Elevated atmospheric CO2 can influence soil C dynamics in agroecosystems.The effects of free-air CO2 enrichment(FACE) and N fertilization on soil organic C(Corg) ,dissolved organic C(DOC) ,microbial biomass C(Cmic) and soil basal respiration(SBR) were investigated in a Chinese wheat field after expose to elevated CO2 for four full years.The results indicated that elevated CO2 has stimulative effects on soil C concentrations regardless of N fertilization.Following the elevated CO2,the concentrations of Corg and SBR were increased at wheat jointing stage,and those of DOC and Cmic were enhanced obviously across the wheat jointing stage and the fallow period after wheat harvest.On the other hand,N fertilization did not significantly affect the content of soil C.Significant correlations were found among DOC,Cmic,and SBR in this study.
【目的】揭示大气CO2浓度升高和氮肥管理对地下生态系统的影响。【方法】采用中国稻麦轮作FACE(Free-Air CO2 Enrichment)系统平台,开展了大气CO2浓度升高和氮肥管理对土壤线虫群落组成影响的研究。【结果】在稻麦轮作系统共观察到线虫35属,15个功能团。拟丽突属、真头叶属、丝尾属和潜根属为优势属,其中丝尾属和真头叶属对CO2浓度升高和氮肥管理反应敏感。在CO2浓度升高条件下土壤线虫总数、功能团Fu2和Om4的线虫多度均显著增加,其中Fu2多度在CO2和氮肥的交互影响下变化明显。【结论】CO2浓度升高和氮肥管理改变了土壤腐屑食物网的结构和有机质的分解途径。高氮条件下,CO2浓度升高降低了线虫的通路指数(CI),细菌为主的分解通道在小麦季的FACE(HN)处理中占优势。不同施氮水平对线虫结构指数(SI)产生显著影响,低氮条件下较高的SI值表明土壤环境受到的扰动较小,食物网处于结构化状态。
为了探讨全球气候变化对农田土壤氮素动态的影响,采用中国稻麦轮作系统FACE(Free-Air CO2 Enrichment)平台,开展了大气CO2浓度升高和氮肥管理对麦田土壤有效氮含量影响的研究。结果表明:在低N和常规N处理下,大气CO2浓度升高使拔节期土壤C/N分别增加了5.6%和10.2%,土壤pH分别降低了2.4%和6.4%(p<0.05)。在小麦生育期内,低N和常规N条件下,大气CO2浓度升高降低了土壤总有效氮和NO3--N含量,相对于低N处理,常规N处理下降的趋势更为明显。在低N条件下,大气CO2浓度使拔节期和成熟期土壤中NH4+-N含量分别增加了7.4%和9.9%,而常规N处理中则表现出相反的趋势。本研究显示,大气CO2浓度升高降低了土壤有效氮含量,而施用氮肥增加了土壤有效氮含量。
