An explanation for the isotopic offset between soil and stem water in a temperate tree species.

Autor: Barbeta A; INRAE, UMR1391 ISPA, 33140, Villenave d'Ornon, France.; BEECA, Department of Evolutionary Biology, Ecology and Environmental Sciences, Universitat de Barcelona, Barcelona, Catalonia, Spain., Gimeno TE; INRAE, UMR1391 ISPA, 33140, Villenave d'Ornon, France.; Basque Centre for Climate Change, 48940, Leioa, Spain.; IKERBASQUE, Basque Foundation for Science, 48008, Bilbao, Spain., Clavé L; INRAE, UMR1391 ISPA, 33140, Villenave d'Ornon, France., Fréjaville B; INRAE, UMR1391 ISPA, 33140, Villenave d'Ornon, France., Jones SP; INRAE, UMR1391 ISPA, 33140, Villenave d'Ornon, France.; Instituto Nacional de Pesquisas da Amazônia, Manaus, CEP 69060-001, Brazil., Delvigne C; INRAE, UMR1391 ISPA, 33140, Villenave d'Ornon, France.; Université Catholique de Louvain, Louvain-la-Neuve, Belgium., Wingate L; INRAE, UMR1391 ISPA, 33140, Villenave d'Ornon, France., Ogée J; INRAE, UMR1391 ISPA, 33140, Villenave d'Ornon, France.
Jazyk: angličtina
Zdroj: The New phytologist [New Phytol] 2020 Aug; Vol. 227 (3), pp. 766-779. Date of Electronic Publication: 2020 May 04.
DOI: 10.1111/nph.16564
Abstrakt: A growing number of field studies report isotopic offsets between stem water and its potential sources that prevent the unambiguous identification of plant water origin using water isotopes. We explored the causes of this isotopic offset by conducting a controlled experiment on the temperate tree species Fagus sylvatica. We measured δ 2 H and δ 18 O of soil and stem water from potted saplings growing on three soil substrates and subjected to two watering regimes. Regardless of substrate, soil and stem water δ 2 H were similar only near permanent wilting point. Under moister conditions, stem water δ 2 H was 11 ± 3‰ more negative than soil water δ 2 H, coherent with field studies. Under drier conditions, stem water δ 2 H became progressively more enriched than soil water δ 2 H. Although stem water δ 18 O broadly reflected that of soil water, soil-stem δ 2 H and δ 18 O differences were correlated (r = 0.76) and increased with transpiration rates indicated by proxies. Soil-stem isotopic offsets are more likely to be caused by water isotope heterogeneities within the soil pore and stem tissues, which would be masked under drier conditions as a result of evaporative enrichment, than by fractionation under root water uptake. Our results challenge our current understanding of isotopic signals in the soil-plant continuum.
(© 2020 The Authors. New Phytologist © 2020 New Phytologist Trust.)
Databáze: MEDLINE
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