European beech, Douglas fir and Norway spruce trees as dependent on neighborhood and nitrogen supply

Sharath S Paligi; Jens Lichter; Martyna Kotowska; Rebecca L Schwutke; Michela Audisio; Klara Mrak; Alice Penanhoat; Bernhard Schuldt; Dietrich Hertel; Christoph Leuschner

doi:10.1093/treephys/tpae044

Water status dynamics and drought tolerance of juvenile European beech, Douglas fir and Norway spruce trees as dependent on neighborhood and nitrogen supply

Tree Physiol. 2024 Apr 25:tpae044. doi: 10.1093/treephys/tpae044. Online ahead of print.

Authors

Affiliations

¹ Plant Ecology and Ecosystems Research, Albrecht von Haller Institute for Plant Sciences, Untere Karspüle 2, University of Goettingen, Göttingen, Germany.
² Chair of Statistics, University of Goettingen, Humboldtallee 3, 37073 Göttingen, Germany.
³ School of Natural Sciences, Macquarie University, Sydney, Australia.
⁴ Forest Botany and Tree Physiology, University of Goettingen, Büsgenweg 2, D-37077 Göttingen, Germany.
⁵ Soil Science of Temperate Ecosystems, University of Goettingen, Büsgenweg 2, D-37077 Göttingen, Germany.
⁶ Department of Spatial Structures and Digitization of Forests, University of Göttingen, Büsgenweg 1, 37077 Göttingen, Germany.
⁷ Chair of Forest Botany, Institute of Forest Botany and Forest Zoology, Technical University of Dresden, Pienner Str. 7, 01737 Tharandt, Germany.
⁸ Centre for Biodiversity and Sustainable Land Use (CBL), University of Goettingen, 37075 Göttingen, Germany.

PMID: 38662576
DOI: 10.1093/treephys/tpae044

Abstract

To increase the resilience of forests to drought and other hazards, foresters are increasingly planting mixed stands. This requires knowledge about the drought response of tree species in pure- and mixed-culture neighborhoods. In addition, drought frequently interacts with continued atmospheric nitrogen (N) deposition. To disentangle these factors for European beech, Norway spruce and Douglas fir, we conducted a replicated three-factorial sapling growth experiment with three moisture levels, (high, medium and low), two N levels (high and ambient) and pure and mixed-culture neighborhoods. We measured biomass, stomatal conductance (GS), shoot water potential (at predawn: ΨPD, midday, and turgor loss point: ΨTLP), branch xylem embolism resistance (Ψ50), and minimum epidermal conductance (Gmin). The three species differed most with respect to Gmin (10-fold higher in beech than in the conifers), hydroscape area (larger in beech), and the time elapsed to reach stomatal closure (TΨGS90) and ΨTLP (TTLP; shorter in beech), while Ψ50 and ΨTLP were remarkably similar. Neighborhood (pure vs. mixed-culture) influenced biomass production, water status and hydraulic traits, notably GS (higher in Douglas fir, but lower in spruce and beech, in mixtures than pure culture), hydraulic safety margin (smaller for beech in mixtures), and TΨGS90 and TTLP (shorter for spruce in mixture). High N generally increased GS, but no consistent N effects on leaf water status and hydraulic traits were detected, suggesting that neighbor identity had a larger effect on plant water relations than N availability. We conclude that both tree neighborhood and N availability modulate the drought response of beech, spruce and Douglas fir. Species mixing can alleviate the drought stress of some species, but often by disadvantaging other species. Thus, our study suggests stabilizing and building resilience of production forests against a drier and warmer climate may depend primarily on the right species choice; species mixing can support the agenda.

Keywords: desiccation tolerance; embolism resistance; mixed forest; monoculture; three-factorial experiment; turgor loss point.