氮素添加和CO_2浓度升高对白羊草根际和非根际土壤水溶性有机碳、氮的影响

Effects of nitrogen addition and elevated CO_2 concentration on soil dissolved organic carbon and nitrogen in rhizosphere and non-rhizosphere of Bothriochloa ischaemum

采用盆栽控制试验对黄土丘陵区白羊草在不同CO_2浓度(400和800μmol·mol^(-1))和施氮水平(0、2.5、5.0 g N·m^(-2)·a^(-1))条件下根际和非根际土壤水溶性有机碳(DOC}和水溶性有机氮(DON)的变化特征进行研究.结果表明:CO_2浓度升高对白羊草根际和非根际土壤DOC、水溶性总氮(DTN)、DON、水溶性铵态氮(NH_4^+-N)、水溶性硝态氮(NO_3^-N)含量均无显著影响.施氮显著提高了根际和非根际土壤DTN、NO_3^-N含量和根际土壤DON含量,显著降低了根际土壤DOC/DON.在各处理条件下,根际土壤DTN、NO_3^-N和DON含量均显著低于非根际土壤,根际土壤DOC/DON显著高于非根际土壤.短期CO_2浓度升高对黄土丘陵区土壤水溶性有机碳、氮含量无显著影响,而氮沉降的増加在一定程度上改善了土壤中水溶性氮素缺乏的状况,但并不足以满足植被对水溶性氮素的需求.

A pot experiment was conducted to study soil dissolved organic carbon （DOC） and dis- solved organic nitrogen （DON） in the rhizosphere and non-rhizosphere of Bothriochloa ischaemum in loess hilly-gully region under the different treatments of CO2 concentrations （400 and 800 μmol · mol-1） and nitrogen addition （0, 2.5, 5.0 g N· m-2 · a-1）. The results showed that elevated CO2 treatments had no significant effect on the contents of DOC, dissolved total nitrogen （DTN）, DON, dissolved ammonium nitrogen （NH4＋-N） and dissolved nitrate nitrogen （NO3--N） in the soil of rhizosphere and non-rhizosphere of B. ischaemum. The contents of DTN, DON, and NO3--N in the rhizosphere soil were significantly increased with the nitrogen application and the similar results of DTN and NO3--N also were observed in the non-rhizosphere of B. ischaemum. Nitrogen application significantly decreased DOC/DON in the rhizosphere of B. ischaemum. The contents of DTN, NO3--N and DON in the soil of rhizosphere were significantly lower than that in the non-rhizosphere soil, and DOC/DON was significantly higher in the rhizosphere soil than that in the non-rhizosphere soil. It indicated that short-term elevated CO2 concentration had no significant influence on the contents of soil dissolved organic carbon and nitrogen. Simulated nitrogen deposition, to some extent, increased the content of soil dissolved nitrogen, but it was still insufficient to meet the demand of dissolved nitrogen for plant growing.