Ecological restoration of native plant communities in a Hawaiian tropical dry ecosystem dominated by the invasive grass Urochloa maxima

Abstract

In Hawai„i, nonnative grass invasions are a primary cause of tropical dry forest loss. In this study, methods for restoring native dry forest communities currently dominated by the invasive grass Urochloa maxima were explored. The garden study objective was to quantify the importance of native functional diversity for suppressing U. maxima. Increasing native functional diversity impacted U. maxima biomass (p<0.001) and decreased reproduction (p=0.05). The field study was designed to quantify the impact of invasive grass control and native species additions for ecological restoration. Survival of native species outplants ranged from 38-67%. Cover of U. maxima did not differ across outplant treatments (p>0.10), but was higher without native additions (p≤0.025). Broadcast seeding was not effective. Results indicate potential for restoring native dry ecosystems in Hawai„i currently dominated by U. maxima. Recommendations for restoration include using competitive native species with high functional diversity, outplanting seedlings, and initial and post-planting grass control.