The Influence Of Litter Removal And Nitrogen And Phosphorus Additions On Soil Greenhouse Gas Emissions Inncinamonum Camphora Plantations

As the main body of terrestrial ecosystem,forest plays an important role in China's environment and ecology.Forest soils are acting as the source or net sink of greenhouse gases(N₂O,CH₄and CO₂).Cinnamonum camphora(L.)Pres is widely distributed,has high economic value and good ecological effect,and occupies an extremely important position in China's forestry.Forest Litterfall and fertilization are important management measures for forest ecosystem,which has a significant impact on the carbon and nitrogen cycles of forest ecosystem and global climate change.We conducted a Forest Litterfall manipulation experiment in Cinnamomum camphora plantation,using Static Chamber-meteorological chromatography,in situ monitoring of soil in greenhouse gas emissions.Litter decomposition used Litter bag Technique,artificially removing of litter and applying nitrogen(N),phosphate(P)to investigate how removal of litter and fertilization determined greenhouse gases flux.This kind of mechanism has an important theoretical and practical significance to formulate the corresponding mitigation measures and give full play to the forest ecological benefits and the sustainable management.After a year of long-term monitoring,the conclusions are as follows:1)There were highly significant difference between soil temperature,humidity,nitrate nitrogen content and N₂O and CO₂emission rates.Soil N₂O and CO₂emission rates have obvious seasonal changes,and summer is higher than winter.Overall,the soil of Cinnamomum camphora plantation is the"source"of atmospheric N₂O and CO₂,and the"sink"of CH₄.Removal of Litter promoted the N₂O and CO₂emission rate,so that soil by"sink"of atmospheric CH₄transformed into"source",which significantly increased the accumulation of N₂O emissions.However,there was no significant increase on the accumulation of CO₂emissions and Litter reserved could stabilize the change of greenhouse gas emissions rate.2)Adding nitrogenous(N)fertilizer improved the N₂O emission rate because of the nitrate nitrogen content increased.N₂O and CO₂emissions rate positively increased,but the limited increase significantly enhanced the accumulation of N₂O emissions rather than the accumulation of CO₂emissions.The increase of N₂O and CO₂emission rate was not caused by the application of nitrogen fertilizer to the decomposition of litter.3)The addition of phosphate(P)fertilizer alleviates the limitation of phosphorus on plants and promoted the plant absorption of nitrate nitrogen and plant root respiration also strengthened,which significantly reduced the emission rate and cumulative emissions of N₂O but CO₂improved.The inhibitory effect of phosphate(P)fertilizer on N₂O emission rate could counteract the effect of nitrogen(N)fertilizer on N₂O.There was no effect on the emission rate of CH₄by applying phosphate fertilizer.4)Quality retention rate and C retention rate of the Litter decomposition rapidly declined in the first two months,which is mainly due to two different decomposition of components,the lignification holocellulose and soluble substances decomposition.In addition,our data suggested that adding nitrogenous(N)fertilizer had no effect on litter decomposition.The application of phosphate(P)fertilizer promoted the release of litter N,and P was transformed from net release to enrichment.Our analysis showed that the release of litter N and P was highly significantly related to the cumulative emissions of CO₂,but N₂O was not.The cumulative emission of CH₄was not related to the decomposition of litter either.In conclusion,the removal of Litter increases the emission of greenhouse gases in the soil.In the forest operating management,the exposed woodland should be avoided and keep the coverage of litter on the ground.When fertilizing in the woodland,although the application of phosphate fertilizer enhances the emission rate of CO₂,it can inhibit the promoting effect of nitrogen fertilizer on N₂O emission rate.Single application of nitrogen fertilizer should be avoided to reduce the greenhouse gas emission in forest soil.In pursuit of economic benefits,we should also give full play to the ecological benefits of forestry.