Data shared here were used in the four main Figures, Extended Data Figures and Supplementary Figures showed in the article 'Substantial contribution of tree canopy nitrifiers to nitrogen fluxes in European forests' by Rossella Guerrieri, Joan Cáliz, Stefania Mattana, Anna Barceló, Marco Candela, David Elustondo, Heike Fortmann, Sofie Hellsten, Nils Koenig, Antti-Jussi Lindroos, Giorgio Matteucci, Päivi Merilä, Greg Michalski, Manuel Nicolas, Anne Thimonier, Silvia Turroni, Elena Vanguelova, Arne Verstraeten, Peter Waldner, Mirai Watanabe, Emilio O. Casamayor, Josep Peñuelas, Maurizio Mencuccini, published in Nature Geoscience (DOI 10.1038/s41561-023-01364-3).Data is provided as Excel files. For methodological information, please refer to the article.

Data shared here were used in the four main Figures, Extended Data Figures and Supplementary Figures showed in the article 'Substantial contribution of tree canopy nitrifiers to nitrogen fluxes in European forests' by Rossella Guerrieri, Joan Cáliz, Stefania Mattana, Anna Barceló, Marco Candela, David Elustondo, Heike Fortmann, Sofie Hellsten, Nils Koenig, Antti-Jussi Lindroos, Giorgio Matteucci, Päivi Merilä, Greg Michalski, Manuel Nicolas, Anne Thimonier, Silvia Turroni, Elena Vanguelova, Arne Verstraeten, Peter Waldner, Mirai Watanabe, Emilio O. Casamayor, Josep Peñuelas, Maurizio Mencuccini, published in Nature Geoscience (DOI 10.1038/s41561-023-01364-3).Data is provided as Excel files. For methodological information, please refer to the article.

Uncertainties surrounding tree carbon allocation to growth are a major limitation to projections of forest carbon sequestration and response to climate change. The prevalence and extent to which carbon assimilation (source) or cambial activity (sink) mediate wood production are fundamentally important and remain elusive. We quantified source-sink relations across biomes by combining eddy-covariance gross primary production with extensive on-site and regional tree ring observations. We found widespread temporal decoupling between carbon assimilation and tree growth, underpinned by contrasting climatic sensitivities of these two processes. Substantial differences in assimilation-growth decoupling between angiosperms and gymnosperms were determined, as well as stronger decoupling with canopy closure, aridity, and decreasing temperatures. Our results reveal pervasive sink control over tree growth that is likely to be increasingly prominent under global climate change.

Data on photosynthesis and photosynthetic parameters of native trees at natural sites measured in the field. Photosynthesis data are from the Farquhar photosynthesis model (e.g., Vcmax, Jmax) using controlled photosynthetic responses to [CO2] for a set of 52 pan-tropical and subtropical sites across South America, Africa, Asia and Australia. Associated with each measurement is leaf N concentration and leaf P concentration as well as leaf mass per unit area. Farquhar photosynthesis model parameters Vcmax and Jmax were fit using the plantecophys package. Inlcuded in this dataset are data measured at tree-top from trees at 6 canopy crane sites. Further details about the measurements and data are in Ellsworth et al. (2022) Nature Communications.

Data on photosynthesis and photosynthetic parameters of native trees at natural sites measured in the field. Photosynthesis data are from the Farquhar photosynthesis model (e.g., Vcmax, Jmax) using controlled photosynthetic responses to [CO2] for a set of 52 pan-tropical and subtropical sites across South America, Africa, Asia and Australia. Associated with each measurement is leaf N concentration and leaf P concentration as well as leaf mass per unit area. Farquhar photosynthesis model parameters Vcmax and Jmax were fit using the plantecophys package. Inlcuded in this dataset are data measured at tree-top from trees at 6 canopy crane sites. Further details about the measurements and data are in Ellsworth et al. (2022) Nature Communications.

1. Forest regrowth following farmland (agriculture and pasture) abandonment has been positively associated with a number of processes including the regulation of hydrological cycling, the enhancement of soil functioning, and an increase in forest productivity and carbon (C) sequestration. Although these changes in ecosystem functioning post-farmland abandonment have been observed in multiple locations and studies, the ecophysiological basis underpinning these patterns remains unclear. Here, we examine whether increased forest expansion following pastureland abandonment is associated with greater water-use efficiency (WUE) and legacies from previous land use in terms of nitrogen (N) availability. 2. We thus explored differences in leaf traits and N availability between recently established (post-1950) beech (Fagus sylvatica L.) forests on former pastureland and long-established beech forests (pre-1950). The investigated leaf traits were leaf specific area (SLA), leaf N concentration (%N) and intrinsic WUE (iWUE, i.e. the ratio between photosynthesis and stomatal conductance); as well, leaf and soil stable N isotope composition (δ15N) and total %N were used to assess changes in N availability. Finally, we compared the correlation strength between the above-mentioned parameters and those associated with tree productivity (wood density and basal area increment, BAI) and the richness of ectomycorrhizal fungi (ECM) in these two forest types. 3. Recent forests had greater iWUE than long-established forests, which was associated more with lower SLA than leaf %N. Leaf and soil δ15N were more robust proxies than %N for detecting differences in N availability. Less negative leaf and soil δ15N values in recent vs. long-established forests suggest, on one hand, greater N availability, probably due to higher historical N input originating from animal excreta on these former pasturelands, and, on the other, an increase in N loss pathways. 4. Our results point to greater correlations between leaf δ15N, tree iWUE, and productivity in recent forests than in long-established forests, thereby suggesting a close link between C and N cycles. Our findings also highlight different N dynamics between the two forest types, with recent forests showing ‘leaky’ N cycling wherever lower N retention by trees and associated ECM fungi occurs as a legacy of previous land use.