X. Le Roux

French National Institute for Agriculture, Food, and Environment (INRAE) | INRAE · ECODIV

In natural systems, different plant species have been shown to modulate specific nitrogen (N) cycling processes so as to meet their N demand, thereby potentially influencing their own niche. This phenomenon might go beyond plant interactions with symbiotic microorganisms and affect the much less explored plant interactions with free‐living microorg...

Understanding the relationship between soil organic carbon (SOC) storage and nitrous oxide (N2O) fluxes is crucial for sustainable land management. In this study, we examined this relationship in different cropping systems, including annual cropping systems with a legacy of varying durations (3 versus 6 years) of grasslands and continuous grassland...

We present the results of our 15th horizon scan of novel issues that could influence biological conservation in the future. From an initial list of 96 issues, our international panel of scientists and practitioners identified 15 that we consider important for societies worldwide to track and potentially respond to. Issues are novel within conservat...

Background and aims High-input agriculture involves low within-field crop genetic diversity, while plant diversity in natural ecosystems was shown to promote ecosystem functioning. Increasing intra-specific diversity in agroecosystems is a promising strategy to stabilize crop productivity and promote the associated diversity of soil biota. We inves...

We present the results of our 15th horizon scan of novel issues that could influence biological conservation in the future. From an initial list of 96 issues, our international panel of scientists and practitioners identified 15 that we consider important for societies worldwide to track and potentially respond to. Issues are novel within conservat...

Redesigning agrosystems to include more ecological regulations can help feed a growing human population, preserve soils for future productivity, limit dependency on synthetic fertilizers, and reduce agriculture contribution to global changes such as eutrophication and warming. However, guidelines for redesigning cropping systems from natural system...

In face of the current environmental challenges, developing multifunctional cropping systems is increasingly needed, and crop variety mixtures are particularly interesting since they can deliver diverse services including grain production, yield stability, N 2 O production regulation, disease control, and reduction of N-fertilizer losses. However,...

Ecosystem functions, such as soil nitrogen cycling, are being altered by climate change. The responses of soil (de)nitrification to climate change are different and sometimes opposite across global grasslands. However, it remains unclear how the local environmental conditions and the duration and magnitude of climate change experiments influence th...

Global climate models predict that the frequency and intensity of precipitation events will increase in many regions across the world. However, the biosphere-climate feedback to elevated precipitation (eP) remains elusive. Here, we report a study on one of the longest field experiments assessing the effects of eP, alone or in combination with other...

Data from functional trait databases have been increasingly used to address questions related to plant diversity and trait-environment relationships. However, such databases provide intraspecific data that combine individual records obtained from distinct populations at different sites and, hence, environmental conditions. This prevents distinguish...

The processes governing soil bacteria biogeography are still not fully understood. It remains unknown how the importance of environmental filtering and dispersal differs between bacterial taxonomic and functional biogeography, and whether their importance is scale-dependent. We sampled soils across the Tibet plateau, with distances among plots rang...

High-input agriculture has been associated with a drastic reduction of within-field crop genetic diversity, while plant (mostly functional) diversity in natural ecosystems has been shown to promote ecosystem functioning. Increasing intra-specific diversity in agroecosystems is a promising strategy to stabilize crop productivity and promote the asso...

The world is struggling to limit greenhouse gas emissions and reduce the human footprint on nature. We therefore urgently need to think about how to achieve more with actions to address mounting challenges for human health and wellbeing from biodiversity loss, climate change effects, and unsustainable economic and social development. Nature-based S...

We present the results of our 14th horizon scan of issues we expect to influence biological conservation in the future. From an initial set of 102 topics, our global panel of 30 scientists and practitioners identified 15 issues we consider most urgent for societies worldwide to address. Issues are novel within biological conservation or represent a...

Microbial diversity can restrict the invasion and impact of alien microbes into soils via resource competition. However, this theory has not been tested on various microbial invaders with different ecological traits, particularly spore-forming bacteria. Here we investigated the survival capacity of two introduced spore-forming bacteria, Bacillus my...

Termites can be a significant source of N2O emissions in tropical and subtropical ecosystems. The emission rates vary greatly between species, with many species creating emission hotspots while others acting as net sinks. We studied the relationships between net and gross N2O production/consumption and the abundances of eight nitrifier and denitrif...

Protists’ selective predation of bacterial cells is an important regulator of soil microbiomes, which might influence the success of bacterial releases in soils. For instance, the survival and activity of introduced bacteria can be affected by selective grazing on resident communities or the inoculant, but this remains poorly understood. Here, we i...

Coastal restoration is often distrusted and, at best, implemented at small scales, which hampers its potential for coastal adaptation. Present technical, economic and management barriers stem from sectoral and poorly coordinated local interventions, which are insufficiently monitored and maintained, precluding the upscaling required to build up con...

The earthworm gut bacterial community and enzyme activities play a key role in many soil ecosystem functions, but how the addition of different types of biochar (used to improve soil quality) regulates soil and earthworm gut bacterial communities and associated enzyme activities is scarcely understood. An experiment was conducted using soil microco...

Background Anthropogenic activities have increased the inputs of atmospheric reactive nitrogen (N) into terrestrial ecosystems, affecting soil carbon stability and microbial communities. Previous studies have primarily examined the effects of nitrogen deposition on microbial taxonomy, enzymatic activities, and functional processes. Here, we examine...

Conventional agricultural practices negatively impact soil biodiversity, carbon stocks, and greenhouse gas emissions in ways that make them unsustainable for supporting future supply of food and fiber. Better management of agrobiodiversity will likely play a critical role in transitioning toward more sustainable practices. In particular, innovation...

For the first time in a savanna, we analysed the joint influence of climate seasonality and plant cover type on the abundances and transcription levels of bacterial and archaeal nitrifiers, and nitrification enzyme activity (NEA). The dominant tree and grass species stimulated and inhibited nitrification, respectively: NEA was 4-fold higher and 5-f...

Biological nitrification inhibition (BNI) has already led to several studies mainly focused on underlying molecular mechanisms and applications to agriculture. We argue that it is also important to study BNI more systematically from the ecological and evolutionary points of view to understand its implications for plants and soil nitrifiers as well...

Microbial inoculations contribute to reducing agricultural systems' environmental footprint by supporting sustainable production and regulating climate change. However, the indirect and cascading effects of microbial inoculants through the reshaping of soil microbiome are largely overlooked. By discussing the underlying mechanisms of plant- and soi...

Background: Anthropogenic activities have increased the inputs of atmospheric reactive nitrogen (N) into terrestrial ecosystems, affecting soil carbon stability and microbial communities. Previous studies have primarily examined the effects of nitrogen deposition on microbial taxonomy, enzymatic activities, and functional processes. Here, we examin...

The processes governing soil bacteria biogeography are still not fully understood. It remains unknown how the importance of environmental filtering and dispersal differs between bacterial taxonomic and functional biogeography, and whether their importance is scale-dependent. We sampled soils at 195 plots across the Tibet plateau, with distances amo...

Climate warming is known to impact ecosystem composition and functioning. However, it remains largely unclear how soil microbial communities respond to long-term, moderate warming. In this study, we used Illumina sequencing and microarrays (GeoChip 5.0) to analyze taxonomic and functional gene compositions of the soil microbial community after 14 y...

BiodivERsA was built on the opportunity offered by the European Commission to promote the coordination of research on biodiversity, ecosystem services and Nature based solutions across Europe, gathering national Ministries, local governments, agencies and foundations that program and fund biodiversity research, in both mainland Europe and outermost...

We evaluated whether and how rapidly temperate forest tree species able to stimulate or inhibit nitrification (through biological nitrification inhibition, BNI) also influence denitrifier activity and abundance in soil and identified the main determinants of changes in denitrification. A reciprocal soil core transfer approach was implemented at a l...

We present the results of our 13th annual horizon scan of issues likely to impact on biodiversity conservation. Issues are either novel within the biological conservation sector or could cause a substantial step-change in impact, either globally or regionally. Our global panel of 26 scientists and practitioners identified 15 issues that we believe...

Higher nitrogen (N) deposition and altered precipitation patterns are two important global change factors contributing to increasing atmospheric concentrations of greenhouse gas nitrous oxide (N2O). In most experiments manipulating global change factors, wet N deposition is simulated by acute N addition once or a few times per year, rather than chr...

Savannas are characterized by the coexistence of grasses and trees. Fires are critical for their coexistence, because they decrease the survival of tree seedlings and saplings and their recruitment to the adult stage. In some humid savannas, perennial grasses inhibit nitrification and trees stimulate nitrification, which likely favors coexistence b...

Global change factors such as changed rainfall regimes and nitrogen (N) deposition contribute to increases in the emission of the greenhouse gas nitrous oxide (N2O) from the soil. In previous research, N deposition has often been simulated by using a single or a series of N addition events over the course of a year, but wet N deposition actually co...

Conventional agricultural practices negatively impact soil biodiversity, carbon stocks, and greenhouse gas emissions in ways that make them unsustainable for supporting future supply of food and fiber. Better management of agrobiodiversity will likely play a critical role in transitioning towards more sustainable practices. In particular, innovatio...

Climate warming is known to impact ecosystem composition and functioning. However, it remains largely unclear how soil microbial communities respond to long-term, moderate warming. In this study, we used Illumina sequencing and microarrays (GeoChip 5.0) to analyze taxonomic and functional gene compositions of the soil microbial community after 14 y...

Although widely used in ecology, trait-based approaches are seldom applied to study agroecosystems. In particular, how functional trait variability among varieties of a crop species compares to the variability among wild plant species and how variety selection can modify trait syndromes needs to be evaluated. Here, we quantified 18 above- and below...

Some forest tree species are able to carry out a process known as biological nitrification inhibition, BNI, i.e. they inhibit nitrifiers through the production of specific compounds. We tested the hypothesis that, by restricting N supply to NO2⁻- and N2O-reducers, BNI would decrease potential N2O production and consumption and in situ N2O emissions...

To understand how and to what extent single or multiple perturbations can alter the relationships between the abundances of different nitrifier groups and nitrification, soil microcosms were exposed to six disturbance treatments: a heat shock, cold shock, or control conditions applied to undisturbed soils or to soils that had previously been subjec...

We present the results from our 12th annual horizon scan of issues likely to impact biological conservation in the future. From a list of 97 topics, our global panel of 25 scientists and practitioners identified the top 15 issues that we believe society may urgently need to address. These issues are either novel in the biological conservation secto...

The objective of this BiodivERsA toolkit is to inform scientists working in the fields of biodiversity and, more generally, in environmental sciences, about the potential benefits of Citizen Science, and to provide a summary of the rationale to develop Citizen Science, current best practices, and useful resources in the field. It is aimed at resear...

Scenarios have been recognised as a powerful tool for exploring plausible future dynamics and uncertainty in complex systems. Yet, produced scenarios are not used enough, and there is a lack of existing guidance on how to ensure that scenarios are relevant to stakeholders and ultimately properly used in decision- making contexts. This handbook inte...

Non-target effects of deliberately releasing organisms into a new environment are of great concern due to their potential impact on the biodiversity and functioning of ecosystems. Whereas these studies often focus on invasive species of macro-organisms, the use of microbial inoculants is often expected to have specific effects on particular functio...

Chemical fertilizers are often used in managed grasslands to alleviate nutrient deficiency, especially for nitrogen (N) and phosphorus (P), and to maximize plant production. Soil microbial communities can respond to N/P fertilization-induced changes in soil environmental variables, like increased N availability or soil acidification, and to fertili...

Some temperate tree species are associated with very low soil nitrification rates, with important implications for forest N dynamics, presumably due to their potential for biological nitrification inhibition (BNI). However, evidence for BNI in forest ecosystems is scarce so far and the nitrifier groups controlled by BNI‐tree species have not been i...

On parle de plus en plus de la « sixième extinction » en référence aux change- ments actuels et récents de l’état de la biodiversité : ce terme est-il seulement un vec- teur médiatique pour la sensibilisation du public ou également un fait scientifique démontré ?

In this horizon scan, we highlight 15 emerging issues of potential relevance to global conservation in 2020. Seven relate to potentially extensive changes in vegetation or ecological systems. These changes are either relatively new, for example, conversion of kelp forests to simpler macroalgal systems, or may occur in the future, for example, as a...

Fire is a crucial event regulating the structure and functioning of many ecosystems. Yet few studies have focused on how fire affects taxonomic and functional diversity of soil microbial communities, along with changes in plant communities and soil carbon (C) and nitrogen (N) dynamics. Here, we analyze these effects in a grassland ecosystem nine‐mo...

A ¹⁵N labeling and lysimeter experiment was conducted with mesocosms of a semi-arid Leymus chinensis grassland. The aim of the study was to evaluate the effects of N fertilization timing (fertilization in fall or spring) and rate (0, 56, and 112 kg-N ha⁻¹ year⁻¹) on ecosystem services (seed yield and forage yield), ecosystem disservices (N leaching...

Seed inoculation by plant growth promoting rhizobacteria (PGPRs) is an agronomic practice that stimulates root carbon (C) exudation and nitrogen (N) uptake. Inoculation thus increases and decreases C and N availabilities to denitrifiers in the rhizosphere, respectively. Hence, denitrification rates in the rhizosphere can be positively or negatively...

Nitrogen (N) and phosphorus (P) often limit biological processes in terrestrial ecosystems. Based on previous studies mainly focusing on plants, the concept of resource limitation has evolved towards a theory of (co)limitations by multiple resources. However, this ecological framework has not been applied to analyse how soil micro‐organisms and pla...

Keywords: Denitrification nirK nirS nosZ Soil nitrate Soil organic carbon A B S T R A C T Increasing attention has been paid to microorganisms able to produce nitrous oxide (N 2 O), a potent greenhouse gas, or reduce it to harmless N 2. Based on previous studies, niche differentiation could exist between nirK-and nirS-nitrite reducers and nosZI-and...

We present the results of our tenth annual horizon scan. We identified 15 emerging priority topics that may have major positive or negative effects on the future conservation of global biodiversity, but currently have low awareness within the conservation community. We hope to increase research and policy attention on these areas, improving the cap...

Increasing attention has been paid to microorganisms able to produce nitrous oxide (N2O), a potent greenhouse gas, or reduce it to harmless N2. Based on previous studies, niche differentiation could exist between nirK- and nirS-nitrite reducers and nosZI- and nosZII-N2O reducers, and nosZII-bacteria would have a key role for N2O reduction in soils....

Nitrate is a limiting resource in heathland acid soils. Nitrate levels increase in heathland soils after Pteridium aquilinum invasions, and this species is assumed to biologically control nitrogen cycle processes, thus increasing nitrate availability. We compared how P. aquilinum (bracken) and Erica cinerea (bell heather) modify processes driving n...

The objective of the present guide is to help researchers to: ✴Better understand what is policy relevance of research, ✴Be aware of what the criteria are for evaluating policy relevance of research in BiodivERsA calls, ✴ Be able to more efficiently identify the most relevant policies and policy making bodies for a given research project. Such polic...

Seed inoculation by plant growth promoting rhizobacteria, PGPRs, is an increasingly used practice that stimulates root growth, N uptake and C exudation. Both C and N availabilities are key factors affecting the ecology of N2O-producers and -reducers in the rhizosphere. However, how does inoculation affect these groups, and ultimately N2O production...

The present document details how the Wheatamix consortium, inspired by ecological experiments exploring relationships between plant biodiversity and ecosystem functioning (e.g. the Jena experiment Weisser et al. 2017), selected bread wheat (Triticum aestivum L.) lines, phenotyped them across a range of functional traits and used this information to...

Temporary (ley) grassland introduced into cropping cycles has been advocated as being beneficial for the delivery of ecosystem services by agricultural soils. The management of these temporary grasslands has unknown effects on soil organic matter (SOM) concentrations and biogeochemical properties of the cropland soils following the grassland phase....