09 Oct 2023
 | 09 Oct 2023
Status: a revised version of this preprint is currently under review for the journal HESS.

Contrasting water use strategies of beech trees along two hillslopes with different slope and climate

Ginevra Fabiani, Julian Klaus, and Daniele Penna

Abstract. Understanding the interaction between topography and vegetation across different environments is important to assess how hydrological and climatic conditions affect tree physiological activity. This becomes especially important given the expected reduction in water availability and increase in water demand driven by climate change. These extremes could enhance the thermal and hydrologic gradients along slopes. Here, we aimed at testing if and how different climatic and hydrological conditions affect the physiological response to environmental variables of beech trees (Fagus sylvatica L.) along two different topographic sequences. For this purpose, we set up a comparative study on a gentle hillslope in the Weierbach catchment in Luxembourg (oceanic climate) and a steep hillslope in the Lecciona catchment in Italy (Mediterranean climate). We combined sap velocity measurements with isotopic measurements of soil, precipitation, stream water, groundwater, and xylem over 2019 and 2020 in the Luxembourgish site and 2021 in the Italian site. We found that in the Weierbach catchment, trees' response to environmental variables (i.e., vapour pressure deficit and relative extractable water in the soil) was similar among hillslope positions and between the two monitored years resulting from homogeneous growing conditions along the topographic sequence. We also did not find any statistical difference in the isotopic composition of xylem water among positions suggesting that beech trees relied on similar water sources across the landscape. In the Lecciona catchment, we observed lower sap velocities and shorter growing season in trees growing in the upper portions of the hillslope, likely related to water redistribution and different soil moisture along the hillslope catena. Xylem isotopic composition was significantly lighter at the footslope location throughout the growing season than in the upslope locations, suggesting location-specific water use. These results emphasize how differing hydrometeorological processes occurring at the hillslope scale can lead to contrasting tree performances.

Ginevra Fabiani, Julian Klaus, and Daniele Penna

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review of hess-2023-225', Conrad Jackisch, 06 Nov 2023
    • AC1: 'Reply on RC1', Ginevra Fabiani, 17 Nov 2023
  • RC2: 'Comment on hess-2023-225', Anonymous Referee #2, 06 Nov 2023
    • AC2: 'Reply on RC2', Ginevra Fabiani, 17 Nov 2023
Ginevra Fabiani, Julian Klaus, and Daniele Penna

Data sets

STEP UP project: the Weierbach dataset 2019-2020 Ginevra Fabiani, Remy Schoppach, Adnan Moussa, Laurent Pfister, Daniele Penna, and Julian Klaus

STEP UP project: the Lecciona dataset 2021 Ginevra Fabiani, Matteo Verdone, Francesca Sofia Manca di Villahermosa, Laurent Pfister, Julian Klaus, and Daniele Penna

Ginevra Fabiani, Julian Klaus, and Daniele Penna


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Short summary
There is a limited understanding of the role that topography and climate play in tree water use. Through a cross-site comparison in Luxembourg and Italy, we investigated beech water use along slopes in different climates. Our findings indicate that in landscapes characterized by stronger hydraulic and climatic gradients there is greater spatial variation in tree physiological responses. This highlights how differing growing conditions across landscapes can lead to contrasting tree performances.