| Since the level of greenhouse gases has increased dramatically during the last two decades,with corresponding consequences on the global climate warming,there is a strong interest in ecological processes which are related to greenhouse gas emissions.Subtropical forest characterize by high temperature and moist is suitable for the activity of biological soil crusts(BSCs).However,little is known about the role of greenhouse gases exchange of BSCs in this area.So our study focus on the differences of CO2,CH4 and N2O exchange of BSCs and their reponses to light and warming treatment.The BSCs soil samples were collected from subtropical young Cunninghamia lanceolate plantation,which was a kind of widespread forest in this region.This study will provide the scientific basis to accurately assess the greenhouse gas fluxes of biological soil crusts in the subtropical region and their response to global change.The main results were as follows:1)The contents of soil organic matter,soluble organic carbon,nitrate nitrogen,and ammonium nitrogen increased significantly in underlying soil layer of algae crust coverage area,and they reduced with the increase of soil depth.There were no obvious differences in soil organic matter between algal crust and bare soil in warming treatment.The contents of soluble organic carbon and soluble organic nitrogen of algal crust and bare soil decreased and nitrate nitrogen content increased after warming.2)There was no significant different of greenhouse gas fluxes between algae crust and bare soil under the dark treatment.Algae crust had significant effects on CO2 and N2O emission fluxes and CH4 absorption flux in dark condition.3)The CO2 and N2O fluxes of algae crust were negative values and less than those of bare soil.Algae crust absorbed the CO2 and N2O in light condition.There was no significant different in CH4 flux between algae crust and bare soil.4)The CO2 flux of algae crust sifnificantly increased and N2O fl ux also increased under warming treatment.The CO2 and N2O fluxes of algae crust were higher than those of bare soil.Warming treatment has no significant influence on CH4 flux of algae crust and three kinds of greenhouse gas fluxes of bare soil.5)In warming and light treatment,the CO2,CH4 and N2O fluxes of algae crust were negative value.There was no significant difference of CO2 flux in the late of cultivation experiment between warming treatment and the control.There were significant differences of CH4 and N2O fluxes between warming treatment and the control in the early months of cultivation experiment.6)Isotope tracer experiments about N2O absorption of algae crust and bare soil were done under light and warming treatments.Compared with bare land,algae crust 15N isotope contents of total nitrogen,organic nitrogen,and ammonium nitrogen at 0-5 cm soil were significantly higher.Nitrate nitrogen content in 1-5 cm soil layer increased under warming and light interaction treatments.Crust covering promoted soil N2O absorption,but warming treatment had no significant effects on 15N isotope contents of nitrogen in algae crust and bare land.The light and crust covering were important influencing factors on N2O absorption of biological soil crust and soil system in humid subtropical region.7)Nitrogenase activity of algal crust under the light treatment was highter than that in bare soil and dark treatment.Soil microbial biomass increased significantly in algal crust covered area.Soil enzyme activity in algae crust coverage area was significantly higher than that in bare soil.There was no significant difference in N2O reductase gene content between algae crust and bare soil.Therefore,the absorption of N2O by algae is mainly through the process of nitrogen fixation. |
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