Soil greenhouse gas fluxes from tropical coastal wetlands and alternative agricultural land uses.

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From: Biogeosciences(Vol. 18, Issue 18)
Publisher: Copernicus GmbH
Document Type: Brief article
Length: 308 words

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Abstract :

Coastal wetlands are essential for regulating the global carbon budget through soil carbon sequestration and greenhouse gas (GHG - CO.sub.2, CH.sub.4, and N.sub.2 O) 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 CH.sub.4 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 N.sub.2 O with 55±9 mgm-2d-1 (wet-hot period) and 11±3 mgm-2d-1 (hot-dry period, coinciding with fertilisation), respectively. Dry pastures were also the highest emitters of CO.sub.2 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 N.sub.2 O and CO.sub.2, respectively, during the dry-hot period. During the sampled period, sugarcane and pastures had higher total cumulative soil GHG emissions (CH.sub.4 +N.sub.2 O) of 7142 and 56 124 CO2-eqkgha-1yr-1 compared to coastal wetlands with 144 to 884 CO2-eqkgha-1yr-1 (where CO.sub.2-eq is CO.sub.2 equivalent). Restoring unproductive sugarcane land or pastures (especially ponded ones) to coastal wetlands could provide significant GHG mitigation.

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Gale Document Number: GALE|A675712914