Title Participants Abstract "Effects of synthetic fertilizer and farm compost on soil nematode community in long-term crop rotation plots: A morphological and metabarcoding approach" "Gisèle L. Herren, Joos Habraken, Lieven Waeyenberge, Annelies Haegeman, Nicole Viaene, Mathias Cougnon, Dirk Reheul, Hanne Steel, Wim Bert" "Soil biodiversity plays a key regulation role in the ecosystem services that underpin regenerative sustainable agriculture. It can be impacted by agricultural management techniques, both positively (through measures such as compost application) and negatively (through, for example, application of synthetic nitrogen). As one of the most numerous members of the soil biota, nematodes are well established as indicators for the soil food web. However, compost application also includes the addition of nematodes present in compost and their subsequent survival in soil is unknown. Nematode communities within the compost applied to soil, and nematode communities in the soil of a multi-year rotational cropping field trial in Melle (Belgium) were studied using morphological and metabarcoding techniques. Compost (C) and nitrogen fertilizer (NF) treated plots were compared. Three replicate plots were investigated for each of the following treatments: C application only; C and NF application; NF only; no C and no NF (control). Plots were sampled six times between 2015–2017, before and after C or NF were added each spring and after crop harvest (except for 2017). NF treatment resulted in a significant decrease of fungal feeding and predatory nematodes, while herbivorous nematodes were positively affected. Remarkably, we did not find compost addition to exert any noticeable effects on the soil nematode community. The morphological and metabarcoding data resulted in different results of the nematode community composition. However, trends and patterns in the two data sets were congruent when observed with NMDS plots and using the nematode maturity index. Metabarcoding of individual compost nematode taxa demonstrated that nematodes originating from compost did not persist in soil." "A global database of soil nematode abundance and functional group composition." "Johan van den Hoogen, Stefan Geisen, Devin Routh, Lieven Waeyenberge, Thomas Ward Crowther" "As the most abundant animals on earth, nematodes are a dominant component of the soil community. They play critical roles in regulating biogeochemical cycles and vegetation dynamics within and across landscapes and are an indicator of soil biological activity. Here, we present a comprehensive global dataset of soil nematode abundance and functional group composition. This dataset includes 6,825 georeferenced soil samples from all continents and biomes. For geospatial mapping purposes these samples are aggregated into 1,933 unique 1-km pixels, each of which is linked to 73 global environmental covariate data layers. Altogether, this dataset can help to gain insight into the spatial distribution patterns of soil nematode abundance and community composition, and the environmental drivers shaping these patterns." "Tillage systems threaten or promote soil biodiversity" "Krista Peltoniemi, Tuomas Mattila, Visa Nuutinen, Stefan Schrader, Lieven Waeyenberge" "Effect of organic by-products used in agriculture on biodiversity" "Lieven Waeyenberge, Krista Peltoniemi" "Crop diversification and soil biodiversity" "Eva Lloret, Lieven Waeyenberge, Stefan Schrader, Juan A. Fernandez, Raul Zornoza" "SoildiverAgro: stabiele en weerbare landbouwsystemen door verrijkt bodemleven" "Hilde Wustenberghs, Lieven Waeyenberge, Jasper Vanbesien, Sander Fleerakkers, Lieven Bauwens" "New Insights Into Nematode DNA-metabarcoding as Revealed by the Characterization of Artificial and Spiked Nematode Communities" "Lieven Waeyenberge, Nancy De Sutter, Nicole Viaene, Annelies Haegeman" "Nematodes are ideal biological indicators to monitor soil biodiversity and ecosystem functioning. For this reason, they have been receiving increasing attention from a broad range of scientists. The main method to characterize soil nematode communities until at least genus level is still based on microscopic observations of nematode morphology. Such an approach is time-consuming, labor-intensive, and requires specialized personnel. The first studies on the potential use of DNA-metabarcoding to characterize nematode communities showed some shortcomings: under- or overestimation of species richness caused by failure to detect a number of nematode species or caused by intraspecific sequence variants increasing the number of OTUs (operational taxonomic units) or 'molecular' species, and flaws in quantification. We set up experiments to optimize this metabarcoding approach. Our results provided new insights such as the drastic effect of different DNA-extraction methods on nematode species richness due to variation in lysis efficacy. Our newly designed primer set (18S rRNA gene, V4-V5 region) showed in silico an improved taxonomic coverage compared with a published primer set (18S rRNA gene, V6-V8 region). However, results of DNA-metabarcoding with the new primer set showed less taxonomic coverage, and more non-nematode reads. Thus, the new primer set might be more suitable for whole soil faunal analysis. Species-specific correction factors calculated from a mock community with equal amounts of different nematode species were applied on another mock community with different amounts of the same nematode species and on a biological sample spiked with four selected nematode species. Results showed an improved molecular quantification. In conclusion, DNA-metabarcoding of soil nematode communities is useful for monitoring shifts in nematode composition but the technique still needs further optimization to enhance its precision." "een wereldkaart van nematoden" "Lieven Waeyenberge" "Distribution and diversity of cyst nematode (Nematoda: Heteroderidae) populations in the Republic of Azerbaijan, and their molecular characterization using ITS-rDNA analysis" "Abdelfattah Amer Dababat, Hafiz Muminjanov, G. Erginbas-Orakci, G. Ahmadova Fakhrtaddin, Lieven Waeyenberge, S. Yildiz, N. Duman, Mustafa Imrem" "Cereal cyst nematodes (Heterodera spp.) are a significant threat to global cereal production systems and choosing the correct management strategy requires knowledge and identification of various species. We conducted a survey across the main cereal-growing regions of the Republic of Azerbaijan in 2017. Cyst-forming nematodes were detected in 34 samples (44.7%), of which 28 were identified as H. filipjevi or H. avenae using internal transcribed spacer (ITS)-rDNA sequencing. Six populations were unidentifiable to species level and were recorded as belonging to the H. avenae group. H. filipjevi was the dominant species, found in 19 samples (25%) from the provinces of Qobustan, İsmailli, Oguz, Sheki, Barda, and Kurdamir. H. avenae was detected in 9 samples (11.8%) across the provinces of İsmailli, Oguz, and Sheki. ITS-rDNA phylogenetic analyses showed that populations of H. filipjevi clustered in one group with two subgroups, all supported by high bootstrap values. Populations of H. avenae also clustered in one group with two subgroups. Genetic dissimilarities were higher within populations of H. filipjevi when compared to populations of H. avenae. The density of many of these cyst populations approached or exceeded the maximum threshold level for economic losses. This is the first report on H. filipjevi and H. avenae in Azerbaijan. The knowledge of cereal cyst nematode presence is extremely important for Azerbaijan’s agricultural industry when assessing the occurrence and distribution of soilborne diseases. Management measures to control cereal cyst nematodes should be directed towards breeding for resistant germplasm, crop rotation, and implementing other management practices." "Soil nematode abundance and functional group composition at a global scale." "Johan van den Hoogen, Stefan Geisen, Devin Routh, Thomas Ward Crowther, Lieven Waeyenberge" "Soil organisms are a crucial part of the terrestrial biosphere. Despite their importance for ecosystem functioning, few quantitative, spatially explicit models of the active belowground community currently exist. In particular, nematodes are the most abundant animals on Earth, filling all trophic levels in the soil food web. Here we use 6,759 georeferenced samples to generate a mechanistic understanding of the patterns of the global abundance of nematodes in the soil and the composition of their functional groups. The resulting maps show that 4.4 ± 0.64 × 1020 nematodes (with a total biomass of approximately 0.3 gigatonnes) inhabit surface soils across the world, with higher abundances in sub-Arctic regions (38% of total) than in temperate (24%) or tropical (21%) regions. Regional variations in these global trends also provide insights into local patterns of soil fertility and functioning. These high-resolution models provide the first steps towards representing soil ecological processes in global biogeochemical models and will enable the prediction of elemental cycling under current and future climate scenarios."