Nitrogen‐fixing trees increase soil nitrous oxide emissions: a meta‐analysis

Kou‐Giesbrecht, Sian; Menge, Duncan N. L.

doi:10.1002/ecy.3415

Cited by 20 publications

(11 citation statements)

References 43 publications

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“…Losses as N 2 O are of particular interest as a greenhouse gas, and direct measurements at our New York site revealed larger N 2 O emissions under Robinia than Betula , as expected from incomplete downregulation of SNF (Kou‐Giesbrecht, Funk, et al, 2021). According to a recent meta‐analysis, N‐fixing trees tend to stimulate (approximately double) N 2 O emissions in general (Kou‐Giesbrecht & Menge, 2021), consistent with widespread obligate SNF or incomplete downregulation of SNF.…”

Section: Discussionmentioning

confidence: 83%

Tree symbioses sustain nitrogen fixation despite excess nitrogen supply

Menge

Wolf

Funk

et al. 2023

Ecological Monographs

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Symbiotic nitrogen fixation (SNF) is a key ecological process whose impact depends on the strategy of SNF regulation—the degree to which rates of SNF change in response to limitation by N versus other resources. SNF that is obligate or exhibits incomplete downregulation can result in excess N fixation, whereas a facultative SNF strategy does not. We hypothesized that tree‐based SNF strategies differed by latitude (tropical vs. temperate) and symbiotic type (actinorhizal vs. rhizobial). Specifically, we expected tropical rhizobial symbioses to display strongly facultative SNF as an explanation of their success in low‐latitude forests. In this study we used 15N isotope dilution field experiments in New York, Oregon, and Hawaii to determine SNF strategies in six N‐fixing tree symbioses. Nitrogen fertilization with +10 and +15 g N m−2 year−1 for 4–5 years alleviated N limitation in all taxa, paving the way to determine SNF strategies. Contrary to our hypothesis, all six of the symbioses we studied sustained SNF even at high N. Robinia pseudoacacia (temperate rhizobial) fixed 91% of its N (%Ndfa) in controls, compared to 64% and 59% in the +10 and +15 g N m−2 year−1 treatments. For Alnus rubra (temperate actinorhizal), %Ndfa was 95%, 70%, and 60%. For the tropical species, %Ndfa was 86%, 80%, and 82% for Gliricidia sepium (rhizobial); 79%, 69%, and 67% for Casuarina equisetifolia (actinorhizal); 91%, 42%, and 67% for Acacia koa (rhizobial); and 60%, 51%, and 19% for Morella faya (actinorhizal). Fertilization with phosphorus did not stimulate tree growth or SNF. These results suggest that the latitudinal abundance distribution of N‐fixing trees is not caused by a shift in SNF strategy. They also help explain the excess N in many forests where N fixers are common.

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Section: Discussionmentioning

confidence: 83%

Tree symbioses sustain nitrogen fixation despite excess nitrogen supply

Menge

Wolf

Funk

et al. 2023

Ecological Monographs

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“…Insensitive to changing soil N conditions, Mimosa and Desmodium continue to bring N into a sufficiently fertilized system, much like the gorse and broom of Drake (2011). Implications of continued fixation range from elevated release of N 2 O (Kou‐Giesbrecht & Menge, 2021), a powerful greenhouse gas, to decreased native plant fitness, since both study species have been introduced to Hawaiian ecosystems (Vitousek et al, 1987). Because introduced species on the whole increase soil N pools even when controlled for SNF capability, Mimosa and Desmodium are likely changing the nutrient environment as both introduced species and N‐fixing species (Allison & Vitousek, 2004; Castro‐Díez et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

“…For example, red alder Alnus rubra has been found to have large effects on nitrate leaching (Binkley et al, 1992; Compton et al, 2003). According to a meta‐analysis, N‐fixers approximately double N 2 O emissions on average (Kou‐Giesbrecht & Menge, 2021), potentially counteracting any CO 2 storage benefits of N‐fixing trees (Kou‐Giesbrecht et al, 2021; Kou‐Giesbrecht & Menge, 2019). Theory predicts that variation in ecosystem‐level effects of N‐fixers arises from variation in SNF strategies; species that fix N in an obligate or incompletely down‐regulated manner (e.g.…”

Section: Introductionmentioning

confidence: 99%

Nitrogen fixation responds to soil nitrogen at low but not high light in two invasive understory species

et al. 2023

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Light and soil nitrogen availability can be strong controls of plant nitrogen (N) fixation, but data on how understory N‐fixing plants respond to these drivers are limited despite their important role in ecosystem N cycling. Furthermore, ecosystem N cycling can be altered by the introduction of species with nutrient use patterns that differ from natives. We assessed how N fixation of two exotic, understory species responded to varying light and soil N environments. We sampled leaf tissue from Mimosa pudica L., Desmodium triflorum (L.) DC., and a nonfixing reference plant (Axonopus) growing in control and two N fertilization treatments under either N‐fixing or non‐N‐fixing trees, which may alter local soil nutrient cycling, across a range of light conditions. We measured N fixation with 15N isotope dilution, and ensured that N‐fixing neighbour trees were in fact fixing N. All understory plants were wild‐growing species not native to the study location. Desmodium and Mimosa acquired 82.6% and 71.6% of their nitrogen from fixation (%Ndfa) in the control, compared to 66.8% and 58.1% in the +10 g N m−2 year−1 treatment and 73.1% and 64.7% in the +15 g N m−2 year−1 treatment. These subtle %Ndfa differences across fertilization treatments were more apparent at low light availability and disappeared at high light availability. The amount of N fixed by neighbouring trees did not influence %Ndfa in the understory species. Synthesis. Our study shows some differences in N fixation across different nutrient environments at low light for two N‐fixing species, though the changes were small, and both species derived most of their N from fixation. These findings imply that introduced N‐fixing species could exacerbate ecosystem N enrichment, particularly under high soil N conditions.

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“…Previous studies also demonstrate that tree species-induced changes in community composition and environmental factors play more important roles in regulating soil N 2 O emissions than the abundance of nitrifier/denitrifier functional genes ( Qin et al, 2019 ). In the present study, we still do not know how the species diversity or the nature of individual species affect nitrification- and denitrification-derived N 2 O production in the field, even though several studies have investigated N 2 O emission from plantation forest soils ( Arai et al, 2008 ; Wang et al, 2014 ; Kou-Giesbrecht and Menge, 2021 ). Further study needs to focus on the role of the identities of specific species in the production processes of N 2 O under different N inputs.…”

Section: Discussionmentioning

confidence: 90%

Nitrogen-Induced Changes in Soil Environmental Factors Are More Important Than Nitrification and Denitrification Gene Abundance in Regulating N2O Emissions in Subtropical Forest Soils

Qiu

Mgelwa²,

Jin

et al. 2022

Front. Plant Sci.

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Subtropical regions are currently experiencing a dramatic increase in nitrogen (N) deposition; however, the contributions of nitrification and denitrification processes to soil N2O emissions and the underlying mechanisms under increasing N deposition remain unclear. Therefore, a 15N-tracing laboratory experiment with four N application rates (0, 12.5, 25, and 50 μg 15N g–1 soil) was conducted to investigate the response of nitrification- and denitrification-derived N2O to N additions in an evergreen broad-leaved forest (BF) and a Pinus forest (PF) in the Wuyi Mountains in southeastern China. Moreover, the abundance of functional genes related to nitrification (amoA), denitrification (nirK, nirS, and nosZ), and soil properties were measured to clarify the underlying mechanisms. Results showed that nitrification-derived N2O emissions were generally decreased with increasing N input. However, denitrification-derived N2O emissions were a non-linear response to N additions, with maximum N2O emissions at the middle N application rate. Denitrification-derived N2O was the dominant pathway of N2O production, accounting for 64 to 100% of the total N2O fluxes. Soil NH4+-N content and pH were the predominant factors in regulating nitrification-derived N2O emissions in BF and PF, respectively. Soil pH and the nirS abundance contributed the most to the variations of denitrification-derived N2O emissions in BF and PF, respectively. Our results suggest that N application has the potential to increase the contribution of denitrification to N2O production in subtropical forest soils. Changes in soil chemical properties induced by N addition are more important than the abundance of nitrification and denitrification functional genes in regulating soil nitrification- and denitrification-derived N2O emissions.

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Nitrogen‐fixing trees increase soil nitrous oxide emissions: a meta‐analysis

Cited by 20 publications

References 43 publications

Tree symbioses sustain nitrogen fixation despite excess nitrogen supply

Tree symbioses sustain nitrogen fixation despite excess nitrogen supply

Nitrogen fixation responds to soil nitrogen at low but not high light in two invasive understory species

Nitrogen-Induced Changes in Soil Environmental Factors Are More Important Than Nitrification and Denitrification Gene Abundance in Regulating N2O Emissions in Subtropical Forest Soils

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