High-intensity fires may have limited medium-term effectiveness for reversing woody plant encroachment in an African savanna

1. Woody thickening or “bush encroachment” is a growing concern in savannas worldwide and can reportedly be reversed by applying high-intensity fires. Preliminary findings following experimental fires in 2010 and 2013 indicated that woody plant cover declined one year after high-intensity fires, but increased after low-intensity fires. However, the longer-term outcomes of high-intensity fires are largely unknown.
2. To establish longer-term outcomes, we re-assessed sites subjected to Low, Medium and High-intensity fire treatments 10 years after the initial experimental fires. We compared woody vegetation structure in 2010 with that in 2020 using both ground surveys and airborne LiDAR.
3. Ground surveys revealed increases in the number of stems and individual shrubs (< 10 m tall) over 10 years, and decreases in shrub height, with no significant differences between treatments. Large trees (≥ 10 m) declined by about 65% in number due to ongoing high mortality across treatments over 10 y..., Data was collected using both ground surveys as well as airborne LiDAR.,