Rhizodeposition and its effects on C fluxes in the soil
type: CreativeWork
description: Organic compounds released from living roots (rhizodeposits) are easily available sources of energy for microorganisms strongly affecting soil organic matter (SOM) dynamics. Although, rhizodeposition is a key driver of microbially mediated processes in the soils, it still remains the most uncertain component of the terrestrial carbon (C) cycle. The input of C through rhizodeposition occurs in temporal and spatial hotspots. The objective of Study 1 was to determine the dynamics of hotspots of recently assimilated C in ryegrass roots. Shoots were 14CO2 pulse labeled and the allocation patterns at increasing time intervals were visualized by phosphor imaging. We could show a quick translocation of assimilated C to the roots. 14C hotspots were detected at the root tips already 6 hours after labeling. The hotspots remained active for at least 2 days. Eleven days after assimilation the hotspots at the tips had disappeared, and the 14C distribution was much more even than after 6 hours and 2 days. Through the availability of rhizodeposits, hotspots create preferred habitats for microbes. Rhizodeposits are an important source of C and energy for microorganisms stimulating their growth and activity. Thereby, roots can influence the rate of native SOM decomposition in the rhizosphere. This rhizosphere priming effect (RPE) was reported to be plant-species specific. Therefore, we hypothesized that also plant inter-species interactions affect the RPE. In Study 2, we used continuous 13CO2 labeling to investigate the RPE of monocultures and mixtures of typical agricultural crops. The RPE was consistently positive for all cultures with an increase of 43% - 136% above the unplanted soil. Of particular interest was the result that plant inter-species interactions between sunflower and wheat significantly reduced the RPE in contrast to mixtures which included soybean as a legume. It was argued that the RPE of the sunflower-wheat mixture was reduced through a more severe competition fo…
abstract: Organic compounds released from living roots (rhizodeposits) are easily available sources of energy for microorganisms strongly affecting soil organic matter (SOM) dynamics. Although, rhizodeposition is a key driver of microbially mediated processes in the soils, it still remains the most uncertain component of the terrestrial carbon (C) cycle. The input of C through rhizodeposition occurs in temporal and spatial hotspots. The objective of Study 1 was to determine the dynamics of hotspots of recently assimilated C in ryegrass roots. Shoots were 14CO2 pulse labeled and the allocation patterns at increasing time intervals were visualized by phosphor imaging. We could show a quick translocation of assimilated C to the roots. 14C hotspots were detected at the root tips already 6 hours after labeling. The hotspots remained active for at least 2 days. Eleven days after assimilation the hotspots at the tips had disappeared, and the 14C distribution was much more even than after 6 hours and 2 days. Through the availability of rhizodeposits, hotspots create preferred habitats for microbes. Rhizodeposits are an important source of C and energy for microorganisms stimulating their growth and activity. Thereby, roots can influence the rate of native SOM decomposition in the rhizosphere. This rhizosphere priming effect (RPE) was reported to be plant-species specific. Therefore, we hypothesized that also plant inter-species interactions affect the RPE. In Study 2, we used continuous 13CO2 labeling to investigate the RPE of monocultures and mixtures of typical agricultural crops. The RPE was consistently positive for all cultures with an increase of 43% - 136% above the unplanted soil. Of particular interest was the result that plant inter-species interactions between sunflower and wheat significantly reduced the RPE in contrast to mixtures which included soybean as a legume. It was argued that the RPE of the sunflower-wheat mixture was reduced through a more severe competition fo…
author: Pausch, Johanna
date published: 2012-09-13
date modified: 2026-07-27T18:49:06Z
provider: Universität Bayreuth
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Universität Bayreuth