Effects of UV‐B radiation on soil carbon conversion and greenhouse gas emission in paddy soil

Abstract

This paper evaluates the relationship between ultraviolet-B (UV-B, 280-315 nm) radiation enhancement on the earth's surface caused by ozone attenuation and climate change. A pot experiment was conducted to investigate the effects of enhanced UV-B radiation on greenhouse gas (GHG) emissions from the paddy soil with rice straw incorporation (SI). The paddy soil was sampled from the Yuanyang Terrace, Yunnan Province, Southwest China. There were four treatments: natural light (control check, CK), 5.0 kJ•m −2 UV-B radiation (UVB), SI, and SI + UVB. The effects of UV-B radiation (5.0 kJ•m −2) on straw degradation, soil carbon invertase activity, active organic carbon content, and GHG emissions were studied. The results showed that UV-B radiation promoted the degradation of straw components (lignin, cellulose, hemicellulose, and water-soluble phenol). The SI treatment significantly increased the activity of soil carbon invertase (P < 0.05), the content of soil active organic carbon (P < 0.05), and the emission rates and amounts of GHGs (P < 0.05). Compared to the SI treatment, SI + UVB treatment reduced soil carbon invertase activity and active organic carbon content, resulting in a 17% reduction in CH 4 emission and a 40% and 16% increase in CO 2 and N 2 O emission (P < 0.05), but had no significant effect on the global warming potential (GWP). Correlation analysis showed that the degradation rate of straw components was positively correlated with the activity of carbon invertase, the contents of microbial biomass carbon (MBC), easily oxidized organic carbon (EOC), and the CO 2 emission rate; the activities of sucrase and cellulase were positively correlated with the contents of MBC and EOC, which were in turn positively correlated with the emission rates of CH 4 and CO 2. Under SI, UV-B radiation reduced the soil carbon conversion, which led to a decreased CH 4 emission and increased emissions of CO 2 and N 2 O, but did not alter the GWP of GHGs from the paddy soil.

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Enhanced ultraviolet-B radiation reduces methane emission in one of the oldest and largest rice terraces in China but triggers new challenges

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