Reserch On The Acid Deposition Characteristics And Its Influence On Soil Biological Activity Of Typical Forest In Yangtze River Delta

The Cunninghamia Lanceolata and Quercus acutissima forests in the Yangtze River delta region were chosen as research objects. In our research, the regional characteristics of rainfall and concentrations of main radical ion in rainfall redistribution process were detected. Meanwhile, the simulated acid rain experiments with 3 kinds of different types of acid rain:sulfate acid rain?S:N 5:1, S?, mixed acid rain?S:N 1:1, E?, nitric acid?S:N 1:5, N? and 3 different intensity of acid rain:p H value of 4.5?AR1?, 3.5?AR2?, 2.5?AR3? were carried out and the soil acidification, soil enzyme activity, and microbial carbon and nitrogen content were analyzed, Aimed to provide a scientific basis for the management of soil acidification, control acid rain pollution in the region, the protection of forest ecosystem. All results showed that:?1? The atmospheric precipitation was sulfuric acid type of acid rain in study area(NO₃^-: SO₄^2- = 1: 4.61). The annually averaged p H value of cumulative rainfall was 6.22, sulfate concentration(SO₄^2-) was 0.0507 mmol/L and nitrate concentration?NO₃^-? was 0.0110 mmol/L. The inputs of H⁺, NO₃^- and SO₄^2- in Cunninghamia Lanceolata forest were 0.081kg/hm2, 18.6 kg/hm2 and 103.11 kg/hm2 separately, while the inputs of H⁺, NO₃^- and SO₄^2- in Quercus acutissima forest were 0.078 kg/hm2, 15.06 kg/hm2 and 96.99 kg/hm2. The relative of main radical ion concentrations in the two forests significantly increased?P< 0.05? under the eluviation of forest canopy.?2? The pH value of simulated acid rain was positively correlated with the acidification of leached soilin each season, and was negative correlated with the exchangable H⁺ and Al3+ in leached soil. The p H value and exchangeable H⁺ and Al3+ ofleached soil by different types of acid rain was not significant?P < 0.05?.This shows that the soil acidity increase mainly related to the H⁺ inputbut the type of acid rain.?3? The soil biological activity in Cunninghamia Lanceolata fores was higher than in the Quercus acutissima forest under the same influence of acid rain,and 0-10 cm deep soil layer> 10-20 cm deep soil layer, while there was no significant difference between different types of acid rain. Additionally, soil enzyme activity showed obvious seasonal change. The urease content was summer> spring> autumn> winter, sucrose and phosphatase was autumn > summer > spring > winter, and catalase was summer > autumn > spring > winter. The soil microbial biomass carbon?MBC? and soil microbial biomass nitrogen?MBN? has obvious seasonal change?P < 0.05?, the results showed that summer > spring > autumn > winter in Cunninghamia Lanceolata forest and summer > autumn > spring > winter in Quercus acutissima forest. There was no significant differences between different treatments?CK, AR1 and AR2?, but AR3 significantly reduced the content of soil microbial biomass carbon and nitrogen?P> 0.05?.?4? The relationship between soil biological activity and exchangable H⁺?Al3+ was significantly?P < 0.05?, and not significantly with p H value. The multivariate regression model between the soil enzyme activity,MBC,MBN and soil acidification factor was established.The model can well explained the relationship between the soil biological activity and soil acidification of Cunninghamia Lanceolata and Quercus acutissima forests in each season.