Effects Of Bamboo Leaf And Its Biochar Additions On Soil Greenhouse Gas Emissions In Chinese Chestnut Stands

Chinese chestnut (Castanea mollissima) is one kind of very important economicforest tree species in China and widely distributed in26provinces and cities. Chinahas1.25million ha of Chinese chestnut forests, accounting for38%of the world’schestnut cultivation. To obtain higher chestnut yield and economic income, variousintensive management practices, mainly including chemical fertilizer application,tillage and understory vegetation removal have been adopted by the farmers. However,long-term intensive management significantly decreased soil organic carbon (C)storage and labile organic C pools. Biochar addition is regarded as an importantapproach to enhance soil carbon sequestration and mitigate global climate change.Study of the effects of biochar addition on the soil greenhouse gas emissions inplantations would have great significance to enhance the carbon sequestration inplantation soils. In this study, the effects of bamboo leaf and its biochar additions onthe soil greenhouse gas and labile organic C pools in Chinese chestnut plantations,and the relationships between soil greenhouse gas emissions and environmentalfactors were discussed. The main results obtained from this study were as follows:(1) Either bamboo leaf or biochar treatment did not change the seasonalvariations of soil greenhouse gas (GHG) emissions in the Chinese chestnut stands,with the highest rates of soil CO2and N2O fluxes appeared in July-August, the lowestin Februray; and with the uptake maximum of soil CH4fluxes in September, theminimum in the Februray-March.(2) In the control treatment, the annual cumulative fluxes of soil CO2, N2O, andCH4in Chinese chestnut stands were13.99t CO2hm-2yr-1,2.22kg N2O hm-2yr-1and-2.97kg CH4hm-2yr-1, respectively. The annual cumulative fluxes of soil CO2andN2O were increased by16.3%and12.8%(P <0.05), respectively, by the bamboo leaftreatment, however, no significant difference was observed between the control andbamboo leaf treatments. The annual cumulative N2O flux was decreased by20.5%bythe biochar treatment (P <0.05), while the annual cumulative CH4uptake wasincreased by25.3%(P <0.05). There was no significant difference in the annual cumulative CO2flux between the control and biochar treatment.(3) The leaf treatment significantly increased the concentrations of soil WSOCand MBC in Chinese chestnut stands (P <0.05). The biochar treatment increased theconcentrations of soil WSOC and MBC only in the first month since application (P <0.05), but such effects diminished hereafter. The bamboo leaf treatment significantlyincreased the concentrations of soil WSON and MBN, while the biochar treatmenthad no significant effects. The bamboo leaf treatment significantly increased the soilNH4+-N and NO3--N concentrations, while the biochar treatment significantlydecreased them.(4) Strong exponential relationships between soil temperature and soil CO2efflux were observed regardless of the treatment (P <0.01). In comparison with thecontrol, both of the bamboo leaf and biochar treatments significantly increased thesoil Q10value (P <0.05), and the soil Q10value in the biochar treatment was lowerthan that in the bamboo leaf treatment. In the bamboo leaf and biochar treatments, thesoil greenhouse gases (including CO2, N2O and CH4) emissions correlated to the soilWSOC concentration (P <0.05), while did not correlate to the soil MBCconcentration. The soil N2O emission was correlated to the soil moisture contentin thebiocar treatment, and it was correlated to concentrations of soil NH4+-N, NO3--N, andWSON (P <0.05).