Köhler, Birgit

[["dc.bibliographiccitation.firstpage","2311"],["dc.bibliographiccitation.issue","8"],["dc.bibliographiccitation.journal","Biogeosciences"],["dc.bibliographiccitation.lastpage","2325"],["dc.bibliographiccitation.volume","7"],["dc.contributor.author","Koehler, B."],["dc.contributor.author","Zehe, E."],["dc.contributor.author","Corre, M. D."],["dc.contributor.author","Veldkamp, E."],["dc.date.accessioned","2017-09-07T11:43:41Z"],["dc.date.available","2017-09-07T11:43:41Z"],["dc.date.issued","2010"],["dc.description.abstract","Soil respiration is the second largest flux in the global carbon cycle, yet the underlying below-ground process, carbon dioxide (CO2) production, is not well understood because it can not be measured in the field. CO2 production has frequently been calculated from the vertical CO2 diffusive flux divergence, known as \"soil-CO2 profile method\". This relatively simple model requires knowledge of soil CO2 concentration profiles and soil diffusive properties. Application of the method for a tropical lowland forest soil in Panama gave inconsistent results when using diffusion coefficients (D) calculated based on relationships with soil porosity and moisture (\"physically modeled\" D). Our objective was to investigate whether these inconsistencies were related to (1) the applied interpolation and solution methods and/or (2) uncertainties in the physically modeled profile of D. First, we show that the calculated CO2 production strongly depends on the function used to interpolate between measured CO2 concentrations. Secondly, using an inverse analysis of the soil-CO2 profile method, we deduce which D would be required to explain the observed CO2 concentrations, assuming the model perception is valid. In the top soil, this inversely modeled D closely resembled the physically modeled D. In the deep soil, however, the inversely modeled D increased sharply while the physically modeled D did not. When imposing a constraint during the fit parameter optimization, a solution could be found where this deviation between the physically and inversely modeled D disappeared. A radon (Rn) mass balance model, in which diffusion was calculated based on the physically modeled or constrained inversely modeled D, simulated observed Rn profiles reasonably well. However, the CO2 concentrations which corresponded to the constrained inversely modeled D were too small compared to the measurements. We suggest that, in well-structured soils, a missing description of steady state CO2 exchange fluxes across water-filled pores causes the soil-CO2 profile method to fail. These fluxes are driven by the different diffusivities in inter- vs. intra-aggregate pores which create permanent CO2 gradients if separated by a \"diffusive water barrier\". These results corroborate other studies which have shown that the theory to treat gas diffusion as homogeneous process, a precondition for use of the soil-CO2 profile method, is inaccurate for pore networks which exhibit spatial separation between CO2 production and diffusion out of the soil."],["dc.identifier.doi","10.5194/bg-7-2311-2010"],["dc.identifier.fs","570252"],["dc.identifier.gro","3150209"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/5240"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/6948"],["dc.language.iso","en"],["dc.notes.intern","Migrated from goescholar"],["dc.notes.status","final"],["dc.relation.issn","1726-4189"],["dc.rights","Goescholar"],["dc.rights.access","openAccess"],["dc.rights.uri","https://goescholar.uni-goettingen.de/licenses"],["dc.subject","CO2 production"],["dc.subject.ddc","570"],["dc.title","An inverse analysis reveals limitations of the soil-CO2 profile method to calculate CO2 production and efflux for well-structured soils"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","2049"],["dc.bibliographiccitation.issue","8"],["dc.bibliographiccitation.journal","Global Change Biology"],["dc.bibliographiccitation.lastpage","2066"],["dc.bibliographiccitation.volume","15"],["dc.contributor.author","Koehler, Birgit"],["dc.contributor.author","Corre, Marife D."],["dc.contributor.author","Veldkamp, Edzo"],["dc.contributor.author","Wullaert, Hans"],["dc.contributor.author","Wright, S. Joseph"],["dc.date.accessioned","2021-12-08T12:27:48Z"],["dc.date.available","2021-12-08T12:27:48Z"],["dc.date.issued","2009"],["dc.description.abstract","Tropical nitrogen (N) deposition is projected to increase substantially within the coming decades. Increases in soil emissions of the climate-relevant trace gases NO and N2O are expected, but few studies address this possibility. We used N addition experiments to achieve N-enriched conditions in contrasting montane and lowland forests and assessed changes in the timing and magnitude of soil N-oxide emissions. We evaluated transitory effects, which occurred immediately after N addition, and long-term effects measured at least 6 weeks after N addition. In the montane forest where stem growth was N limited, the first-time N additions caused rapid increases in soil N-oxide emissions. During the first 2 years of N addition, annual N-oxide emissions were five times (transitory effect) and two times (long-term effect) larger than controls. This contradicts the current assumption that N-limited tropical montane forests will respond to N additions with only small and delayed increases in soil N-oxide emissions. We attribute this fast and large response of soil N-oxide emissions to the presence of an organic layer (a characteristic feature of this forest type) in which nitrification increased substantially following N addition. In the lowland forest where stem growth was neither N nor phosphorus (P) limited, the first-time N additions caused only gradual and minimal increases in soil N-oxide emissions. These first N additions were completed at the beginning of the wet season, and low soil water content may have limited nitrification. In contrast, the 9- and 10-year N-addition plots displayed instantaneous and large soil N-oxide emissions. Annual N-oxide emissions under chronic N addition were seven times (transitory effect) and four times (long-term effect) larger than controls. Seasonal changes in soil water content also caused seasonal changes in soil N-oxide emissions from the 9- and 10-year N-addition plots. This suggests that climate change scenarios, where rainfall quantity and seasonality change, will alter the relative importance of soil NO and N2O emissions from tropical forests exposed to elevated N deposition."],["dc.identifier.doi","10.1111/j.1365-2486.2008.01826.x"],["dc.identifier.gro","3150159"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/95455"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-476"],["dc.notes.status","public"],["dc.relation.eissn","1365-2486"],["dc.relation.issn","1354-1013"],["dc.rights.uri","http://doi.wiley.com/10.1002/tdm_license_1.1"],["dc.subject","climate change; deposition; fertilization; nitric oxide; nitrification; nitrogen; nitrous oxide; organic layer; trace gases; tropical forest"],["dc.title","Immediate and long-term nitrogen oxide emissions from tropical forest soils exposed to elevated nitrogen input"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dspace.entity.type","Publication"]]

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[["dc.bibliographiccitation.firstpage","715"],["dc.bibliographiccitation.issue","1-3"],["dc.bibliographiccitation.journal","Biogeochemistry"],["dc.bibliographiccitation.lastpage","717"],["dc.bibliographiccitation.volume","111"],["dc.contributor.author","Koehler, Birgit"],["dc.contributor.author","Corre, Marife D."],["dc.contributor.author","Steger, Kristin"],["dc.contributor.author","Well, Reinhard"],["dc.contributor.author","Zehe, Erwin"],["dc.contributor.author","Sueta, Juvia P."],["dc.contributor.author","Veldkamp, Edzo"],["dc.date.accessioned","2018-11-07T09:03:42Z"],["dc.date.available","2018-11-07T09:03:42Z"],["dc.date.issued","2012"],["dc.identifier.doi","10.1007/s10533-012-9780-6"],["dc.identifier.isi","000314063200044"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/24950"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Springer"],["dc.relation.issn","0168-2563"],["dc.title","An in-depth look into a tropical lowland forest soil: nitrogen-addition effects on the contents of N2O, CO2 and CH4 and N2O isotopic signatures down to 2-m depth (vol 111, pg 715, 2012)"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","5367"],["dc.bibliographiccitation.issue","8"],["dc.bibliographiccitation.journal","Biogeosciences"],["dc.bibliographiccitation.lastpage","5379"],["dc.bibliographiccitation.volume","10"],["dc.contributor.author","Veldkamp, Edzo"],["dc.contributor.author","Koehler, Birgit"],["dc.contributor.author","Corre, Marife D."],["dc.date.accessioned","2017-09-07T11:54:55Z"],["dc.date.available","2017-09-07T11:54:55Z"],["dc.date.issued","2013"],["dc.description.sponsorship","Open-Access-Publikationsfonds 2013"],["dc.identifier.doi","10.5194/bg-10-5367-2013"],["dc.identifier.fs","601952"],["dc.identifier.gro","3150147"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9220"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/6879"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.relation.issn","1726-4189"],["dc.rights.access","openAccess"],["dc.title","Indications of nitrogen-limited methane uptake in tropical forest soils"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]