As soil ecosystem engineers, termites transport soil particles when they build under- and above-ground chambers, tunnels and nests. They change soil properties by decomposing matter, facilitating nutrient cycling, and regulating soil moisture, thus enabling soil nutrient flow, especially in times of drought. In Australia, where drought is the primary environmental driver, termites are extremely successful and common with over 300 species of termites present and mounds as dense as 313/hectare for some species. With landscapes so densely populated by mounds that can last for centuries to millennia, termites are impacting soil properties. In northern Queensland, we observe high turnover in termite diversity and abundance over a precipitation gradient, shaped largely by shifts between rainforest and savannah. Here, we asked whether this turnover in species across habitats leads to changes in termite mound construction that affect the mound longevity. We sampled termite mounds from two savanna sites, two rainforest sites, and one intermediate site and measured mound height and diameter, width of mound edge, mound density, water content and carbon and nitrogen content. We analyzed differences in these mound properties among the different habitat types.
Results/Conclusions
We found that termites in savanna areas build mounds that are taller, wider, have thicker and denser edges and more variable C:N than termites in rainforest areas, while rainforest termites build mounds that have higher water content. The size difference may be because having a big mound is more advantageous for termites living in dry habitats, necessary for protection against drought or heat, or could be a reflection of the ease of mound building given substrate dryness. Some termite mounds are built to last, with densities much greater than surrounding soils, possibly due to higher proportions of clays and increased levels of minerals, organic matter, lignin, inorganic nitrogen, and microbes mineralizing carbon and nitrogen. Similar to what we found looking at taxonomic species turnover in termites, precipitation has big implications for how termites are using and affecting soil dynamics through their constructions.Termite mounds cover a considerable portion of soil area, but are ignored by soil scientists. Without taking termites into account, it is impossible to correctly estimate soil ecosystem function, e.g., fertility or stoichiometry.