Elevated O3 and wheat cultivars influence the relative contribution of plant and microbe-derived carbohydrates to soil organic matter

• Elevated O3 decreased the total neutral sugars of two wheat cultivars.
• Elevated O3 altered the relative contribution of plant and microbe-derived carbohydrates to SOM.
• Microbe-derived carbohydrates were dominant in the O3-sensitive wheat.

Soil carbohydrates are sensitive to changes in soil C inputs because of their fast turnover rates. However, the effects of elevated O3 on the content and composition of soil carbohydrates are rarely reported in agroecosystem. The objectives of this study were to investigate the effects of elevated O3 on the content and composition of soil neutral sugars in the two wheat cultivars with different O3-tolerance. Our results showed that elevated O3 decreased the total soil neutral sugars. At the wheat ripening stage, elevated O3 increased the contents of galactose (Gal), arabinose (Ara) and mannose (Man) in the O3-tolerant wheat and decreased the contents of xylose (Xyl), Gal and Ara in the O3-sensitive wheat. Significant interactive effects between elevated O3 and wheat cultivar were found in the ratios of (Man + Gal)/(Ara + Xyl) and Man/(Ara + Xyl). These two ratios increased with elevated O3 at the wheat ripening stage in both wheat cultivars, with higher ratios observed in the O3-sensitive wheat relative to the O3-tolerant wheat. Our results indicated that elevated O3 decreased the total neutral sugars and altered the relative contribution of plant- and microbe-derived carbohydrates to soil organic matter. Microbe-derived carbohydrates were dominant contribution to the total carbohydrates in the O3-sensitive wheat. These changes in the accumulation and origins of soil carbohydrates will influence the accumulation and decomposition of soil organic matter and ecosystem functioning in agroecosystem.