Effects Of Different Glucose Addition Pattern On Soil Organic Carbon Priming Effect Under Nitrogen Deposition

Priming effect（PE）of soil organic carbon（SOC）decomposition induced by exogenous organic C is an important ecological process in regulating the soil C cycle.The direction and magnitude of this priming effect depends on the pattern of N and C addition.However,in which manner the pattern of N and C addition affect priming effect remains poorly understood.In this study,the soil of Phyllostachy pubescens forest with 6 years of field simulated nitrogen deposition was incubation for 90 days in laboratory to study the effect of single and repeated addition of ¹³C-labeled glucose on SOC decomposition.In this study,¹³C-PLFA and 16S amplification sequencing were used to determine the bacterial community composition and explore the role of specific microbial groups in the priming effect by combining isotope probe technology and molecular biology.By measuring soil CO₂ emission,soil basic physical and chemical properties and microbial characteristics,the following conclusions were drawn:（1）Glucose addition induced a significant positive priming effect,and the stimulation effect induced by single addition was larger than that induced by repeated addition.Simulated nitrogen deposition reduced soil priming effect,and high deposition addition inhibited soil priming effect more strongly than low nitrogen deposition.With the passage of time,the intensity of priming effect decreases gradually.（2）Glucose addition improved soil nutrient availability,provided sufficient nutrients for soil microorganisms,and increased soil microbial biomass carbon and enzyme activities,and single addition was larger than repeated addition.Simulated nitrogen deposition decreased soil microbial biomass carbon and oxidase activities.（3）Glucose addition changed bacterial community structure,decreased Gram-positive/gram-negative bacteria ratio and increased bacterial diversity.Simulated nitrogen deposition increased Gram-positive/gram-negative bacteria ratio and decreased fungi/bacteria ratio and bacterial diversity.¹³C-PLFA showed that glucose source ¹³C was mainly used by Gram-negative bacteria,gram-positive bacteria and actinomyces at the later stage of incubation.（4）Abiotic and biological factors jointly regulate the direction and size of the priming effect.In the early stage of incubation,abiotic factors such as available nitrogen,available phosphorus and p H were the main factors affecting soil priming effect.With the passage of incubation time,the importance of abiotic factors gradually decreased,andβ-glucosidase,β-N-acetylglucosaminidase and microbial biomass carbon were the main factors affecting soil priming effect.