N supply mediates the radiative balance of N<sub>2</sub>O emissions and CO<sub>2</sub> sequestration driven by N‐fixing vs. non‐fixing trees

Kou‐Giesbrecht, Sian; Funk, Jennifer L.; Perakis, Steven S.; Wolf, Amelia A.; Menge, Duncan N. L.

doi:10.1002/ecy.3414

Cited by 7 publications

(5 citation statements)

References 25 publications

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“…Consistent with previous studies, the current study indicates that leguminous trees attained more biomass than non-leguminous trees at eCO 2 . This was expected, given that leguminous trees use symbiosis to fix N, which gives them advantage over non-leguminous trees, especially in N-limited soils (Chen and Markhan 2021;Kou-Giesbrecht et al 2021). Similar findings where a leguminous plant attained more biomass than nonleguminous plant grown at eCO 2 were reported by Lee et al (2003).…”

Section: Influence Of Woody Plant Functional Traits On Responses To Ecosupporting

confidence: 73%

A global meta-analysis of woody plant responses to elevated CO2: implications on biomass, growth, leaf N content, photosynthesis and water relations

et al. 2022

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Background Atmospheric CO2 may double by the year 2100, thereby altering plant growth, photosynthesis, leaf nutrient contents and water relations. Specifically, atmospheric CO2 is currently 50% higher than pre-industrial levels and is projected to rise as high as 936 μmol mol−1 under worst-case scenario in 2100. The objective of the study was to investigate the effects of elevated CO2 on woody plant growth, production, photosynthetic characteristics, leaf N and water relations. Methods A meta-analysis of 611 observations from 100 peer-reviewed articles published from 1985 to 2021 was conducted. We selected articles in which elevated CO2 and ambient CO2 range from 600–1000 and 300–400 μmol mol−1, respectively. Elevated CO2 was categorized into < 700, 700 and > 700 μmol mol−1 concentrations. Results Total biomass increased similarly across the three elevated CO2 concentrations, with leguminous trees (LTs) investing more biomass to shoot, whereas non-leguminous trees (NLTs) invested to root production. Leaf area index, shoot height, and light-saturated photosynthesis (Amax) were unresponsive at < 700 μmol mol−1, but increased significantly at 700 and > 700 μmol mol−1. However, shoot biomass and Amax acclimatized as the duration of woody plants exposure to elevated CO2 increased. Maximum rate of photosynthetic Rubisco carboxylation (Vcmax) and apparent maximum rate of photosynthetic electron transport (Jmax) were downregulated. Elevated CO2 reduced stomatal conductance (gs) by 32% on average and increased water use efficiency by 34, 43 and 63% for < 700, 700 and > 700 μmol mol−1, respectively. Leaf N content decreased two times more in NLTs than LTs growing at elevated CO2 than ambient CO2. Conclusions Our results suggest that woody plants will benefit from elevated CO2 through increased photosynthetic rate, productivity and improved water status, but the responses will vary by woody plant traits and length of exposure to elevated CO2.

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Section: Influence Of Woody Plant Functional Traits On Responses To Ecosupporting

confidence: 73%

A global meta-analysis of woody plant responses to elevated CO2: implications on biomass, growth, leaf N content, photosynthesis and water relations

et al. 2022

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“…Though multiple mechanisms may explain high soil C under N fixers, the presence of excess N due to obligate and incomplete SNF in particular may stabilize old organic C (i.e., slow or prevent decomposition) via inhibition of oxidative enzymes(Chen et al, 2018).Obligate and incomplete downregulation of SNF can also explain high rates of N leaching and gaseous N loss under N-fixing trees(Devotta et al, 2021;Williard et al, 2005), including the tree species we studied(Binkley et al, 1992;Compton et al, 2003;Erickson & Perakis, 2014;Jackson et al, 2018). 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.…”

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confidence: 80%

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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“…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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N supply mediates the radiative balance of N₂O emissions and CO₂ sequestration driven by N‐fixing vs. non‐fixing trees

Abstract: Running head: Climate change driven by N-fixing trees N supply mediates the radiative balance of N 2 O emissions and CO 2 sequestration driven by N-fixing vs. non-fixing trees

Cited by 7 publications

References 25 publications

A global meta-analysis of woody plant responses to elevated CO2: implications on biomass, growth, leaf N content, photosynthesis and water relations

A global meta-analysis of woody plant responses to elevated CO2: implications on biomass, growth, leaf N content, photosynthesis and water relations

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

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N supply mediates the radiative balance of N2O emissions and CO2 sequestration driven by N‐fixing vs. non‐fixing trees

Abstract: Running head: Climate change driven by N-fixing trees N supply mediates the radiative balance of N 2 O emissions and CO 2 sequestration driven by N-fixing vs. non-fixing trees

Cited by 7 publications

References 25 publications

A global meta-analysis of woody plant responses to elevated CO2: implications on biomass, growth, leaf N content, photosynthesis and water relations

A global meta-analysis of woody plant responses to elevated CO2: implications on biomass, growth, leaf N content, photosynthesis and water relations

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

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N supply mediates the radiative balance of N₂O emissions and CO₂ sequestration driven by N‐fixing vs. non‐fixing trees