Effects Of Biological Soil Crusts On Soil Carbon Flux In Alpine Sandy Area

Biological soil crusts are widely spreading in the world and they are the crucial part in Arid and semi-arid regions.Compared with the cover of the vascular plants,the cover of the biological soil crusts was more than 70% of the total cover.As the important species in desert ecosystem,they have rich species composition,complicated structure and they have particular physiological and ecological characteristics.They are also significant sources of ecosystem nitrogen and carbon.They can absorb carbon dioxide and release oxygen,and fixed carbon dioxide through photosynthesis,while returning carbon dioxide to the air as a product of respiration.This photosynthetic process could affect the soil carbon cycle in arid and semi-arid ecosystem,and the contribution of biological soil crust to carbon cycle in this area could not be ignored.In this study,different treatment?algae crusted soil,moss crusted soil in artificial vegetation?were uesd as the research object in Shazhuyu comprehensive experimental station in Qinghai province.The diffirent dynamic changes of CO₂ flux in daily and monthly temporal scales and in addition of simulated precipitation were measured with LI-8100 A.Carrying out the research of net CO₂ flux of biological soil crusted soil in Qinghai-Tibet Plateau can fill biological soil crust gaps in carbon cycle and assess accurately the role of biological soil crusts in carbon cycle in alpine sandy land.The main results and conclusions from this study included:?1?Biological soil crust increased the CO₂ flux of soil,and played the role of carbon source in carbon cycle.Net carbon flux?NCF?,respiration rates?R?of two types of biological soil crusted soil had obviously temporal dynamics.The daily dynamics of the NCF and R for 2types of biological soil crusted soil were unimodal.The monthly dynamics of the NCF and R were unimodal as well with the peak in July.The net carbon flux and dark respiration of algae crusted soil were higher than that of moss and bareland.the photosynthetic rate of moss crusts was greater than which of algea crusts in the monthly dynamics of Pn.?2?Precipitation could promote the NCF and R of two types biological soil crust.Net carbon flux and dark respiration of biological soil crust were both trigged and stimulated by all levels simulated precipitation.There are significant differences in net carbon and dark respiration between addition simulated precipitation treatment and control,but the differences between the additions of 2mm,5mm and 10 mm simulated precipitation are not significant.Under the condition of same amount of precipitation,the maximum photosynthetic rate,mean photosynthetic rate,dark respiration rate and carbon release of moss crusts covered soil are significantly greater than that of the algae crusts.After the simulated precipitation,the biological soil crusted soil is the carbon source in the entire progress.?3?The biological soil crusts increased total carbon release.The carbon emissions of crust were obviously smaller than crust soil and bareland.The dynamics of monthly carbon emissions of crust soil and bareland for biological soil crust were unmoral,with the peak in June?2.13?1.58 g.m-2?,taking 38% and 42% of the total carbon emissions of growing season.The carbon emissions of algae crusts were higher than that of moss and bareland.The carbon emissions of moss crusted soil and algae crusted soil increased compared with bareland.And the carbon emissions of the moss crusts take account for 28% of the moss crust covered soil,the carbon emissions of the moss crusts take account for 31% of the moss crust covered soil.