Deciphering earth mound origins in central Brazil

Abstract

Mound fields are a common landscape throughout the world and much of the evidence for their origin has been of a circumstantial nature. It has been hypothesized that earth mounds emerge over grasslands by termite activity; alternatively, they might be formed after erosion. We tested whether a mound field in central Brazil was generated by termite activity or erosion. We used soil organic matter isotopic composition, soil chemical, physical and floristic composition to determine the origin of a mound field. If the mounds emerged by termite activity in an established grassland the soil organic matter below the mound should have the isotopic signature of C 4 dominated grassland, which contrasts with savanna C 3 + C 4 signature. Additionally, soil traits should resemble those of the grassland. All markers indicate that the mounds were formed by erosion. The soil isotopic composition, chemical traits and texture below the mound resembled those of the savanna and not those of the grassland. Moreover, most of the species present in the mound were typical of savanna. Concrete evidence is provided that mound fields in the studied area were produced by erosion of a savanna ecosystem and not termite activity. The use of the techniques applied here would improve the assessments of whether analogous landscapes are of a biogenic nature or not.

Arbuscular mycorrhizal fungi in soil aggregates from fields of "murundus" converted to agriculture

“…These areas are vegetated by species tolerant to temporary flooding, whereas the dried part of the soil (upper-third of the murundus) presents typical vegetation of the Cerrado stricto sensu, with shrubs and trees (Marimon et al, 2012). Analogous formations to the murundus are also found in Africa, Australia, and North America (Silva et al, 2010). To convert these areas to agriculture, it is necessary to build drainage channels and flatwork, removing the murundus, besides performing soil homogenization, correction, and fertilization.…”

Lower ant Diversity on Earth Mounds in a Semi-Arid Brazilian Ecosystem: Natural or a Sign of Degradation?

“…The mounds are piles of soil or a type of micro relief in landscapes associated with poor drainage conditions (Resende et al, 2002). Their origin remains controversial (Renard et al, 2012) with two competing hypotheses (Silva et al, 2010) -a termite mound origin versus differential erosion over time. The termite mound hypothesis suggests successful colonization by successive generations of termites that thereby increases the diameter and height of these structures, which are further acted upon by earthworms and ants (Resende et al, 2002).…”

Chemical and physical attributes and calcium, magnesium, potassium, and phosphorus in the soil of murundu fields in Brazil

“…Nas áreas ora estudadas os baixos teores provavelmente se devem ao predomínio da fração areia nesses solos, que não favorece a adsorção de P (Resende et al 2007), bem como à pobreza do material de origem nesse elemento e aos baixos teores de matéria orgânica em ambos ambientes (Silva et al 2010). No entanto, apesar de baixos, no murundu, em todas as profundidades, os teores de P são cerca de três vezes mais elevados que na APC.…”