Résumé
Soil biota are a major component of agroecosystems, playing a decisive role in ecosystem services with synergistic effects on crop production. The conservation of their diversity has become a key component of a strategy towards agricultural sustainability. Over four years (2010–2014), under the “SOil Functional diversity as an Indicator of sustainable management of Agroecosystems” (SOFIA) project, we followed soil Collembola assemblages in response to the set-up of 5 cropping systems differing in crop rotations (annual or perennial), rate of N fertilization, and in tillage intensity (annual ploughing vs. shallow). Our results demonstrated that shifting from a conventional to conservation cropping system had a strong positive effect upon species richness and density of Collembola. Specifically, all treatments with a reduction in intensity of soil tillage fostered Collembola assemblages. At the end of our study, density and species richness were 3 to 4 times higher in reduced tillage (RT) than in conventional tillage (CT). Nevertheless, differentiation between the assemblages only occurred after 2 years but steadily increased until 4 years. At the last sampling date, all treatments contained significantly different Collembola assemblages (Anosim with Bray-Curtis distance). In parallel, we noticed shifts in the functional structure of the assemblages, even if globally, all life-forms were promoted under reduced tillage. However, contrary to our expectations, euedaphic Collembola were not promoted by restitution of crop residues. Our study over several years under field conditions showed that Collembola assemblages were more sensitive to tillage intensity than to either residue management or N fertilization. Clearly, conservation agriculture can foster one of the numerous services provided by the soil compartment, namely the soil biodiversity and therefore improve soil quality and health.
Auteurs, date et publication :
Auteurs Sékou F. M. Coulibaly , Valérie Coudrain , Mickaël Hedde , Nicolas Brunet , Bruno Mary , Sylvie Recous , Matthieu Chauvat
Publication : Applied Soil Ecology
Date : 2017
Volume : 119
Pages : 354-366
Catégorie(s)
#ACBB #ACBB Mons #INRAERésumé
This study generated new insight into the effect of bedrock grain sizes on pedogenesis under identical topographic and climatic environment. The physico-chemical and mineralogical properties of two adjacent Typic Dystrochrepts (USDA, 1999) respectively developed from fine and coarse textured granites were compared. This research study was performed in the Morvan Mountains (France). Analysis of the two underlying bedrocks revealed similar chemical and mineralogical properties, with the crystal grain size being the only parameter which differed. In these soils, bedrock played the key role in the particle size fraction distribution, the main factor controlling water retention in the soils. Weathering reactions of clay minerals were more marked in the fine textured granite soil. In this soil, both clay mineral swelling and mica transformation into expansible phyllosilicates were greater compared to the coarse textured granite soil. In the clay fraction of the fine textured granite soil, there were smaller amounts of low crystallised Fe and Al minerals, with higher carbon content in the topsoil, as compared to the coarse granite soil. The exchangeable cation analysis of the fine textured granite soil revealed a higher proportion of base saturation and a smaller proportion of Al-tit than in coarse textured granite soil which could be explained by preferential leaching of Al cations. The decrease in exchangeable Al, the higher swelling of the smectitic layer and the smaller proportion of Fe and Al-oxy-hydroxides could be explained by the complexing acid conditions, which increased mineral weathering and Al leaching. The higher water retention increased the time of contact between minerals and the soil solution, and the higher carbon content in the topsoil could have enhanced the complexing acid conditions. (C) 2015 Elsevier B.V. All rights reserved.
Auteurs, date et publication :
Auteurs L. Mareschal , M. P. Turpault , J. Ranger
Publication : Geoderma
Date : 2015
Volume : 249
Pages : 12-20
Catégorie(s)
#FORET Breuil #INRAERésumé
Background: Over the last 30 years, extensive studies have revealed the crucial roles played by microbes in aquatic ecosystems. It has been shown that bacteria, viruses and protozoan grazers are dominant in terms of abundance and biomass. The frequent interactions between these microbiological compartments are responsible for strong trophic links from dissolved organic matter to higher trophic levels, via heterotrophic bacteria, which form the basis for the important biogeochemical roles of microbial food webs in aquatic ecosystems. To gain a better understanding of the interactions between bacteria, viruses and flagellates in lacustrine ecosystems, we investigated the effect of protistan bacterivory on bacterial abundance, production and structure [determined by 16S rRNA PCR-DGGE], and viral abundance and activity of two lakes of contrasting trophic status. Four experiments were conducted in the oligotrophic Lake Annecy and the mesotrophic Lake Bourget over two seasons (early spring vs. summer) using a fractionation approach. In situ dark vs. light incubations were performed to consider the effects of the different treatments in the presence and absence of phototrophic activity.
Results: The presence of grazers (i.e. < 5-μm small eukaryotes) affected viral production positively in all experiments, and the stimulation of viral production (compared to the treatment with no eukaryotic predators) was more variable between lakes than between seasons, with the highest value having been recorded in the mesotrophic lake (+30%). Viral lysis and grazing activities acted additively to sustain high bacterial production in all experiments. Nevertheless, the stimulation of bacterial production was more variable between seasons than between lakes, with the highest values obtained in summer (+33.5% and +37.5% in Lakes Bourget and Annecy, respectively). The presence of both predators (nanoflagellates and viruses) did not seem to have a clear influence upon bacterial community structure according to the four experiments.
Conclusions: Our results highlight the importance of a synergistic effect, i.e. the positive influence of grazers on viral activities in sustaining (directly and indirectly) bacterial production and affecting composition, in both oligotrophic and mesotrophic lakes.
Auteurs, date et publication :
Auteurs Lyria Berdjeb , Thomas Pollet , Isabelle Domaizon , Stéphan Jacquet
Publication : BMC Microbiology
Date : 2025
Volume : 11
Issue : 1
Pages : 88
Catégorie(s)
#INRAE #OLAAuteurs, date et publication :
Auteurs Vinicius Resende Castro , Paula Gabriella Surdi , Carlos Roberto Sette Junior , Mario Tomazello Filho , Gilles Chaix , Jean Paul Laclau
Publication : Ciência Florestal
Date : 2017
Volume : 27
Issue : 3
Pages : 1017
Catégorie(s)
#CIRAD #FORET Itatinga #INRAEAuteurs, date et publication :
Auteurs J.-P. Bouillet , M. Voigtlaender , J.-P. Laclau , J.-L. de Moraes Gonçalves , J.-L. Gava , F. Palha Leite , R. Eiji Hakamada , L. Mareschal , A. Mabiala , Y. Nouvellon
Publication : Série Técnica IPEF
Date : 2025
Volume : 18
Issue : 39
Pages : 26-36
Catégorie(s)
#CIRAD #FORET Itatinga #INRAERésumé
Considerable areas of forest plantations of fast-growing of eucalyptus in Brazil and in other regions of the world are under the influence of climate change, water stress and low soil fertility, affecting the growth and the quality of the wood from the trees. This study aimed to evaluate the growth of the trunk of Eucalyptus grandis trees for 24 months, evaluating the reduction in rainfall and potassium and sodium nutrition. The treatments were defined by two water treatments (100 and 66% of rainfall, with artificial exclusion with polyethylene sheeting) and three types of nutrition: K (K - 4.5 kmol/ha), Na (Na - 4.5 kmol/ha) and control. 54 eucalyptus trees per treatment were selected and installed with a dendrometric band at DAP height. The results showed the effect of the climatic seasonality in the increase in diameter of the trunk of the tree, with maximum and minimum periods of growth rate and the cambial meristem and, therefore, the measurement of the diameter of the trunk with the dendrometers indicate that the response to a given climatic event is expressed after the period of 15, 30 and up to 45 days. Tree treatments with 100% of rainfall had higher cumulative growth, as well as treatments with application K. The results may be used as subsidies for the adoption of silvicultural practices in forest plantations in areas with water stress, as well as replacement part of K by Na.
Auteurs, date et publication :
Auteurs Vinicius Resende Castro , Paula Gabriella Surdi , Mario Tomazello Filho , Gilles Chaix , Jean Paul Laclau
Publication : Scientia Forestalis
Date : 2017
Volume : 45
Issue : 113
Catégorie(s)
#CIRAD #FORET Itatinga #INRAEAuteurs, date et publication :
Auteurs C.-R. Sette Jr , I.-R. Oliveira , M.-T. Filho , F.-M. Yamajie , J. P. Laclau
Publication : Revista Arvor, Viçosa-MG
Date : 2025
Volume : 36
Pages : 1183-1190
Catégorie(s)
#CIRAD #FORET Itatinga #INRAEAuteurs, date et publication :
Auteurs Christophe Jaeger , Joël Aubin
Publication : Aquatic Living Resources
Date : 2025
Volume : 31
Pages : 36
Catégorie(s)
#INRAE #PEARLRésumé
Le protoxyde d’azote (N2O) est un gaz à effet de serre (GES) important et la principale substance attaquant la couche d'ozone. Les sols agricoles sont la principale source anthropique de ce GES. La concentration de N2O dans l'atmosphère est en constante augmentation, mais nous manquons de connaissances sur les facteurs contrôlant sa production et sa consommation dans les sols. La réduction du N2O en N2 par des microorganismes porteurs du gène codant pour la N2O réductase (nosZ) est le seul processus biologique capable de réduire ce GES. Des études récentes ont mis en évidence un clade précédemment inconnu de réducteurs du N2O qui interfère de manière significative avec la quantité de N2O produite dans les sols. Cette thèse a cherché à mieux comprendre l'écologie des réducteurs du N2O dans les sols agricoles. Une combinaison d'expériences d'incubation en laboratoire mais aussi d’expériences en plein champs a été utilisée pour essayer de mieux comprendre la production de N2O dans le sol, en analysant l’influence conjointe des producteurs et réducteurs de N2O. Nous avons aussi évalué l’impact des pratiques agricoles et leurs potentiels à modifier ces communautés microbiennes. Suite aux essais réalisés en laboratoire, nous avons montré que l'ajout d'une souche non-dénitrifiante Dyadobacter fermentans,possédant la N2O réductase NosZII, permettait de réduire la production de N2O dans 1/3 des sols testés. Certains sols sont même devenus consommateurs de N2O suite à l'ajout de la souche nosZII. Cette expérience a démontré la contribution des bactéries nosZII non-dénitrifiantes dans la consommation de N2O dans le sol. D’autre part, nos analyses en contexte agricole ont montré que les pratiques agricoles testées ont peu d’influence sur les communautés microbiennes considérées, les exceptions étant le travail du sol (labour), et le système de culture (annuel ou pérenne). L’intensifiant du travail du sol induit une augmentation de la diversité de nosZII. Nous observons le même phénomène dans le système de culture annuel comparé au système de culture pérenne. D’autres résultats nous permettent aussi d’affirmer que le clade récemment identifié de réducteurs du N2O est plus sensible aux variables environnementales que le clade précédemment connu (nosZI). Les variations de propriétés du sol, notamment pH et C:N structurent les communautés microbiennes appartenant à ces 2 clades indiquant une spécialisation de niche pour chacun de ces deux clades de N2O-réducteurs. Pour mieux comprendre les relations entre les communautés microbiennes et les processus impliqués, nous avons évalué les activités potentielles de dénitrification et de nitrification, et les émissions de N2O in situ. La production potentielle de N2O et l'activité potentielle de dénitrification ont été utilisées pour calculer le ratio de production de N2O (N2O:N2). La diversité du clade nosZII est négativement corrélée au ratio N2O:N2, et explique à elle seule la plus grande part de variance observée du ratio N2O:N2. Les variations de production potentielle de N2O et d'activité potentielle de dénitrification sont elles expliquées principalement par les variations de propriétés du sol. Afin de mieux évaluer la contribution des différents facteurs édaphiques et microbiologiques aux variations d’émission in situ de N2O, 70000 mesures ont été subdivisées en différentes gammes d’émission de N2O, d‘émissions dites de base à des émissions élevées. Fait intéressant, les variations d’émissions in situ de N2O dites de base sont seulement liées à des variations du pH du sol, alors que les variations d’émissions dites élevées sont également fortement associées aux variations de diversité des communautés microbiennes. Parmi les variables microbiennes importantes, nous avons constaté que la diversité des nosZII est négativement liée aux émissions de N2O in situ dites élevées. En conclusion, nos résultats mettent en évidence l’importance du clade nosZII pour le cycle du N2O dans le sol. Ce clade nosZII semble plus sensible aux variables environnementales mais relativement robuste aux pratiques agricoles évaluées. D’autres études de l’écologie de ces réducteurs de N2O sont nécessaires afin de démêler les facteurs contrôlant leur structure et leur diversité, pour évaluer leur potentiel d’atténuation pour les émissions de N2O.
Auteurs, date et publication :
Auteurs Luiz A Domeignoz Horta
Date : 2025
Catégorie(s)
#ACBB #ACBB Mons #INRAERésumé
Alternative cropping systems have been proposed to enhance sustainability of agriculture, but their mid and long-term effects on soil biodiversity should be studied more carefully. Earthworms, having important agro-ecological functions, are regarded as indicators of soil biological health. Species composition, abundance, and biomasses of earthworms were measured in autumn 2005–2007 (period 1) and 2011–2013 (period 2) in a trial initiated in 1997 near Paris, France. A conventional, an organic and a direct seeded living mulch-based cropping systems were compared. Earthworms were sampled in a wheat crop by combining the application of a chemical expellant and hand-sorting.
Auteurs, date et publication :
Auteurs Céline Pelosi , Michel Bertrand , Jodie Thénard , Christian Mougin
Publication : Applied Soil Ecology
Date : 2025
Pages : 8