Variation in savanna vegetation on termite mounds in north-eastern Namibia

Abstract

Abstract:In savanna, termite mounds support more diverse vegetation than off-mound areas, but little is known of the patterns in plant assemblages on mounds. To explain vegetation differentiation between (1) component structures of termite mounds (conical centre vs. pediment), (2) active and inactive mounds (termites present vs. termites absent), and (3) sites on and off mounds (on mounds vs. surrounding savanna), species composition, richness and abundances of woody plants were recorded on 70 mounds and in 13 savanna plots (each 20 × 20 m) in north-eastern Namibia, focusing on soil hardness, mound status (active or not) and mound micro-topography as explanatory factors. Woody plants were absent from 33% of active mounds (54% of active cones) but were absent from only 5% of inactive mounds. Species richness and abundance per mound (mean ± SD) were lower on active mounds with (2.0 ± 1.8 and 4.6 ± 6.6, respectively) and without pediments (0.6 ± 0.6 and 0.9 ± 1.1, respectively) than on inactive mounds (4.4 ± 2.7, 19.4 ± 18.8, respectively). Despite the lower woody plant cover, some characteristic species, such as Salvadora persica, occurred preferentially on active mounds; this species occurred on 42% of active mounds. Mean soil hardness (± SD) was higher on conical parts of active mounds (4300 ± 2620 kPa) than on adjacent pediments (583 ± 328 kPa) and inactive mounds (725 ± 619 kPa). This study suggested that mound status, mound micro-topography, and soil hardness promote variability in the vegetation on mounds.

Importance of bird seed dispersal in the development of characteristic vegetation on termite mounds in north-eastern Namibia

“…In addition, germination and establishment should be ex amined as processes after seed dispersal. Although some trees were established on the cones of active mounds, the cones have greater soil hardness and consequently suppress the establishment of woody plants (Yamashina 2013). Therefore, particular plant traits, such as the dynamics of root system development and germination, might explain plant preferences for mounds as habitat.…”

Termites and savannas – an overview on history and recent scientific progress with particular respect to West Africa and to the genus Macrotermes

“…• Studies analyzing the spatial distribution of species on mounds have shown spatial differentiation within mound microhabitats (Lawson & Jenik 1967;Kirchmair et al 2012;Yamashina 2013), offering soil properties, microclimatic effects and protection from fire as possible explanations for the spatial distribution of species on mounds.…”

Seed Dispersal by Animals Influences the Diverse Woody Plant Community on Mopane Woodland Termite Mounds

“…J. Kirk ex J. Léonard) woodland (White 1984). Although C. mopane is a dominant species both on and off termite mounds, there is higher density and species richness of woody plants on these mounds than in the surrounding savannah matrix (Yamashina 2013). Avian seed dispersal may contribute to this unique woody plant community (Yamashina 2014); however, clear evidence is lacking.…”