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Ddoyle Mckey

Bio: Ddoyle Mckey is an academic researcher from Centre national de la recherche scientifique. The author has contributed to research in topics: Ecosystem & Ecosystem engineer. The author has an hindex of 1, co-authored 1 publications receiving 89 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, the authors propose a conceptual framework for sustainable use of the soil resource and present seven general research questions whose resolution will provide a firmer base for the proposed conceptual framework.
Abstract: Soils are self-organized ecological systems within which organisms interact within a nested suite of discrete scales. Microorganisms form communities and physical structures at the smallest scale (microns), followed by the community of their predators organized in microfoodwebs (tens of microns), the functional domains built by ecosystem engineers (centimeters to meters), ecosystems, and landscapes. Ecosystem engineers, principally plant roots, earthworms, termites, and ants, play key roles in creating habitats for other organisms and controlling their activities through physical and biochemical processes. The biogenic, organic, and organomineral structures that they produce accumulate in the soil space to form three-dimensional mosaics of functional domains, inhabited by specific communities of smaller organisms (microfauna and mesofauna, microorganisms) that drive soil processes through specific pathways. Ecosystem engineers also produce signaling and energy-rich molecules that act as ecological mediators of biological engineering processes. Energy-rich ecological mediators may selectively activate microbial populations and trigger priming effects, resulting in the degradation, synthesis, and sequestration of specific organic substrates. Signaling molecules inform soil organisms of their producers' respective presences and change physiologies by modifying gene expression and through eliciting hormonal responses. Protection of plants against pests and diseases is largely achieved via these processes. At the highest scales, the delivery of ecosystem services emerges through the functioning of self-organized systems nested within each other. The integrity of the different subsystems at each scale and the quality of their interconnections are a precondition for an optimum and sustainable delivery of ecosystem services. Lastly, we present seven general research questions whose resolution will provide a firmer base for the proposed conceptual framework while offering new insights for sustainable use of the soil resource.

129 citations


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01 Dec 2013
TL;DR: It is postulate that rhizosphere priming may enhance N supply to plants in systems that are N limited, but thatrhizospherePriming may not occur in Systems that are phosphorus (P) limited, because under P limitation, rhizodeposition may be used for mobilization of P, rather than for decomposition of SOM.
Abstract: Rhizosphere priming is the change in decomposition of soil organic matter (SOM) caused by root activity. Rhizosphere priming plays a crucial role in soil carbon (C) dynamics and their response to global climate change. Rhizosphere priming may be affected by soil nutrient availability, but rhizosphere priming itself can also affect nutrient supply to plants. These interactive effects may be of particular relevance in understanding the sustained increase in plant growth and nutrient supply in response to a rise in atmospheric CO2 concentration. We examined how these interactions were affected by elevated CO2 in two similar semiarid grassland field studies. We found that an increase in rhizosphere priming enhanced the release of nitrogen (N) through decomposition of a larger fraction of SOM in one study, but not in the other. We postulate that rhizosphere priming may enhance N supply to plants in systems that are N limited, but that rhizosphere priming may not occur in systems that are phosphorus (P) limited. Under P limitation, rhizodeposition may be used for mobilisation of P, rather than for decomposition of SOM. Therefore, with increasing atmospheric CO2 concentrations, rhizosphere priming may play a larger role in affecting C sequestration in N poor than in P poor soils.

353 citations

Journal Article

328 citations

Journal ArticleDOI
TL;DR: The objective of the present article is to review progress achieved to date in the significant research program that has ensued, namely the quantification and modeling of the physical-, (bio)chemical-, and microbiological properties of soils, and the integration of these different perspectives into a unified theory.
Abstract: Over the last 60 years, soil microbiologists have accumulated a wealth of experimental data showing that the usual bulk, macroscopic parameters used to characterize soils (e.g., granulometry, pH, soil organic matter and biomass contents) provide insufficient information to describe quantitatively the activity of soil microorganisms and some of its outcomes, like the emission of greenhouse gases. Clearly, new, more appropriate macroscopic parameters are needed, which reflect better the spatial heterogeneity of soils at the microscale (i.e., the pore scale). For a long time, spectroscopic and microscopic tools were lacking to quantify processes at that scale, but major technological advances over the last 15 years have made suitable equipment available to researchers. In this context, the objective of the present article is to review progress achieved to date in the significant research program that has ensued. This program can be rationalized as a sequence of steps, namely the quantification and modeling of the physical-, (bio)chemical-, and microbiological properties of soils, the integration of these different perspectives into a unified theory, its upscaling to the macroscopic scale, and, eventually, the development of new approaches to measure macroscopic soil characteristics. At this stage, significant progress has been achieved on the physical front, and to a lesser extent on the (bio)chemical one as well, both in terms of experiments and modeling. In terms of microbial aspects, whereas a lot of work has been devoted to the modeling of bacterial and fungal activity in soils at the pore scale, the appropriateness of model assumptions cannot be readily assessed because relevant experimental data are extremely scarce. For the overall research to move forward, it will be crucial to make sure that research on the microbial components of soil systems does not keep lagging behind the work on the physical and (bio)chemical characteristics. Concerning the subsequent steps in the program, very little integration of the various disciplinary perspectives has occurred so far, and, as a result, researchers have not yet been able to tackle the scaling up to the macroscopic level. Many challenges, some of them daunting, remain on the path ahead.

171 citations

Journal ArticleDOI
TL;DR: The objective of this review is to synthesize the existing literature concerning the influence of earthworms on the structure and function of soil microbial communities, as well as to understand how earthworm-induced changes in the soil microbiota would in turn impact soil processes, particularly those occurring in the rhizosphere and involved in plant growth and health.
Abstract: The positive effect of earthworms on soil processes and plant growth has been extensively documented. The capacity of earthworms to decompose organic matter has been attributed to the microbial communities that inhabit their digestive track or the structures they build, which in turn contribute to make up the drilosphere, a hotspot for microbial activity. However, how earthworms modify the structure of soil microbial communities and how these changes affect soil microbial processes is still unclear. Do earthworms reduce microbial abundance and activity because they feed on microorganisms or do they select and stimulate specific microbial groups? We hypothesise that “the effect of earthworms on nutrient cycling and plant growth is not only a direct effect but is mainly mediated indirectly, via modifications of the microbial community.” The objective of this review is to synthesize the existing literature concerning the influence of earthworms on the structure and function of soil microbial communities, as well as to understand how earthworm-induced changes in the soil microbiota would in turn impact soil processes, particularly those occurring in the rhizosphere and involved in plant growth and health. Recent reports have shown that specific bacterial groups consistently increase in soils where earthworms are present, regardless of the earthworm functional group. The extent of this increase seems to be dependent upon the type of substrate under study. Our synthesis also reveals that endogeic and anecic earthworms regularly induce an increase in soil nutrients, whilst this positive effect is not as evident in the presence of epigeic earthworms. The effect of earthworms on nutrient cycling has been further investigated with microbial functional genes, although existing reports largely focus on nitrogen cycling. Earthworms seem to enhance denitrification, most likely through the increase in organic compounds due to organic matter decomposition. By enhancing soil nutrient availability, earthworms indirectly promote plant growth, which has also been attributed to the induction of signal molecules. However, no experiment to date has been able to prove a direct causal relationship between specific signal molecules, earthworms and plant growth promotion. Finally, we propose a framework for earthworm-microbiota interactions and recommend further research.

157 citations

Journal ArticleDOI
15 Mar 2019-Geoderma
TL;DR: In this article, the fertility of earthworm casts was quantified using meta-analysis, and the authors identified its controlling factors, such as the presence of plants, availability of available pools of N (total mineral N) and available P (available P: P-Olsen, P-Bray or comparable metrics), C-to-N ratio and microbial biomass C.

111 citations