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

Soil carbohydrates are sensitive to changes in soil C inputs because of their fast turnover rates. However, the effects of elevated O-3 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 O-3 on the content and composition of soil neutral sugars in the two wheat cultivars with different O-3-tolerance. Our results showed that elevated O-3 decreased the total soil neutral sugars. At the wheat ripening stage, elevated O-3 increased the contents of galactose (Gal), arabinose (Ara) and mannose (Man) in the O-3-tolerant wheat and decreased the contents of xylose (Xyl), Gal and Ara in the O-3-sensitive wheat. Significant interactive effects between elevated O-3 and wheat cultivar were found in the ratios of (Man + Gal)/(Ara + Xyl) and Man/(Ara + Xyl). These two ratios increased with elevated O-3 at the wheat ripening stage in both wheat cultivars, with higher ratios observed in the O-3-sensitive wheat relative to the O-3-tolerant wheat. Our results indicated that elevated O-3 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 O-3-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. (C) 2014 Elsevier B.V. All rights reserved.