Cultivar specific plant-soil feedback overrules soil legacy effects of elevated ozone in a rice-wheat rotation system

Tropospheric ozone has been recognized as one of the most important air pollutants. Many studies have shown that elevated ozone negatively impacts yields of important crops such as wheat or rice, but how ozone influences soil ecosystems of these crops and plant growth in rotation systems is less well understood. Using soil collected from a free-air ozone enrichment experiment running for 5 years, we carried out a plant-soil feedback experiment under greenhouse conditions to evaluate the influence of wheat cultivars (Triticum aestivum L.) with different ozone-tolerance on rice (Oryza sativa L.) grown in soils with or without a history of ozone exposure. Our results indicate that there were interactive effects of wheat cultivar and history of ozone exposure on soil respiration and the abundance of fungivorous nematodes. Moreover, the soil microbial community and the abundance of omnivorours-predatory nematodes varied in different wheat cultivars. These differences in the soil, in turn, had feedback effects on the succeeding growth of rice. Rice grown in soil in which previously the ozone-sensitive wheat cultivars Yangmai 2 or Yangmai 19 had grown, had lower shoot biomass than rice grown in the ozone-tolerant wheat cultivars Yangmai 16 soil. However, these cultivar specific effects on rice growth were independent from the previous ozone exposure of the soil. Our results suggest that, in rice-wheat rotation systems, when selecting wheat cultivars to cope with changing climatic conditions, such as elevated ozone, growers should consider the soil-feedback effects of these cultivars on the succeeding crop.