Rhizosphere effects of Betula platyphylla and Quercus mongolica and their seasonal dynamics in Dongling Mountain,Beijing
Aims The objective of this study was to explore the seasonal variations of the rhizosphere effects of woody plants and their driving factors,and to assess the importance of plant functional traits in the control of rhizosphere processes.Methods We collected paired rhizosphere and bulk soils of the dominant tree species of two main types of vegetation in Dongling Mountain,Beijing,Betula platyphylla forest and Quercus mongolica forest.Soil physiochemical properties,microbial biomass,carbon and net nitrogen mineralization rates,extracellular enzyme activities and vector characteristics of rhizosphere and bulk soils,as well as plant root and leaf functional traits,in spring(May),summer(July),autumn(September),and winter(December)of 2017 were measured to analyze the seasonal dynamics of rhizosphere effects and their driving factors.Important findings(1)There were significant differences in soil pH,NH4-N,microbial biomass,carbon and net nitrogen mineralization rates,extracellular enzyme activities and vector characteristics between rhizosphere soil and bulk soil,and these rhizosphere effects were mainly positive.(2)The rhizosphere effects had significant seasonal dynamics,usually being strongest in autumn.(3)There were often significant correlations between rhizosphere effects and plant root and leaf functional traits.Among them,fine root biomass was significantly and positively correlated with the rhizosphere effect on contents of extractable organic carbon,soil total carbon and total nitrogen.Leaf dry matter content and leaf carbon and nitrogen ratio were significantly and positively correlated with the rhizosphere effect on microbial biomass carbon content,microbial biomass nitrogen content,carbon mineralization rate,and acid phosphatase activity.These results showed that the functional traits of plants were of great significance in rhizosphere processes.In the temperate deciduous broadleaf forest in Dongling Mountain,the highest belowground carbon allocation of plants leads to an increase in the biomass and activity of rhizosphere microorganisms in autumn,which makes the rhizosphere effect of microbial biomass and activity in autumn higher than that in other seasons.
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