Photosynthesis, growth and plant maintenance respiration are closely related to tree tissue nitrogen (N) concentrations. Earlier studies of the variation in tissue N concentrations and underlying controls have mostly focused on leaves. Here we present a novel database of N concentrations in stems, roots and branches covering all common northern hemisphere boreal and temperate tree species, combined with data for leaves mostly available from existing databases. Additional information on mean annual temperature (MAT), mean annual precipitation (MAP), soil N concentration, tree height, age, and biomass is extracted from the considered studies, when available. The database can be used, for instance, for studying the controls of tree tissue N concentrations (as in Thurner et al., accepted for publication in Biogeosciences, https://doi.org/10.5194/egusphere-2024-1794), or for improving the implementation of the N cycle in dynamic global vegetation models (DGVMs), which currently usually assume fixed ratios between tissue N concentrations and thus oversimplify effects of N limitation on the carbon (C) cycle.
We collect a novel database of N concentration measurements in stems (i.e., trunks), roots and branches of northern hemisphere boreal and temperate trees by an extensive literature research. ... mehrFor this task, we search Web of Science for stem, root and branch nitrogen concentrations for all common boreal and temperate tree genera (for search criteria see Supporting Information S1 of the associated primary article). To a lesser extent, we also collect leaf N concentration measurements from the literature, because numerous measurements of leaf N concentration are already available from the TRY database (Kattge et al., 2020). Since measurements are rare in Russian boreal forests, we include own measurements for Larix gmelinii in the central part of the Nizhnyaya Tunguska River basin in Central Siberia (ca. 64° N 100° E; Larjavaara et al., 2017; Prokushkin et al., 2018). Moreover, data sources from the Russian and Chinese literature, the TRY database (Kattge et al., 2020) and the biomass and allometry database (BAAD; Falster et al., 2015) are considered.
Only measurements of N concentration under natural conditions (no greenhouses, no trees grown in pots, no fertilizer, and no other experiments) are included in the database. In addition, we only include studies with explicit information on the measurement location and the investigated tree species. We only analyse measurements of total root N concentration, but do not include measurements of N concentration specifically for fine roots. In cases where separate measurements are available for (stem) sapwood and heartwood, we include only N concentrations of sapwood. Replicate measurements, if available from the studies, are retained. All tissue N concentrations are expressed in g N / g dry weight. In total, the compiled database comprises 1048 stem, 267 root, 599 branch, and 5944 leaf N concentration measurements. While almost all of the stem (911 collected from literature, 1 own, 52 from TRY, 84 from BAAD), root (266 collected from literature, 1 own) and branch (all collected from literature) N concentration measurements have been collected from in total 192 studies from the literature, leaf N concentration measurements are to a large extent available from existing databases (188 collected from literature, 5 own, 5522 from TRY, 229 from BAAD). The spatial distribution of N concentration measurements is shown in Fig. 1 of the associated primary article.
Information on MAT, MAP, soil N concentration, tree height, age, and biomass is extracted from the respective studies, when available. Growth / leaf type classes categorise tree species according to their growth rate (fast-growing, slow-/medium-growing) and leaf type (broadleaf deciduous, needleleaf deciduous, needleleaf evergreen). We exclude data without information on tree species as well as broadleaf evergreen trees from the analysis since available measurements for this leaf type are scarce. Due to missing information on actual growth rates of the species at the specific measurement sites, we assign their typical growth rate (slow/medium: <= 2 feet/year; fast: > 2 feet/year) to each investigated tree species based on our expert judgement and an online research (see Supporting Information S2 of the associated primary article). As a measure of dryness, we calculate the aridity index (AI = MAP / potential evapotranspiration) from CHELSA Version 2.1 long-term climate data at the study locations (1981-2010; 30 arcsec resolution; Brun et al., 2022), as information on potential evapotranspiration is usually not available from the compiled studies.
References:
Brun P, Zimmermann NE, Hari C, Pellissier L, Karger DN. 2022. Global climate-related predictors at kilometer resolution for the past and future. Earth System Science Data 14(12): 5573-5603.
Falster DS, Duursma RA, Ishihara MI, Barneche DR, FitzJohn RG, Vårhammar A, Aiba M, Ando M, Anten N, Aspinwall MJ, et al. 2015. BAAD: a biomass and allometry database for woody plants. Ecology 96(5): 1445.
Kattge J, Bonisch G, Diaz S, Lavorel S, Prentice IC, Leadley P, Tautenhahn S, Werner GDA, Aakala T, Abedi M, et al. 2020. TRY plant trait database - enhanced coverage and open access. Glob Chang Biol 26(1): 119-188.
Larjavaara M, Berninger F, Palviainen M, Prokushkin A, Wallenius T. 2017. Post-fire carbon and nitrogen accumulation and succession in Central Siberia. Sci Rep 7(1): 12776.
Prokushkin A, Hagedorn F, Pokrovsky O, Viers J, Kirdyanov A, Masyagina O, Prokushkina M, McDowell W. 2018. Permafrost Regime Affects the Nutritional Status and Productivity of Larches in Central Siberia. Forests 9(6).
Related works: We sincerely thank the TRY initiative on plant traits (http://www.try-db.org) for contributing to leaf N and the Biomass And Allometry Database (BAAD; https://github.com/dfalster/baad) for contributing to leaf and stem N concentration data of this database. The TRY initiative and database is hosted, developed and maintained by J. Kattge and G. Boenisch (Max Planck Institute for Biogeochemistry, Jena, Germany). The BAAD is hosted, developed and maintained by D. Falster (University of New South Wales, Sydney, Australia).
