Variations of bioavailable Sr concentration and 87Sr/86Sr ratio in boreal forest ecosystems. Role of biocycling, mineral weathering and depth of root uptake

• Main Authors: Poszwa, A., Ferry, Bruno, Dambrine, Etienne, Pollier, Benoit, Wickman, Tonie, Loubet, Michel, Bishop, Kevin
• Other Authors: Unité de recherche Biogéochimie des Ecosystèmes Forestiers (BEF), Institut National de la Recherche Agronomique (INRA), Laboratoire d'Etudes des Ressources Forêt-Bois (LERFoB), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, Royal Institute of Technology in Stockholm (KTH), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Department of Environmental Assessment, Swedish University of Agricultural Sciences (SLU)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2004
• Subjects: PINUS SYLVESTRIS; EPICEA COMMUN; ABSORPTION D'EAU; [SDV.BIO]Life Sciences [q-bio]/Biotechnology; Norway; Northern Sweden
• Online Access: https://hal.inrae.fr/hal-02683596; https://doi.org/10.1023/B:BIOG.0000015162.12857.3e

International audience The mean depth of Sr and water uptake in mixed Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) stands was investigated, using natural variations of 87Sr/86Sr and 18O/16O in soils in relation to depth. Three spruce-pine pairs were studied on a podzol and a peat site in Northern Sweden. Tree leaf and wood, as well as soils, soil solutions and roots below each tree were analysed for Sr and Ca concentrations and 87Sr/86Sr ratio. The 18O/16O ratio was also determined in xylem sap and soil solutions in relation to depth. Soil solution 18O/16O decreased in relation to depth. Comparing with xylem sap 18O/16O data indicated a deeper uptake of soil water by pine than spruce on the podzol site and a superficial uptake by both species on the peat. The 87Sr/86Sr ratio of bioavailable Sr generally increased in soils in relation to depth. Contrastingly, the 87Sr/86Sr ratio in spruce wood was generally higher than in pine wood suggesting a deeper uptake of Sr by spruce. But the 87Sr/86Sr ratio and concentrations of bioavailable Sr were systematically higher below spruce than below pine. In order to explain these unexpected results, we built a simple flux model to investigate the possible effects of interspecific variations in Sr cycling, soil mineral weathering and depth of Sr uptake on soil and tree 87Sr/86Sr ratio. At the study sites, spruce cycled in litterfall up to 12 times more strontium than pine. The use of the model showed that this difference in Sr cycling could alone explain higher isotopic signatures of trees and topsoils below spruce. Besides, high isotopic signatures of roots in the A/E horizons below spruce led us to hypothesise a species-specific weathering process. Finally, the comparison between the 87Sr/86Sr ratios in wood and root or soil solutions below each species suggested that the average depth of Sr and water uptake were close, but irregular variations of the Sr isotopic ratio with depth reduce the accuracy of the results. Tree species strongly influence Sr ...