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- Title
Soil greenhouse gas fluxes from tropical coastal wetlands and alternative agricultural land uses.
- Authors
Iram, Naima; Kavehei, Emad; Maher, Damien T.; Bunn, Stuart E.; Rezaei Rashti, Mehran; Farahani, Bahareh Shahrabi; Adame, Maria Fernanda
- Abstract
Coastal wetlands are essential for regulating the global carbon budget through soil carbon sequestration and greenhouse gas (GHG – CO2 , CH4 , and N2O) fluxes. The conversion of coastal wetlands to agricultural land alters these fluxes' magnitude and direction (uptake/release). However, the extent and drivers of change of GHG fluxes are still unknown for many tropical regions. We measured soil GHG fluxes from three natural coastal wetlands – mangroves, salt marsh, and freshwater tidal forests – and two alternative agricultural land uses – sugarcane farming and pastures for cattle grazing (ponded and dry conditions). We assessed variations throughout different climatic conditions (dry–cool, dry–hot, and wet–hot) within 2 years of measurements (2018–2020) in tropical Australia. The wet pasture had by far the highest CH4 emissions with 1231±386 mgm-2d-1 , which were 200-fold higher than any other site. Dry pastures and sugarcane were the highest emitters of N2O with 55±9 mgm-2d-1 (wet–hot period) and 11±3 m gm-2d-1 (hot-dry period, coinciding with fertilisation), respectively. Dry pastures were also the highest emitters of CO2 with 20±1 gm-2d-1 (wet–hot period). The three coastal wetlands measured had lower emissions, with salt marsh uptake of -0.55±0.23 and -1.19±0.08 gm-2d-1 of N2O and CO2 , respectively, during the dry–hot period. During the sampled period, sugarcane and pastures had higher total cumulative soil GHG emissions (CH4+N2O) of 7142 and 56 124 CO2-eqkgha-1yr-1 compared to coastal wetlands with 144 to 884 CO2-eqkgha-1yr-1 (where CO2-eq is CO2 equivalent). Restoring unproductive sugarcane land or pastures (especially ponded ones) to coastal wetlands could provide significant GHG mitigation.
- Subjects
AUSTRALIA; COASTAL wetlands; FARMS; WETLAND soils; SOIL air; GREENHOUSE gases; POTTING soils
- Publication
Biogeosciences, 2021, Vol 18, Issue 18, p5085
- ISSN
1726-4170
- Publication type
Article
- DOI
10.5194/bg-18-5085-2021