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von Sperber C, Chadwick OA, Casciotti KL, Peay KG, Francis CA, Kim AE, Vitousek PM. Controls of nitrogen cycling evaluated along a well-characterized climate gradient. Ecology 2018; 98:1117-1129. [PMID: 28130777 DOI: 10.1002/ecy.1751] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 01/05/2017] [Accepted: 01/19/2017] [Indexed: 11/11/2022]
Abstract
The supply of nitrogen (N) constrains primary productivity in many ecosystems, raising the question "what controls the availability and cycling of N"? As a step toward answering this question, we evaluated N cycling processes and aspects of their regulation on a climate gradient on Kohala Volcano, Hawaii, USA. The gradient extends from sites receiving <300 mm/yr of rain to those receiving >3,000 mm/yr, and the pedology and dynamics of rock-derived nutrients in soils on the gradient are well understood. In particular, there is a soil process domain at intermediate rainfall within which ongoing weathering and biological uplift have enriched total and available pools of rock-derived nutrients substantially; sites at higher rainfall than this domain are acid and infertile as a consequence of depletion of rock-derived nutrients, while sites at lower rainfall are unproductive and subject to wind erosion. We found elevated rates of potential net N mineralization in the domain where rock-derived nutrients are enriched. Higher-rainfall sites have low rates of potential net N mineralization and high rates of microbial N immobilization, despite relatively high rates of gross N mineralization. Lower-rainfall sites have moderately low potential net N mineralization, relatively low rates of gross N mineralization, and rates of microbial N immobilization sufficient to sequester almost all the mineral N produced. Bulk soil δ15 N also varied along the gradient, from +4‰ at high rainfall sites to +14‰ at low rainfall sites, indicating differences in the sources and dynamics of soil N. Our analysis shows that there is a strong association between N cycling and soil process domains that are defined using soil characteristics independent of N along this gradient, and that short-term controls of N cycling can be understood in terms of the supply of and demand for N.
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Affiliation(s)
| | - Oliver A Chadwick
- Department of Geography, University of California, Santa Barbara, California, 93106, USA
| | - Karen L Casciotti
- Department of Earth System Science, Stanford University, Stanford, California, 94305, USA
| | - Kabir G Peay
- Department of Biology, Stanford University, Stanford, California, 94305, USA
| | - Christopher A Francis
- Department of Earth System Science, Stanford University, Stanford, California, 94305, USA
| | - Amy E Kim
- Earth Systems Program, Stanford University, Stanford, California, 94305, USA
| | - Peter M Vitousek
- Department of Biology, Stanford University, Stanford, California, 94305, USA
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2
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Menge DNL, Levin SA. Spatial heterogeneity can resolve the nitrogen paradox of tropical forests. Ecology 2017; 98:1049-1061. [DOI: 10.1002/ecy.1733] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Revised: 11/20/2016] [Accepted: 01/03/2017] [Indexed: 11/06/2022]
Affiliation(s)
- Duncan N. L. Menge
- Department of Ecology, Evolution, and Environmental Biology Columbia University 1200 Amsterdam Avenue, Schermerhorn Ex 1014A New York New York 10027 USA
| | - Simon A. Levin
- Department of Ecology and Evolutionary Biology Princeton University 106A Guyot Hall Princeton New Jersey 08544 USA
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Wurzburger N, Brookshire ENJ, McCormack ML, Lankau RA. Mycorrhizal fungi as drivers and modulators of terrestrial ecosystem processes. THE NEW PHYTOLOGIST 2017; 213:996-999. [PMID: 28079936 DOI: 10.1111/nph.14409] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Affiliation(s)
- Nina Wurzburger
- Odum School of Ecology, University of Georgia, Athens, GA, 30602, USA
| | - E N Jack Brookshire
- Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, 59717, USA
| | - M Luke McCormack
- Department of Plant and Microbial Biology, University of Minnesota, St Paul, MN, 55108, USA
| | - Richard A Lankau
- Plant Pathology Department, University of Wisconsin, Madison, WI, 53705, USA
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Kearsley E, Verbeeck H, Hufkens K, Van de Perre F, Doetterl S, Baert G, Beeckman H, Boeckx P, Huygens D. Functional community structure of African monodominant Gilbertiodendron dewevrei forest influenced by local environmental filtering. Ecol Evol 2017; 7:295-304. [PMID: 28070293 PMCID: PMC5216677 DOI: 10.1002/ece3.2589] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 09/30/2016] [Accepted: 10/11/2016] [Indexed: 01/23/2023] Open
Abstract
Monodominant patches of forest dominated by Gilbertiodendron dewevrei are commonly found in central African tropical forests, alongside forests with high species diversity. Although these forests are generally found sparsely distributed along rivers, their occurrence is not thought to be (clearly) driven by edaphic conditions but rather by trait combinations of G. dewevrei that aid in achieving monodominance. Functional community structure between these monodominant and mixed forests has, however, not yet been compared. Additionally, little is known about nondominant species in the monodominant forest community. These two topics are addressed in this study. We investigate the functional community structure of 10 one-hectare plots of monodominant and mixed forests in a central region of the Congo basin, in DR Congo. Thirteen leaf and wood traits are measured, covering 95% (basal area weighted) of all species present in the plots, including leaf nutrient contents, leaf isotopic compositions, specific leaf area, wood density, and vessel anatomy. The trait-based assessment of G. dewevrei shows an ensemble of traits related to water use and transport that could be favorable for its location near forest rivers. Moreover, indications have been found for N and P limitations in the monodominant forest, possibly related to ectomycorrhizal associations formed with G. dewevrei. Reduced leaf N and P contents are found at the community level for the monodominant forest and for different nondominant groups, as compared to those in the mixed forest. In summary, this work shows that environmental filtering does prevail in the monodominant G. dewevrei forest, leading to lower functional diversity in this forest type, with the dominant species showing beneficial traits related to its common riverine locations and with reduced soil N and P availability found in this environment, both coregulating the tree community assembly.
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Affiliation(s)
- Elizabeth Kearsley
- Department of Applied Ecology and Environmental BiologyComputational and Applied Vegetation Ecology – CAVElabGhent UniversityGentBelgium
- Department of Applied Analytical and Physical ChemistryIsotope Bioscience Laboratory – ISOFYSGhent UniversityGentBelgium
- Service of Wood BiologyRoyal Museum for Central AfricaTervurenBelgium
| | - Hans Verbeeck
- Department of Applied Ecology and Environmental BiologyComputational and Applied Vegetation Ecology – CAVElabGhent UniversityGentBelgium
| | - Koen Hufkens
- Department of Organismic and Evolutionary BiologyHarvard UniversityCambridgeMAUSA
| | | | - Sebastian Doetterl
- Department of Applied Analytical and Physical ChemistryIsotope Bioscience Laboratory – ISOFYSGhent UniversityGentBelgium
- Institute of GeographyAugsburg UniversityAugsburgGermany
| | - Geert Baert
- Department of Applied BiosciencesGhent UniversityGentBelgium
| | - Hans Beeckman
- Service of Wood BiologyRoyal Museum for Central AfricaTervurenBelgium
| | - Pascal Boeckx
- Department of Applied Analytical and Physical ChemistryIsotope Bioscience Laboratory – ISOFYSGhent UniversityGentBelgium
| | - Dries Huygens
- Department of Applied Analytical and Physical ChemistryIsotope Bioscience Laboratory – ISOFYSGhent UniversityGentBelgium
- Instituto Multidisciplinario de Biología VegetalUniversidad Nacional de Córdoba & CONICETCordobaArgentina
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Thomas RQ, Brookshire ENJ, Gerber S. Nitrogen limitation on land: how can it occur in Earth system models? GLOBAL CHANGE BIOLOGY 2015; 21:1777-93. [PMID: 25643841 DOI: 10.1111/gcb.12813] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 11/04/2014] [Indexed: 05/11/2023]
Abstract
The representation of the nitrogen (N) cycle in Earth system models (ESMs) is strongly motivated by the constraint N poses on the sequestration of anthropogenic carbon (C). Models typically implement a stoichiometric relationship between C and N in which external supply and assimilation by organisms are adjusted to maintain their internal stoichiometry. N limitation of primary productivity thus occurs if the N supply from uptake and fixation cannot keep up with the construction of tissues allowed by C assimilation. This basic approach, however, presents considerable challenges in how to faithfully represent N limitation. Here, we review how N limitation is currently implemented and evaluated in ESMs and highlight challenges and opportunities in their future development. At or near steady state, N limitation is governed by the magnitude of losses from the plant-unavailable pool vs. N fixation and there are considerable differences in how models treat both processes. In nonsteady-state systems, the accumulation of N in pools with slow turnover rates reduces N available for plant uptake and can be challenging to represent when initializing ESM simulations. Transactional N limitation occurs when N is incorporated into various vegetation and soil pools and becomes available to plants only after it is mineralized, the dynamics of which depends on how ESMs represent decomposition processes in soils. Other challenges for ESMs emerge when considering seasonal to interannual climatic oscillations as they create asynchronies between C and N demand, leading to transient alternations between N surplus and deficit. Proper evaluation of N dynamics in ESMs requires conceptual understanding of the main levers that trigger N limitation, and we highlight key measurements and observations that can help constrain these levers. Two of the biggest challenges are the mechanistic representation of plant controls on N availability and turnover, including N fixation and organic matter decomposition processes.
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Affiliation(s)
- R Quinn Thomas
- Department of Forest Resources and Environmental Conservation, Virginia Tech, Blacksburg, VA, 24061, USA
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Brookshire ENJ, Thomas SA. Ecosystem consequences of tree monodominance for nitrogen cycling in lowland tropical forest. PLoS One 2013; 8:e70491. [PMID: 23936215 PMCID: PMC3723728 DOI: 10.1371/journal.pone.0070491] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Accepted: 06/20/2013] [Indexed: 11/18/2022] Open
Abstract
Understanding how plant functional traits shape nutrient limitation and cycling on land is a major challenge in ecology. This is especially true for lowland forest ecosystems of the tropics which can be taxonomically and functionally diverse and rich in bioavailable nitrogen (N). In many tropical regions, however, diverse forests occur side-by-side with monodominant forest (one species >60% of canopy); the long-term biogeochemical consequences of tree monodominance are unclear. Particularly uncertain is whether the monodominant plant-soil system modifies nutrient balance at the ecosystem level. Here, we use chemical and stable isotope techniques to examine N cycling in old-growth Mora excelsa and diverse watershed rainforests on the island of Trinidad. Across 26 small watershed forests and 4 years, we show that Mora monodominance reduces bioavailable nitrate in the plant-soil system to exceedingly low levels which, in turn, results in small hydrologic and gaseous N losses at the watershed-level relative to adjacent N-rich diverse forests. Bioavailable N in soils and streams remained low and remarkably stable through time in Mora forests; N levels in diverse forests, on the other hand, showed high sensitivity to seasonal and inter-annual rainfall variation. Total mineral N losses from diverse forests exceeded inputs from atmospheric deposition, consistent with N saturation, while losses from Mora forests did not, suggesting N limitation. Our measures suggest that this difference cannot be explained by environmental factors but instead by low internal production and efficient retention of bioavailable N in the Mora plant-soil system. These results demonstrate ecosystem-level consequences of a tree species on the N cycle opposite to cases where trees enhance ecosystem N supply via N2 fixation and suggest that, over time, Mora monodominance may generate progressive N draw-down in the plant-soil system.
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Affiliation(s)
- E. N. Jack Brookshire
- Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, Montana, United States of America
- * E-mail:
| | - Steven A. Thomas
- School of Natural Resources, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
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Vitousek PM, Menge DNL, Reed SC, Cleveland CC. Biological nitrogen fixation: rates, patterns and ecological controls in terrestrial ecosystems. Philos Trans R Soc Lond B Biol Sci 2013; 368:20130119. [PMID: 23713117 DOI: 10.1098/rstb.2013.0119] [Citation(s) in RCA: 257] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
New techniques have identified a wide range of organisms with the capacity to carry out biological nitrogen fixation (BNF)-greatly expanding our appreciation of the diversity and ubiquity of N fixers-but our understanding of the rates and controls of BNF at ecosystem and global scales has not advanced at the same pace. Nevertheless, determining rates and controls of BNF is crucial to placing anthropogenic changes to the N cycle in context, and to understanding, predicting and managing many aspects of global environmental change. Here, we estimate terrestrial BNF for a pre-industrial world by combining information on N fluxes with (15)N relative abundance data for terrestrial ecosystems. Our estimate is that pre-industrial N fixation was 58 (range of 40-100) Tg N fixed yr(-1); adding conservative assumptions for geological N reduces our best estimate to 44 Tg N yr(-1). This approach yields substantially lower estimates than most recent calculations; it suggests that the magnitude of human alternation of the N cycle is substantially larger than has been assumed.
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Affiliation(s)
- Peter M Vitousek
- Department of Biology, Stanford University, Stanford, CA 94305, USA.
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Nitrogen limitation, 15N tracer retention, and growth response in intact and Bromus tectorum-invaded Artemisia tridentata ssp. wyomingensis communities. Oecologia 2012; 171:1013-23. [DOI: 10.1007/s00442-012-2442-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 08/16/2012] [Indexed: 11/26/2022]
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Gundale MJ, Nilsson M, Bansal S, Jäderlund A. The interactive effects of temperature and light on biological nitrogen fixation in boreal forests. THE NEW PHYTOLOGIST 2012; 194:453-463. [PMID: 22329746 DOI: 10.1111/j.1469-8137.2012.04071.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Plant productivity is predicted to increase in northern latitudes as a result of climate warming; however, this may depend on whether biological nitrogen (N)-fixation also increases. We evaluated how the variation in temperature and light affects N-fixation by two boreal feather mosses, Pleurozium schreberi and Hylocomium splendens, which are the primary source of N-fixation in most boreal environments. We measured N-fixation rates 2 and 4 wk after exposure to a factorial combination of environments of normal, intermediate and high temperature (16.3, 22.0 and 30.3°C) and light (148.0, 295.7 and 517.3 μmol m(-2) s(-1)). Our results showed that P. schreberi achieved higher N-fixation rates relative to H. splendens in response to warming treatments, but that the highest warming treatment eventually caused N-fixation to decline for both species. Light strongly interacted with warming treatments, having positive effects at low or intermediate temperatures and damaging effects at high temperatures. These results suggest that climate warming may increase N-fixation in boreal forests, but that increased shading by the forest canopy or the occurrence of extreme temperature events could limit increases. They also suggest that P. schreberi may become a larger source of N in boreal forests relative to H. splendens as climate warming progresses.
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Affiliation(s)
- Michael J Gundale
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE901-83 Umeå, Sweden
| | - Madeleine Nilsson
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE901-83 Umeå, Sweden
| | - Sheel Bansal
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE901-83 Umeå, Sweden
| | - Anders Jäderlund
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE901-83 Umeå, Sweden
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