Spatial Variability of the Physicochemical Properties of Soils from Seasonally Flooded Forest Fragments on a Tropical Plain

Abstract

Flooded ecosystems are conditioned to seasonal floods that promote specific soil conditions, such as low oxygen, hydromorphism, and peculiar chemical reactions. These environments are dependent on flood pulses that determine specific ecological conditions. Ipucas are seasonally flooded discontinuous forest patches that occur exclusively in the Araguaia Plain in Central Brazil. They are located 0.40 to 1.20 m lower than the surrounding plain, which promotes an accumulation of rainwater for five to six months of the year, being entirely or partially dry during the dry season. The aim of this study was to evaluate the horizontal (centre and edge) and vertical (depths: 0–0.20 m and 0.20–0.40 m) variability of physicochemical parameters in Ipucas soils, attempting to establish the importance of flood pulses and the leaching of surrounding areas in soil formation and composition. Samples were collected during the dry season in three Ipucas of similar size and circularity using a Dutch auger. The results reveal that flood pulses promote the deposition of sediments eroded from the surrounding plain, homogenizing the characteristics of the surface soil, from the edge to the centre of the Ipucas. However, biogeochemical processes, also linked to temporary flooding, account for the differences between the surface and deeper soil horizons because anoxic conditions during flooding promote chemical reactions characteristic of anaerobic environments, modifying the pH and organic matter content, in addition to the gleying of soils subjected to flooding, which are then covered by sediments after the dry season. Finally, Ipucas soils are susceptible to anthropic changes and are dependent on seasonal flood pulses.

Soil fertility of fluvial islands increases with proximity to an Amazonian white-water river

“…The high acidity recorded is a common feature in ooded environments (Barrios and Herrera 1994;Barbosa et al 2019). Soil nutrient concentrations can be also directly related to low pH (Schroth et al 2003;Hillel 2003), which negatively contributes to the availability of effective cation exchange capacity (ECEC).…”

Abordagem interdisciplinar dos conceitos relacionados a depressões doliniformes na Planície do Araguaia, Brasil

“…Possuem baixa riqueza florística (Marimon e Lima 2001;Martins et al 2001), as espécies de menor porte correspondem às arbustivas e lianas (Santos 2011;Oliveira et al 2013). Os indivíduos arbóreos de maior frequência são tolerantes aos pulsos de inundação, destacando-se a dominância de Calophyllum Brasiliense (Landi); Sclerolobium paniculatum (Carvoeiro) e Licania apetala (farinha-seca) (Eiten 1985;Brito et al 2006;Barbosa et al 2019).…”

“…Os fragmentos florestais, nomeados ipucas e impucas, ocorrem em depressões naturais do terreno (Nascimento e Morais 2012;Maracahipes et al 2014;Silva et al 2015) com alta influência do lençol freático (Martins et al 2002), formando bacias circundadas por vegetação (Marimon e Lima 2001;Dias 2014), na sua composição litológica superficial prevalecem sedimentos finos como argila e silte, além de frequentes depósitos de matéria orgânica no seu interior (Irion et al 2016;Barbosa et al 2019). As ipucas e impucas tendem a coalescer por processos associados à dissolução e subsidência de substrato calcário subjacente do Grupo Tocantins, formando dolinas e uvalas (Martins et al 2006).…”