2.1 Study site
The studied area is located in the upper basin of the Rio Claro
(19°28’08”S, 47°48’20”W), at an altitude of 966 m a.s.l (above sea
level), in the municipality of Uberaba-MG (Figure 1). The wetland is a
distinct, upstream depression on a flat plateau, occupying a shallow
concavity covered with grassy savanna vegetation on hydric soil; it
forms the first headwater of the Rio Claro River. The seasonally flooded
area extends over 426,064.80 m². On the flat plateau, the upland soils
are well-drained ferruginous concretionary soils (Ferralsols by IUSS,
2014), which have been planted with soybean, corn, and sugarcane crops
since the 1970s. This wetland formation corresponds to a topographic
depression, the soils of which developed in an aquic moisture regime
(Gleysol by IUSS, 2014). The wetland areas have been drastically reduced
by agricultural land conversion. Distinct original vegetation covers
both Ferralsol and Gleysol soils; the Ferralsols are covered by tree
savanna. Wetlands are a grass-dominated ecosystem, with scattered woody
plants and small trees covering mounds (locally known asmurundus ), a microtopographic characteristic of the landscape.
Mounds are found exclusive in the waterlogged area, up to the border the
plateau. The entire area is part of the Cerrado, which has been
developed as an agricultural frontier and is becoming a biodiversity
extinction hotspot (Anache, Flanagan & Srivastava, 2018). The climate
is characterized by a pronounced dry season in the winter, from April to
October, followed by a rainy season during the summer months, from
November to March. The average annual rainfall and temperature are 1,516
mm and 23°C, respectively. Geologically, the area is characterized by
upper Cretaceous sandstones, with iron-rich silt and clay layers
belonging to the Serra da Galga Member of the Marília Formation
(Fernandes & Ribeiro, 2015). The catchment has gentle slopes (declivity
< 5 %) and a flat, wide and imperfectly drained valley.