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Cover crops alter the soil nematode food web in banana agroecosystems

Djigal D., Chabrier C., Duyck P.F., Achard R., Quénéhervé P., Tixier P.. 2012. Soil Biology and Biochemistry, 48 : p. 142-150.

DOI: 10.1016/j.soilbio.2012.01.026

Cover crops are increasingly being used in agriculture, primarily for weed or erosion management. The addition of cover crops increases the primary productivity of the system and diversifies basal resources for higher trophic levels. How increases in the quality and quantity of basal resources affect bottom-up and top-down control remains a key question in soil food web ecology.We evaluated the response of the nematode community to the introduction of cover crops between rows of a banana plantation. We measured changes in nematode food web structure and inferred the prevalence of bottom-up and topdown effects on the abundance of phytophagous nematodes (i.e., plant-feeding and root-hair-feeding species) 1.5 years after plots with cover crops (Poaceae or Fabaceae species) or bare soil were established. The addition of a cover crop greatly affected the structure and the abundance of the soil nematode community 1.5 years after planting. The abundance of all trophic groups except for plant-feeding nematodes tended to increase with the addition of cover crops. The ShannoneWeaver diversity index and the enrichment index increased with the addition of cover crops, indicating that opportunistic, bacterivorous and fungivorous nematodes benefited from the added resources. Plant-feeding nematodes were least abundant in plots with Poaceae cover crops, while bacterivorous, omnivorous, and root-hairfeeding nematodes were more abundant with Fabaceae cover crops than with bare soil, indicating that cover crop identity or quality greatly affected soil food web structure. Bottom-up effects on all trophic groups other than plant-feeding nematodes were evident with Poaceae cover crops, suggesting an topdown control of plant-feeding nematodes by omnivorous nematodes. Conversely, plant-feeding nematodes were evidently not suppressed in Fabaceae cover crops, perhaps because bottom-up effects on omnivorous nematodes were weaker (hence, top-down control by omnivorous nematodes was weaker), and because Fabaceae cover crops probably served as good hosts for some plant-feeding nematodes.

Mots-clés : musa; fabaceae; poaceae; nematoda; plante de couverture; système de culture; agroécosystème; lutte antinématode; lutte intégrée; gestion intégrée des ravageurs; dynamique des populations; nématode des plantes; nématode à vie libre; régime alimentaire; préférence alimentaire; Écologie animale; cosmopolites sordidus; interactions biologiques; martinique; france

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