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| Titel |
Modelling changes in nitrogen cycling to sustain increases in forest productivity under elevated atmospheric CO2 and contrasting site conditions |
| VerfasserIn |
R. F. Grant |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 11 ; Nr. 10, no. 11 (2013-11-28), S.7703-7721 |
| Datensatznummer |
250085444
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| Publikation (Nr.) |
 copernicus.org/bg-10-7703-2013.pdf |
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| Zusammenfassung |
| If increases in net primary productivity (NPP) caused by rising
concentrations of atmospheric CO2 (Ca) are to be sustained, key N
processes such as soil mineralization, biological fixation, root uptake and
nutrient conservation must also be increased. Simulating the response of
these processes to elevated Ca is therefore vital for models used to
project the effects of rising Ca on NPP. In this modelling study,
hypotheses are proposed for changes in soil mineralization, biological
fixation, root nutrient uptake and plant nutrient conservation with changes
in Ca. Algorithms developed from these hypotheses were tested in the
ecosystem model ecosys against changes in N and C cycling measured over several
years under ambient vs. elevated Ca in Free Air CO2 Enrichment
(FACE) experiments in the USA at the Duke Forest in North Carolina, the Oak Ridge
National Laboratory forest in Tennessee, and the USDA research forest in
Wisconsin. More rapid soil N mineralization was found to be vital for
simulating sustained increases in NPP measured under elevated vs. ambient
Ca at all three FACE sites. This simulation was accomplished by priming
decomposition of N-rich humus from increases in microbial biomass generated
by increased litterfall modelled under elevated Ca. Greater nonsymbiotic
N2 fixation from increased litterfall, root N uptake from increased
root growth, and plant N conservation from increased translocation under
elevated Ca were found to make smaller contributions to simulated
increases in NPP. However greater nutrient conservation enabled larger
increases in NPP with Ca to be modelled with coniferous vs. deciduous
plant functional types. The effects of these processes on productivity now
need to be examined over longer periods under transient rises in Ca and
a greater range of site conditions. |
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