Terrestrial nitrogen cycling in Earth system models revisited

Stocker, Benjamin D.; Prentice, Iain Colin; Cornell, Sarah; Davies‐Barnard, Taraka; Finzi, Adrien C.; Franklin, Oskar; Janssens, Ivan A.; Larmola, Tuula; Manzoni, Stefano; Näsholm, Torgny; Raven, John A.; Rebel, Karin T.; Reed, Sasha C.; Vicca, Sara; Wiltshire, Andy; Zaehle, Sönke

doi:10.1111/nph.13997

Cited by 41 publications

(44 citation statements)

References 25 publications

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“…), and of the role of symbiotic N‐fixers in particular (Stocker et al . ), have been highlighted as key uncertainties in global carbon‐cycle and climate projections. Our results suggest that future efforts to study N‐fixing trees and N fixation, and thus to better understand global carbon storage and climate, should focus on niche‐based ecological mechanisms.…”

Section: Discussionmentioning

confidence: 99%

Nitrogen‐fixing tree abundance in higher‐latitude North America is not constrained by diversity

et al. 2017

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The rarity of nitrogen (N)-fixing trees in frequently N-limited higher-latitude (here, > 35°) forests is a central biogeochemical paradox. One hypothesis for their rarity is that evolutionary constraints limit N-fixing tree diversity, preventing N-fixing species from filling available niches in higher-latitude forests. Here, we test this hypothesis using data from the USA and Mexico. N-fixing trees comprise only a slightly smaller fraction of taxa at higher vs. lower latitudes (8% vs. 11% of genera), despite 11-fold lower abundance (1.2% vs. 12.7% of basal area). Furthermore, N-fixing trees are abundant but belong to few species on tropical islands, suggesting that low absolute diversity does not limit their abundance. Rhizobial taxa dominate N-fixing tree richness at lower latitudes, whereas actinorhizal species do at higher latitudes. Our results suggest that low diversity does not explain N-fixing trees' rarity in higher-latitude forests. Therefore, N limitation in higher-latitude forests likely results from ecological constraints on N fixation.

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Section: Discussionmentioning

confidence: 99%

Nitrogen‐fixing tree abundance in higher‐latitude North America is not constrained by diversity

et al. 2017

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Section: Introductionmentioning

confidence: 99%

“…Understanding the extent to which nitrogen (N) availability constrains plants’ responses to global climate change is critical for predicting future terrestrial carbon uptake (Hungate, Dukes, Shaw, Luo, & Field, ; Stocker et al., ). In particular, one of the main challenges of improving Earth System Models is understanding the capacity for biological N fixation to alleviate local N limitation (Stocker et al., ). Symbiotic N fixation, particularly the symbiosis between bacteria and angiosperms, has the capacity to overcome N limitation because it can bring over 100 kg N ha −1 year −1 into ecosystems (Binkley, Cromack, & Baker, ; Binkley & Giardina, ; Ruess, McFarland, Trummer, & Rohrs‐Richey, ) and it can function as a “nitrostat” (Menge & Hedin, ), ramping up in response to N limitation.…”

Section: Introductionmentioning

confidence: 99%

Global climate change will increase the abundance of symbiotic nitrogen‐fixing trees in much of North America

Liao

Menge

Lichstein

et al. 2017

Global Change Biology

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Symbiotic nitrogen (N)-fixing trees can drive N and carbon cycling and thus are critical components of future climate projections. Despite detailed understanding of how climate influences N-fixation enzyme activity and physiology, comparatively little is known about how climate influences N-fixing tree abundance. Here, we used forest inventory data from the USA and Mexico (>125,000 plots) along with climate data to address two questions: (1) How does the abundance distribution of N-fixing trees (rhizobial, actinorhizal, and both types together) vary with mean annual temperature (MAT) and precipitation (MAP)? (2) How will changing climate shift the abundance distribution of N-fixing trees? We found that rhizobial N-fixing trees were nearly absent below 15°C MAT, but above 15°C MAT, they increased in abundance as temperature rose. We found no evidence for a hump-shaped response to temperature throughout the range of our data. Rhizobial trees were more abundant in dry than in wet ecosystems. By contrast, actinorhizal trees peaked in abundance at 5-10°C MAT and were least abundant in areas with intermediate precipitation. Next, we used a climate-envelope approach to project how N-fixing tree relative abundance might change in the future. The climate-envelope projection showed that rhizobial N-fixing trees will likely become more abundant in many areas by 2080, particularly in the southern USA and western Mexico, due primarily to rising temperatures. Projections for actinorhizal N-fixing trees were more nuanced due to their nonmonotonic dependence on temperature and precipitation. Overall, the dominant trend is that warming will increase N-fixing tree abundance in much of the USA and Mexico, with large increases up to 40° North latitude. The quantitative link we provide between climate and N-fixing tree abundance can help improve the representation of symbiotic N fixation in Earth System Models.

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“…Despite a long history of recognition that rock‐derived N is important (Cornwell & Stone, ; Dahlgren, ; Dixon et al, ; Hendry et al, ; Montross, McGlynn, Montross, & Gardner, ), the majority of published N cycles assume that the sole sources of N inputs to terrestrial ecosystems are atmospheric, via the processes of biological N fixation (BNF) and deposition of atmospheric N (Cleveland et al, ; Galloway et al, ; Stocker et al, ; Vitousek, Menge, Reed, & Cleveland, ; Walker & Syers, ). Yet, it has been recognized that N cycles remain incomplete, because measurements of the accumulation of N in vegetation and soil exceeded measured inputs from the atmosphere.…”

Section: Ecological and Evolutionary Significance Of Rock N Weatheringmentioning

confidence: 99%

“…Other long‐held assumptions about N still underlie our understanding of ecosystem ecology, three of which we address in this review. First is the assumption that sources of N to terrestrial ecosystems are only derived from the atmosphere by N fixation or deposition (Galloway, Leach, Bleeker, & Erisman, ; Stocker et al, ; Walker & Syers, ). Although the hypothesis that atmospheric N is the dominant source of N to ecosystems has been challenged over the past 50 years (Cornwell & Stone, ; Hendry, McCready, & Gould, ), only recently did evidence demonstrate the extent that rock N weathering contributes to the terrestrial N cycle (Dixon, Campbell, & Durham, ; Houlton, Morford, & Dahlgren, ; Morford, Houlton, & Dahlgren, ).…”

Section: Introductionmentioning

confidence: 99%

Changing perspectives on terrestrial nitrogen cycling: The importance of weathering and evolved resource‐use traits for understanding ecosystem responses to global change

et al. 2019

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Our understanding of terrestrial nitrogen (N) cycling is changing as new processes are uncovered, including the sources, turnover and losses of N from ecosystems. We integrate recent insights into an updated N‐cycling framework and discuss how a new understanding integrates eco‐evolutionary dynamics with nutrient cycling. These insights include (a) the significance of rock weathering as a biologically meaningful N source to plants and microbes; (b) the lack of consistent N limitation of organic matter decomposition by soil microbes; (c) species‐specific variation in plant N limitation; and (d) how fire effects on soil N shift with ecosystem properties. Using an eco‐evolutionary framework and revised knowledge of N cycling, we describe how (a) rock N weathering could have contributed more strongly to gradients in soil N availability than previously recognized, (b) evolution and co‐evolution of plant and soil microbial resource‐use traits underlie whether decomposition and production are N‐limited, and (c) the effects of fire on soil N pools are mediated by composition of plant species and time‐scale. Our revised framework of N cycling provides a way forward for improving biogeochemical models to more accurately estimate rates of plant production and decomposition, and total soil N. A free Plain Language Summary can be found within the Supporting Information of this article.

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Terrestrial nitrogen cycling in Earth system models revisited

Cited by 41 publications

References 25 publications

Nitrogen‐fixing tree abundance in higher‐latitude North America is not constrained by diversity

Nitrogen‐fixing tree abundance in higher‐latitude North America is not constrained by diversity

Global climate change will increase the abundance of symbiotic nitrogen‐fixing trees in much of North America

Changing perspectives on terrestrial nitrogen cycling: The importance of weathering and evolved resource‐use traits for understanding ecosystem responses to global change

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