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Active interventions accelerate native plant recolonization following agricultural abandonment

Pizza, Riley1; Overlie, Benjamin2; Como, Danielle1; Marmorella, Anthony1; Schwarz, Eva2; Brudvig, Lars1

Research facility: Savannah River National Laboratory
Published Apr 29, 2026 on Dryad. https://doi.org/10.5061/dryad.9cnp5hr03

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Abstract

A key challenge in restoration planning is predicting how passive and active processes may best be used together to promote successful landscape recovery. While passive recolonization of native plant communities can drive recovery, this process is often slow, and success is variable. Active restoration practices, such as reinstating historical disturbance regimes, may accelerate recolonization. However, few studies have empirically tested how specific active interventions can be used to facilitate recovery across heterogenous landscapes.

We conducted a 13-year field experiment monitoring the recolonization of longleaf pine savanna ground-layer communities in landscapes recovering from agricultural use in the southeastern USA. Across 12 sites, we established pairs of 1-ha plots in untilled, fire-suppressed remnant savannas and adjacent pine plantations previously under agriculture (recovering areas). Each pair was randomly assigned a restoration treatment: canopy thinning in the remnant, the recovering area, both, or neither (control), combined with either low or high frequency of prescribed fire. In each recovering area, we measured the spread of remnant indicator plant species along a 100 m transect extending away from the remnant.

We found that remnant savanna indicator species can slowly recolonize recovering areas after 70 years without active interventions. However, high fire frequency and canopy thinning in the remnant or recovering area resulted in 3-4× more remnant indicator species in recovering areas. These patterns were modified by seed dispersal mode: species with vertebrate and short-distance (e.g., by gravity or ants) dispersal modes spread further into recovering areas with combined thinning and burning treatments whereas species dispersed by wind were rare regardless of treatment.

Synthesis and applications: Our results show that combined canopy thinning, and prescribed burning can accelerate natural recolonization in savanna systems. However, additional measures (e.g. seed addition) may be needed for weak-dispersing species. These findings highlight the utility of integrating passive processes with active interventions to conduct efficient landscape-scale restoration.