Responses Of Soil Greenhouse Gas Emissions To Application Of Biochar-based Urea And Common Urea In The Moso Bamboo Plantation

Moso bamboo(Phyllostachys edulis)is an important subtropical economic forest resource.It has unique advantages and great potential in forest carbon sequestration and greenhouse gas emission reduction.Common urea application will increase soil greenhouse gas emissions,while biochar application has a good effect on reducing soil greenhouse gas emissions,but previous studies on the effects of biochar-based urea on soil greenhouse gas emissions are still relatively rare.This experiment is based on the intensive management of Moso bamboo plantation in Lin'an District,Hangzhou City,Zhejiang Province.Through one year of positioning experiments,different levels of biomass carbon-based urea and common urea were applied(0 t ha-1:control Low level urea(100 kg N ha-1):LU;high level urea(300 kg N ha-1):HU;low level carbon based urea(100 kg N ha-1):LBU;high level carbon-based urea(300 kg N ha-1):HBU)Effects on greenhouse gas emission flux,temperature,moisture,pH,carbon and nitrogen pool,water-soluble carbon and nitrogen,microbial carbon and nitrogen,and enzyme activities in bamboo forest soil The relationship between greenhouse gas emission flux and the above-mentioned soil environmental factors reveals the impact of biomass carbon-based urea and common urea input on greenhouse gas emissions from bamboo forest soil and its mechanism.The main findings obtained are as follows:(1)Under the input of different levels of biochar-based urea and common urea,the greenhouse gas emissions of Moso bamboo forest soil showed obvious seasonal variation characteristics.Low and high levels of common urea input have the effect of increasing soil CO2 emissions,while biochar-based urea input has no significant effect on soil CO2 emissions;low and high levels of common urea treatment reduce the annual cumulative absorption of CH4 in Moso bamboo forest soil(P<0.05).And under the high level of common urea treatment,the effect was significant;while the low and high levels of carbon-based urea treatment increased the annual cumulative absorption of CH4 in the bamboo forest soil(P<0.05),and at high levels of urea treatment,the effect is more significant.Low and high levels of common urea treatment significantly increased the annual cumulative flux of N2O in the soil of the bamboo forest<0.05),and the effect was significant under the high level of ordinary urea treatment;while the low and high levels of carbon-based urea treatment were all effective.The annual cumulative emission flux of N2O in the soil of bamboo forest was reduced(P<0.05),and the effect was more significant under the treatment of high level carbon-based urea.(2)Different levels of biochar-based urea and common urea had no significant effect on soil temperature and soil moisture content of Moso bamboo forest Compared with the control treatment,the input of LU,HU,LBU and HBU increased the soil WSOC content by 3.8%,12.8%,4.3%and 15.6%,respectively and increased soil MBC content by 5.0%,7.0%,8.0%and 13.0%,respectively,compared to the control treatment.The LU,HU,LBU and HBU treatments all significantly increased the NH4+-N and NO3--N content of the Moso bamboo forest soil(P<0.01).Different levels of common urea treatment(LU,HU)increased the WSON content of Moso bamboo forest soil by 3.3%and 15.2%,respectively;while different levels of biochar-based urea treatment(LBU,HBU)reduced the WSON content of Moso bamboo forest soil,respectively reduced by 6.4%and 13.2%.The four treatments of LU,HU,LBU and HBU had no significant effect on the MBN content of Moso bamboo forest soil.(3)The activities of soil enzymes(sucrose and urease)showed a certain seasonal variation,which generally reached the lowest value in winter and reached the highest value in summer.The effect of common urea application on soil sucrose enzyme activity was significant(P<0.05),the effect of biochar-based urea application on soil sucrose enzyme activity was not significant(P>0.05).Both LU and HU treatments increased soil urease enzyme activity by 11.1%and 15.6%,respectively,while LBU and HBU treatments reduced soil urease enzyme activity by 3.5%and 12.9%,respectively.(4)Under any treatment,the CO2,CH4 and N2O fluxes of the Moso bamboo forest soil were significantly correlated with soil temperature(P<0.01),and there was no significant correlation with soil moisture content(P>0.05);There was a significant correlation between soil CO2 and CH4 emissions and WSOC content(P<0.05),and no significant correlation with MBC content(P>0.05);soil N2O emission flux was significantly correlated with the NH4+-N content,NO3--N content and WSON content(P<0.05).Under Control,HU,LBU and HBU treatment,soil N2O emission flux was significantly correlated with MBN content(P<0.05),but there was no significant correlation between LU and LU treatment(P>0.05).