Evaluation of soil metazoan communities under short-term elevated CO2 and O3 concentrations in paddy soils

Soil biota mediates key ecological processes and delivers a range of societally important ecosystem services. However, the impacts of atmospheric changes on soil metazoans have been understudied. To address this knowledge gap, we evaluated the short-term responses of soil metazoans to elevated CO2 and O3 with two commonly grown rice varieties (Nanjing 5055 and Wuyujing 3) in paddy soils. A combined increase of CO2 and O3 concentrations had a negligible effect on the diversity of Annelida, Mollusca, Porifera, and total soil metazoans, suggesting that soil metazoan taxa had potential inherent resilience to atmospheric changes. However, elevated CO2 alone significantly enhanced the diversity and relative abundance of Craniata and Platyhelminthes for Wuyujing 3 under ambient O3 conditions. However, increasing O3 decreased the diversity and relative abundance of Craniata by 42.7% and 47.7%, respectively, especially under elevated CO2 conditions for Wuyujing 3, leading to significant interactive effects. Furthermore, soil NO3--N and NH4+-N concentrations mostly shaped the changes in the diversity and composition of soil metazoans. These results highlight the crucial role of rice variety in the complex interaction between short-term elevated CO2 and O3 in the soil metazoan community. Thus, to better understand the mechanisms and processes within soil food webs, future studies should include the combined effects of climate change factors and crop varieties on the soil metazoan communities.