Global terrestrial nitrogen uptake and nitrogen use efficiency

Yunke Peng*, Iain Colin Prentice, Keith J. Bloomfield, Matteo Campioli, Zhiwen Guo, Yuanfeng Sun, Di Tian, Xiangping Wang, Sara Vicca, Benjamin D. Stocker

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    2 Citations (Scopus)
    20 Downloads (Pure)

    Abstract

    1. Plant biomass production (BP), nitrogen uptake (Nup) and their ratio, and nitrogen use efficiency (NUE) must be quantified to understand how nitrogen (N) cycling constrains terrestrial carbon (C) uptake. But the controls of key plant processes determining Nup and NUE, including BP, C and N allocation, tissue C:N ratios and N resorption efficiency (NRE), remain poorly known. 

    2. We compiled measurements from 804 forest and grassland sites and derived regression models for each of these processes with growth temperature, vapour pressure deficit, stand age, soil C:N ratio, fAPAR (remotely sensed fraction of photosynthetically active radiation absorbed by green vegetation) and growing-season average daily incident photosynthetic photon flux density (gPPFD; effectively the seasonal concentration of light availability, which increases polewards) as predictors. An empirical model for leaf N was based on optimal photosynthetic capacity (a function of gPPFD and climate) and observed leaf mass per area. The models were used to produce global maps of Nup and NUE. 

    3. Global BP was estimated as 72 Pg C/year; Nup as 950 Tg N/year; and NUE as 76 g C/g N. Forest BP was found to increase with growth temperature and fAPAR and to decrease with stand age, soil C:N ratio and gPPFD. Forest NUE is controlled primarily by climate through its effect on C allocation—especially to leaves, being richer in N than other tissues. NUE is greater in colder climates, where N is less readily available, because below-ground allocation is increased. NUE is also greater in drier climates because leaf allocation is reduced. NRE is enhanced (further promoting NUE) in both cold and dry climates. 

    4. Synthesis. These findings can provide observationally based benchmarks for model representations of C–N cycle coupling. State-of-the-art vegetation models in the TRENDY ensemble showed variable performance against these benchmarks, and models including coupled C–N cycling produced relatively poor simulations of Nup and NUE.

    Original languageEnglish
    Pages (from-to)2676-2693
    Number of pages18
    JournalJournal of Ecology
    Volume111
    Issue number12
    Early online date18 Oct 2023
    DOIs
    Publication statusPublished - Dec 2023

    Bibliographical note

    Copyright the Author(s) 2023. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

    Keywords

    • carbon
    • climate
    • data-driven model
    • global change ecology
    • nitrogen uptake
    • nitrogen use efficiency
    • stand age
    • terrestrial ecosystem

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