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International audience; In addition to protected areas, sustainable working landscapes are key to successful biodiversity conservation. Yet such landscapes are threatened by rapid crop expansion, in particular in Brazil. In this context, this study explores the influence of farming systems on farm-scale vegetation patterns around the Serra da Bodoquena National Park in Mato Grosso do Sul. To collect data on farming systems and how they are evolving, we conducted interviews at 40 farms covering 120,000 ha, including eight farms with land within the national park. To assess vegetation patterns, we conducted pixel-wise and landscape analyses based on MapBiomas land cover maps from which we calculated seven metrics over the 2009-2019 period. Using multivariate methods, we identified the activities that differentiated farming systems, isolating five farm types with contrasting involvement in crop cultivation and ranching. We found that most farm-scale landscape metrics were only weakly influenced by farming systems. Temporal analyses and interviews suggested that biophysical and legislative contexts limit crop expansion, which mainly occurred at the expense of old pastures and did not directly impact forest proportion within farms. As a consequence, crop expansion in the region seemed to mainly affect small tree patches in pasture areas, making its effect on vegetation patterns barely detectable with 30-m resolution imagery. These findings suggest that rather than focusing solely on deforestation, monitoring the dynamics of wooded pastures with high-resolution images is crucial to assess the early effects of crop expansion on vegetation patterns and to ensure the conservation of biodiversity-friendly agricultural matrices around protected areas in Brazil.

Meloidogyne spp. and Hirschmanniella spp. are among the most damaging plant-parasitic nematodes (PPNs). They threaten rice production, the main staple food in Asia. Cropping systems that promote natural biocontrol and plant tolerance to diseases are put forward as sustainable solutions to protect rice from these pests. In particular, cropping systems managed under conservation agriculture (CA) are promising because they improve soil health and functioning. We investigated the effects of two cropping system components in a Cambodian field, (i) CA practices, i.e., no-tillage with a cover crop Stylosanthes guianensis (cv. Nina), versus conventional plow-based tillage with no cover crop, and (ii) using IR504, IR64, Azucena and Zhonghua 11 rice varieties, on PPNs in roots and on communities (bacteria, fungi and nematodes) in the rhizosphere. We used a sequencing approach via amplicon barcoding to target microbial marker genes (16 S and ITS rRNA gene) and a microscopic approach to identify and quantify nematodes in the rhizosphere compartment. The variety had less effect than agricultural practices on the infection by PPNs and on the assembly of the three rhizosphere communities. Under CA, the abundance of PPNs extracted from the roots was reduced by 88%. Soil quality was substantially improved (+83% of total Kjeldahl nitrogen, +34% of available phosphorus, +10% of exchangeable potassium, +110% of soil organic carbon, +30% for the cation exchange capacity), thus providing more basal resources for microbial decomposers, especially fungi (+164% putative saprotrophs). Characterization of the three rhizosphere communities revealed a shift in the structure associated with soil enrichment. Both microbial richness (+3% for bacteria and +38% for fungi) and diversity (Shannon index, +11% for fungi and +5% for nematodes) increased. The relative abundance of taxa was modified by CA with notably more mycorrhizal fungi (+329% Glomeromycota spp.) and fewer Pratylenchidae nematodes (−92% Hirschmanniella spp.) in the rhizosphere. The reassembly of the communities using CA was associated with regulation of PPN populations. The reduction in Meloidogyne spp. abundance in roots (−64%) was correlated with the maturity of the food web (maturity index, +10% under CA) and with the increase in the relative abundance of omnivorous nematodes in the rhizosphere (+68% under CA). Seven years of CA in this field enabled the whole soil food web to mature thus creating a favorable niche for potentially predatory nematodes and microbes antagonistic against PPNs. This study confirms that CA is an alternative to nematicides to limit infection by PPNs in rice cropping systems.

International audience; The ecosystem service framework has been instrumental in navigating local to global sustainability issues. Yet as ecosystem services (ES) focus on nature's positive contributions to people, some have argued that 'ecosystem disservices' (EDS), or nature's negative contributions, should also be taken into account to better orient sustainability policies. However, joint ES and EDS assessments remain rare in sustainability research, partly because of the persisting conceptual ambiguity around the EDS concept. This study aimed to develop these joint assessments and test their relevance in addressing sustainability issues. To this end, we devised a novel cascade model that helps to define ES and EDS in a multi-level context that considers both as coproduced by ecosystems and people. In order to explore the potential and limitations of this model, we then applied it in a Brazilian landscape where reconciling agriculture and forest conservation is a critical sustainability challenge. Using the model in comprehensive interviews with farmers about their perceptions and management practices of forests, we found that they had an overall positive valuation of forests, but identified both positive and negative interactions between forests and farms at different organizational levels. The model also revealed a vicious circle between crop expansion, a resulting decrease in certain ES and an increase in certain EDS, which might exacerbate tensions between agriculture and forest conservation in the future. Additionally, the model allowed a window on the diverse preventive and regulating practices that the interviewed farmers have adopted to cope with increasing EDS without necessarily harming biodiversity. Based on this case study, this novel cascade model seems a promising conceptual tool to uncover the interactions between ES and EDS, opening new research and policy avenues to support sustainability.

Meloidogyne graminicola, also known as the rice root-knot nematode, is one of the most damaging plant-parasitic nematode, especially on rice. This obligate soilborne parasite induces the formation of galls that disturb the root morphology and physiology. Its impact on the root microbiome is still not well described. Here, we conducted a survey in Northern Vietnam where we collected infected (with galls) and non-infected root tips from the same plants in three naturally infested fields. Using a metabarcoding approach, we discovered that M. graminicola infection caused modifications of the root bacterial community composition and network structure. Interestingly, we observed in infected roots a higher diversity and species richness (+24% observed ESVs) as well as a denser and more complex co-occurrence network (+44% nodes and +136% links). We identified enriched taxa that include several hubs, which could serve as potential indicators or biocontrol agents of the nematode infection. Moreover, the community of infected roots is more specific suggesting changes in the functional capabilities to survive in the gall environment. We thus describe the signature of the gall microbiome (the ‘gallobiome’) with shifting abundances and enrichments that lead to a strong restructuration of the root microbiome.

A survey conducted on newly cultivated lowland rice fields by direct seeding method in Hai Duong Province, Viet Nam, in March 2017 revealed high devastation of the field. In these fields, farmers used an annual crop rotation cycle of rice-scallion-rice. Investigations on the devastated fields revealed that the chemical and physical soil properties were appropriate for rice cultivation. On the other hand, observations done on the root systems showed that the dead plants have symptomatic root galls suggesting the presence of plant parasitic nematodes. Sequencing of the internal transcribed spacer (ITS) region of the rDNA genes of the nematodes showed that the root nematodes extracted from the infested fields belonged to Meloidogyne graminicola. The reproductive factor of the isolated M. graminicola population on the IR64 rice variety (Oryza sativa indica) was normal, suggesting that the impact of this plant pest was not due to the emergence of an unusual virulent population. The combination of the three factors (wrong cropping choice for rotation, using rice variety susceptible to M. graminicola and direct seeding) were obviously promoting the nematode infection and its high proliferation in the surveyed fields. Meloidogyne graminicola could parasitize and propagate in scallions of Vietnam. Since this plant is annually cultivated on a paddy field for crop rotation, preventive measures or alternative plant for crop rottion is necessary.