1. Methane and nitrous oxide fluxes from the tropical Andes.
- Author
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Teh, Y. A., Diem, T., Jones, S., Huaraca Quispe, L. P., Baggs, E., Morley, N., Richards, M., Smith, P., and Meir, P.
- Subjects
NITROUS oxide ,METHANE ,EMISSIONS (Air pollution) ,REMOTE sensing ,INVERSION (Geophysics) ,EMPIRICAL research ,CLIMATE change - Abstract
Remote sensing and inverse modelling studies indicate that the tropics emit more CH
4 and N2 O 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 N2 O often overlooked by past empirical and modelling studies. To address this knowledge gap, we investigated spatial, temporal and environmental trends in CH4 and N2 O fluxes across a long elevation gradient (600-3700ma.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 CH4 and N2 O fluxes from representative habitats within this region, and to identify the proximate controls on soil CH4 and N2 O dynamics. Ecosystems across this altitudinal gradient were both atmospheric sources and sinks of CH4 on an annual basis. Montane grasslands (or, puna; 3200-3700ma.s.l.) were strong atmospheric sources, emitting 56.94±7.81 kgCH4 -Cha-1 yr-1 . Upper montane forest (2200-3200ma.s.l.) and lower montane forest (1200-2200ma.s.l.) were net atmospheric sinks (-2.99±0.29 kgCH4 -Cha-1 yr-1 and -2.34±0.29 kgCH4 -Cha-1 yr-1 , respectively); while premontane forests (600-1200ma.s.l.) fluctuated between source or sink depending on the season (wet season: 1.86±1.50 kgCH4 -Cha-1 yr-1 ; dry season: -1.17±0.40 kgCH4 -Cha-1 yr-1 ). Analysis of spatial, temporal and environmental trends in CH4 flux across the study site suggest that soil redox was a dominant control on net CH4 flux. CH4 emissions were greatest from elevations, landforms and during times of year when soils were sub-oxic, and CH4 efflux was inversely correlated with soil O2 concentration (r² = 0.82, F1,125 = 588.41, P < 0.0001). Ecosystems across the region were net atmospheric N2 O sources. N2 O fluxes declined with increasing elevation; N2 O emissions from premontane forest, lower montane forest, upper montane forest and montane grasslands averaged 2.23±1.31 kgN2 O-Nha-1 yr-1 , 1.68±0.44 kgN2 O- Nha-1 yr-1 , 0.44±0.47 kgN2 O-Nha-1 yr-1 and 0.15±1.10 kgN2 O-Nha-1 yr-1 , respectively. N2 O 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 N2 O fluxes from this region were primarily driven by denitrification; that nitrate (NO3 - ) availability was the principal constraint on N2 O fluxes; and that soil moisture and water-filled porosity played a secondary role in modulating N2 O emissions. Any current and future changes in N management or anthropogenic N deposition may cause shifts in net N2 O fluxes from these tropical montane ecosystems, further enhancing this emission source. [ABSTRACT FROM AUTHOR]- Published
- 2013
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