Elevated CO2 and nitrogen addition have minimal influence on the rhizospheric effects of Bothriochloa ischaemum

The influence of elevated CO2 and nitrogen (N) addition on soil microbial communities and the rhizospheric effects of Bothriochloa ischaemum were investigated. A pot-cultivation experiment was conducted in climate-controlled chambers under two levels of CO2 (400 and 800 mu mol mol(-1)) and three levels of N addition (0, 2.5, and 5 g N m(-2) y(-1)). Soil samples (rhizospheric and bulk soil) were collected for the assessment of soil organic carbon (SOC), total N (TN), total phosphorus (TP), basal respiration (BR), and phospholipid fatty acids (PLFAs) 106 days after treatments were conducted. Elevated CO2 significantly increased total and fungal PLFAs in the rhizosphere when combined with N addition, and N addition significantly increased BR in the rhizosphere and total, bacterial, fungal, Gram-positive (G(+)), and Gram-negative (G-) PLFAs in both rhizospheric and bulk soil. BR and total, bacterial, G(+), and G(+)/G-PLFAs were significantly higher in rhizospheric than bulk soil, but neither elevated CO2 nor N addition affected the positive rhizospheric effects on bacterial, G(+), or G(+)/G-PLFAs. N addition had a greater effect on soil microbial communities than elevated CO2, and elevated CO2 and N addition had minor contributions to the changes in the magnitude of the rhizospheric effects in B. ischaemum.