Effects Of Intensities And Frequencies Of Drying-rewetting Cycles On Soil Respiration,Soil Carbon And Nitrogen In Zoige Wetland

With global climate change,the frequency of extreme precipitation and drought events will increase,which will alternate the frequency and intensity of soil drying-rewetting cycle,thus affect soil water content and soil respiration.Based on the field precipitation events,we set up high and low intensities,high(8 days per cycle)and low(16 days per cycle)frequencies of soil drying-rewetting cycles,provided the optimal measurement time of soil respiration under different drying-rewetting cycles,analyzed the effects of drying-rewetting cycles on soil respiration,soil carbon and nitrogen contents.The main results are as follows(1)The optimum sampling time was on the 4th day of the high-frequent drying-rewetting cycle.During the low-frequent drying-rewetting cycle,the optimum sampling time was on the 6th day for the high intensity and the 4th day for the low intensity,respectively.(2)The intensity and frequency of drying-rewetting cycles have significant effects on soil respiration.Soil respiration increased with the increasing intensity and decreasing frequency of drying-rewetting cycle.Moreover,the incubation substrate had significant effect on soil respiration.Soil respiration was higher from the substrate of soil and litter than that from the soil substrate alone.(3)The intensity of drying-rewetting cycle had significant effect on soil microbial biomass carbon content.Soil microbial biomass carbon content increased with the increasing intensities.The intensity of drying-re wetting cycle,substrate and their interaction had significant effects on soil inorganic nitrogen content,nitrogen mineralization and nitrification rate and their resistance index.In the soil and litter substrate,soil inorganic nitrogen,nitrogen mineralization and nitrification rate decreased with the increasing intensities.Soil carbon stability decreased with increasing intensities.(4)Soil respiration was positively correlated with soil water content and dissolved organic carbon content,negatively correlated with microbial nitrogen content.Soil respiration increased firstly and then decreased with the increased ammonium nitrogen content.These results showed that the alternant intensities and frequencies of drying-wetting cycles,which caused by global climate change,had significant effect on soil respiration in alpine wetlands.Our study provides a reference for further understanding of soil respiration response to climate change and the process of soil carbon and nitrogen cycles in alpine wetlands.