FRAME (FoRests Among Managed Ecosystems) – Plant community and seed bank composition in forests, Philadelphia metropolitan area, USA, 2017-2019

Our study objectives were to conduct a Rosa multiflora (multiflora rose) removal experiment in three forest sites experiencing different invasion intensities and to restore native plant biodiversity while preventing secondary invasion. The study was conducted in and around Newark, DE, from 2017-2019, and data collection is complete. We utilized three management strategies: invasive plant removal, removal followed by native seed addition, and removal plus native seed and mulched invasive stem addition. We investigated the similarity between seed bank species composition and existing vegetation before and after removal to assess the potential for passive restoration. Two seasons after removal, we found that simply removing rose increased native species richness, Native Floristic Quality Assessment (FQAIN), and native shrub abundance in our medium invasion site, and total species richness in our low and medium invasion sites. Compared to removal alone, native seed addition, with and without mulch addition, resulted in larger native and total species richness and FQAIN increases at all sites, larger increases in native shrub abundance and exotic species richness in our medium invasion site, and larger reductions in exotic and total shrub abundance in our low and medium invasion sites. Following removal, species similarity between seed bank and vegetation improved for all three sites. Our results indicate that removal of Rosa multiflora (multiflora rose) alone increased native plant biodiversity in the medium invasion scenario, but the seed bank may not provide a large native species pool. Additional management strategies lead to improved outcomes, especially in our most invaded forest, demonstrating the need to conduct multiple plant removal treatments across forests with varying site conditions and plant invasion intensity to improve management recommendations.

本研究的目标为在三个不同入侵程度的森林样地开展多花蔷薇（Rosa multiflora，英文名multiflora rose）清除实验，在恢复本土植物生物多样性的同时防范次生入侵。本研究于2017-2019年在特拉华州纽瓦克市及其周边开展，目前数据采集工作已全部完成。本研究采用三种管理策略：入侵植物清除、清除后添加本土种子、清除并添加本土种子与入侵植物茎秆覆盖物。为评估被动修复的潜力，本研究对比了清除前后种子库物种组成与现存植被的相似性。清除后的两个生长季，研究发现仅清除多花蔷薇即可在中度入侵样地提升本土物种丰富度、本土植物质量评估（Native Floristic Quality Assessment，缩写FQAIN）得分以及本土灌木丰度，并在轻度与中度入侵样地提升总物种丰富度。相较于单独清除方案，无论是否添加覆盖物，添加本土种子的处理在所有样地均能更显著地提升本土与总物种丰富度及FQAIN得分；在中度入侵样地可更显著提升本土灌木丰度与外来物种丰富度，并在轻度与中度入侵样地更显著降低外来灌木与总灌木丰度。清除处理后，三个样地的种子库与现存植被间的物种相似性均得到提升。本研究结果表明，仅清除多花蔷薇即可在中度入侵场景下提升本土植物生物多样性，但种子库可能无法提供充足的本土物种库。额外的管理策略可进一步优化修复效果，尤其是在重度入侵的森林样地中，这表明需在立地条件与植物入侵程度各异的森林中开展多种植物清除处理，以完善植物入侵管理建议。