EGU21-8211, updated on 11 Jan 2022
https://doi.org/10.5194/egusphere-egu21-8211
EGU General Assembly 2021
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Apple trees, larches and their water uptake: distinct ecohydrological systems in contrasting environmental settings?

Stefano Brighenti1, Giacomo Bertoldi2, Agnese Aguzzoni1, Damiano Zanotellii1, Nikolaus Obojes2, Massimo Tagliavini1, Giulia Zuecco3, Marco Borga3, Daniele Penna4, Ginevra Fabiani4,5, and Francesco Comiti1
Stefano Brighenti et al.
  • 1Free University of Bolzano/Bozen, Faculty of Science and Technology, Italy (stefano.brighenti@unibz.it)
  • 2Institute for Alpine Environment, EURAC Research, Bolzano/Bozen, Italy
  • 3Department of Land, Environment, Agriculture and Forestry, University of Padova, Italy
  • 4Department of. Agriculture, Food, Environment and Forestry, University of Florence, Italy
  • 5Department of Environmental Research and Innovation, Luxembourg Institute of Science and Technology (LIST), Luxembourg

Different water sources can contribute to plant transpiration in Alpine environments, such as rainfall, snowmelt, irrigation and/or stream waters that are temporarily stored in the vadose and saturated zones. Particularly, the proportion of water uptake from different soil depths can strikingly differ depending on the species and the local environmental conditions such as the availability of freshwater resources, and local climatic and pedological settings.

We aim at estimating the relative contributions of different water sources (i.e., soil water at various depths and groundwater) to tree transpiration with the use of stable water isotopes. Our work is part of a wider national project (WATZON: WATer mixing in the critical ZONe) studying the relationship between plants, soil and water in contrasting natural and semi-natural environments of Italy. Here we report the results of monitoring activities in two different ecosystems in South-Tyrol (Eastern Italian Alps): an apple orchard growing on a deep (>2.5 m) sandy soil of the Adige floodplain (Binnenland), and a sub-alpine conifer forest located on steep slopes with a shallow (10-60 cm) skeletal soil (Mazia, 2000 mt a.s.l.), where we selected European larch (Larix decidua) as a model-species. Water (precipitation, stream water, groundwater), soil at different depths and twigs samples were collected fortnightly from May to November 2020, and weather conditions (automatic stations), soil parameters (moisture and temperature) at different depths and sapflow were continuously recorded over the entire period.

At both locations, precipitation waters had a heavier isotopic composition than stream water and groundwater, that did not show any significant difference between each other in terms of isotopic signature. While all these potential water sources plotted on the local meteoric water line, shallow soil water samples (5-15 cm) deviated from it revealing a stronger and more variable evaporative fractionation when compared with those of deeper soil (25-65 cm). Xylem water samples from apple trees at Binnenland overlapped with soil water samples, more consistently at 10-30 cm depths. This water mostly derived from infiltrated rainwater but with a non-negligible contribution from groundwater during July and August. In contrast, xylem water from larch trees at Mazia plotted on the local meteoric water line, and had an isotopic composition more similar to that of precipitation than soil water even for samples collected after several days of drying out. As sapflow measurements of larches revealed a continuous transpiration, it is unlikely that trees took up water only soon after precipitation events. Instead, we hypothesize that larches at Mazia likely rely on a water pool which is different from the soil (e.g., rock moisture).

These contrasting ecohydrological systems reveal different strategies of water use by dwelling plants in natural and anthropic systems, showing a distinct sensitivity and resilience to changing climate.

How to cite: Brighenti, S., Bertoldi, G., Aguzzoni, A., Zanotellii, D., Obojes, N., Tagliavini, M., Zuecco, G., Borga, M., Penna, D., Fabiani, G., and Comiti, F.: Apple trees, larches and their water uptake: distinct ecohydrological systems in contrasting environmental settings?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8211, https://doi.org/10.5194/egusphere-egu21-8211, 2021.

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