Dinâmica de Cirsium arvense em campos do Planalto de Saclay: Diferenças morfológicas entre sexos, reprodução, distribuição e manejo

Abstract

This study primarily aims to highlight relevant aspects of the biology and ecology of the plant Cirsium arvense in the fields of IDEEV (Institut Diversité Écologie Évolution du Vivant), located on the Saclay Plateau, France. This plant causes economic losses to farmers. Its spread may be related to the processes of urbanization and the historical agricultural activities common in the Saclay Plateau region, which combines rural areas with urbanized zones. Populations of C. arvense show variation in reproductive systems and sex ratios, with significant differences between male and female plants. A description of some morphological differences between male and female traits (including the identification of possible cases of hermaphroditism) was carried out in the field environment, and the spatial distribution of male and female plants was mapped—first in the experimental wheat-pea plot, and later in a broader area covering a long transect on the Saclay Plateau. This approach seeks to better understand how the plant occupies and utilizes different habitats. Finally, an experiment was conducted to evaluate the effectiveness of mechanical control methods and herbicide use in agricultural areas for combating C. arvense, providing an analysis of the impact of interventions on the root reserves of C. arvense in order to deepen the understanding of the species' reproduction, morphology, and population dynamics. Sexual dimorphism was observed in the species, and significant morphological differences between the sexes were confirmed, including the complete absence of pollen grains in female flowers and differences in pollen adhesion and germination between sexes. Female populations showed higher density and a greater number of shoots than male populations. The species exhibited a non-random distribution pattern. The regional survey confirmed the tendency for smaller populations to be mostly pure, while larger populations were mixed. The control using manual weeding and herbicide reduced the biomass of C. arvense but did not eliminate the plant after six weeks; however, it was more effective in reducing biomass, allowing better corn growth, with an average increase of 25 cm in the height of corn plants in the treated micro-parcels.