ORIGINAL RESEARCH article
Front. Plant Sci.
Sec. Functional Plant Ecology
Volume 16 - 2025 | doi: 10.3389/fpls.2025.1625076
Recurrent summer drought temporarily stimulates fine root growth but enhances winter root losses in alpine grassland
Provisionally accepted
- 1University of Basel, Basel, Switzerland
- 2Centre for Sustainable Soils, Lancaster Environment Centre, Lancaster, United Kingdom
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By the end of the 21st century, frequent droughts and substantial shifts in snowmelt are expected to massively impact the biomass production of alpine grasslands. While the biomass of alpine plants consists to >80% of roots, little is known about the root growth dynamics in these ecosystems. To fill this gap, we capitalized on a longer-term experiment in the Swiss Alps with annually recurring treatments imposing advanced and delayed snowmelt and summer drought lasting 5 and 10 weeks. Over 3–4 growing seasons (2019–2022), we weekly quantified total root length of the plant community at two different soil depths (0–10 cm and 10–20 cm) using 90 minirhizotrons in 45 plots. We jointly assessed leaf elongation (of six abundant plant species) as proxies for the dynamics of biomass production. Increases in root length during summer continued beyond canopy development, with the duration of net root growth roughly double that of leaf expansion. Earlier and later snowmelt did not affect the proxies for total growth of leaves or roots but simply shifted their growing phases. Drought reduced leaf elongation across plant species whereas root length was stimulated by the 5-wk (not the 10-wk) drought in two seasons (+19% on average, 2020–2021). Natural rewetting after drought increased root growth by 38–77% compared to controls, but only in the 2020 growing season. Total root length in the topsoil declined by 7–15% during the last two winters, amounting to about one fourth of the previous seasons’ increase in root length. These root losses were 1.5 times higher following the 10-wk drought treatment. Our results highlight that earlier snowmelt alone will not stimulate productivity in alpine grassland. Root growth responses to drought depend on its duration and the long winter periods contribute to root losses, particularly in combination with severe drought in the preceding growing season.
Keywords: Climate Change, leaf length, machine learning, Neural Network, Rhizotron, Root phenology, winter, snowmelt
Received: 08 May 2025; Accepted: 01 Jul 2025.
Copyright: © 2025 Möhl and Hiltbrunner. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Patrick Möhl, University of Basel, Basel, Switzerland
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