Exploring the role of landscape context in the recovery of understory plant richness following invasive shrub removal

Introduction: Forest restoration projects often prioritize the management of native understory species. Recovery of understory plants within temperate forests, however, is complicated by the interplay of factors, such as invasive species and land development. Understory species recovery is likely a function of the landscape surrounding a restoration, as particular types of species (e.g. wind-dispersed) may be more common in certain landscapes. Objectives: We sought to determine whether landscape context influences the effectiveness of invasive shrub removal on understory plant species recovery. Methods: We established a large-scale manipulation of invasive shrub cover across 16 temperate forest sites occurring along a gradient of forest-landscape contexts (i.e. rural forests, forest adjacent to agriculture, and urban forests). We measured and characterized forest understory species richness 12 months post-treatment. Results: Removal of invasive shrubs increased richness of native species across all landscape contexts and this effect was most pronounced in urban forests. Shrub removal also increased introduced species richness within urban forests and seed dispersal mode (i.e. wind-dispersed vs. animal-dispersed) provided insights into the recovery of species richness, but again most prominently in urban forests. Regardless of shrub removal treatment, fewer native animal-dispersed understory species were observed in urban contexts than rural or agricultural contexts. Conclusions: Our work demonstrates how urban context can interact with a common management practice (i.e. invasive shrub removal) and plant species traits (i.e. dispersal mode) to define early establishment dynamics in actively managed forests.