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Estimating intraseasonal intrinsic water‐use efficiency from high‐resolution tree‐ring δ 13 C data in boreal Scots pine forests

2022; Wiley; Volume: 237; Issue: 5 Linguagem: Inglês

10.1111/nph.18649

1469-8137

Yu Tang, Elina Sahlstedt, Giles Young, Pauliina Schiestl‐Aalto, Matthias Saurer, Pasi Kolari, Tuula Jyske, Jaana Bäck, Katja T. Rinne‐Garmston,

Forest ecology and management

Summary Intrinsic water‐use efficiency (iWUE), a key index for carbon and water balance, has been widely estimated from tree‐ring δ 13 C at annual resolution, but rarely at high‐resolution intraseasonal scale. We estimated high‐resolution iWUE from laser‐ablation δ 13 C analysis of tree‐rings (iWUE iso ) and compared it with iWUE derived from gas exchange (iWUE gas ) and eddy covariance (iWUE EC ) data for two Pinus sylvestris forests from 2002 to 2019. By carefully timing iWUE iso via modeled tree‐ring growth, iWUE iso aligned well with iWUE gas and iWUE EC at intraseasonal scale. However, year‐to‐year patterns of iWUE gas , iWUE iso , and iWUE EC were different, possibly due to distinct environmental drivers on iWUE across leaf, tree, and ecosystem scales. We quantified the modification of iWUE iso by postphotosynthetic δ 13 C enrichment from leaf sucrose to tree rings and by nonexplicit inclusion of mesophyll and photorespiration terms in photosynthetic discrimination model, which resulted in overestimation of iWUE iso by up to 11% and 14%, respectively. We thus extended the application of tree‐ring δ 13 C for iWUE estimates to high‐resolution intraseasonal scale. The comparison of iWUE gas , iWUE iso , and iWUE EC provides important insights into physiological acclimation of trees across leaf, tree, and ecosystem scales under climate change and improves the upscaling of ecological models.