Effects of Clipping an Invasive Plant Species on the Growth of Planted Plants of Two Co-Occurring Species in a Greenhouse Study

SIMPLE SUMMARY: Invasive exotic plant species are threats to native flora and other taxa. No effective and environmentally friendly approaches are available for controlling Solidago canadensis, an aggressively invasive plant species in China and Europe. We determined that in addition to the traditional measure of clipping, planting plants of two co-occurring and competitive species can further suppress regrowth of clipped S. canadensis plants and both the aboveground and belowground part of S. canadensis contributed to its suppression effects on planted co-occurring species. These results suggest that incorporation of utilizing biotic resistance from some highly competitive plant species and overcoming belowground priority effects of invasive species into a comprehensive management plan will substantially increase the efficiency of invasive plant control. ABSTRACT: The restoration of native plants in invaded habitats is constrained with the presence of highly competitive exotic species. Aboveground removal, such as clipping or mowing, of invasive plants is required for successful restoration. The effects of clipping an invasive plant species, Solidago canadensis, grown at five densities (1–5 plants per pot), and planting two co-occurring and competitive species, Sesbania cannabina and Imperata cylindrica, on the growth of both the invasive species and the co-occurring species were investigated in a greenhouse experiment. The established S. canadensis suppressed the growth of planted seedlings with 47.8–94.4% reduction in biomass, with stronger effects at higher densities; clipping significantly reduced 97.5–97.4% of biomass of S. canadensis and ameliorated the suppression effects (with only 8.7–52.7% reduction in biomass of the co-occurring plants), irrespective of density. Both the aboveground and belowground part of S. canadensis contributed to its suppression effects on planted co-occurring species. Seed sowing of co-occurring species reduced the belowground growth, but not the underground growth of S. canadensis. S. cannabina appeared to be more effective at reducing the growth of S. canadensis than I. cylindrica. Therefore, clipping together with planting competitive species that can overcome the belowground priority effects of S. canadensis could be a promising strategy for controlling S. canadensis invasion and restoring native plant communities.