Evaluating rehabilitation practices to inform invasion resistance in designed urban meadows

Abstract

Efforts to restore urban green spaces (UGSs) aim to enhance benefits for both people and nature. Right-of-way (ROW) corridors, such as those beneath powerlines, offer key opportunities. By removing invasive species and introducing native plants through urban-adapted management practices, these spaces could become biodiverse UGSs in expanding cities. In this study we evaluate the effectiveness of invasive species management at “The Meadoway”, a ROW turned 16-km linear urban park underneath powerlines in Toronto, Canada. Here, newly-established sites were in progress and experienced rototilling, cover crops, and seed drilling of prepared native plant seed mixes to support the seed bank. Sites at the fully restored stage (i.e., 5–8 years old) were completed and had established targeted native vegetation and litter biomass without further management. Between these restoration stages, we tested the relative role of invasibility (i.e., biomass production and species richness of the resident community), disturbance from rototilling, and propagule pressure (i.e., seed rain of Vincetoxicum rossicum, seed bank density and richness) on degree of invasion from multiple species. Overall, we found that degree of invasion is 78 % higher in newly-established sites that have experienced large-scale disturbance, and a denser seed bank reduces invasibility by 50 %. We recommend rototilling as a form of disturbance to prepare seed banks as 12 invasive species were found to be of low management priority. Second, existing practices can also be adapted to encourage more native seeds to delay incipient biological invasions. Our findings and recommendations are adaptable, making them suitable for widespread application in ROWs, which are common. This flexibility allows for the broad implementation of designed urban meadows.