Nitrous oxide and methane fluxes from soils of the Orinoco savanna under different land uses

Abstract

The study investigates the effect of land-use change on nitrous oxide (N 2 O) and methane (CH 4 ) fluxes from soil, in savanna ecosystems of the Orinoco region (Venezuela). Gas fluxes were measured by closed static chambers, in the wet and dry season, in representative systems of land management of the region: a cultivated pasture, an herbaceous savanna, a tree savanna and a woodland (control site). Higher N 2 O emissions were observed in the cultivated pasture and in the herbaceous savanna compared with the tree savanna and the woodland, and differences were mainly related to fine soil particle content and soil volumetric water content measured in the studied sites. Overall N 2 O emissions were quite low in all sites (0-1.58 mg N 2 O-N m À2 day À1 ). The cultivated pasture and the woodland savanna were on average weak CH 4 sinks (À0.05 AE 0.07 and À0.08 AE 0.05 mg CH 4 m À2 day À1 , respectively), whereas the herbaceous savanna and the tree savanna showed net CH 4 production (0.23 AE 0.05 and 0.19 AE 0.05 mg CH 4 m À2 day À1 , respectively). Variations of CH 4 fluxes were mainly driven by variation of soil waterfilled pore space (WFPS), and a shift from net CH 4 consumption to net CH 4 production was observed at around 30% WFPS. Overall, the data suggest that conversion of woodland savanna to managed landscape could alter both CH 4 and N 2 O fluxes; however, the magnitude of such variation depends on the soil characteristics and on the type of land management before conversion.

Impacts of climate and land use on N2O and CH4 fluxes from tropical ecosystems in the Mt. Kilimanjaro region, Tanzania

“…As in our study (Table 4), Rees et al (2006) also reported a strong positive correlation between N 2 O fluxes and soil moisture. The lower emissions in our study are thus most likely related to dryer soil conditions: 23% WFPS in our study vs. 60% WFPS observed by Castaldi et al (2004) and 75% WFPS observed by Br€ ummer et al (2008). As previously shown for tropical forest ecosystems , we also found that N 2 O emissions positively correlated with total soil nitrogen contents (N tot ) and…”

“…DOC concentrations were highest at 10 cm soil depth, with significantly higher values in homegarden (median: 4.7 mg C L À1 ) and forest ecosystems (median: 1.5-14.5 mg C L À1 ) than in the coffee plantation (median: 2.5 mg C L À1 ). for herbaceous and open tree savanna in Venezuela (Castaldi et al, 2004); 0.25-0.52 kg N ha À1 year À1 for grass and woodland savanna in Zimbabwe (Rees, Wuta, Furley, & Li, 2006); and 0.52-0.67 kg N ha À1 year À1 for shrub and woodland savanna in Burkina Faso (Br€ ummer et al, 2008). As in our study (Table 4), Rees et al (2006) also reported a strong positive correlation between N 2 O fluxes and soil moisture.…”

Nitrous oxide emissions from an apple orchard soil in the semiarid Loess Plateau of China

“…Soil WFPS at all sites was always below 60.0% except during freeze-thaw cycle and immediately after heavy rainfall. The coarse texture and the low water retention capacity of soils limited the possibility of the formation of anaerobic microsites, where N 2 O production could take place (Castaldi et al 2004). Nitrous oxide emission is affected by soil moisture (Ciarlo et al 2008), and indeed higher N 2 O emission occurred after raining in this study.…”

Rotação de culturas no sistema plantio direto em Tibagi (PR): I - Sequestro de carbono no solo

“…O metano também não foi considerado para os cál-culos, porque estudos (Simona et al, 2004;Six et al, 2004;Metay et al, 2007) têm mostrado que seus fluxos não são significativos (-0,01 ± 0,07 mg CH 4 m -2 d -1 ) em áreas agrícolas, sendo as maiores emissões encontradas no cultivo de arroz irrigado por inundação (Agostinetto et al, 2002). Além disso, a fertilização nitrogenada aumenta a emissão de N 2 O do solo para a atmosfera, como também diminui a absorção de CH 4 atmosférico pelos solos (Mosier et al, 1991).…”