Fire-herbivory feedbacks strongly influence the formation of grazing lawns
in savanna ecosystems. Preliminary findings suggest that small-scale
(< 25 ha) fires can engineer grazing lawns by concentrating
herbivores on the post-burn green flush; however, the persistence of such
grazing lawns over the longer term and without repeated fire is unknown.
We used high-resolution Light Detection and Ranging (LiDAR) to investigate
the long-term effects of fire manipulation on short grass structure
(height, cover, volume, and spatial continuity) and grazing lawn
establishment in Kruger National Park, South Africa. We analysed the
effects of fire exclusion and experimental burns applied over a 7-year
period (2013-2019) followed by a one-year cessation of burning at varying
spatial scales during the early and late dry seasons. Fires contributed a
fourfold increase in short grass cover, regardless of fire season or size.
The distribution of grass height differed significantly between
fire-induced grazing lawns and recently unburnt parts of the landscape
where controlled fires were excluded over the experimental period. The
volume (corresponding to bulk density) of short grass on the landscape
responded strongly to fires, with grass volume <20 cm in height
increasing with both early and late dry season fires. Early dry season
fires caused larger and more homogeneous short grass patches. Furthermore,
early dry season fires were more influential in increasing the cover of
the shortest grass height class (1-5 cm). Synthesis and applications. Our
results demonstrate that fire-induced grazing lawns can persist over the
longer-term, even when fires are no longer applied, leading to the
creation of vertical and horizontal heterogeneity in the grass layer.
Small-scale fires, therefore, represent a feasible management approach to
expanding grazing lawn extent, potentially benefiting grazer coexistence
and diversity.