Successful recovery of native plants post-invasive removal in forest understories is driven by native community features

Abstract

Temperate forest understories hold the majority of the plant diversity present in these ecosystems and play an essential role in the recruitment and establishment of native trees. However, the long-term persistence of diverse and functional forest understories is threatened by the impacts of invasive plants. As a result, a common practice is the removal of the agent of invasion. Despite this, we know little about the success of these practices and lack a comprehensive understanding of what intrinsic and extrinsic factors shape the recovery. In a multiyear field experiment, we investigated (Q1) whether native propagule availability drove native community recovery, (Q2) what the characteristics of successfully recovering communities were, and (Q3) under which environmental conditions native community recovery rates were faster. After initial removal of invasives, we seeded native species to manipulate assembly history and mimic restoration practices, we also implemented a repeated, versus once, removal treatment, all in a full-factorial design. We collected data on plant species composition and abundance (i.e., species level percent cover) and on environmental conditions (i.e., light and soil water availability) in the three subsequent summers. Our results show that native community recovery rates were independent of seeding additions or frequency of invasive plant removal. The fastest rates of recovery were associated with high native species richness, native communities with higher values of specific leaf area (SLA), and low drought stress years. Our results suggest that restoration practices post-invasive plant removal should be tailored to enhance natural dispersal, or artificial addition if the resident community is species-poor, of native species with traits compatible with high resource availability, such as species with high SLA. In addition to the importance of the native community characteristics, our results underscore the need for assessing environmental conditions, favoring management practices during years of low drought stress to maximize native community recovery.