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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.

The Tocantins-Araguaia Basin is one of the largest river systems in South America, located entirely within Brazilian territory. In the last decades, capital-concentrating activities such as agribusiness, mining, and hydropower promoted extensive changes in land cover, hydrology, and environmental conditions. These changes are jeopardizing the basin's biodiversity and ecosystem services. Threats are escalating as poor environmental policies continue to be formulated, such as environmentally unsustainable hydropower plants, large-scale agriculture for commodity production, and aquaculture with non-native fish. If the current model persists, it will deepen the environmental crisis in the basin, compromising broad conservation goals and social development in the long term. Better policies will require thought and planning to minimize growing threats and ensure the basin's sustainability for future generations. [ABSTRACT FROM AUTHOR]

We studied the rates of leaf decomposition and loss of leaf constituents (lignin and cellulose) of a native plant species using the litterbag experiment during different seasonal periods (flood and drought) in periodically flooded ecosystems, locally known as "Ipucas". The effects of flood, edge and fungal colonization on leaf degradation were evaluated. The results show that leaf decomposition is very slow, and influenced by seasonality, flooding and leaf chemical quality. Low moisture and leaf structural components contribute to the slow rate of decomposition. In addition, the fungal biomass was sensitive to the edge effect, with higher values in the center, probably due to the edge losing moisture earlier than the center after the end of rainy season. In addition, the positive correlation of fungal biomass with flooding demonstrates the importance of seasonality in these temporally flooded ecosystems, indicating that global changes in rainfall patterns may disrupt carbon cycling and probably nutrient cycling in periodically flooded environments. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Reservoirs cause hydrological changes (i.e., water level stabilization) that favor the colonization of aquatic macrophytes. Knowing the ecological factors that determine the occurrence of these plants is critical for water management (e.g., plant control) and biodiversity conservation. In this sense, the present study investigated colonization patterns of Ludwigia sedoides in Lajeado reservoir (Tocantins River, Amazon Basin), in order to identify variables that influence colonization at habitat scale. We investigated the relationship between colonization (coverage area and occurrence) and morphometric (fetch, slope, depth and distance from shoreline) and biotic variables (local diversity of macrophytes and co-occurrence patterns). Stepwise regression selected fetch, depth and slope as the best variables to explain the variation in L. sedoides coverage, which together explained 46% of data variability. Fetch and slope were negatively correlated with coverage, whereas depth showed a positive correlation. No biotic variable was included in the model (P>0.05). However, the investigation of the geometric shape of bivariate correlations (null models) showed positive relationships with local species richness and richness of life forms (i.e., submerged, emergent, floating and epiphytic). In addition, an analysis of species co-occurrence (C-score) revealed that L. sedoides is negatively associated with some macrophyte species. We believe, however, that these results may be associated with species preferences for particular environmental conditions. In conclusion, the present study indicated that morphometric variables are potential predictors of the colonization of L. sedoides in Lajeado reservoir. Sheltered sites with low slope and moderate depths represent favorable environment for colonization and growth. [ABSTRACT FROM PUBLISHER]