| With the acceleration of industrialization,acid rain has become one of the most serious environmental problems.Acid rain can slow plant growth and reduce forest soil fertility.Soil preferential flow is a common form of soil moisture migration,through the study of soil preferential flow zone and matrix flow zone soil properties to the response of different acidity of simulated acid rain,can get better soil affected by acid rain changes of various physical and chemical properties,which can form,analysis of soil solute migration to plantation tending management such as provide a scientific basis for precision fertilization,etc.In this paper,the artificial chestnut forest in Jurong city,Jiangsu province was taken as the research object,and the changes of soil nutrient,soil enzyme activity and soil microbial activity were studied under the simulated acid rain treatment with different acidity(pH2.5,3.5,4.5).The results are as follows:(1)Under simulated acid rain leaching with different acidity,soil nutrients were lost to different degrees.Soil nutrients showed different trends in the preferential flow zone and the matrix flow zone.The total soil carbon content in the soil priority flow area decreased with the increase of soil depth under the same pH acid rain treatment.The total carbon content of the topsoil in 0?10cm was the highest(18.0g/kg)under the acid treatment of pH3.5,the total carbon content of the middle soil in 10?20cm was the highest(9.63g/kg)under the acid treatment of pH4.5,the total carbon content of the bottom soil in 20?30cm was not significantly different(3.85%?9.89%),and the total carbon content of the matrix flow zone in each soil layer under the four treatments was between 3.10%?64.64%.Under the simulated acid rain treatment with the same pH,the total nitrogen content of the soil decreased gradually with the increase of depth.As a result of acid application,the total nitrogen content in the preferential flow zone of the soil was higher than that in the matrix flow zone(0?69.23%).Acid rain leaching results in a significant change in the soil C-N ratio in the matrix flow zone(2.90%?90.64%).In the 0?10cm topsoil,the contribution rate of the priority flow to the soil C-N ratio was 4.46%?18.85%,and in the 10?20cm middle soil,the contribution rate of the priority flow to the soil C-N ratio was-12.26?55.99%.In the subsoil of 20?30cm,the contribution rate of the preferential flow to the carbon nitrogen ratio was-10.26%?-1.01%.Except under the acid treatment of pH3.5,there was a significant difference in the carbon nitrogen ratio between the soil matrix flow zone and the preferential flow zone in the bottom soil of 20-30cm(P <0.05).In the preferential flow zone,the total sulfur content in the same soil layer increased with the decrease of pH,and the matrix flow zone also showed a similar trend.The total sulfur content in the pH2.5 acid treatment group was the highest(0.34g/kg)and the lowest(0.09g/kg)in the control group.There were significant differences in total sulfur content between 0?10cm topsoil flow priority zone and matrix flow zone in the acid treatment group and the control group(P <0.05).(2)Simulated acid rain had different effects on the enzyme activity of soil preferential flow zone and matrix flow zone.Acid rain on soil enzyme activity of acidic phosphatase activity has a promoting effect,the preferential flow zone soil under the acid treatment of the activity of acid phosphatase in pH4.5 highest(0.185 mu g/d.g),flow in the substrate region of soil under the acid treatment of the activity of acid phosphatase in pH3.5 highest(0.191 mu g/d.g),look from the average,preferential flow in soil enzyme activity of acidic phosphatase activity is generally higher than that of matrix flow area.Acid rain had a certain inhibitory effect on the catalase activity of the soil in the preferential flow area,but the soil enzyme activity in the matrix flow area was less affected,and the catalase activity in the control group was the highest(80.97?82.45 mol/d·g).Under the acid treatment of pH2.5,the catalase activity in the matrix flow area in all soil layers was higher than that in the priority flow area(0.63%?0.92%),and there was a significant difference in the catalase activity between the priority flow area and the matrix flow area in the 0?10cm topsoil(p <0.05).Acid rain also had a certain inhibitory effect on cellulase activity.With the increase of soil depth,cellulase activity in the preferred flow area decreased by 27%?53% compared with the control group.The cellulase activity of the acid treatment group decreased by 10.44?43.42% compared with the control group.The enzyme activities in the preferential flow zone and matrix flow zone of the 20?30cm bottom soil were significantly lower than those in the 10?20cm middle soil and the 0?10cm top soil(P <0.05).Acid rain also had a certain inhibitory effect on soil urease activity,and the soil urease activity in the matrix flow area was higher than that in the priority flow area.Under the same acidity treatment,the urease activity decreased layer by layer with the increase of soil depth.In the preferential flow zone,the urease activity of the control group was higher than that of the soil after acid treatment(5.02%?25.38%)in the matrix flow zone,and the urease activity of the control group was also higher than that of the soil after acid treatment(5.78%?27.14%).The inhibition of acid rain on soil urease,catalase and cellulase may lead to decomposition of litters and adversely affect soil carbon and nitrogen cycle.(3)Simulated acid rain has certain inhibitory effect on soil microbial activity.From chestnut forest soil microbial community's overall activity,0 ? 10 cm in the surface layer of soil microorganism overall activity in the preferential flow zone and matrix flow zone shows a high level,and the microbial activity is higher than matrix flow area of preferential flow area,the acid rain on soil microbial activity showed relatively strong inhibitory effect,under the acid treatment of pH4.5,microorganism overall activity showed lower level(0.017 0.407).The soil diversity index in the preferential flow area was generally higher than that in the matrix flow area.The activity of soil cellulase had the most significant correlation with the microbial activity of the six carbon sources,among which there was a significant positive correlation with the microbial activity of the carbon sources of polymerized sugars,acids and amino acids(p <0.05),and the activity of soil urease had a significant positive correlation with the microbial activity of the carbon sources of polymerized sugars and amino acids(p <0.05). |
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