Abstract:
In landscapes with high elephant density, trees often exhibit more open canopies with fewer branches and foliage due to browsing
pressure. This can result in altered tree morphology, with trees exhibiting stunted growth, multiple stems or unusual branching
patterns in response to repeated damage from browsing. The objectives of this research were to (i) model the vegetation structure
allometries, (ii) assess the impact of African savannah elephant (Loxodonta africana) herbivory on the vegetation structure and
(iii) assess tree cover change and vegetation performance over time in Mana Pools National Park in Zimbabwe. We established 26
plots of 30 × 30 m size. Selection of sampling plots was done following several steps. First, a fish net grid with 30 × 30 m polygons
was created and projected on the polygon of Mana Pools National Park. The polygons for exclusion zones were then clipped from
the fish net grid using the clip tool in ArcGIS Pro 3.0. Then, selection of sampling plots was done initially by stratified random
sampling using the Sampling Design Tool add in for ArcGIS Pro 3.0. Landsat images for the years 2003, 2013 and 2023 were
used to assess land use land cover (LULC) time series and to calculate Normalised Difference Vegetation Index (NDVI) and
Soil Adjusted Vegetation Index (SAVI) for the period. A generalised linear model (GLM) was used to analyse tree allometries.
Further statistical investigations were performed using Bayesian piecewise regression (BPR) and Bayesian regression modelling
(BRM). Basal area, number of stems, height, long canopy, diameter and basal circumference were all significantly different
(p < 0.05) across all sampled plots. The change in growing conditions occurring as a tree grows beyond the reach of the African
savannah elephant browsing indicates a natural system breakpoint. The best-fitting
models were a simple linear model and a two
breakpoint model for the plant population exposed to elephant herbivory. LULC, NDVI and SAVI confirm evidence of high tree
regeneration over 2 decades. Understanding the dynamics in vegetation and LULC changes is critical for effective conservation
and management of the habitats for African savannah elephants, as well as for maintaining the health and resilience of forest
ecosystems.
