Plant clipping decelerates the mineralization of recalcitrant soil organic matter under multiple grassland species

Shahzad, Tanvir; Chenu, Claire; Repinçay, Cedric; Mougin, Christian; Ollier, Jean-Luc; Fontaine, Sébastien

doi:10.1016/j.soilbio.2012.04.014

Cited by 82 publications

(82 citation statements)

References 44 publications

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“…Diminished net C fixation and root growth with clipping are consistent with previous studies summarised by Ferraro and Oesterheld (2002). Diminished root exudation and plant-derived soil respiration with clipping are also consistent with previous work (Shahzad et al, 2012;Schmitt et al, 2013), including in Kikuyu grass (Roper et al, 2013).…”

Section: Actual Rhizodepositionsupporting

confidence: 91%

Effects of soil type and composition of rhizodeposits on rhizosphere priming phenomena

Lloyd

Ritz

Paterson

et al. 2016

Soil Biology and Biochemistry

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Inputs of fresh plant-derived C may stimulate microbially-mediated turnover of soil organic matter (SOM) in the rhizosphere. But studies of such 'priming' effects in artificial systems often produce conflicting results, depending on such variables as rates of substrate addition, substrate composition, whether pure compounds or mixtures of substrates are used, and whether the addition is pulsed or continuous. Studies in planted systems are less common, but also produce apparently conflicting results, and the mechanisms of these effects are poorly understood.To add to the evidence on these matters, we grew a C4 grass for 61 d in two contrasting soilsan acid sandy soil and a more fertile clay-loam -which had previously only supported C3 vegetation. We measured total soil respiration and its C isotope composition, and used the latter to partition the respiration between plant-and soil-C sources. We found SOM turnover was enhanced (i.e. positive priming) by plant growth in both soils. In treatments in which the grass was clipped, net growth was greatly diminished, and priming effects were correspondingly weak. In treatments without clipping, net plant growth, total soil respiration and SOM-derived respiration were all much greater. Further, SOM-derived respiration increased over time in parallel with increases in plant growth, but the increase was delayed in the less fertile soil. We conclude the observed priming effects were driven by microbial demand for N, fuelled by deposition of C substrate from roots and competition with roots for N. The extent of priming depended on soil type and plant growing conditions.In a further experiment, we simulated rhizodeposition of soluble microbial substrates in the same two soils with near-continuous additions for 19 d of either C4-labelled sucrose (i.e. a simple single substrate) or a maize root extract (i.e. a relatively diverse substrate), and we measured soil respiration and its C isotope signature. In the more fertile soil, sucrose induced increasingly positive priming effects over time, whereas the maize root extract produced declining priming effects over time. We suggest this was because N and other nutrients were provided from the mineralization of this more diverse substrate. In the less-fertile soil, microbial N demand was probably never satisfied by the combined mineralization from added substrate and soil organic matter. Therefore priming

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Section: Actual Rhizodepositionsupporting

confidence: 91%

Effects of soil type and composition of rhizodeposits on rhizosphere priming phenomena

Lloyd

Ritz

Paterson

et al. 2016

Soil Biology and Biochemistry

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“…Similarly, our estimates of rhizosphere effects are almost certainly conservative given that we did not include the activities fine roots growing below 15 cm depth, and rhizosphere effects were quantified using root-free soil incubations. Much of the C exuded by roots is assimilated by rhizosphere microbes within hours (H€ ogberg et al, 2008;Shahzad et al, 2012), and so a substantial fraction of the labile C that exists in the rhizosphere is likely depleted shortly after soil collection -a process that should reduce differences in microbial C and N cycling between rhizosphere and bulk soils.…”

Section: Measurement and Scaling Considerationsmentioning

confidence: 99%

Root-induced changes in nutrient cycling in forests depend on exudation rates

Yin

Wheeler

Phillips

2014

Soil Biology and Biochemistry

192

120

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a b s t r a c t(1) While it is well-known that trees release carbon (C) to soils as root exudates, the factors that control the magnitude and biogeochemical impacts of this flux are poorly understood.(2) We quantified root exudation and microbially-mediated nutrient fluxes in the rhizosphere for four 80 year-old tree species in a deciduous hardwood forest, Indiana, USA. We hypothesized that trees that exuded the most carbon (C) would induce the strongest rhizosphere effects (i.e., the relative difference in nutrient fluxes between rhizosphere and bulk soil). Further, we hypothesized that tree species that associate with ectomycorrhizal (ECM) fungi would exude more C than tree species that associate with arbuscular mycorrhizal (AM) fungi, resulting in a greater enhancement of nutrient cycling in ECM rhizospheres.(3) Mass-specific exudation rates and rhizosphere effects on C, N and P cycling were nearly two-fold greater for the two ECM tree species compared to the two AM tree species (P < 0.05). Moreover, across all species, exudation rates were positively correlated with multiple indices of nutrient cycling and organic matter decomposition in the rhizosphere (P < 0.05). Annually, we estimate that root exudation represents 2.5% of NPP in this forest, and that the exudate-induced changes in microbial N cycling may contribute~18% of total net N mineralization.(4) Collectively, our results indicate that the effects of roots on nutrient cycling are consequential, particularly in forests where the C cost of mining nutrients from decomposing soil organic matter may be greatest (e.g., ECM-dominated stands). Further, our results suggest that small C fluxes from exudation may have disproportionate impacts on ecosystem N cycling in nutrient-limited forests.

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“…On the other hand, some N-rich compounds in root exudates can be directly consumed by plants, particularly under lowtemperature and N-limited conditions (Beltran-Garcia et al 2014). Therefore, prediction of the effects of grazing on the uptake and export of N becomes difficult, as inherently complex linkages are present among different species of N and different storage compartments (Shahzad et al 2012). Thus, the combination of 13 C stable isotopes, community analysis by PLFA and microarray-based functional gene analysis may provide an important approach to understanding the microbial community connection between root C and SOM priming.…”

Section: Discussionmentioning

confidence: 99%

Responses of root exudation and nutrient cycling to grazing intensities and recovery practices in an alpine meadow: An implication for pasture management

et al. 2017

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Plant clipping decelerates the mineralization of recalcitrant soil organic matter under multiple grassland species

Cited by 82 publications

References 44 publications

Effects of soil type and composition of rhizodeposits on rhizosphere priming phenomena

Effects of soil type and composition of rhizodeposits on rhizosphere priming phenomena

Root-induced changes in nutrient cycling in forests depend on exudation rates

Responses of root exudation and nutrient cycling to grazing intensities and recovery practices in an alpine meadow: An implication for pasture management

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