Rapid and Transient Changes During 20 Years of Restoration Management in Savanna-Woodland-Prairie Habitats Threatened by Woody Plant Encroachment

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Plant Ecology

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Open-structured habitats, such as heathlands, grasslands, and savannas, support unique plant diversity but are threatened by woody plant encroachment in diverse locations globally. During 20 years of vegetation management aimed at restoring and sustaining oak savannas, woodlands, and wet prairies in a Midwestern USA oak savanna region, we examined change in 17 plant community metrics ranging from cover of rare species to pollinator floral resources. Metrics indicative of open-habitat quality increased rapidly but also declined rapidly with time since disturbance spanning a first decade of intensive management (tree cutting and 4–5 fires/decade) and a second decade of less-intensive management (> 4 years between fires). After initial restoration treatments reduced overstory tree density, changes in cover of open-habitat specialist species correlated with fluctuations of a brushy layer of small trees 1–10 cm in stem diameter. Between 2002 and 2018, 92% of sites where small trees increased by over 100/ha had declines in open-habitat species, whereas 72% of sites not experiencing that level of woody encroachment had sustained or increasing open-habitat species. Conserving open habitats in contemporary environments likely requires perpetually frequent low-severity disturbance (at least every 3–4 years), periodic severe disturbance (e.g., growing-season fires), or multiple treatment types (e.g., managed herbivory and fire) to synergistically limit woody encroachment. Fluctuations between positive and negative trends in the 20-year dataset also highlight that perhaps restoration success should not be evaluated on the basis of a net change from beginning to end, but rather on a time-weighted accrual of restoration benefits.


Community Dynamics; Ecological; Restoration; Floristic Quality; Open Habitat; Quercus; Specialist Species; Rare Species


Life Sciences | Plant Sciences



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