Effects of Introducing Other Tree Species of Different Ages into Pinus massoniana Plantation on Activities and Stoichiometric Ratios of Enzymes Associated with Soil Aggregates
The activities and stoichiometric ratios of soil enzymes are important indicators to characterize soil microbial nutrient demand and nutrient limitation status.This study aims to investigate the effects of intro-ducing broadleaved tree species of different ages into pure Pinus massoniana plantation on the activities and stoichiometric ratios of enzymes in soil aggregates and their response mechanisms.The activities of enzymes involved in carbon(C),nitrogen(N),and phosphorus(P)cycling in original soil and soil aggregates with dif-ferent particle sizes,soil physicochemical properties,and microbial biomass were measured in a pure P.mas-soniana plantation(PP),an uneven-aged mixed plantation(MP)of P.massoniana and Castanopsis hystrix,and a multiple species uneven-aged mixed plantation(MMP)of P.massoniana.The relationships between the indicators were evaluated,and the major factors driving the variations in the activities and stoichiometric ratios of soil enzymes were identified.The results showed that:①Introducing other tree species of different a-ges into the plantation significantly altered soil enzyme activities,which were higher in MP and MMP than in PP and had no significant difference between MP and MMP.The enzyme activities were the highest in micro-aggregates(＜0.25 mm);③Litterfall mass,fine root biomass,soil physicochemical properties,and microbial biomass were correlated with the activities and stoichiometric ratios of soil enzymes.Redundancy Analysis(RDA)revealed that Microbial Biomass Carbon(MBC),Total Nitrogen(TN),Total Phosphorus(TP),Mi-crobial Biomass Phosphorus(MBP),and microbial biomass carbon to phosphorus ratio(MBC∶MBP)were the main drivers affecting soil enzyme activities,and TN,MBC,and nitrate nitrogen(NO3--N)were the main environmental factors affecting enzyme stoichiometric ratios;③The stoichiometric ratios of C,N,and P of soil enzymes in PP,MP,and MMP were 1.20∶1.03∶1,1.17∶1.07∶1,and 1.16∶1.04∶1,respectively,which indicated that the soil microorganisms in this area had high demand for C and were easily limited by C source.The findings suggested that introducing other tree species of different ages alleviated the C source limitation of soil microbial growth and metabolism.In conclusion,introducing broadleaved species into the pure P.massoniana plantation can effectively increase soil enzyme activities,promote soil nutrient cycling,and improve soil quality.However,attention should be paid to the application of nitrogen fertilizer in the in-troducing process in order to maintain the high productivity and sustainable development of the plantation.
Pinus massoniana plantationbroadleaved tree speciesintroducing other tree species of different agessoil enzyme activityenzyme stoichiometric rationutrient limitation
万方数据
维普
