Effects Of Exogenous Carbon Input On Soil Organic Carbon Mineralization In Moso Bamboo Forest

Moso bamboo(Phyllostachysedulis)is an important forest resource in subtropical region.Due to its rapid accumulation of biomass,Moso bamboo forest has a unique advantage and great potential in carbon sequestration.Appropriate management practices can significantly improve the carbon sink function of forest ecosystem.However,long-term intensive management,mainly including application of chemical fertilizer and removal of understory vegetation,led to a significant decrease in soil organic carbon stock in Moso bamboo plantations.The depletion of soil organic carbon(SOC)has negative effects on soil fertility and carbon sink function of bamboo forests.Therefore,exogenous carbon input may be a necessary means for the long-term sustainable management of bamboo plantation.SOC mineralization is one of the key processes of soil carbon cycle.The study of the mechanism of exogenous carbon input on the mineralization of SOC in bamboo plantation can provide a theoretical basis for improving the carbon sink function of bamboo plantation soil.In this study,the effects of exogenous carbon input on SOC mineralization in Moso bamboo plantation at different incubation temperatures(25?and 35?)were studied through laboratory incubation experiments,and the effects of exogenous carbon input on SOC mineralization in different soil depths(0-20,20-40 and 40-60 cm)in bamboo plantation were also studied,and the soil labile carbon pool,enzyme activity and microbal community were measured,to explore the relationship between SOC mineralization and soil environmental factors in Moso bamboo plantation.The main findings are as follows:(1)Incubationat 25?and 35?,the cumulative CO₂ release from SOC mineralization was significantly increased by bamboo leaf(BL)and bamboo leaf biochar(BLB)(P<0.05),and the cumulative CO₂ release from BLB treatment was significantly lower than BL treatment(P<0.05).With the increase of incubation temperature,the cumulative CO₂ release of SOC mineralization under three treatments increased significantly(P<0.05).Both BL and BLB treatments significantly increased soil water soluble organic carbon(WSOC)and microbial biomass carbon(MBC)contents(P<0.05),and significantly increased soil?-glucosidase and dehydrogenase activities(P<0.05).Under the two incubation temperatures,the content of O-alkyl C in soil was increased by BL treatment,but the content of aromatic C was decreased by BL treatment,and BLB treatment significantly increased the aromatic C content(P<0.05).(2)Incubation at 25?and 35?,the cumulative CO₂ release of SOC mineralization was significantly correlated with WSOC,MBC,dehydrogenase activity,O-alkyl C and carbonyl C(P<0.01).The results of redundancy analysis(RDA)showed that the soil available phosphorus(AP),available potassium(AK)and cumulative CO₂ release were significantly correlated with the bacterial community(P<0.05),while the soil available potassium(AK),aromatic C and cumulative CO₂ release were significantly correlated with the fungal community(P<0.05).Under 35?,soil total carbon(TC),WSOC and?-glucosidase activities had significant correlation with the bacterial community(P<0.05),and soil WSOC,MBC and alkyl C had significant correlation with the fungal community(P<0.05).Further analysis showed that the dominant bacterial and fungal order affected the release of CO₂ from SOC mineralization changed significantly with the change of incubation temperature.(3)The results of experiments on the effect of exogenous carbon input on SOC mineralization in different soil layers of bamboo forest showed that the cumulative CO₂ release from SOC mineralization in three soil layers(0-20,20-40 and 40-60 cm)was significantly increased by the treatment of maize straw(MS)and maize straw biochar(MSB)(P<0.05).Compared with the control,the cumulative CO₂release in the three soil layers under MS treatment increased by 481.82%,371.03%and 390.80%,respectively.The cumulative CO₂ release in the three soil layers under MSB treatment increased by80.60%,26.93%and 37.86%,respectively.MS treatment had positive priming effect on SOC mineralization,while MSB treatment had non-significant priming effect on soil organic carbon mineralization.(4)In the experiment regarding the effect of exogenous carbon input on SOC mineralization in different soil layers,after 8 days of incubation,there were significant correlations between soil p H,AP,AK,WSOC,MBC,?-glucosidase activity,dehydrogenase activity,invertase activity,alkyl C,O-alkyl C,aromatic C with SOC mineralized CO₂ release(P<0.05).After 40 days ofincubation,there were significant correlations between soil AP,AK,WSOC,MBC,?-glucosidase activity,dehydrogenase activity,invertase activity,O-alkyl C,aromatic C,carbonyl C with SOC mineralized cumulative CO₂release(P<0.05).The results of RDA showed that after 8 days of incubation,soil p H,WSOC,?-glucosidase,alkyl C and aromatic C had significant correlation with bacterial community(P<0.05).Soil p H,TC,AP,alkyl C and aromatic C were significantly correlated with fungal community(P<0.05).After40 days of incubation,soil WSOC,TC,dehydrogenase activity,invertase activity and aromatic C had significant correlation with bacterial community(P<0.05).The cumulative release of soil TC,MBC,WSOC,AK,and?-glucosidase,aromatic C and CO₂were significantly correlated with the fungal community(P<0.05).Further analysis showed that the dominant bacterial and fungal order affected the release of CO₂ from SOC mineralization changed significantly with the change of soil depth.