title: Microbial processes and community composition in the rhizosphere of European beech - The influence of plant C exudates.
abstract: Plant roots strongly influence C and N availability in the rhizosphere via rhizodeposition and uptake of nutrients. This study aimed at investigating the effect of resource availability on microbial processes and community structure in the rhizosphere. We analyzed C and N availability, as well as microbial processes and microbial community composition in rhizosphere soil of European beech and compared it to the bulk soil. Additionally, we performed a girdling experiment in order to disrupt root exudation into the soil. By this novel approach we were able to demonstrate that enhanced resource availability positively affected N mineralization and hydrolytic enzyme activities in the rhizosphere, but negatively affected nitrification rates and oxidative enzyme activities, which are involved in the degradation of soil organic matter. Both rhizosphere effects on N mineralization and oxidative enzyme activities disappeared in the girdling treatment. Microbial community structure in the rhizosphere, assessed by phospholipid fatty acid analysis, differed only slightly from bulk soil but was markedly altered by the girdling treatment, indicating additional effects of the girdling treatment beyond the reduction of root exudation. Differences in oxidative enzyme activities and nitrification rates between rhizosphere soil and bulk soil, however, suggest considerable differences in the (functional) microbial community composition.
authors.affiliation: University of Vienna, Department of Chemical Ecology and Ecosystem Research, Althanstr 14, A-1090 Vienna, Austria.
authors.forename: Marianne
authors.initials: M
authors.lastname: Koranda
authors.forename: Jörg
authors.initials: J
authors.lastname: Schnecker
authors.forename: Christina
authors.initials: C
authors.lastname: Kaiser
authors.forename: Lucia
authors.initials: L
authors.lastname: Fuchslueger
authors.forename: Barbara
authors.initials: B
authors.lastname: Kitzler
authors.forename: Claus Florian
authors.initials: CF
authors.lastname: Stange
authors.forename: Angela
authors.initials: A
authors.lastname: Sessitsch
authors.forename: Sophie
authors.initials: S
authors.lastname: Zechmeister-Boltenstern
authors.forename: Andreas
authors.initials: A
authors.lastname: Richter