不同冻融条件下高寒沼泽草甸土壤碳矿化及δ13C值特征OA

To investigate the mechanisms of the effects of different frequencies and intensities of freeze-thaw cycles on the soil carbon mineralization process and the characteristics of stable carbon isotope(δ¹³C)fraction-ation in alpine swamp meadows,this study focused on the soil of alpine swamp meadows on the Qinghai-Tibet Plateau.Two freeze-thaw intensities(-15 to 15℃and-10 to 10℃,a total of 15 freeze-thaw cycles)and a control group at 10℃were established.A 15-day indoor continuous monitoring experiment was conducted to compare the dynamics of carbon mineralization and changes in δ¹³C.The results showed that low-intensity freeze-thaw cycles significantly inhibited the rate of carbon mineralization,causing a decrease of 7.67%.In con-trast,high-intensity freeze-thaw cycles significantly promote the cumulative carbon mineralization,with an increase of 2.70%.The differences among treatments were relatively small after the first 3 freeze-thaw cycles,but the growth rate of carbon mineralization significantly slowed down under the low-intensity treatment after the third cycle.The δ13C values under different freeze-thaw intensities ranged from-21.49‰ to-28.03‰,which showed-15-15℃>10℃>-10-10℃,and showed a trend of first decreasing and then increasing with the increase of freeze-thaw frequency.Redundancy analysis(RDA)showed that ammonium nitrogen(NH4+-N)and microbial biomass nitrogen(MBN)were the key factors regulating carbon mineralization and isotope fractionation.Under the-15-15℃treatment,δ13C values were significantly positively correlated with nitrate nitrogen(NO3--N).In contrast,under the-10-10℃treatment,the carbon mineralization rate was signifi-cantly negatively correlated with MBN and significantly positively correlated with microbial biomass carbon to microbial biomass nitrogen ratio(MBC/MBN).Additionally,its stable isotopes were significantly positively correlated with NH4+-N and MBC/MBN.Overall,the reduced freeze-thaw intensity significantly inhibits soil carbon mineralization processes and causes changes in microbial metabolic pathways.It is crucial to pay atten-tion to the long-term impacts of the continued weakening in freeze-thaw intensity on the carbon sequestration function of alpine wetlands.