| Acid rain refers to the phenomenon that acidic chemicals with p H < 5.6 in the atmosphere are transferred to the ground and water surface in the form of precipitation,which has caused a series of effects on the ecosystem,such as soil acidification,nutrient loss,decline of soil buffer,and some interference on the energy flow and material cycle of the ecosystem.The study on the decomposition of litter by acid rain is conducive to explore the impact of acid rain on nutrient cycling in terrestrial ecosystem.In this study,10 kinds of leaf litter(Caragana korshinskii,Salix psammophila,sunflower,millet,Pinus tabulaeformis,Platycladus orientalis,poplar,corn,maple leaf and Heather)were studied by litter net bag method under different acid rain treatment conditions.The dynamic changes of litter mass residue rate,nutrient content and physical and chemical properties of leaching solution were discussed to reveal the response mechanism of leaf litter decomposition to acid rain,It provides a basis for the prediction of material cycle model of terrestrial ecosystem.The following results were obtained:(1)Under different acid rain types,the self composition of leaf litter affects the quality residue rate of litter.Leaf litter C/N is an important index to measure its decomposition rate.The smaller the C/N value of leaf litter,the faster the litter decomposition.Among the 10 kinds of litter,the initial C/N value of Pinus tabulaeformis and Platycladus orientalis litter is the largest and the decomposition rate is the slowest,while the initial C/N value of Caragana korshinskii litter is the smallest and the decomposition rate is the fastest.Acid rain treatment inhibited the decomposition of leaf litter of Caragana korshinskii,sunflower,millet,poplar,corn,maple leaf and Photinia,promoted the decomposition of leaf litter of Pinus tabulaeformis,but had little effect on the leaf litter of Salix mandshurica and Platycladus orientalis.Decomposition time and ambient temperature significantly affect the quality residue rate of litter.In the case of high ambient temperature for 3-6 months,the decomposition rate of litter is very fast,and in the case of temperature decline for 6-12 months,the change is slow.(2)Acid rain treatment had different effects on nutrient release of leaf litter.After decomposition for 12 months,acid rain inhibited the release of carbon from leaf litter of Caragana korshinskii,sunflower,Pinus tabulaeformis and corn,and promoted the release of carbon from leaf litter of Salix psammophila,millet and poplar.The release of nitrogen from litter showed a enrichment release model.Nitric acid rain promoted the release of nitrogen from leaf litter of Pinus tabulaeformis.All acid rain inhibited the release of phosphorus from leaf litter of Caragana korshinskii,sunflower and maize.(3)Different acid rain had different effects on ph and conductivity of leaf litter leaching solution.Under the same acid deposition conditions,the change trend of p H value between different leaf litter leaching solutions was similar,and the p H value showed a gradual upward trend as a whole.The type of acid rain had a significant effect on the p H value of litter leaching solution,and the alternating acid rain treatment was the largest.In the same acid rain treatment,the conductivity of litter leaching solution has a similar change law with the decomposition process.There is a correlation between the conductivity of leaching solution and its p H value.Acid rain treatment promoted the increase of conductivity by directly reducing the p H value of leaching solution,and the conductivity of leaching solution was significantly increased under alternating acid rain treatment.(4)Acid rain treatment affected the nutrient content of leaf litter leaching solution.The total carbon content of leaf litter of Caragana korshinskii and Salix psammophila was the highest in the control treatment;The total carbon content of litter leaching solution of sunflower,millet,Pinus tabulaeformis,Platycladus orientalis,poplar,maple leaf and Photinia leaf was the highest in alternating acid rain.Nitrate acid rain treatment significantly increased the nitrogen content of litter leaching solution.In the alternating acid rain treatment,the phosphorus content of each litter leaching solution was the highest. |
