大气CO2浓度增高对麦田土壤硝化和反硝化细菌的影响

硝化和反硝化细菌是土壤中与氮转化有关的微生物菌群 ,大气CO2 浓度升高可能对它们的数量产生影响。位于中国无锡的稻 麦轮作农田生态系统FACE平台 2 0 0 1年 6月开始运行。本试验在 2 0 0 3年小麦生长季研究了土壤 (0～ 5cm和 5～ 10cm土层 )中硝化和反硝化细菌在大气CO2 浓度升高条件下的变化。试验采用最大可能法 (MPN)计这两种微生物菌群的数量。结果表明 ,0～ 5cm土层硝化菌数拔节期和成熟期FACE低于对照 ,而孕穗期FACE高于对照 ,5～ 10cm土层硝化菌数越冬期与成熟期FACE低于对照 ,大气CO2 浓度升高使得麦田土壤硝化细菌数目减少。 0～ 5cm土层各个生长期反硝化菌数FACE与对照均没有明显差异 ,5～ 10cm土层反硝化菌数拔节期FACE低于对照 ,大气CO2 浓度升高对麦田土壤反硝化菌的影响不大。

Effects of FACE (free-air carbon dioxide enrichment) on nitrifiers and denitrifiers in wheat field soil

Elevated atmospheric CO 2 concentrations may alter nitrifiers and denitrifiers which are related to soil N turnover.A free-air CO 2 enrichment (FACE) experiment was conducted to evaluate changes in the rice-wheat rotation ecosystem under enriched CO 2 conditions from 2001 at Wuxi,China.We measured numbers of nitrifiers and denitrifers from FACE wheat fields and wheat fields with ambient levels of CO 2 during the 2003 wheat-growing seasons.Nitrifiers and denitrifiers populations were estimated by the most probable number (MPN) method.The results showed that raised atmospheric CO 2 concentrations decreased nitrifiers numbers in the upper soil layer at jointing and ripening stages,whereas at booting stage, nitrifiers number from FACE plots was higher than that from ambient plots.Nitrifiers populations from FACE plots were lower than that from ambient plots at wintering and ripening stages in the lower soil layer.Increased CO 2 has negative influence on nitrifiers number.There is no significant difference between denitrifiers numbers from FACE plots and ambient plots in the upper soil layer.At jointing stage denitrifiers numbers from FACE plots were lower than that from ambient plots in the lower soil layer.Denitrifiers are not sensitive to changes that altered by elevated CO 2.