title: Rhizosphere processes are quantitatively important components of terrestrial carbon and nutrient cycles.
abstract: While there is an emerging view that roots and their associated microbes actively alter resource availability and soil organic matter (SOM) decomposition, the ecosystem consequences of such rhizosphere effects have rarely been quantified. Using a meta-analysis, we show that multiple indices of microbially mediated C and nitrogen (N) cycling, including SOM decomposition, are significantly enhanced in the rhizospheres of diverse vegetation types. Then, using a numerical model that combines rhizosphere effect sizes with fine root morphology and depth distributions, we show that root-accelerated mineralization and priming can account for up to one-third of the total C and N mineralized in temperate forest soils. Finally, using a stoichiometrically constrained microbial decomposition model, we show that these effects can be induced by relatively modest fluxes of root-derived C, on the order of 4% and 6% of gross and net primary production, respectively. Collectively, our results indicate that rhizosphere processes are a widespread, quantitatively important driver of SOM decomposition and nutrient release at the ecosystem scale, with potential consequences for global C stocks and vegetation feedbacks to climate.
authors.affiliation: Department of Biology and PhD Program in Biogeoscience, Boston University, Boston, MA, 02215, USA.
authors.forename: Adrien C
authors.initials: AC
authors.lastname: Finzi
authors.forename: Rose Z
authors.initials: RZ
authors.lastname: Abramoff
authors.forename: Kimberly S
authors.initials: KS
authors.lastname: Spiller
authors.forename: Edward R
authors.initials: ER
authors.lastname: Brzostek
authors.forename: Bridget A
authors.initials: BA
authors.lastname: Darby
authors.forename: Mark A
authors.initials: MA
authors.lastname: Kramer
authors.forename: Richard P
authors.initials: RP
authors.lastname: Phillips
mesh_terms: D057486:Carbon Cycle / Q000502:physiology*; D017753:Ecosystem; D065928:Forests; D006812:Humic Substances / Q000382:microbiology*; D018517:Plant Roots / Q000382:microbiology* / Q000502:physiology*; D058441:Rhizosphere
chemical_list: D006812:Humic Substances
keywords: carbon cycle; global change; nitrogen cycle; priming effects; soil organic matter