Floodplain ‘murundus’ of Central Brazil: evidence for the termite-origin hypothesis

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Abstract
‘Campos de murundus’ are a typical landscape of Central Brazil characterized by countless rounded earthmounds (the ‘murundus’), which are covered by woody ‘cerrado’ (savanna) vegetation and are found scattered over a grass-covered surface (the ‘campo’). A detailed study was carried out in the region of Cuiabá, state of Mato Grosso on a particular campo de murundus (area of 5.065 ha) lying in a sedimentary depression where the earthmounds are true islands during the annual floods, allowing the colonization both by cerrado plants and by termites. The mounds were mapped and measured for their size and shape. Mounds' diameters ranged from 0.2 to 22.0 m and heights ranged from 0.1 to 1.1m. The 445 smaller mounds (< 0.8 m diameter) were found to have a clumped distribution, occupying 0.1% of the area. They are actually small termite nests built byArmitermes euamignathus. The 80 larger mounds (> 0.8 m diameter) were uniformly distributed, occupying 6.3%, of the area. These mounds are colonized byCornitermes snyderiandCornitermes bequaertiwhich build big termite nests on the summit of the mounds. Soil analyses indicated a close similarity between the campo and the surrounding cerrado whose soils had coarser texture and were poor in nutrients. Soils of the earthmounds and termite nests showed finer texture, lower pH and higher amounts of mineral nutrients. It is suggested here that this particular type of campo de murundus is formed mainly from the localized activity of nest-building by termites, followed by nest degradation, during many generations of termite colonies.