Effect of Elevated UV-B Radiation on Microbial Biomass C and Soil Respiration in Different Barley Cultivars Under Field Conditions

Elevated ultraviolet-B (UV-B) radiation effect on soil carbon (C) cycling has been regarded as one of the important issues in global change. Field simulating experiment was conducted to investigate the effects of elevated UV-B radiation on the content of microbial biomass C in rhizosphere and non-rhizosphere soils as well as soil respiration in three barley cultivars. The UV-B radiation was set at two levels, i.e., reference (A, ambient UV-B radiation), and elevated by 20% (E, elevated UV-B radiation, 14.4 kJ m(-2) day(-1)). Three barley cultivars were tested including Dan 2, Supi 3, and Supi 4, respectively. The results indicated that elevated UV-B radiation obviously decreased the content of microbial biomass C in rhizosphere and non-rhizosphere soil, but had no effect on the tendency of microbial biomass C in rhizosphere and non-rhizosphere soil during the entire barley growing season. Compared with control (ambient UV-B radiation), elevated UV-B radiation depressed soil respiration rate and its temperature sensitivity coefficients (Q(10)), especially in barley cultivar Dan 2 and cultivar Supi 3. It is suggested that the different responses of three barley cultivars to elevated UV-B radiation were related to the changes of microbial biomass C and soil respiration.