Centaurea cyanus L. as a biological indicator of segetal species richness in arable fields
Résumé
Agricultural intensification has resulted in a loss of biological diversity within European agroecosystems. Biological indicator species are important tools for monitoring species diversity. The aim of this study was to determine whether cornflower, Centaurea cyanus, an arable land specialist segetal species that is easily identified in the countryside, is an appropriate indicator of weed species diversity in the Poitou-Charentes region of western France. The study zones selected were those in which C. cyanus was present in agricultural fields when monitoring was conducted in both 2006 and 2007. All plant species in sample fields sown with winter crops (cereals and oilseed rape) within the study zones were then inventoried in two consecutive years: 2008 and 2009. For these winter crops, C. cyanus presence was not a good indicator of overall species richness within the fields. However, C. cyanus presence did correlate with the presence of other arable land specialists, herein called segetal species. Reciprocally, the presence of most other segetal species found at low frequencies in the study zones also correlated with higher segetal richness. We discuss the conditions for using C. cyanus as an indicator of segetal diversity with regards to conservation and ecosystem services.