Light Availability Prevails Over Soil Fertility and Structure in the Performance of Asian Knotweeds on Riverbanks: New Management Perspectives

Abstract

Asian knotweeds (Fallopia spp.) are considered one of the world's most invasive species. Restoring habitats dominated by these exotic species requires a better understanding of the importance of abiotic factors controlling the invasive knotweeds performance. We used observational data obtained on the embankment of the Isère River (France) to study the performance of Fallopia spp. under different soil, light, and disturbance conditions. On the Isère riverbanks, light intensity assessed by light quantity transmitted through canopy was the most important factor explaining the variability observed on knotweed performance expressed as above-ground biomass per square meter. Asian knotweeds were more productive under intensive light conditions. Alternatively other factors such as mowing (twice a year), soil fertility, soil texture, position on the bank or exposure to the sun had no significant effect on knotweed biomass production. We conclude that decreasing light resources, for example, by increasing competitive pressure on sites dominated by Asian knotweeds could be included in management plans to control the populations of this invasive taxon.

Stream Structural Limitations on Invasive Communities in Urban Riparian Areas

“…The strongest limitation on invasive species presence and richness was imposed by tree canopy cover-likely a proxy for light availability and temperature (Warren 2010a,b). Although some invasive species tolerate shade and invade beneath forest canopy (Martin et al 2009), invasive species generally are shade-intolerant, including the species studied here (Dommanget et al 2013;Marlor et al 2014;Phillips-Mao et al 2014). Lythrum and Phragmites presence decreased significantly in our plots with greater canopy coverage, but Alliaria presence actually increased.…”

Evaluation of Light-Dependent Photosynthetic Reactions in Reynoutria japonica Houtt. Leaves Grown at Different Light Conditions

“…However, one of the major environmental factors that can control its performance is the availability of light. It affects the above- and below-ground biomass of knotweed directly by reducing its performance and, consequently, its invasiveness ( Dommanget et al, 2013 ; Dommanget et al, 2019 ). Specifically, the below-ground system of the knotweeds presents the majority of its biomass.…”

A Case Study: The Implementation of a Nature-Based Engineering Solution to Restore a <i>Fallopia japonica</i>-Dominated Brook Embankment

“…However, little is known about the effectiveness of different native riparian species when competing with IAPs. Dommanget et al (2013) found that the allelopathic effect of Fallopia japonica influenced the growth of Salicaceae species to a different degree and that the choice of resistant species could prove crucial for restoration success. In the present study, the effectiveness of a willow brush mattress (a frequent technique for controlling riverbank erosion) in combination with adapted management strategies was tested.…”