Naoise Nunan

French National Centre for Scientific Research / Sorbonne Université

Elevational gradients are often used to reveal how soil microorganisms will respond to climate change. However, inconsistent microbial distribution patterns across different elevational transects have raised doubts about their practical applicability. We hypothesized that variations in bedrock, which influence soil physical and chemical properties,...

Microbial carbon use efficiency (CUE) affects the fate and storage of carbon in terrestrial ecosystems, but its global importance remains uncertain. Accurately modeling and predicting CUE on a global scale is challenging due to inconsistencies in measurement techniques and the complex interactions of climatic, edaphic, and biological factors across...

Background and aims Most studies of the relationships between the composition of soil organic matter and plant cover have been carried out at the plant genera level. However, they have largely overlooked the potential effects that plant varieties, belonging to the same genus, can have on soil organic matter. Methods We investigated whether plant v...

Pore surfaces in soil are considered to be sparsely colonised, dispersed only with isolated cells or colonies of bacteria and archaea. Here, we question this ‘empty space’-concept by combining microstructure analysis with molecular biology and provide a data-driven update on habitable surface areas (HSA) in soil. Our unique approach allowed us to p...

Background and aims Most studies of the relationships between the composition of soil organic matter and plant cover have been carried out at the plant genera level. Yet, they have largely overlooked the potential effects that plant varieties belonging to the same genus can have on soil organic matter. Methods We investigated whether plant varietie...

We invite you to submit your abstracts to the session SSS5.8 Bioenergetics in soil systesm. Details in the attached file or under https://meetingorganizer.copernicus.org/EGU24/session/50100

Trophic interactions between soil-living organisms occur largely in soil pores and are essential for soil functioning. As soil is a three-dimensional environment where resources are distributed in pores of contrasting size, and higher trophic level consumers (grazers) are typically larger than their microbial food sources, the location of microbial...

Bloom-forming phytoplankton dynamics are still unpredictable, even though it is known that several abiotic factors, such as nutrient availability and temperature, are key factors for bloom development. We investigated whether biotic factors, i.e. the bacterioplankton composition (via 16SrDNA metabarcoding), were correlated with phytoplankton dynami...

Soil microbial responses to anthropogenic nitrogen (N) enrichment at the overall community level has been extensively studied. However, the responses of community dynamics and assembly processes of the abundant versus rare bacterial taxa to N enrichment have rarely been assessed. Here, we present a study in which the effects of short- (2 years) and...

Soil organic matter (SOM) is important in maintaining soil fertility and other ecosystem functions. Yet, land management in intensive agriculture has caused SOM level to decrease, with knock-on effects for soil fertility and quality. Therefore, land management options that ensure that SOM is not depleted and that soil functions are better sustained...

Microbial communities are a critical component of the soil carbon (C) cycle as they are responsible for the decomposition of both organic inputs from plants and of soil organic C. However, there is still no consensus about how to explicitly represent their role in terrestrial C cycling. The objective of the study was to determine how the molecular...

The soil microhabitat is a heterogeneous and complex environment where local variations can modulate phenomena observed at the plot scale. Most of the current methods used to describe soil functioning are bulk soil analyses which do not account for fine-scale spatial variability and cannot fully account for the processes that occur under the influe...

Recent advances in molecular ecology have dramatically improved our knowledge of soil microbial diversity and offers new indicators of soil quality. The usefulness of diversity indices has never been greater as the astronomical amounts of data generated in the literature needs to be synthesized. Despite technical guidelines have been proposed to ch...

A healthy soil plant continuum is critical for maintaining agroecosystem functions and ensuring food security, which is the basis of sustainable agricultural development. Diverse soil microorganisms form a complex assembly and play an important role in agroecosystems by regulating nutrient cycling, promoting plant growth, and alleviating biotic and...

Bacterial decomposition of organic matter in soils is generally believed to be mainly controlled by the access bacteria have to organic substrate. The influence of bacterial traits on this control has, however, received little attention. Using the concentration-dependent Monod growth model, we develop a bioreactive transport model to screen the int...

Microbial spatial distribution has mostly been studied at field to global scales (i.e., ecosystem scales). However, the spatial organization at small scales (i.e., centimeter to millimeter scales), which can help improve our understanding of the impacts of spatial communities structure on microbial functioning, has received comparatively little att...

The microscale physical characteristics of microbial habitats considerably affect the decomposition of organic matter in soils. One of the challenges is to identify microheterogeneities in soil that can explain the extent of carbon mineralization. The aim of this study was therefore to identify descriptors of μm-scale soil heterogeneity that can ex...

Minerals are widely assumed to protect organic matter (OM) from degradation in the environment, promoting the persistence of carbon in soil and sediments. In this Review, we describe the mechanisms and processes operating at the mineral–organic interface as they relate to OM transformation dynamics. A broad set of interactions occur, with minerals...

Microbial communities are a critical component of the soil carbon (C) cycle, as they are responsible for the decomposition of both organic inputs from plants and of soil organic C. However, there is still no consensus about how to explicitly represent their role in terrestrial C cycling. We suggest that a full understanding of microbial communities...

Organic amendments are believed to help increase the soil carbon storage and therefore improve soil quality, which may be important in the context of climate change. However, the added value of organic amendments for farmers must be clearly demonstrated in order to convince them of the utility of their use. The aims of this study were: (i) to inves...

Soil heterogeneity influences microbial access to substrates and creates habitats varying in substrate concentrations , thus leading to local variations in carbon (C) dynamics. Based on theoretical considerations, we expected that higher heterogeneity would decrease microbial activity. To test this hypothesis, we modified substrate spatial heteroge...

Bacterial decomposition of organic matter in soils is generally believed to be mainly controlled by the access bacteria have to their substrate. The influence of bacterial traits on this control has, however, received little attention. Here, we develop a bioreactive transport model to screen the interactive impacts of dispersion and bacterial trait...

Any change in the intensity and sign of CO2 flux between soil and atmosphere is expected to have a significant impact on climate. The net emission of CO2 by soils depends on antagonistic processes: the persistence of dead plant matter and the mineralization of soil organic matter. These two processes are partly interdependent: their interaction is...

Urban soils are a crucial component of urban ecosystems, especially in public green spaces, because of the ecosystem services they provide (e.g. public recreation, urban cooling or water infiltration). In this study we describe the chemical, physical and hydrostructural characteristics of 180 forest and lawn surface soil samples, taken along an urb...

Soil organic carbon management has the potential to aid climate change mitigation through drawdown of atmospheric carbon dioxide. To be effective, such management must account for processes influencing carbon storage and re-emission at different space and time scales. Achieving this requires a conceptual advance in our understanding to link carbon...

Heterogeneity is a fundamental property of soil that is often overlooked in microbial ecology. Although it is generally accepted that the heterogeneity of soil underpins the emergence and maintenance of microbial diversity, the profound and far-reaching consequences that heterogeneity can have on many aspects of microbial ecology and activity have...

The distribution of organic substrates and microorganisms in soils is spatially heterogeneous at the microscale. Most soil carbon cycling models do not account for this microscale heterogeneity, which may affect predictions of carbon (C) fluxes and stocks. In this study, we hypothesize that the mean respiration rate R‾ at the soil core scale (i) is...

The distribution of organic substrates and microorganism in soils is spatially heterogeneous at the micro-scale. Most soil carbon cycling models do not account for this micro-scale heterogeneity, which may affect predictions of carbon (C) fluxes and stocks. In this study, we hypothesize that the mean respiration rate R at the soil-core scale (i) is...

An accurate representation of soil organic matter (SOM) decomposition dynamics in large scale Earth system models is required for a better prediction of carbon storage and its fluxes. Often, the dynamics of soil carbon decomposition are simplified – assuming soils as well-mixed homogeneous compartments of varying substrate quality and microorganism...

This chapter discusses importance of biodiversity in the functioning of soils. It also summarizes several potential explanations for the delayed interest of the scientific community in the relationship between soil biodiversity and functioning. The chapter then argues that there are some privileged lines of research and important developments of sc...

Over the last 60 years, soil microbiologists have accumulated a wealth of experimental data showing that the bulk, macroscopic parameters (e.g., granulometry, pH, soil organic matter, and biomass contents) commonly used to characterize soils provide insufficient information to describe quantitatively the activity of soil microorganisms and some of...

Root surfaces are major sites of interactions between plants and associated microorganisms. Here, plants and microbes communicate via signaling molecules, compete for nutrients, and release substrates that may have beneficial or harmful effects on each other. Whilst the body of knowledge on the abundance and diversity of microbial communities at ro...

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

In order to differentiate the effects of root functioning and aboveground litter inputs on soil bacterial communities , a pot experiment was designed using different combinations of three plant species with contrasting chemical characteristics (0, 1, 2 or 3 species per plot) grown with or without aboveground litter inputs from the same plant specie...

The concentration, degree of contamination and pollution of 7 trace elements (TEs) along an urban pressure gradient were measured in 180 lawn and wood soils of the Paris region (France). Iron (Fe), a major element, was used as reference element. Copper (Cu), cadmium (Cd), lead (Pb) and zinc (Zn) were of anthropogenic origin, while arsenic (As), chr...

An underlying assumption of most soil carbon (C) dynamics models is that soil microbial communities are functionally similar; in other words, that microbial activity under given conditions is not dependent on the composition or diversity of the communities. Although a number of studies have indicated that microbial communities are not intrinsically...

The microbial habitat is rarely studied in soil microbial ecology even though microbial cells are exposed and adapt to their local environmental conditions. The physical environment also constrains interactions among organisms. The nature of microbial communities and their functioning can only be fully understood if their habitat is accounted for....

Amazonian podzols store huge amounts of carbon and play a key role in transferring organic matter to the Amazon River. In order to better understand their C dynamics, we modelled the formation of representative Amazonian podzol profiles by constraining both total carbon and radiocarbon. We determined the relationships between total carbon and radio...

Localisation des matières organiques et des activités microbiennes : conséquences pour le fonctionnement du sol

Nitrogen (N) addition is known to affect soil microbial communities, but the interactive effects of N addition with other drivers of global change remain unclear. The impacts of multiple global changes on the structure of microbial communities may be mediated by specific microbial groups with different life-history strategies. Here, we investigated...

The international 4 per 1000 initiative aims at supporting states and non-governmental stakeholders in their efforts towards a better management of soil carbon (C) stocks. These stocks depend on soil C inputs and outputs. They are the result of fine spatial scale interconnected mechanisms, which stabilise/destabilise organic matter-borne C. Since 2...

How soil microbial communities respond to precipitation seasonality change remains poorly understood, particularly for warm-humid forest ecosystems experiencing clear dry-wet cycles. We conducted a field precipitation manipulation experiment in a subtropical forest to explore the impacts of reducing dry-season rainfall but increasing wet-season rai...

Amazonian podzols store huge amounts of carbon and play a key role in transferring organic matter to the Amazon river. In order to better understand their C dynamics, we modelled the formation of representative Amazonian podzol profiles by constraining both total carbon and radiocarbon. We determined the relationships between total carbon and radio...

The aim of the international "4 per 1 000" initiative is to support States and non-governmental actors in their efforts towards a better management of carbon (C) stocks in soils. These stocks depend on the inputs and outputs of C in soils. Stocks are the result of interconnected mechanisms acting at fine spatial scales, leading to stabilisation/des...

Soil respiration is very heterogeneous at scales from the landscape to the aggregate/pore scale, but geostatistical studies suggest that much of the spatial variability is due to processes that occur at microscales. Microbial communities live in the soil pore network and therefore the access they have to organic substrate, oxygen and water is likel...

The majority of carbon on earth is in the form of soil organic mat- ter. And its degradation by microfauna leads to the remineralization of carbon as carbon dioxide. The microbial activity causes a reduction of soil carbon and increases atmospheric carbon. However, most models of organic matter does not explicitly take into account this reality. We...

Many studies have assessed the responses of soil microbial functional groups to increases in atmospheric CO2 or N deposition alone and more rarely in combination. However, the effects of elevated CO2 and N on the (de)coupling between different microbial functional groups (e.g., different groups of nitrifiers) have been barely studied, despite poten...

Les changements de régime hydrique seront une des composantes principales des changements climatiques à venir. Or, si l’effet de la température sur les stocks de C des sols a fait l’objet de nombreuses études récentes, il n’en est pas de même pour l’effet du régime hydrique, alors que l’humidité du sol influence fortement l’activité microbienne (Mo...

This paper deals with the simulation of microbial degradation of organic matter in soil within the pore space at a microscopic scale. Pore space was analysed with micro- computed tomography and described using a sphere network coming from a geometrical modelling algorithm. The bio- logical model was improved regarding previous work in or- der to in...