Distribution, competitive ability, and seed production of Bidens frondosa L. in the Middle Urals

Аннотация

The distribution, plant size and biomass allocation, leaf traits, and seed production of the invasive Bidens frondosa L. plant in the Middle Urals were studied. This species was found in disturbed riverside habitats in the upper stream of the Iset’ River in habitats extending approximately 100 km (from the city of Aramil’ to the city of Kamensk-Ural’sky). Comparative analysis showed that the B. frondosa plant was 35% taller than the native species of the genus Bidens. The dry mass of the B. frondosa plant exceeded the biomass of B. tripartita and B. radiata by 1.5 and 4.9 times, respectively. The large size and biomass of B. frondosa indicated a higher competitive ability of this species than the native species of the genus Bidens. Given the same leaf thickness in the three studied species, the smaller leaf density (LD) of B. frondosa determined a lower (by 1.2 times) dry leaf mass per unit area (LMA) than that of B. tripartita and B. radiata. These structural features of B. frondosa leaves contributed to the optimization of gas exchange processes within a leaf and made it possible to develop a greater assimilation area per unit plant weight (the leaf area ratio (LAR)), which should provide a high growth rate of this species. Analysis of seed production parameters showed that the number of capitula per plant increased in the series B. radiata–B. tripartita–B. frondosa; however, the number of achenes per capitulum and per plant decreased in this sequence. The mass of 100 achenes was 1.6 and 2.3 times higher in B. frondosa than in B. tripartita and B. radiata, respectively. On the whole, the frequent occurrence of B. frondosa in the extended area (approximately 100 km) in the upper stream of the Iset’ River and the values of production parameters (the size and weight of plants and the mass and number of seeds) indicate a successful naturalization of this species in the Middle Urals.