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| Titel |
Methane and nitrous oxide fluxes across an elevation gradient in the tropical Peruvian Andes |
| VerfasserIn |
Y. A. Teh, T. Diem, S. Jones, L. P. Huaraca Quispe, E. Baggs, N. Morley, M. Richards, P. Smith, P. Meir |
| 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 ; 11, no. 8 ; Nr. 11, no. 8 (2014-04-25), S.2325-2339 |
| Datensatznummer |
250117377
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| Publikation (Nr.) |
 copernicus.org/bg-11-2325-2014.pdf |
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| Zusammenfassung |
| Remote sensing and inverse modelling studies indicate that the tropics emit
more CH4 and N2O than predicted by bottom-up emissions inventories,
suggesting that terrestrial sources are stronger or more numerous than
previously thought. Tropical uplands are a potentially large and important
source of CH4 and N2O often overlooked by past empirical and
modelling studies. To address this knowledge gap, we investigated spatial,
temporal and environmental trends in soil CH4 and N2O fluxes across
a long elevation gradient (600–3700 m a.s.l.) in the Kosñipata Valley,
in the southern Peruvian Andes, that experiences seasonal fluctuations in
rainfall. The aim of this work was to produce preliminary estimates of soil
CH4 and N2O fluxes from representative habitats within this region,
and to identify the proximate controls on soil CH4 and N2O
dynamics. Area-weighted flux calculations indicated that ecosystems across
this altitudinal gradient were both atmospheric sources and sinks of CH4
on an annual basis. Montane grasslands (3200–3700 m a.s.l.) were strong
atmospheric sources, emitting 56.94 ± 7.81 kg
CH4-C ha−1 yr−1. Upper montane forest
(2200–3200 m a.s.l.) and lower montane forest (1200–2200 m a.s.l.) were
net atmospheric sinks (−2.99 ± 0.29 and −2.34 ± 0.29 kg
CH4-C ha−1 yr−1, respectively); while premontane forests
(600–1200 m a.s.l.) fluctuated between source or sink depending on the
season (wet season: 1.86 ± 1.50 kg CH4-C ha−1 yr−1;
dry season: −1.17 ± 0.40 kg CH4-C ha−1 yr−1).
Analysis of spatial, temporal and environmental trends in soil CH4 flux
across the study site suggest that soil redox was a dominant control on net
soil CH4 flux. Soil CH4 emissions were greatest from habitats,
landforms and during times of year when soils were suboxic, and soil
CH4 efflux was inversely correlated with soil O2 concentration
(Spearman's ρ = −0.45, P < 0.0001) and positively correlated with
water-filled pore space (Spearman's ρ = 0.63, P <0.0001). Ecosystems
across the region were net atmospheric N2O sources. Soil N2O fluxes
declined with increasing elevation; area-weighted flux calculations indicated
that N2O emissions from premontane forest, lower montane forest, upper
montane forest and montane grasslands averaged 2.23 ± 1.31,
1.68 ± 0.44, 0.44 ± 0.47 and 0.15 ± 1.10 kg
N2O-N ha−1 yr−1, respectively. Soil N2O fluxes from
premontane and lower montane forests exceeded prior model predictions for the
region. Comprehensive investigation of field and laboratory data collected in
this study suggest that soil N2O fluxes from this region were primarily
driven by denitrification; that nitrate (NO3−) availability was the
principal constraint on soil N2O fluxes; and that soil moisture and
water-filled porosity played a secondary role in modulating N2O
emissions. Any current and future changes in N management or anthropogenic N
deposition may cause shifts in net soil N2O fluxes from these tropical
montane ecosystems, further enhancing this emission source. |
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