The Influence Of Nitrogen And Phosphorus Addition And Different Litter Ages Decomposition On Soil Greenhouse Gas Emission In Chinese Fir Plantations

In recent years,human activities have intensified and increased greenhouse gas concentrations.The annual average temperature in the coming decades will continue to rise at a faster rate.Similarly,climate and environmental changes have modified soil consumption and greenhouse gas emissions.Carbon dioxide（CO₂）,methane（CH₄）and nitrous oxide（N₂O）are the three major greenhouse gases to global warming.Chinese fir（Cunninghamia lanceolata）is an evergreen conifer,is the main timber species in southern China.Litter and fertilization are important measures for plantation to improve soil fertility and forestry management,especially nitrogen（N）and phosphorus（P）fertilizer.Nitrogen and P are the most restricted biological nutrients in terrestrial ecosystems and play an important role in controlling plant productivity and microbial function.Litter decomposition is a complex multi-nutrient process that provides organic and inorganic elements to the soil on forest ecosystems.Litter of different ages may have distinct physical and chemical properties,which in turn affect the rate of litter decomposition.Litter decomposition driven by global change may alter soil processes.It has potentially important effects on soil greenhouse gas emissions and nutrient resorption cycling.In this paper,the long-term field N and P additions of the Chinese fir plantation in Qianyanzhou,Jiangxi Province（blank control（Con）,low nitrogen（N1）,high nitrogen（N2）,phosphorus（P）,low nitrogen and phosphorus（N1P）,high nitrogen and phosphorus（N2P））base was the research object.We were set up six treatments and four repeated randomized block experiments.Through the collection of sample soil and the litter of different ages of Chinese fir（one-year old leaf and second-year old leaf）,and the greenhouse gas emissions and litter（one-year old leaf litter,second-year old leaf litter,control）were added at different incubation temperature（20°C,25°C,30°C）decomposition culture test.We were understood the response dynamics of greenhouse gases to plant litter diversity and explored the association.To know the impact of terrestrial ecosystem function and climate change.The nutrient turnover process of different litter ages was studied to provide a theoretical basis for forest resource management and rational fertilization.The research results were as follows:1)The addition of N promoted the N₂O emission in Chinese fir forest soil,and the N₂O emission increased with the increase of N concentration.Phosphorus addition has an inhibitory effect on soil N₂O emissions.The interaction of N and P had no effect on soil N₂O emissions.Under N2 treatment,soil N₂O emission rate and cumulative emission were the highest.Under N1 treatment.The incubation temperature had significant difference in soil N₂O emission rate and cumulative discharge.At 20°C,the N₂O emission rate and cumulative emission of soil with added litter were higher.The CO₂ emission of soil increased with the increase of incubation temperature without the addition of litter.The interaction between incubation temperature and different litter ages had significant effect on the cumulative CO₂ emission of soil.The addition of litter promotes CO₂ emission from soil.The different litter ages had significant effects on soil mineralization,nitrification and ammoniation.The mineralization rate of soil under one-year old leaf litter was higher than that of second-year old leaf litter.2)The addition of litter promoted soil N₂O emission and CO₂ emission.There was a significant difference between one-year old leaf litter and second-year old leaf litter,and the one-year old leaf litter treatment were higher.3)During the decomposition of litter,the decomposition rate of one-year old leaf litter was greater than second-year old leaf litter,and it needed shorter time for complete decomposition.During the decomposition process,the C element was enriched and then released,the N element was enriched,and the P element was released.One-year old leaf litter had higher C/N and C/P than second-year old leaf litter,and N/P was smaller than second-year old leaf litter.4)There were significant differences in C,N content and C/N of different litter ages.The C content and C/N of second-year old leaf were higher than that of one-year old leaf litter,and the N content of one-year old leaf was higher.The different addition of N had a significant effect on the N content,C/N and N/P of litter.The N content and C/N of litter were higher under N2 concentration,the lowest under Con,and the lowest N/P of litter under N2 concentration.5)The C/N of litter,soil available nitrogen,available phosphorus and soil p H had affected soil N₂O emissions.Nitrogen addition increases soil N₂O emissions by increasing functional genotyping and increasing soil p H.Litter affected soil N₂O emissions through litter C/N.Phosphorus was added to soil available nitrogen,soil available phosphorus,soil p H and the litter C/N to regulate soil N₂O emissions.In summary,the addition of N and P had a significant effect on the greenhouse gas emission of Chinese fir forest soil.The addition of litter could promote soil CO₂ emission,One-year old leaf litter contained higher N content and lower C/N,and the rate of decomposition of one-year old leaf litter was higher,the decomposition time was shorter,the soil N₂O and CO₂ emission of one-year old leaf litter added were higher.Therefore,in the management of Chinese fir forest,especially in the management of Chinese fir thinning and forest ecosystem litter management,the potential impact of litter decomposition with N addition and P addition interaction on soil carbon and nitrogen cycling in different litter ages.It should be considered to realize forest soil with greenhouse gas increased C storage and reduced N₂O emissions.