Effects of Land Use Types on CH4 and CO2 Production Potentials in Subtropical Wetland Soils.
Xu, J., D. Y. F. Lai, and S. Neogi, . 2020.
Abstract
Changes in land use types can alter the soil and environmental characteristics of wetlands,
which in turn influence the magnitude of greenhouse gas production by soil microbes. However,
the effects of land use change on the production potential of methane (CH4) and carbon dioxide
(CO2) in subtropical wetland soils and the underlying controls are still largely unknown. In this
study, we examined the soil CH4 and CO2 production potentials under five different land use types
(natural mangrove, Gei Wai water channel, Gei Wai forest, reedbed, and freshwater pond) and
their relationships with soil physico-chemical properties in a subtropical wetland in Hong Kong
using aerobic and anaerobic laboratory incubation experiments. Our results showed an overall
decreasing trend of CH4 and CO2 production potentials down the soil profile at all sites, which could
be attributed to a reduction in the concentrations of soil organic matter (SOM), total Kjeldahl
nitrogen (TKN) and ammonium nitrogen (NH4 -N). Moreover, the soil CH4 and CO2 production
potentials varied significantly in the surface soils among land use types, but were more similar
across the sites in the deeper soils. The conversion of natural mangrove to other land use types
significantly reduced both the aerobic and anaerobic CO2 production potentials in the top 10 cm
soils, except for Gei Wai forest, which demonstrated significantly higher CO2 production rates
(61.15 - 97.91 µg g-1 day-1). Meanwhile, the mean CH4 production potential in the surface soils
of natural mangrove (0.05 µg g-1 d-1) was significantly lower than that in the GeiWai forest and
GeiWai channel (0.26 - 0.27 µg g-1 day-1) but slightly higher than that in the freshwater pond and
reedbed (0.00 - 0.02 µg g-1 day-1). The high soil CH4 and CO2 production potentials observed in
the GeiWai forest could be explained by the high soil concentrations of SOM, TKN and NH4 -N.
On the other hand, the lower anaerobic CH4 and aerobic CO2 productions observed in the reedbed
could be attributed to the lower concentrations of NH4 -N and available phosphorus. Our findings
highlighted the significant impacts of land use types on the CH4 and CO2 production potentials of
subtropical wetland soils, which had practical implications for wetland management for climate
change mitigation.
Key Words
carbon dioxide; gas production potential; greenhouse gas; land use; mangrove; methane; soil properties; wetland
