The significance of biomass allocation to population growth of the invasive species Ambrosia artemisiifolia and Ambrosia trifida with different densities

Abstract

Background Ambrosia artemisiifolia and Ambrosia trifida are globally distributed harmful and invasive weeds. High density clusters play an important role in their invasion. For these two species, the early settled populations are distributed at low densities, but they can rapidly achieve high population densities in a short period of time. However, their response to intraspecific competition to improve the fitness for rapid growth and maintenance of high population densities remains unclear. Therefore, to determine how these species form and maintain high population densities, individual biomass allocations patterns between different population densities (low and high), and plasticity during seedling, vegetative, breeding and mature stages were compared. In 2019, we harvested seeds at different population densities and compared them, and in 2020, we compared the number of regenerated plants across the two population densities. Results Most biomass was invested in the stems of both species. Ambrosia trifida had the highest stem biomass distribution, of up to 78%, and the phenotypic plasticity of the stem was the highest. Path analysis demonstrated that at low-density, total biomass was the biggest contributor to seed production, but stem and leaf biomass was the biggest contributors to high-density populations. The number of seeds produced per plant was high in low-density populations, while the seed number per unit area was huge in high-density populations. In the second year, the number of low-density populations increased significantly. A. artemisiifolia and A. trifida accounted for 75.6% and 68.4% of the mature populations, respectively. Conclusions High input to the stem is an important means to regulate the growth of the two species to cope with different densities. These two species can ensure reproductive success and produce appropriate seed numbers. Therefore, they can maintain a stable population over time and quickly form cluster advantages. In the management, early detection of both species and prevention of successful reproduction by chemical and mechanical means are necessary to stop cluster formation and spread.

Climate warming can reduce biocontrol efficacy and promote plant invasion due to both genetic and transient metabolomic changes

“…These increased daily mean temperature by 2.2°C, matching the predicted future change in climate obtained from http://www.worldclim.org for the current distribution of Ambrosia (Sun et al, 2017). The cages were hand weeded to maintain monocultures of Ambrosia , an ecological situation that is not uncommon when Ambrosia invades disturbed sites (Essl et al, 2015; Savić et al, 2021; Zhao et al, 2021). Ambrosia plants were allowed to shed seeds and regenerate naturally within each field cage.…”

Soil patch heterogeneity improves plant productivity and nutrients regulated by arbuscular mycorrhizal fungi

“…Therefore, the biomass distribution of the root can be increased in the whole plant. Moreover, Zhao et al (2021) presented that plants can invest more photosynthetic products into their stems to compete for light resources, particularly in denser plant population with better growth. This may explain the increase of B. pilosa biomass allocation in the stem and the decrease in the leaf.…”

Reduced Invasiveness of Common Ragweed (Ambrosia artemisiifolia) Using Low-Dose Herbicide Treatments for High-Efficiency and Eco-Friendly Control

“…Indeed, A. artemisiifolia seems to readily colonize an area through characteristics related to seed production (propagule pressure), germination, and seedling survival ( Kempel et al, 2013 ). Studies have shown that A. artemisiifolia undergoes a rapid growth phase from the vegetative stage to the reproductive stage ( Zhao et al, 2021 ), when biomass accumulation is higher in short time, and that herbicide application at this time may activate its growth-defense trade-off mechanism ( Coley et al, 1985 ; Figueroa-Macías et al, 2021 ), i.e., the activation of defense mechanisms at the cost of suspending growth. This reduces the effective accumulation of biomass in each organ and ultimately reduces seed production ( Zhao et al, 2021 ), or might even render the plant unable to produce any seeds at all.…”

“…Studies have shown that A. artemisiifolia undergoes a rapid growth phase from the vegetative stage to the reproductive stage ( Zhao et al, 2021 ), when biomass accumulation is higher in short time, and that herbicide application at this time may activate its growth-defense trade-off mechanism ( Coley et al, 1985 ; Figueroa-Macías et al, 2021 ), i.e., the activation of defense mechanisms at the cost of suspending growth. This reduces the effective accumulation of biomass in each organ and ultimately reduces seed production ( Zhao et al, 2021 ), or might even render the plant unable to produce any seeds at all. Moreover, this process is not aimed at killing all A. artemisiifolia plants, so the required herbicide dosage should be lower than the guideline dosage.…”