Dataset Information

A spatially explicit, empirical estimate of tree-based biological nitrogen fixation in forests of the United States.

ABSTRACT: Quantifying human impacts on the N cycle and investigating natural ecosystem N cycling depend on the magnitude of inputs from natural biological nitrogen fixation (BNF). Here, we present two bottom-up approaches to quantify tree-based symbiotic BNF based on forest inventory data across the coterminous US plus SE Alaska. For all major N-fixing tree genera, we quantify BNF inputs using (1) ecosystem N accretion rates (kg N ha^-1 yr^-1) scaled with spatial data on tree abundance and (2) percent of N derived from fixation (%N_dfa) scaled with tree N demand (from tree growth rates and stoichiometry). We estimate that trees fix 0.30-0.88 Tg N yr^-1 across the study area (1.4-3.4 kg N ha^-1 yr^-1). Tree-based N fixation displays distinct spatial variation that is dominated by two genera, Robinia (64% of tree-associated BNF) and Alnus (24%). The third most important genus, Prosopis, accounted for 5%. Compared to published estimates of other N fluxes, tree-associated BNF accounted for 0.59 Tg N yr^-1, similar to asymbiotic (0.37 Tg N yr^-1) and understory symbiotic BNF (0.48 Tg N yr^-1), while N deposition contributed 1.68 Tg N yr^-1 and rock weathering 0.37 Tg N yr^-1. Overall, our results reveal previously uncharacterized spatial patterns in tree BNF that can inform large-scale N assessments and serve as a model for improving tree-based BNF estimates worldwide. This updated, lower BNF estimate indicates a greater ratio of anthropogenic to natural N inputs, suggesting an even greater human impact on the N cycle.

SUBMITTER: Staccone A

PROVIDER: S-EPMC7359885 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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A spatially explicit, empirical estimate of tree-based biological nitrogen fixation in forests of the United States.

Staccone Anika A Liao Wenying W Perakis Steven S Compton Jana J Clark Christopher C Menge Duncan D

Global biogeochemical cycles 20200201 2

Quantifying human impacts on the N cycle and investigating natural ecosystem N cycling depend on the magnitude of inputs from natural biological nitrogen fixation (BNF). Here, we present two bottom-up approaches to quantify tree-based symbiotic BNF based on forest inventory data across the coterminous US plus SE Alaska. For all major N-fixing tree genera, we quantify BNF inputs using (1) ecosystem N accretion rates (kg N ha<sup>-1</sup> yr<sup>-1</sup>) scaled with spatial data on tree abundance ...[more]

PMID: 32665747

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Dataset Information

A spatially explicit, empirical estimate of tree-based biological nitrogen fixation in forests of the United States.

Publications

A spatially explicit, empirical estimate of tree-based biological nitrogen fixation in forests of the United States.

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