South American Savannas

Borghetti, Fabian; Barbosa, Eduardo R. M.; Ribeiro, Leandro Carvalho; Ribeiro, J. F.; Walter, Bruno Machado Teles

doi:10.1002/9781119081111.ch4

Cited by 22 publications

(27 citation statements)

References 147 publications

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“…of Roraima State, but they also extend to the country of Guyana (Barbosa and Fearnside, 2005b;Barbosa et al, 2007;Meneses et al, 2013). The Cerrado biome covers around 2 million km 2 in Central Brazil, representing the largest continuous savanna area in South America (Borghetti et al, 2019). Much of the Cerrado is distributed over the Brazilian Central Plateau (Sano et al, 2010).…”

Section: Study Sites: a General Viewmentioning

confidence: 99%

“…Much of the Cerrado is distributed over the Brazilian Central Plateau (Sano et al, 2010). The Cerrado vegetation has a gradient of physiognomies; from pure grasslands to forests, however, savanna predominates (Bueno et al, 2017;Borghetti et al, 2019). Although separated by the Amazon basin, these two regions share several species, suggesting that they were in some way connected in the past (Silva and Bates, 2002;Prance, 2006;Furley, 2007).…”

Section: Study Sites: a General Viewmentioning

confidence: 99%

“…In Brazil, there are two large savanna areas separated by the Amazon basin: (i) Rio Branco savannas, occurring in the state of Roraima, northern Brazil and (ii) Cerrado savannas, occurring within the Cerrado, a biome largely distributed over Central Brazil (Borghetti et al, 2019). They share several plant species and are subjected to a similar fire frequency and mean annual precipitation (see Table 1 for more details).…”

Section: Introductionmentioning

confidence: 99%

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How regional climate and seed traits interact in shaping stress–tolerance of savanna seeds?

2021

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Functional traits related to regeneration responses to the environment are highly determinants of distribution patterns of plant communities. A large body of studies on seed traits suggests that regional climate may act as a strong filter of plant recruitment; however, few studies have evaluated the relative importance of seed traits and environmental filters for seed persistence at the population level. We tested the role of seed mass, water content and desiccation tolerance, as well as the germination time as proxies for seed tolerance to environmental filters (water deficit, heat shock and high temperatures) by comparing the response of tree species co-occurring in savannas located in different regions: Cerrado biome of Central Brazil and the Rio Branco savannas of northern Brazil. Seeds collected in savannas of Rio Branco showed a higher tolerance to environmental filters than those collected in savannas of the Cerrado. While the germination percentages largely varied in response to the treatments, the germination times were virtually unaffected by them, irrespective of seed origin, seed mass and water content. At the population level, the regional environment was a key determinant of seed tolerance to stress, irrespective of seed traits. Germination time was shown to represent a conservative seed trait and more linked to a species-specific germination strategy than to regional characteristics. Our results suggest that recruitment patterns of Cerrado savannas may be more impacted than Rio Branco savannas by the climate scenarios predicted for the future.

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Section: Study Sites: a General Viewmentioning

confidence: 99%

Section: Study Sites: a General Viewmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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How regional climate and seed traits interact in shaping stress–tolerance of savanna seeds?

2021

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“…The large areas of savannas are seen as the main alternative to avoid agricultural expansion in tropical areas of greater ecological fragility, such as the Amazon rainforests (López-Hernández et al, 2005). Although most of their soils suffer from physical and chemical limitations to agricultural production (López-Hernández et al, 2005), large areas of South American savannas have been turned into monocultures or pastures (Borghetti et al, 2019). The Colombian Orinoco River basin savannas, also known as "Llanos", particularly, the flat High Plains region, has also been rapidly transformed into mechanized agriculture.…”

Section: Introductionmentioning

confidence: 99%

Carbon Exchange and Accumulation in an Orinoco High Plains Native Savanna Ecosystem as Measured by Eddy Covariance

Morales-Rincon

Hernandez

Rodriguez-Hernandez

et al. 2021

Front. Environ. Sci.

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Savanna ecosystems cover ∼20% of the total land surface and account for ∼30% of the terrestrial global net primary production. They are also highly sensitive to climate change, since their carbon (C) sink capacity may decline under rising temperatures and irregular rainfall. These responses, which will define the future climate role of the savanna ecosystems, are currently not well understood. The Colombian Orinoco River basin (“Llanos”) natural savannas are being rapidly converted to agriculture. The impact of this transformation on C fluxes and accumulation is not clear. It is thus urgent to understand the Llanos natural savanna ecosystem services, including their C cycle and underlying mechanisms. Here we report and analyze 2 years of measurements of carbon dioxide fluxes from a naturally-restored (secondary) Llanos High Plains savanna ecosystem, using eddy covariance. Meteorological conditions, particularly rainfall, were quite variable during the measurement period. During the first year of measurements, the savanna was a weak carbon source (35 gC m−2), while during the second year, the system was a comparatively strong carbon sink (−273 gC m−2), despite receiving less rainfall than during the first year. As expected, the savanna net ecosystem exchange (NEE) was highly dependent on global solar radiation, soil water content, and ecosystem respiration. We found that after ∼10 days of nominal drought, i.e., with less than ∼5 mm/day of precipitation, the NEE became highly dependent on drought duration. The ecosystem reached a critical condition of low photosynthetic activity after ∼60 days of nominal drought. Based on these findings, we developed and applied a simple standard meteorology-based model that properly reproduced the observations. Our results indicate that a shift to a climate with similar total precipitation but split into extreme dry and wet seasons might eventually suppress the savanna C uptake capacity.

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“…In the Neotropics, the Cerrado (Brazilian savanna) is a fire-prone ecosystem that forms a vegetation mosaic of grasslands, savannas, and forests (Coutinho 1978;Borghetti et al 2020), and is one of the world's biodiversity hotspots (Myers et al 2000). Fires have been present in the Cerrado for the past 10 million years (Simon et al 2009) and, as in other savannas, are key in maintaining ecosystem structure and biodiversity (Hoffmann et al 2012a;Abreu et al 2017;Durigan et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Experimental burns in an open savanna: Greater fuel loads result in hotter fires

et al. 2022

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Fire is a main disturbance structuring vegetation worldwide, but few studies have addressed differences in time since last fire and its relationship to fuel load characteristics and fire behavior in Neotropical savannas. We aimed to investigate fire behavior in a Cerrado open savanna of Central Brazil by conducting prescribed fires in areas with different fire-free intervals: one year (FI-1), two years (FI-2), and four years (FI-4). Specifically, we evaluated (1) the amount of live, dead, and total biomass (components of the fuel load); (2) fire behavior, including fire temperatures in three different heights (1 cm belowground, on the soil surface, and 50 cm aboveground), fire duration, residence time, fire intensity, rate of spread, and flame height; and (3) the relationship between soil heating, fuels, and fire by identifying the most important parameters driving soil heating. Total and dead fuel loads were greater in areas with longer fire-free intervals in comparison with areas burned the previous year, with the greatest increment to the fuel bed occurring in the first two years after fire. Greater fuel loads (consequently greater dead fuel loads) resulted in differences in belowground soil heating (-1 cm), where temperatures varied from 39 to 82°C in FI-2 plots and from 40 to 131°C in FI-4 plots; in FI-1 plots temperatures belowground varied from 29 to 68°C. Temperatures on the soil surface and 50 cm aboveground were also greater in plots with longer fire-free intervals, reaching over 400°C on the soil surface and exceeding 500°C 50 cm aboveground. Finally, amount of dead fuel was the best predictor of belowground soil heating, highlighting the importance of fuel loads, which is a key factor to be monitored in fire management plans of Cerrado open savannas.

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South American Savannas

Cited by 22 publications

References 147 publications

How regional climate and seed traits interact in shaping stress–tolerance of savanna seeds?

How regional climate and seed traits interact in shaping stress–tolerance of savanna seeds?

Carbon Exchange and Accumulation in an Orinoco High Plains Native Savanna Ecosystem as Measured by Eddy Covariance

Experimental burns in an open savanna: Greater fuel loads result in hotter fires

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