| In this study,Quercus acutissima was selected as the experimental object in the Tongshan Forest Farm in the outskirts of Nanjing.The different pH values(4.5,3.5,2.5)were added in the field(5:1,1:1,1:5).A total of nine types of acid rain for one year to simulate different types of acid rain(control for the flow of mountain fire water,pH was 6.6,while each treatment of three repetitions),explore the complex forest environment conditions The effect of acid rain on the growth of fine root and the content of main components in the forest were studied.The results showed that:(1)After adding acid rain,the biomass,root number,length and living root ratio showed 4.5>CK(6.6)>3.5>2.5,and the average root diameter showed 4.5<CK(6.6)<3.5<2.5characteristic rule,fine root turnover rate also decreased with the acid rain pH value in creased first and then decreased.Indicating that with the acid rain ph value decreased,acid rain on the fine root for the first to promote the role of inhibition.The ratio of root biomass,root length,length,rooting ratio and turnover rate showed a trend of 5:1>1:1>1:5,and the average root diameter was the same between different sulfur and nitrogen treatments.The difference between the treatment of different sulfur and nitrogen and acid treatment decreased with the decrease of pH value of acid rain,which was 5:1<1:1<1:5.It is shown that the stress effect of N is stronger than that of S,and the decrease of sulfur and nitrogen ratio in acid rain is the increase of nitrogen,which is not conducive to the growth of fine roots.Under the same treatment,the change of root tip density and root length density was very large,and the change of biomass quantity was relatively small,which indicated that the effect of acid rain on fine roots was mainly in the small diameter(primary and secondary roots),The effect on the root(three,four,five root)is not significant.(2)After adding acid rain,the fine root carbon content increased in May,and there was no obvious characteristic rule.In August and February,the carbon content of fine root showed a trend of 4.5>CK>3.5>2.5,and the trend of CK>4.5,3.5>2.5 was observed in November,and 5:1>1:1>1:5.At pH 2.5,the carbon content in August,November and February decreased by 2.52%,0.7% and 1.6%,respectively,compared with the control.There was no significant effect of pH on the carbon content of fine root(P>0.5),and the other months had significant effect(P<0.05).The sulfur and nitrogen ratios of acid rain in May and August had a significant effect on the carbon content of fine roots,and there was no significant effect in November and February.There was a significant difference between different sulfuric acid rain treatments,but the difference characteristics varied with acid rain duration and acid rain acidity.The content of fine root nitrogen increased with the increase of acid nitrogen in 1 month(August),and the pH value of pH value was 4.5,3.5 and 2.5 in February,respectively.The average root nitrogen content decreased by 13%,16% and 18%,respectively.Under the action of acid rain,the ratio of carbon to nitrogen in fine roots showed a significant increase trend.The pH value of acid rain had no significant effect on the content of fine root and nitrogen.The ratio of sulfur to nitrogen had significant effect on the content of fine root and nitrogen in November and February,and the interaction had significant effect on the content of fine root nitrogen.The content of fine root and phosphorus in some types of acid rain treatment increased,but the difference was not significant,and the content of fine root phosphorus under acid rain was mainly decreased.The average phosphorus content of fine roots decreased by 10.5% and 23.6%,respectively,in the treatment of pH value of 2.5 at the 9th and 12 th month.The phosphorus content in February and February showed a trend of CK>4.5>3.5>2.5.The pH value of acid rain in May and August had no significant effect on the content of fine root phosphorus.In November and February,the phosphorus content had significant effect,and the ratio of sulfur to nitrogen was opposite to that of pH value.The sulfur content of fine root was increased by 16% and 12%,respectively,in the treatment of pH value of 2.5 in August and February,respectively.The sulfur and nitrogen ratio of acid rain had a significant effect on the contents of carbon,nitrogen,phosphorus and sulfur,but the difference pattern varied with time and acid rain pH value.(3)After adding acid rain,the content of fine root potassium decreased significantly,showing the trend of CK>4.5>3.5>2.5.The content of root potassium in the acid rain treated in May,August and November was 51% lower than that of the control %,37%.There were significant differences between the different sulfur and nitrogen treatments in the treatment of different sulfur and nitrogen ratios in May,but the difference pattern was different with the acid rain duration and pH value The The pH value of acid rain in May,August and November had a significant effect on the content of fine root potassium(P<0.05),and had no significant effect in February(P>0.5).In May and August,the ratio of sulfur to nitrogen had a significant effect on the content of fine root,and there was no significant effect in November and February.After adding acid rain,the content of fine root calcium increased significantly,and the pH value was 3.5 and 2.5% in May.The average calcium content of fine root was increased by 55% and 93% respectively.In May and November,the calcium content of fine roots showed the regularity of CK<4.5<3.5<2.5.May pH had a significant effect on the content of fine root calcium,and had no significant effect in other months.The sulfur and nitrogen ratios had a significant effect on the content of fine calcium in May,and had no significant effect in other months.After adding acid rain,the content of fine root magnesium increased mainly by 8%,19% and 6%,respectively.The content of root magnesium in pH was 4.5,3.5 and 2.5 in February.May and August had no significant effect on the magnesium content.In November and February,the pH value had a significant effect on the magnesium content.In May and February,the ratio of sulfur to nitrogen had a significant effect onthe content of fine root,and had no significant effect in August.The content of fine aluminum in the oil increased significantly,and the average aluminum content increased by 39%,81%,87% and 33% respectively after adding acid rain in May,August and November.The content of aluminum in the treatment of different pH value of acid rain showed a characteristic rule of CK<4.5<3.5<2.5,and the variation of fine aluminum co ntent between different sulfur and nitrogen treatments was 5:1<1:1<1:5 The May pH had no significant effecton the content of fine root aluminum,and had significant effect in other months(P<0.01).There was no significant effect of sulfur and nitrogen on the content of fine root in February,and the other months had significant effects.(4)There were positive correlations with fine root biomass,root length,apical and pH value,sulfur and nitrogen ratio,potassium and phosphorus in May,and negatively correlated with calcium.Diameter shows the opposite characteristics of the law,and calcium ions showed significant positive correlation characteristics.There was no correlation between aluminum,carbon and nitrogen,pH value,biomass,root tip and length,and negatively correlated with sulfur and nitrogen ratio.pH value,sulfur and nitrogen ratio,potassium and calcium were the main controlling factors.August aluminum ions and other indicators began to show a more significant correlation,and diameter is positively correlated with other indicators were negative correlation,calcium ions showed the opposite of the characteristics of May,pH,aluminum is the master factor.November nitrogen showed the opposite characteristics of August,and aluminum content was positively correlated with other indicators similar to August,pH,aluminum,carbon,phosphorus is the main control factor.In February,the calcium ions showed a regularity similar to that of adding acid rain,and positively correlated with aluminum.The pH value,aluminum,carbon and phosphorus were the main controlling factors. |
