{
  "abstract": "Understanding how carbon-water coupling scales from leaves to ecosystems remains a major challenge because water-use efficiency (WUE) metrics integrate physiological, hydrological, and ecological processes. We integrated tree-ring width, triple stable isotopes ({delta}13C, {delta}18O and {delta}2H), eddy covariance (EC) observations, and a process-based model to investigate the drivers of intrinsic (iWUE) and ecosystem water-use efficiency (WUEeco) across biological scales in a mature Fagus sylvatica forest between 2004 and 2023. Modelled and isotope-derived iWUE were strongly correlated (r = 0.61, p < 0.05) and both indicated an approximately 20% long-term increase, consistent with increasing gross primary productivity. In contrast, WUEeco derived from EC was lower than model estimates and exhibited a positive trend not reproduced by the model. This divergence primarily reflected differences in biological representation and hydrological integration, as the single-species model underestimated ecosystem evapotranspiration by excluding co-occurring deciduous and evergreen species together with understory vegetation. Triple-isotope analyses showed that the long-term increase in iWUE was driven by enhanced photosynthetic assimilation rather than sustained stomatal closure, whereas {delta}18O and {delta}2H variability was mainly controlled by source-water dynamics. These findings provide a mechanistic framework for reconciling leaf- and ecosystem-scale WUE and improving predictions of forest carbon-water coupling under climate change.",
  "abstract_shown": true,
  "affiliations": [
    "Italian National Reserach Center"
  ],
  "article_type": "New results",
  "arxiv": null,
  "author_total": 9,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "P. F. Puchi"
    },
    {
      "name": "D. Dalmonech"
    },
    {
      "name": "D. Castagneri"
    },
    {
      "name": "E. Vangi"
    },
    {
      "name": "M. H. Lehmann"
    },
    {
      "name": "M. Saurer"
    },
    {
      "name": "S. Klesse"
    },
    {
      "name": "L. Hortnagl"
    },
    {
      "name": "A. Collalti"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/8stpm5wjnygqc.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.10.07.757244",
  "fulltext_url": "https://www.biorxiv.org/content/10.64898/2026.10.07.757244v1.full",
  "id": "8stpm5wjnygqc",
  "issns": [],
  "landing_url": "https://www.biorxiv.org/content/10.64898/2026.10.07.757244v1",
  "language": null,
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "biorxiv",
      "ecology"
    ],
    [
      "openalex",
      "2306|Plant Water Relations and Carbon Dynamics"
    ]
  ],
  "openalex": "W7166103675",
  "pdf_url": "https://www.biorxiv.org/content/10.64898/2026.10.07.757244v1.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-07",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/8stpm5wjnygqc.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:26:34Z",
      "native_id": "10.64898/2026.10.07.757244",
      "source": "biorxiv",
      "url": "https://www.biorxiv.org/content/10.64898/2026.10.07.757244v1"
    }
  ],
  "subjects": [
    {
      "field": "biology",
      "origin": "biorxiv:ecology",
      "subfield": "ecology"
    }
  ],
  "title": "Reconciling intrinsic and ecosystem water-use efficiency reveals physiological mechanisms underlying carbon-water coupling across biological scales",
  "title_text": "Reconciling intrinsic and ecosystem water-use efficiency reveals physiological mechanisms underlying carbon-water coupling across biological scales",
  "type": "preprint",
  "updated_at": "2026-10-30T12:26:34Z",
  "url": "https://research.draconitic.com/paper/8stpm5wjnygqc",
  "venue": "bioRxiv",
  "versions": []
}