Responses Of Rhizosphere Soil Chemical Properties And Enzyme Activity Of Four Tree Species In Three Gorges Reservoir Area To Simulated Acid Rain

The Three Gorges reservoir area is an important forest ecosystem in the middle and lower reaches of the Yangtze River,but there is a long-standing problem of acid rain in the area.Acid rain can cause acidification of lakes and rivers,hinder the growth of aquatic plants and animals,leading to forest degradation and reduced productivity.In addition,the chemical composition of precipitation in the reservoir area is gradually changing,and the type of acid rain is being converted to mixed type and nitric type.In this study,Pinus massoniana,Cunninghamia lanceolate,Cyclobalanpsis glauca and Phyllostachys edulis were selected as research objects,combined with the acid rain characteristics of the Three Gorges reservoir area,by simulating different intensity(pH=2.5,3.5,4.5)and different type acid rain(sulfuric,mixed and nitric),analysis of short-term treatment(60d)and long-term treatment(120d)data,exploring response mechanism of the chemical properties of rhizosphere soil(soil pH,organic matter,cation exchange capacity,exchangeable base ion,exchangeable Al3+and H+)and the enzyme activity(invertase,urease,phosphatase)to acid rain to provide theoretical support for soil acidification and forest degradation in the region.The main conclusions are as follows:(1)Short-term treatment with low intensity acid rain can increase soil enzyme activity,and high intensity acid rain reduces soil pH,organic matter content,cation exchange capacity,exchangeable base ion and invertase,urease,phosphatase activity,and exchangeable Al3+ and H+ content which is toxic to soil increase as the acid rain intensity increases.(2)Soil organic matter is more sensitive to sulfuric acid rain,soil cation exchange capacity is more sensitive to mixed acid rain,and soil exchangeable Na+and K+are more sensitive to nitric acid rain.Soil invertase,urease and phosphatase are more sensitive to sulfuric acid rain in short-term treatment,while three enzymes are more sensitive to mixed acid rain in long-term treatment.(3)The soil relative activity is followed by phosphatase>urease>invertase.The exchangeable H+ and Al3+ in the rhizosphere soil of Pinus massoniana,Cunninghamia lanceolate,and Phyllostachys edulis were significantly negatively correlated with soil pH and exchangeable base ions(p<0.05).There was a significant correlation between the exchangeable cations and the organic matter content in the rhizosphere soil of the four species(p<0.05).The three enzyme activities in the rhizosphere soil of four tree species were significantly correlated with the exchangeable H+.The three enzyme activities in the rhizosphere soil of Pinus massoniana,Cyclobalanpsis glauca and Phyllostachys edulis were significantly correlated with the exchangeable Al3+(p<0.05).(4)The content of organic matter and base ions in the rhizosphere soil of Pinus massoniana and Cunninghamia lanceolata were the highest,and the acid rain buffer capacity of sulfuric acid rain was stronger.The soil organic matter content and the base ion content of Cyclobalanopsis glauca under short-term acid rain treatment were lower than other tree species.The enzyme activity was higher than that of other tree species under long-term treatment.Under sulfuric acid rain,the acid buffer capacity of Cyclobalanopsis glauca was weak,but its nutrient transformation ability was stronger.