| In recent years,global warming,acid rain and food shortage are increasingly prominent.It is generally believed that the increase of the concentration of greenhouse gases in the atmosphere is one of the main causes of global warming,and the increasing oxides of nitrogen,sulfur in the atmosphere is the main cause to the aggravating acid rai.Farmland ecosystem is not only one of the major sources of greenhouse gases,but also the suffer of the acid rain,acting on each other,the three factors affect human survival and development in together.In this study,Wufeng Experimental Station of Fujian Rice Institute was chosen as the plot,and the influences of acid rain on the nutrient dynamic and the change of the greenhouse gas emission in the rice paddies were studied by simulating different acidity(pH4.5,pH3.5,pH2.5)acid rain,so as to provide reference to the sustainable food production and carbon sequestration and mitigating.The main results are showed as follows:(1)Compared to the control,acid rain made the SOC content increase in the whole growing stages,and the DOC content changed in the recovering date under the influence of acid rain in the early and late rice paddy.Under the action of acid rain,the soil EOC content was not different from the control in the whole growing stages of the early rice,while the soil EOC in the late rice paddy decreased significantly under the action of the pH4.5 and 3.5 acid rain(P<0.05).Acid rain increased the content of soil MBC early rice in the recovering date and mature period and decreased its content in elongation stage in the early rice field,and in particular,the pH4.5、pH3.5 and pH2.5 acid rain made the soil MBC higher than the control 37.01%、52.61%and 41.56%in turn in the mature period(P<0.05),while in jointing stage,acid rain reduced the soil MBC content reduce signally(P<0.05)in the early rice paddy.However,in the late rice field,acid rain enhanced the soil MBC during the recovering date and inhibited its content in mature period markedly(P<0.05).Both in the early and late rice paddy,acid rain made soil TN and SAN content increase during the three growth periods.During the recovering and elongation stage,the influence of acid rain on the soil MBN in early and late rice paddy had no obvious change rule,and mature period,under the action of acid rain,compared with the control,the soil MBN reduced significantly in late rice paddy(P<0.05).Under the action of acid rain,the soil TP content was obviously higher than that of control in the whole growth periods of the early and late rice(P<0.05).The pH 4.5 and 3.5 acid rain reduced soil SAP content during early rice reviving period significantly(P<0.05),and the soil SAP content of early rice acid rain treatments were higher than the control(P<0.05);and in late rice field,acid rain made SAP content increase significantly in recovering period(P<0.05).(2)Acid rain had significant effects on the contents of C,N,P of early rice root(P<0.05),but no significant effect on the nutrient content of late rice root.Compared with the control,when acid rain pH was 3.5,contents of early rice roots TC,TN reduced in recovering and elongation stage,and increased in mature period,while when acid rain pH was 4.5 or 2.5,early rice roots TC,TN content gradually increased during the whole growth period.In elongation and mature stage,pH2.5 acid rain made the content of TP in early rice root increase by 45.59%and 45.59%respectively(P<0.05).Compared with control group,acid rain made the TC in early rice stem increased in recovering and elongation period and reduced in mature stage,while the TN in early rice stem add in recovering and mature period,and reduce in elongation stage(except the pH4.5 acid rain treatment).Under the action of pH2.5 acid rain,the TP in early rice stem was more than the control in recovering and mature period,while pH 4.5or 3.5 acid rain made the content of TP less than the control.The TP content in late rice stem was reduced significantly by acid rain(P<0.05).The contents of TC,TN,TP in early rice leaf were affected significantly by acid rain,while the influence in late rice was not significant.Under the action of acid rain,the TN,TP in early rice leaves were was more than the control in elongation stage and less than the control in mature stage(P<0.05).(3)Compared with the control,acid rain had no obvious effect on the early rice yield,while pH4.5 acid rain significantly inhibited the setting rate of the late rice(P<0.05);the pH3.5 acid rain had improved significantly on the setting rate and yield of the late rice(P<0.05),yet the pH4.5 and 2.5 acid rain had no significant effect on them.(4)The whole growth period of early and late rice,the emission of N2O had no obvious regularity.Acid rain reduced the emission fluxes of CO2,CH4 and N2O,but did not change the seasonal variation characteristics of CO2 and CH4 in early and late rice paddies.Compared to the control,pH4.5,3.5 and 2.5 acid rain decreased the comprehensive greenhouse effect by 16.40%,14.37%,4.65%in early rice paddy,and 31.91%,18.43%,6.63%in late rice field,which indicated that acid rain could inhibit the greenhouse effect in rice paddy. |
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