Changes in soil nematode abundance and composition under elevated [CO2] and canopy warming in a rice paddy field

Global climate change is characterized by enhanced atmospheric carbon dioxide concentration ([CO2]) and temperature, with unknown consequences for soil nematode communities. Soil nematode in response to elevated [CO2], warming and their interaction in paddy field remain largely unknown. Here we aimed to understand how factorial combinations of elevated [CO2] and canopy warming affect soil nematode in a rice paddy field. A rice paddy field was consistently treated with elevated [CO2] (500 ppm), canopy warming (+2 °C) or their combinations. Soil samples after a two-year treatment were collected during the rice growing season and nematode communities were extracted with a modified Baermann funnel extraction to examine the changes in nematode abundance and composition under climate change. Soil nematode communities were altered by elevated [CO2] and warming, but these responses were dependent on rice growing stages. When averaged over the four stages, total nematode abundances were increased by 31.5% under elevated [CO2], and by 25.7% under warming. Elevated [CO2] had no effect on nematode diversity, but slightly altered the composition of different trophic groups. In contrast, warming decreased nematode diversity, but increased plant parasite index, which was negative correlated with crop production. This was attributed to increases in the relative abundance of herbivores under simulated climate change conditions. Elevated [CO2] and warming had a positive effect on nematode abundance, but potentially reduced nematode diversity and soil health. These results suggest that multi-factors interactively affect the responses of soil nematode communities, which is important for food productivity under climate change.