Paleoecology explains Holocene chemical changes in lakes of the Nhecolândia (Pantanal-Brazil)

Guerreiro, Renato Lada; McGlue, Michael M.; Stone, Jeffery R.; Bergier, Ivan; Parolin, Mauro; Silva-Caminha, Silane A.F. da; Warren, Lucas Veríssimo; Assine, Mário Luís

doi:10.1007/s10750-017-3429-3

Cited by 17 publications

(33 citation statements)

References 70 publications

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“…2). This fits with the timing of precipitation increase Mid-Holocene climate and Bolivian dry forests in the late Holocene suggested by regional palaeoclimate records, including lake levels at Laguna Titicaca (Baker et al, 2001), δ 18 O records from the Andes (Bird et al, 2011), and sponge and diatom records from the Pantanal (Guerreiro et al, 2017). This precipitation increase is also reflected in the vegetation at Laguna Mandioré by peak aquatic plant pollen abundance (Fig.…”

Section: Dry Forest-upland Savannah Ecotone At Laguna Mandiorésupporting

confidence: 84%

Long-term impacts of mid-Holocene drier climatic conditions on Bolivian tropical dry forests

2019

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The Bolivian Chiquitano dry forest is the largest block of intact seasonally dry tropical forest in South America and is a priority ecoregion for conservation due to its high threat status. However, the long-term impacts of drier climatic conditions on tropical dry forests are not well understood, despite climate models predicting increased droughts over Bolivia in the coming century. In this paper, we assess the impacts of drier climatic conditions during the mid-Holocene on the Bolivian Chiquitano tropical dry forest using fossilised pollen, phytoliths, macro-charcoal, and geochemical proxies from a sediment core from a large lake (Laguna Mandioré) on the Bolivia–Brazil border. Our results show that drier climatic conditions during the mid-Holocene caused a local-scale, ecotonal expansion of upland savannah at the expense of dry forest. Interaction between drier climatic conditions and fire regime likely exerted a stronger control over the position of the dry forest–savannah ecotone than edaphic factors. However, the majority of the dry forest within the lake catchment maintained a closed canopy throughout the drier conditions of the mid-Holocene, despite floristic turnover towards more drought-tolerant taxa. These findings imply overall resilience of the Chiquitano dry forest biome to future drought, albeit with floristic changes and upland savannah encroachment at ecotones.

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Section: Dry Forest-upland Savannah Ecotone At Laguna Mandiorésupporting

confidence: 84%

Long-term impacts of mid-Holocene drier climatic conditions on Bolivian tropical dry forests

2019

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“…8), Mendes (2015) interpreted that sand ridges were formed by eolian sand accumulation during the Holocene. A significant period of eolian deflation during the early and middle Holocene is considered to have occurred before establishing the perennial lakes in the Nhecolândia around 3,300-3,200 cal yrs BP (McGlue et al 2017, Guerreiro et al 2018. While our data clearly demonstrates the non-channelized nature of the processes responsible for the deposition of Unit 3, it is yet unclear if it was deposited by sheet-flow or eolian processes, or indeed a combination of both.…”

Section: Discussionmentioning

confidence: 63%

How Ground Penetrating Radar helps to understand the Nhecolândia lakes landscape in the Brazilian Pantanal wetland

et al. 2021

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The Pantanal wetland is an active sedimentary basin representing a relevant depositional setting for alluvial sedimentation studies. However, sedimentation homogeneity and the lack of outcrops makes sedimentary analysis more difficult. The Lower Nhecolândia is located at the Southern edge of the Taquari river megafan, whose genetic origin has been disputed as fluvial or eolian deposition. GPR analysis was used to characterize the subsurface stratigraphy and understand the region's geomorphic evolution. The 100 MHz GPR provided continuous good quality sections up to a depth of 8 m. Two continuous reflections are disconformities that bound three depositional sequences characterized by distinct radar facies. The lower facies presents an upper erosional truncation followed by reflections presenting ~1.5 m deep channelized forms and concave-up low amplitude reflections. The intermediate facies (~4 m thick) presents a base with erosional truncation followed by concave-upward forms, ~10 m wide, 1-3 m deep, separated by 1-2 m, and offlapping geometry. The upper facies has a flat base and thickness of 2-4 m, with parallel reflections; it shows a strong correlation between the radar facies and the forms preserved in the landscape, suggesting that channelized fluvial streams did not form them. The results obtained indicate that GPR use in the Pantanal is an important method to elucidate its geologic evolution.

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“…6b). Salinas are topographically closed and remain isolated during flooding during the wet season, whereas the grasslands become inundated during the seasonal flood (Guerreiro et al 2018). In the rainy season, the water levels in the baías rise and they may connect with the flooded grassland.…”

Section: Nhecolândia Brazilmentioning

confidence: 99%

Chemical sedimentation as a driver of habitat diversity in dryland wetlands

Humphries

McCarthy

2021

Wetlands Ecol Manage

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Freshwater wetlands located in dryland environments are characterised by high evapotranspiration rates and frequent periods of desiccation, which strongly influence the water chemistry and solute budgets of these systems. The transpiration of groundwater, especially by trees, is an important mechanism through which dryland wetlands can lose water. This process can lead to groundwater salinization and the precipitation of substantial quantities of mineral phases within the soil, the accumulation of which can have profound consequences for wetland structure and function. This paper aims to bring together current knowledge on the processes that result in solute accumulation and chemical sedimentation which assist in maintaining freshwater conditions in many seasonal dryland wetlands. Examples from central and southern Africa, Australia and South America are presented to illustrate the geomorphically diverse settings under which chemical sedimentation can occur, and the importance of these processes for the resilience and longevity of dryland wetlands. We show that the localised development of saline groundwater and subsurface precipitation of minerals within soils can play a key role in creating and maintaining the habitat diversity of dryland wetlands. Wetland vegetation focuses the accumulation of deleterious constituents, thereby preventing widespread salinization and playa-lake formation, and thus ensuring that the bulk of the surface water remains fresh. Although such processes remain widely understudied, we suggest that chemical sedimentation could be a common phenomenon in many dryland wetlands and have important implications for the future management of these ecosystems.

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Paleoecology explains Holocene chemical changes in lakes of the Nhecolândia (Pantanal-Brazil)

Cited by 17 publications

References 70 publications

Long-term impacts of mid-Holocene drier climatic conditions on Bolivian tropical dry forests

Long-term impacts of mid-Holocene drier climatic conditions on Bolivian tropical dry forests

How Ground Penetrating Radar helps to understand the Nhecolândia lakes landscape in the Brazilian Pantanal wetland

Chemical sedimentation as a driver of habitat diversity in dryland wetlands

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