Elevated carbon dioxide stimulates nitrous oxide emission in agricultural soils: A global meta-analysis

Abstract

Elevated carbon dioxide (CO 2 ) (eCO 2 ) has been shown to affect the nitrous oxide (N 2 O) emission from terrestrial ecosystems by altering the interaction of plants, soils, and microorganisms. However, the impact of eCO 2 on the N 2 O emission from agricultural soils remains poorly understood. This meta-analysis summarizes the effect of eCO 2 on N 2 O emission in agricultural ecosystems and soil physiochemical and biological characteristics using 50 publications selected. The eCO 2 effect values, which equal to the percentage changes of N 2 O emission under eCO 2 , were calculated based on the natural logarithm of the response ratio to eCO 2 . We found that eCO 2 significantly increased N 2 O emission (by 44%), which varied depending on experimental conditions, agricultural practices, and soil properties. In addition, eCO 2 significantly increased soil water-filled pore space (by 6%), dissolved organic carbon content (by 11%), and nitrate nitrogen content (by 13%), but significantly reduced soil pH (by 1%). Moreover, eCO 2 significantly increased soil microbial biomass carbon (by 28%) and soil microbial biomass nitrogen (by 7%) contents. Additionally, eCO 2 significantly increased the abundances of ammonia-oxidizing bacteria (AOB) amoA (by 21%), nirK (by 15%), and nirS (by 15%), but did not affect the abundances of ammonia-oxidizing archaea (AOA) amoA and nosZ . Our findings indicate that eCO 2 substantially stimulates N 2 O emission in agroecosystems and highlight that optimization of nitrogen management and agronomic options might suppress this stimulation and aid in reducing greenhouse effect.