Effects of consecutive dry and wet days on the forest–savanna boundary in north‐west South America

Hoyos, Natalia; Correa‐Metrio, Alex; Jaramillo, Carlos; Villegas, Juan; Escobar, Jaime

doi:10.1111/geb.13432

Cited by 5 publications

(5 citation statements)

References 34 publications

(106 reference statements)

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“…While Caatinga shrublands are characterized by distinctly lower precipitation values than the surrounding Cerrado savanna, the boundary between the Llanos savanna and the Amazon rainforest in the northern portion of the continent features continuously high MAP values (Figure 1). Here, the boundary between savanna and rainforest is heavily dependent on the duration of wet spells during the dry season (Hoyos et al., 2022). Likewise, the boundary between the Cerrado and the drier southern part of the Amazon rainforest is also not defined by a distinct MAP boundary (Figure 1).…”

Section: Methodsmentioning

confidence: 99%

Using Multi‐Homolog Plant‐Wax Carbon Isotope Compositions to Reconstruct Tropical Vegetation Types

Häggi,

Bertassoli,

Akabane

et al. 2024

JGR Biogeosciences

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The stable carbon isotope composition (δ13C) of plant components such as plant wax biomarkers is an important tool for reconstructing past vegetation. Plant wax δ13C is mainly controlled by photosynthetic pathways, allowing for the differentiation of C4 tropical grasses and C3 forests. Proxy interpretations are however complicated by additional factors such as aridity, vegetation density, elevation, and the considerable δ13C variability found among C3 plant species. Moreover, studies on plant wax δ13C in tropical soils and plants have focused on Africa, while structurally different South American savannas, shrublands and rainforests remain understudied. Here, we analyze the δ13C composition of long‐chain n‐alkanes and fatty acids from tropical South American soils and leaf litter to assess the isotopic variability in each vegetation type and to investigate the influence of climatic features on δ13C. Rainforests and open vegetation types show distinct values, with rainforests having a narrow range of low δ13C values (n‐C29 alkane: ‰ ; Suess‐effect corrected). This allows for the detection of even minor incursions of savanna (δ13C n‐C29 alkane ‰) into rainforests. While Cerrado savannas and semi‐arid Caatinga shrublands grow under distinctly different climates, they can yield indistinct δ13C values for most compounds. Cerrado soils and litter show pronounced isotopic spreads between the n‐C33 and n‐C29 alkanes, while Caatinga shrublands show consistent values across the two homologs, thereby enabling the differentiation of these vegetation types. The same multi‐homolog isotope analysis can be extended to differentiate African shrublands from savannas.

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Section: Methodsmentioning

confidence: 99%

Using Multi‐Homolog Plant‐Wax Carbon Isotope Compositions to Reconstruct Tropical Vegetation Types

Häggi,

Bertassoli,

Akabane

et al. 2024

JGR Biogeosciences

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“…1). Rather than on MAP, the boundary between Llanos savanna and rainforest is heavily dependent on the duration of wet spells during the dry season (Hoyos et al, 2022). Likewise, the boundary between the Cerrado and the drier southern part of the Amazon rainforest is also not defined by a distinct MAP boundary (Fig.…”

Section: 1study Areamentioning

confidence: 99%

Using Multi-Homologue Plant-Wax Carbon Isotope Signatures to Reconstruct Tropical Vegetation Types

Häggi,

Jr,

Akabane

et al. 2023

Preprint

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The stable carbon isotope composition (δ13C) of plant components such as plant wax biomarkers is an important tool for reconstructing past vegetation. Plant wax δ13C is mainly controlled by photosynthetic pathways, allowing for the differentiation of C4 tropical grasses and C3 forests. Proxy interpretations are however complicated by additional factors such as aridity, vegetation density, elevation, and the considerable δ13C variability found among C3 plant species. Moreover, studies on plant wax δ13C in tropical soils and plants have focused on Africa, while structurally different South American savannas, shrublands and forests remain understudied. Here, we analyze the δ13C composition of long-chain n-alkanes and fatty acids from tropical South American soils and leaf litter to assess the isotopic variability in each vegetation type and to investigate the influence of climatic features on δ13C. Rainforests and open vegetation types show distinct values, with rainforests having a narrow range of low δ13C values (n-C29 n-alkane: -34.5 +0.9/-0.6 ‰ ; Suess-effect corrected) allowing for the detection of even minor incursions of savanna into rainforests (13C-enriched). While Cerrado savannas and semi-arid Caatinga shrublands grow under distinctly different climates, they can yield indistinct δ13C values for most compounds. Cerrado soils and litter show pronounced isotopic spreads between the n-C33 and n-C29 alkanes, while Caatinga shrublands show consistent values across the two homologues, thereby enabling the differentiation of these vegetation types. The same multi-homologue isotope analysis can be extended to differentiate African shrublands from savannas.

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“…It is true that nutrient‐poor, acidic soils rich in aluminum are associated with savannas (Pennington et al ., 2000; Dexter et al ., 2018), but the soil itself can be derived from the presence of grasslands. For example, Llanos and TRF share the same type of parent rock and geological history and yet, their soils are different (Hoyos et al ., 2022).…”

Section: Neogene: Pebas Savanna Xerophytic and Andean Biomesmentioning

confidence: 99%

“…The role of precipitation in determining the presence of forest or savanna is complicated. The literature indicates that both precipitation and the length of the dry season play major roles in determining whether TRF or savanna exists, with forests being present in areas with high MAP (> 2500 mm) and a short dry season (< 4 months), and savannas being present when MAP is between 1000 and 1400 mm (Hoyos et al ., 2022). At MAP below 1000 mm, only XFs and some TDF exist while savannas are no longer present (Dexter et al ., 2018; Fig.…”

Section: Neogene: Pebas Savanna Xerophytic and Andean Biomesmentioning

confidence: 99%

“…This observation spawned the idea of alternative stable states, also called bistability, within this climatic envelope (Staver et al ., 2011). However, a recent analysis of the Llanos‐TRF boundary found that bistability may not be the case; instead, the biome shift is associated with the number of consecutive rainy days during the dry season (Hoyos et al ., 2022).…”

Section: Neogene: Pebas Savanna Xerophytic and Andean Biomesmentioning

confidence: 99%

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The evolution of extant South American tropical biomes

Jaramillo

2023

New Phytologist

Self Cite

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This review explores the evolution of extant South American tropical biomes, focusing on when and why they developed. Tropical vegetation experienced a radical transformation from being dominated by non-angiosperms at the onset of the Cretaceous to full angiosperm dominance nowadays. Cretaceous tropical biomes do not have extant equivalents; lowland forests, dominated mainly by gymnosperms and ferns, lacked a closed canopy. This condition was radically transformed following the massive extinction event at the Cretaceous-Paleogene boundary. The extant lowland tropical rainforests first developed at the onset of the Cenozoic with a multistratified forest, an angiosperm-dominated closed canopy, and the dominance of the main families of the tropics including legumes. Cenozoic rainforest diversity has increased during global warming and decreased during global cooling. Tropical dry forests emerged at least by the late Eocene, whereas other Neotropical biomes including tropical savannas, montane forests, p aramo/puna, and xerophytic forest are much younger, greatly expanding during the late Neogene, probably at the onset of the Quaternary, at the expense of the rainforest.

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Effects of consecutive dry and wet days on the forest–savanna boundary in north‐west South America

Cited by 5 publications

References 34 publications

Using Multi‐Homolog Plant‐Wax Carbon Isotope Compositions to Reconstruct Tropical Vegetation Types

Using Multi‐Homolog Plant‐Wax Carbon Isotope Compositions to Reconstruct Tropical Vegetation Types

Using Multi-Homologue Plant-Wax Carbon Isotope Signatures to Reconstruct Tropical Vegetation Types

The evolution of extant South American tropical biomes

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