Pedogeomorphology of a Mound-building termite savanna in Roraima, Brazilian Amazonia

Abstract

Termite mounds are key biogeomorphological structures in tropical drylands, yet their role in Amazonian savannas remains poorly documented. We assessed termite diversity, nesting habits, mound morphology, and soil attributes across Plinthosols and Acrisols in the Surumu Depression, northeastern Roraima, an extensive murundu field in a savanna-caatinga ecotone. Transect sampling recorded 16 species/morphospecies from eight genera and two families, with Termitidae representing most encounters. Frequent species were shared across soil classes, whereas rare species differed. Although Amitermes excellens was not numerically dominant in the assemblage, it was the main builder of the large conical and cathedral-shaped mounds that structure the local landscape. Mounds showed marked physical and chemical contrasts with adjacent soils, especially selective incorporation of fine particles and enrichment in bases, nitrogen, and organic matter. Mound density was higher on poorly drained Plinthosols, whereas larger and older mounds occurred on better-drained Acrisols, where erosion and vegetation succession were more advanced. These results show that A. excellens acts as a major pedobioturbation agent, redistributing subsurface materials, creating fertility islands, and maintaining pedogeomorphological heterogeneity in the northern Amazonian savanna. Their spatial pattern therefore records hydrogeomorphic controls, with first-order bioturbation estimates of 47.5-85.3 mm ka-1 along the toposequence.