Community shifts and carbon translocation within metabolically-active rhizosphere microorganisms in grasslands under elevated CO 2

By K. Denef, H. Bubenheim, K. Lenhart, J. Vermeulen, O. Cleemput, P. Boeckx, Christoph Müller. 2007

189 citations recorded by the source corpus.

Abstract. The aim of this study was to identify the microbial communities that are actively involved in the assimilation of rhizosphere-C and are most sensitive in their activity to elevated atmospheric CO2 in a temperate semi-natural low-input grassland ecosystem. For this, we analyzed 13C signatures in microbial biomarker phospholipid fatty acids (PLFA) from an in-situ 13CO2 pulse-labeling experiment in the Giessen Free Air Carbon dioxide Enrichment grasslands (GiFACE, Germany) exposed to ambient and elevated (i.e. 50% above ambient) CO2 concentrations. Short-term 13C PLFA measurements at 3 h and 10 h after the pulse-labeling revealed very little to no 13C enrichment after 3 h in biomarker PLFAs and a much greater incorporation of new plant-C into fungal compared to bacterial PLFAs after 10 h. After a period of 11 months following the pulse-labeling experiment, the 13C enrichment of fungal PLFAs was still largely present but had decreased, while bacterial PLFAs were much more enriched in 13C compared to a few hours after the pulse-labeling. These results imply that new rhizodeposit-C is rapidly processed by fungal communities and only much later by the bacterial communities, which we attributed to either a fungal-mediated translocation of rhizosphere-C from the fungal to bacterial biomass or a preferential bacterial use of dead root or fungal necromass materials as C source over the direct utilization of fresh root-exudate C in these N-limited grassland ecosystems. Elevated CO2 caused an increase in the proportional 13C enrichment (relative to the universal biomarker 16:0) of the arbuscular mycorrhizal fungal biomarker PLFA 16:1ω5 and one gram-positive bacterial biomarker PLFA i16:0, but a decrease in the proportional 13C enrichment of 18:1ω9c, a commonly used though questionable fungal biomarker PLFA. This suggests enhanced fungal rhizodeposit-C assimilation only by arbuscular mycorrhizal fungal species under elevated CO2.

Subfields: Ecology, Plant Science, Soil Science

View Paper: https://www.semanticscholar.org/paper/adf77a53e3b5e909cec41b32ca6360833d942b0c

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Citations in the corpus

Microbial response to rhizodeposition depending on water regimes in paddy soils (2013, background): “…and fungi actively utilize more newly rhizo-C, and those microorganisms are important initial rhizodeposition sinks under non-flooded and alternating water regime conditions in paddy soils as did in upland systems (Treonis et al., 2004; Leake et al., 2006; Denef et al., 2007; Jin and Evans, 2010).”
Acquisition of phosphorus and other poorly mobile nutrients by roots. Where do plant nutrition models fail? (2011, background): “Isotope-based studies in grassland (Denef et al. 2007) suggest that the first step of C delivery from roots to the soil is mediated by fungi (both mycorrhizal and saprotrophic).”
Elevated atmospheric CO2 increases microbial growth rates in soil: results of three CO2 enrichment experiments (2010, background): “…communities – DNA content, total PLFA and diversity estimated based on PLFA analysis – registered no or only a subtle effect of elevated CO2 (Griffiths et al., 1998; Zak et al., 2000b; Ebersberger et al., 2004; Lipson et al., 2006; Denef et al., 2007; Kanerva et al., 2008; Paterson et al., 2008).”
The rhizosphere zoo: An overview of plant-associated communities of microorganisms, including phages, bacteria, archaea, and fungi, and of some of their structuring factors (2009, background): “Upon pulselabeling of grassland plants with 13CO2, Denef et al. (2007) showed rapid incorporation of 13C in PLFAs that are characteristic for general fungi (18:2ω6,9) and arbuscular mycorrhizal fungi (16:1ω5).”