Effects Of Simulated Nitrogen Deposition On Decomposition And Nutrient Release Of Leaf Litter Of Acer Saccharum

Acer Saccharum is a deciduous native tree in North America.Because of tall stem,colorful leaves,and highly ornamental,it was introduced into China as the main landscape tree species.Hefei city locates in the key areas of acid deposition in south of China.In order to know nitrogen deposition effects on the decomposition of leaf litter-fall and its nutrient release ofcity landscape tree,3 levels nitrogen treatments were established inthe plots where planted Acer Saccharumof 7 years old.The treatment was produced by spraying NH₄NO₃ solution simulated nitrogen deposition method,and CK?N₀,0g N/m²/yr?,low nitrogen group?N₅,5 g N/m²/yr?and high nitrogen group(N₁₀,10 g N/m²/yr)were set.This helped to explore the process of decomposition and response to nitrogen deposition characteristics of soil nutrients,to provide a theoretical basis for the settlement of nutrient cycling the forest ecosystem of the city further analysis of nitrogen.The results showed that:?1?In the first 6 months of decomposition,simulated nitrogen deposition promoted the decomposition of litter and accelerated with the increase of nitrogen deposition.Fromsixth to twelth months,5 g N/m²/yr nitrogen fertilizer treatment promoted the decomposition of leaf litter of Acer Saccharum,thus 10 g N/m²/yr nitrogen fertilizer played an inhibitory role.?2?The leaf litter decomposition model was y=ae^-kt which fits well.Turnover period in N₀,N₅,and N₁₀treatment was 2.58a,2.40a,and 2.81a,respectively.Compared with the N₀,N₅ reduced the litter decomposition time,while N₁₀ prolonged the decomposition time.?3?After 1 years of simulated nitrogen deposition,the content of C in leaves of N₀ group was significantly higher than that of N₅ and N₁₀?P<0.01?,and the difference between N₅ and N₁₀ was significant?P<0.05?.The C content of N₅ and N₁₀ group was lower than that of control group 23.43%³1.82%,simulated nitrogen deposition treatment decreased C content of litter.Simulated nitrogen deposition increased the Acer Saccharum leaf litter nitrogen content,and increase with the level of settlement.The average nitrogen content in N₅ and N₁₀ group was higher than that of N₀ group with 9.38%¹6.67%,there was a significant difference between the control group and the control group?P<0.01?.The N content of N₁₀ treatment was significantly higher than that of N₅?P<0.05?.Simulated nitrogen deposition leads to a decrease in C/N ratio.?4?The correlation analysis showed that there was a significant correlation between N content and decomposition rate of leaf litter of Acer Saccharum,the content of N of Acer Saccharum litter is the main factor affecting the decomposition.?5?Simulated nitrogen deposition changed the release patterns of C and N elements,the release patterns of C in N₀ and N₁₀ were leaching-enrichment-release,the N₅ treatment showed the enrichment release pattern.The N elements under the treatment of N₀ and N₁₀ showed the leaching-enrichment-release pattern,the release mode of N was direct release.?6?There was a significant positive correlation between the residual rate of C and the residual rate of dry matter?P<0.01?,there was a negative correlation between the residual rate of N and the residual rate of dry matter?P<0.01?.The positive correlation between C/N ratio and dry matter residue rate was significantly enhanced by simulated nitrogen deposition?P<0.01?.?7?In the process of decomposition of Acer Saccharum litter,simulated nitrogen deposition reduced the content of C of soil,the soil layer containing C were N₀>N₅>N₁₀,under the same nitrogen deposition,the soil C content was0-5cm>5-10cm>10-15cm.The decomposition of litter increased the amount of N in soil.Under the same nitrogen level,the N content in different soil layers showed as follows:0-5cm>5-10cm>10-15cm.The N content in the same soil layer was N₁₀>N₅>N₀.The C/N ratio of soil decreased with the increase of soil depth,and the smallest C/N ratio was 5-10cm soil layer.?8?The content of C,N and C/N in soil were significantly correlated with the nutrient content of litter,and with the increase of soil depth,the correlation decreased.