长期大气CO_(2)浓度和温度升高对玉米生物量及根际磷组分的影响

Long-term effect of atmospheric CO_(2)concentration and temperature co-elevation on maize biomass and the phosphorus fraction in the rhizosphere of maize

在农业系统中,作物通过刺激根系生长和调节根际生化特征从土壤中获取更多磷(P)以满足产量增长需求,根际有效磷的吸收势必影响土壤磷转化。然而,长期大气CO_(2)浓度和温度升高对作物生长、土壤磷组分以及相关微生物机制的影响鲜有研究。本研究利用开顶式生长室(OTC)重点探究了气候变化对黑土区玉米根际土壤磷组分和相关磷转化微生物功能基因的影响。结果表明,连续4年CO_(2)浓度和温度升高使玉米生物量增加10%~40%,磷吸收增加20%~80%。另外,大气CO_(2)浓度和温度升高使玉米根际NaHCO_(3)可提取无机磷(NaHCO_(3)-Pi)下降了24%,而NaHCO_(3)可提取有机磷(NaHCO_(3)-Po)增加了22%。然而,大气CO_(2)浓度、温度以及两者同时升高使NaOH可提取有机磷(NaOH-Po)分别降低了27%、74%和20%。大气CO_(2)浓度和温度同时升高显著增加了酸性磷酸酶活性(P<0.05),并且玉米根际磷酸酶活性与NaOH-Po呈负相关关系。大气CO_(2)浓度和温度同时升高增加了根际土壤phoC(酸性磷酸酶合成基因)、phoD(碱性磷酸酶合成基因)和pstS(磷转运因子)基因拷贝数。长期大气CO_(2)浓度和温度升高能够促进玉米生长,并通过刺激根际微生物磷矿化基因丰度和相关酶活性影响土壤磷组分,气候变化可能改变根际磷转化的微生物生态功能,进而影响黑土磷循环。

In agrosystems,crop plants normally increase phosphorus acquisition to achieve yield gain by increasing root growth and changing biochemical characteristics in the rhizosphere,which likely affects soil phosphorus transformation.However,few studies have investigated the long-term effect of elevated CO_(2)concentration and temperature on crop growth,soil phosphorus fraction and relevant microbial mechanisms.The study used open-top growth chambers to mainly investigate the effect of elevated CO_(2)and warming on soil phosphorus fractions and relevant functional genes in Mollisols.The results showed that the elevated CO_(2)concentration and temperature for 4 consecutive years increased the maize biomass by 10%~40%and phosphorus uptake by 20%~80%.Long-term CO_(2)and temperature co-elevation decreased NaHCO_(3)-extractable inorganic phosphorus(NaHCO_(3)-Pi)concentration in the rhizosphere by 24%while increased NaHCO_(3)-extractable organic phosphorus(NaHCO_(3)-Po)by 22%compared with the control.However,elevated CO_(2)concentration,warming,and CO_(2)plus warming reduced NaOH-Po by 27%,74%,and 20%,respectively.In addition,CO_(2)and temperature co-elevation increased the activity of acid phosphatase,which was negatively correlated with NaOH-Po.The CO_(2)and temperature co-elevation increased the copy numbers of phoC(acidic phosphatases producing gene),phoD(alkaline phosphatases producing gene)and pstS(phosphate-specific transporter gene)genes in the rhizosphere.These results suggest that long-term CO_(2)and temperature co-elevation promotes crop growth and alters soil phosphorus fractions through changing the abundance of functional genes and phosphatase activity.Climate change may impact the microbial eco-function on phosphorus transformation and consequent phosphorus cycling in Mollisols.