Termite mounds are keystone structures in African savannas, affecting multiple ecosystem processes. Despite the large size of termite mounds having the potential to modify conditions around them, patterns of mound-induced ecosystem effects have been assumed to be isotropic, with little attention given to how effects might vary around mounds. We measured soil nitrogen content, grass species composition, and mammalian grazing on and off termite mounds in the four cardinal directions, and across wet and dry seasons at three savanna sites varying in mean annual rainfall in South Africa's Kruger National Park. Evidence of directional effects (anisotropy) on ecosystem properties around termite mounds varied with site. Grass species composition differed between north- and south-facing slopes at the two drier sites where mounds were taller. However, differences in grazing extent and soil nitrogen content around mounds were only present at the intermediate rainfall site where mammalian herbivore biomass was highest, and mounds were of medium height. Our results suggest that termite mound effects display significant variation with direction, but that the emergence of directional effects is context dependent. Our results further suggest that such context-dependent directional effects can lead to positive feedback loops between termites, abiotic conditions, and mammalian herbivores.

This work focuses on the feasibility of improving the mechanical strength of Compressed Earth Blocks (CEBs) made from Macrotermes termite mound soil with corn starch gel to provide an ecological and sustainable building material. The results demonstrate the suitability of raw earth collected from termite mounds for the production of compressed earth blocks (CEB) at the Proctor optimum. Mechanical tests on 4 x 4 x16 cm(3) specimens showed an increase in the compressive strength with decreasing water content (0%, 2%, 4%, 6%, 8%, 10% and 13.6%). In addition, unstabilised CEB and CEB stabilised with corn gel (5%, 10% and 15%) concentrated at 10% in water are compared in the dry state. Our results show that corn gel improves the mechanical properties by more than 50% and has a negligible effect on the thermal conductivity of compressed earth blocks. In short, starch seems to give CEBs improved thermal properties. This new family of composite materials - termite mound soil and starch - would be ideal for the construction of modern, sustainable, renewable buildings with a low carbon footprint.