Effects Of Different Application Rates Of Biochar On The Soil Greenhouse Gas Emission In Chinese Chestnut Stands

Chinese chestnut?Castanea mollissima?is one of the very important economic species in China,and it occupies approximately 1.25 million ha in China.The Chinese chestnut forest is widely distributed in Zhejiang Province,and it is an important part of plantation resources in Zhejiang Province.intensive management practices applied in Chinese chestnut forests can increase the yield of chestnut,but it also cause some negative environmental problems,mainly including an increased soil erosion,a significant reduction of soil microbial activity and an increased greenhouse gas emissions.Biochar addition can significantly increase the soil organic carbon storage,and reduce the soil greenhouse gas emission as well.However,the reponsed of the plantation soil to different application rate of biochar and associated mechanisms are still unclear..In this study,a typically intensively managed Chinese chestnut plantation was secleted to conduct the experiment.The effects of different application rates of biochar on the soil labile C and N pools and greenhouse gas emission were investigated,the relationships between soil greenhouse gas emissions and soil environmental factors in Chinese chestnut plantations were analyzed,and the cumulative soil greenhouse gas emissions during the first year and second year after the application of biochar among differet treatments were compard.The main results obtained from the present study were listed as follows:?1?The soil greenhouse gas emissions in Chinese chestnut forests undere the treatments of biochar addition and control were associated with the dynamics of atmospheric temperature similar and higher in summer and autumn and lower in spring and winter.The maximum values for soil CO₂ and N₂O emissions appeared in August to September,minimum in January and February.The maximum value of soil CH₄ uptake flux appeared in July and August,minimum at December to January.?2?The soil WSOC and MBC concentration in the treatments of 5 t hm^-2 and 10 t hm^-2of biochar application were higher than that in the Control in the first 3 monts since the application of biochar?P < 0.05?.Biochar treatment significantly reduced soil NH₄⁺-N and NO₃^--N content?P < 0.05?,and decreased amplitude with the increased application rate of biochar..The soil WSON concentration in the treatments of 5 t hm^-2and 10 t hm^-2of biochar application were higher than that in the Control,but no difference were observed between the 2 t hm^-2of biocar application and Control treatments.The treatments of biochar addition had no significant effect on the soil MBN concentration.?3?In the first year after the application of biochar,the cumulative soil CO₂ emission in the treatements of biochar addition was higher that that in the Control?P < 0.05?,but no significant different was observed in the second year after the biochar addition.Under different treatment conditions,the soil CO₂ emission in the Chinese chestnut forests was significantly correlated to the soil temperature?at a depth of 5 cm?,but no significant difference in Q10 were observed among different treatments.In the treartments of Control,2 t hm^-2and 5 t hm^-2of biochar application,the soil CO₂ flux and WSOC concentration was significantly correlated?P < 0.01?.In the treartments of Control and 2 t hm^-2 of biochar application,the soil CO₂ flux and MBC concentration was significantly correlated?P < 0.01?.Regardless of the treatment,the soil CO₂ emission in the Chinese chestnut forests did not correlate to the soil moisture content.?4?All of the biochar treatments significantly decreased the soil N₂O cumulative emission as compared to the Control,and the emission became lower as the result of higher amount of biocar addition.Regardless of the treatment,the soil N₂O emission in the Chinese chestnut forests was significantly correlated to the soil temperature,NO₃^--N and NH₄⁺-N concentration?P < 0.01?.In the treatments of 2 t hm^-2 and 5 t hm^-2 of biochar application,the soil N₂O emission was correlated to the WSON?P < 0.05?,and the soil N₂O emission was correlated to the WSON?P < 0.01?in the treatment of 10 t hm^-2 of biochar application.In the treartments of 2 t hm^-2and 5 t hm^-2of biochar application,the soil N₂O flux and WSOC concentration was significantly correlated?P < 0.05?.In the treartments of 2 t hm^-2and 10 t hm^-2of biochar application,the soil N₂O flux and MBC concentration was significantly correlated?P < 0.05?.Regardless of the treatment,the soil N₂O emission in the Chinese chestnut forests did not correlate to either the soil moisture content and MBN concentration.?5?In comparisom with the Control,the treatments of 5 t hm^-2and 10 t hm^-2biochar additions significantly increased the cumulative uptake of soil CH₄ in Chinese chestnut forests,while the treatment of 2 t hm^-2biochar addition had no significant effect.Regardless of the treatment,the soil CH₄ uptake in Chinese chestnut forests was significantly correlated to the soil temperature.In the treartments of Control,2 t hm^-2and 5t hm^-2of biochar application,the soil CH₄ uptake and WSOC concentration was significantly correlated?P < 0.05?.Regardless of the treatment,the soil CH₄ uptake in the Chinese chestnut forests did not correlate to either the soil moisture content and MBC concentration.