Diversity and abundance of macro-invertebrates on abandoned cattle kraals in a semi-arid savanna.

Abandoned cattle () kraals are sources of habitat heterogeneity in dystrophic semi-arid African savannas with a strong positive effect on soil nutrients and plant productivity. However, little is known regarding how macro-invertebrate assemblages vary between abandoned kraals and the surrounding savanna matrix. We tested whether herbaceous biomass and basal and aerial covers and soil nutrients have an effect on aboveground and belowground macro-invertebrate assemblages. Twelve abandoned kraals were contrasted with their paired control plots for soil characteristics, herbaceous productivity, and macro-invertebrate assemblages in Save Valley Conservancy, Zimbabwe. Abandoned kraals had significantly higher concentrations of soil nitrogen (N), phosphorus (P), potassium (K), and calcium (Ca) as well as herbaceous biomass and basal and aerial covers than control plots. Both aboveground and belowground macro-invertebrate species richness were higher on abandoned kraals. However, only belowground macro-invertebrate diversity (Shannon and Hill number 1) was significantly higher on abandoned kraals. Soil nutrients and herbaceous productivity had positive and significant correlations with the dominant taxa (Coleoptera, Hymenoptera, Hemiptera, Isoptera, and Myriapoda) on abandoned kraals. These results add to the growing body of evidence that abandoned kraals exert significant effects on savanna spatial heterogeneity years later, with implications on ecosystem processes and functioning.