Responses of greenhouse-gas emissions to land-use change from rice to jasmine production in subtropical China

Publication date: Available online 28 December 2018

Source: Atmospheric Environment

Author(s): Chun Wang, Qingwen Min, Weiqi Wang, Jordi Sardans, Congsheng Zeng, Chuan Tong, Josep Peñuelas

Abstract

We studied the impacts of an increasingly common change in land use from paddy field to jasmine fields on the emission of greenhouse gases (GHGs), which have supposed the transformation of more than 1200 ha only in the last decade in the surroundings of Fuzhou city in response to economic changes. The possible increases that this can suppose constitutes and environmental concern in China. We studied areas dedicated to rice crop that have been partially converted to jasmine cultivation with some parts still kept as rice fields. Emissions of CO₂, CH₄ and N₂O varied significantly among the seasons. CO₂ and CH₄ cumulative emissions and the global-warming potential (GWP) of these emissions were significantly lower in the jasmine than the paddy field. N₂O emission, N₂O cumulative emission, however, were higher in the jasmine than the paddy field, despite in some concrete studied periods the differences were not statistically significant. The total decrease in GHG emissions from the conversion from rice to jasmine production was strongly influenced by the indirect effects of various changes in soil conditions. The expected changes due to the great differences in water and fertilization use and management and organic matter input to soil between these two crops were in great part due to modified soil traits. According to structural equation models, the strong direct effects of the change from rice to Jasmine crop reducing the emissions of CO₂ and N₂O were partially decreased by the indirect effects of crop type change decreasing soil pH and soil [Fe²⁺] for CO₂ emissions and by decreasing soil salinity and soil [Fe³⁺] for N₂O emissions. The negative effects of the crop conversion on CH₄ emissions were mostly due to the globally negative indirect effects on soil conditions, by decreases in soil salinity, water content and [Fe²⁺]. Soil salinity, water content, pH, [Fe²⁺], [Fe³⁺] and [total Fe] were significantly lower in the jasmine than the paddy field, but temperature had the opposite pattern. CO₂ emissions were generally correlated positively with salinity, temperature, and water content and negatively with [Fe³⁺] and [total Fe] in both fields. CH₄ emissions were positively correlated with salinity, temperature, water content and pH in both fields. N₂O emissions were positively correlated with temperature and were negatively correlated with water content, pH, [Fe²⁺], [Fe³⁺] and [total Fe] in both fields. CO₂ was the most important GHG for the GWPs, and the total GWP was significantly lower for the jasmine than for the rice cropland field. The change in the land use in this area of paddy fields will decreased the global GHG emission, and the effect on the GWPs was mostly due to changes in soil properties.

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