Dominance of Ricinus communis in the Semi‐Arid Region Mediated by Allelopathy

ABSTRACT The introduction of invasive alien species can adversely affect the functioning of natural ecosystems. Ricinus communis L., widely present in the Brazilian semi‐arid region, establishes itself in areas with native species, such as Handroanthus impetiginosus (Mart. ex DC.) Mattos, because it does not go dormant and disperses balocorically, which can affect the latter's plant succession. This study aimed to evaluate whether the leaf biomass of R. communis exerts a negative allelopathic effect associated with its introduction into natural ecosystems. Leaves of R. communis , collected at the end of senescence, were mixed in alternating layers with Caatinga soil and allowed to decompose for 90 days at different concentrations by total soil mass (w/w). The chemical constituents of the decomposed R. communis material were identified using GC–MS. The GC–MS chromatographic analysis revealed the presence of 10 compounds, grouped into five main classes: monoglycerides, alkanes, fatty acids, terpenes and monosaccharides. Key compounds identified include Phytol (C 20 H 40 O) and palmitic acid (C 16 H 32 O 2 ). The byproducts of R. communis leaf decomposition had negative effects on seedling germination. At the two highest leaf litter concentrations, a 90% reduction in the seed germination rate was observed. For the post‐germination period, results showed a correlation between the residence time of allelochemicals in the substrate and the concentration of leaf biomass, with negative effects being most prominent at the highest concentration of R. communis leaves. Regarding the morpho‐anatomical analysis, significant variations in the tissue thickness of the radicle and hypocotyl were observed, in addition to pronounced qualitative changes. The results of this study confirm R. communis exhibits negative allelopathic potential against H. impetiginosus . This may lead to the reduction or elimination of the latter species in the medium to long term, directly impacting plant succession within the natural ecosystem.