Distribution And Mineralization Characteristics Of Soil Organic Carbon In Alpine Shrub Meadow Of The Western Sichuan

In order to reveal the dynamic changes of soil organic carbon composition and its mineralization season at different altitudes in alpine shrub meadow,to analyze effects of different soil carbon components on soil organic carbon mineralization,and the factors affecting the change of soil organic carbon composition,and explore the correlation between soil carbon composition and soil physical and chemical properties.Seasonal variation of soil organic carbon mineralization at different altitudes is crucial for better understanding of soil organic carbon dynamics.We selected the alpine mountains of3800m,4000m,4200m at the semi-shady slopes and the semi-sunny slopes in Zheduo Mountains as the research object,and discussed them with field investigation and indoor analysis methods to explor the changes of soil organic carbon pools and soil carbon mineralization characteristics at different altitudes,seasons and slopes.The main developments and conciusions are as follows:?1?Soil carbon pools due to ecosystem type,vegetation type,land use pattern,soil texture and other environmental factors,with spatial and temporal heterogeneity.Except for3800m podzolic soil,soil organic carbon content showed that the soil leaching layer was significantly higher than the soil sedimentary layer in all seasons,and showed the same elevation ranked as follows:4200m>4000m>3800m.Soil organic carbon content generally shows that the semi-shady slope is slightly higher than the semi-sunny slope.The seasonal variation of soil organic carbon in the soil leaching layer at the same elevation ranked as follows:autumn>spring>summer,the soil sedimentary layer ranked as follows:autumn>summer>spring,and the seasonal differences were not significant.?2?The soil activated carbon in the soil leaching layer is significantly higher than the soil sedimentary layer,and in addition to the reasily oxidized organic carbon,the soil activated carbon content of the semi-shady slope is higher than the semi-sunny slope.The altitude variation of soil microbial biomass carbon and dissolvable organic carbon in the semi-shady at leaching layer ranked as follows:4200m>4000m>3800m.The microbial biomass carbon and reasily oxidized organic carbon in the semi-shady at sedimentary layer ranked as follows:3800m>4200m>4000m.This is consistent with soil organic carbon.But the microbial biomass carbon and reasily oxidized organic carbon in the semi-sunny at leaching layer ranked as follows:4000m>4200m>3800m,and was no consistent elevation trend of soil active carbon content in the sedimentary layer.Soil reasily oxidized organic carbon showed the highest in summer in the upper and lower soil layers,but microbial biomass carbon and dissolvable organic carbon had no consistent seasonal trends.The ratio of soil active organic carbon to total organic carbon ranked as follows:reasily oxidized organic carbon>dissolvable organic carbon>microbial biomass carbon.The ratio of soil active organic carbon to total organic carbon were significantly higher at semi-shade slope,indicating that the soil organic carbon quality was higher.?3?All of the carbon mineralization parameters decreased gradually with increasing soil depth,and the difference is significant.The cumulative carbon mineralization showed the highest summer at all altitudes and ascept,and the semi-shady slope was greater than the semi-sunny slope,and the cumulative mineralization was the largest of the podzolic soil.The soil carbon mineralization rate was decreased with the cultivation time at each altitude gradually and the first 7-day reduction was significantly higher.There is no consistent change in soil carbon mineralization rate and cumulative carbon mineralization at altitude,but the soil leaching layer were significant higher than the soil sedimentary layer?P<0.05?.?4?The carbon mineralization process could fitted by the first-order kinetics.The potential mineralizable organic carbon?C₀?,mineralizable organic carbon?C₁?and C₀/SOC value were significantly higher at summer and semi-shady slope,and reached maximum at 3800m.It indicates that the carbon sequestration capacity is the weakest in summer in high altitude areas,and the semi-shady slope soil was relatively lower than the semi-sunny slope.The podzolic soil was weakest under same ambient temperature.?5?There was a significant correlation between soil total nitrogen and soil organic carbon,and soil organic carbon significantly correlated with activated carbon components.Soil cumulative carbon mineralization were significantly correlated with Soil moisture content?soil organic carbon and activated carbon,and microbial biomass carbon could directly affect organic carbon mineralization.