Terrestrial biome distribution in the Late Neogene inferred from a black carbon record in the northeastern equatorial Pacific

Abstract

The appearance and expansion of C4 plants in the Late Cenozoic was a dramatic example of terrestrial ecological change. The fire hypothesis, which suggests fire as a major cause of C4 grassland is gaining support, yet a more detailed relationship between fire and vegetation-type change remains unresolved. We report the content and stable carbon isotope record of black carbon (BC) in a sediment core retrieved from the northeastern equatorial Pacific that covers the past 14.3 million years. The content record of BC suggests the development process of a flammable ecosystem. The stable carbon isotope record of BC reveals the existence of the Late Miocene C4 expansion, the ‘C4 maximum period of burned biomass’ during the Pliocene to Early Pleistocene, and the collapse of the C4 in the Late Pleistocene. Records showing the initial expansion of C4 plants after large fire support the role of fire as a destructive agent of C3-dominated forest, yet the weak relationships between fire and vegetation after initial expansion suggest that environmental advantages for C4 plants were necessary to maintain the development of C4 plants during the late Neogene. Among the various environmental factors, aridity is likely most influential in C4 expansion.

Variations of the Indian summer monsoon over the last 30 000 years inferred from a pyrogenic carbon record from south‐west China

“…Thus, this proxy is increasingly being used for paleo-vegetation and paleoclimate reconstruction (e.g. Bird and Gr€ ocke, 1997;Wang et al, 2013a;Sun et al, 2015;Zhang et al, 2015;Kim et al, 2016). In this study, we provide a continuous d 13 C PyC record from Lake Lugu in south-west China.…”

Mineral magnetic record of the Miocene-Pliocene climate transition on the Chinese Loess Plateau, North China

“…Examples include decreased eolian detrital fluxes on the CLP (Sun and An, 2002) and into the North Pacific Ocean (Rea et al, 1998), globally increased chemical weathering intensity (Filippelli, 1997), reorganization of the western Himalayan river system (Clift and Blusztajn, 2005), increased flux of clastic material to the South China Sea (Clift et al, 2014), decreased hematite/goethite ratios at ODP Site 1148 from the South China Sea (Clift, 2006), a positive shift of soil carbonate δ 13 C from the Siwalik Basin, and positive shifts of hydrogen (δD) and carbon (δ 13 C) isotope ratios of leaf wax C 31 n-alkane and increased abundance of the planktonic foraminifer Globorotalia bulloides and the radiolarian Actinomma in the Arabian Sea (Quade et al, 1989; Sanyal et al, 2004; Huang et al, 2007), which are indicative of an intensified ASM. The MPB also coincides with an increase in humidity over the Mediterranean region (Eronen et al, 2009) and with increased moisture availability in tropical America, as indicated by a positive shift of black carbon δ 13 C in the northeastern equatorial Pacific Ocean (Kim et al, 2016). The percentage of terrestrial mollusks on the CLP that prefer cold or dry environments decreases across the MPB (Fig.…”

“…Siwalik Basin, and positive shifts of hydrogen (δD) and carbon (δ 13 C) isotope ratios of leaf wax C 31 n-alkane and increased abundance of the planktonic foraminifer Globorotalia bulloides and the radiolarian Actinomma in the Arabian Sea (Quade et al, 1989;Sanyal et al, 2004;Huang et al, 2007), which are indicative of an intensified ASM. The MPB also coincides with an increase in humidity over the Mediterranean region (Eronen et al, 2009) and with increased moisture availability in tropical America, as indicated by a positive shift of black carbon δ 13 C in the northeastern equatorial Pacific Ocean (Kim et al, 2016). The percentage of terrestrial mollusks on the CLP that prefer cold or dry environments decreases across the MPB (Fig.…”

New sedimentary evidence reveals a unique history of C4 biomass in continental East Asia since the early Miocene

“…3 ). A subsequent expansion of C 4 taxa during the late Miocene in western and southern Asia has been linked to aridification 64 , although other factors, such as increased burning 15 , 25 and lower p CO 2 may have played a role. Evidence of an expansion of C 4 biomass from ~8–6 Ma that peaked in the early to mid Quaternary in Asia, the South Atlantic (ODP Site 1081) 65 , and Gulf of Mexico (DSDP Site 94) 9 implies the possible effect of global decreases in moisture availability along with ice sheet formation and expansion that commenced during the late Miocene, as recorded in δ 18 O variations preserved in the tests of foraminifera 66 .…”

“…Pyrogenic carbon (PyC), also known as elemental carbon (EC) or black carbon (BC), is produced through the incomplete combustion of biomass and can preserve the original C isotope value of the parent plants 23 . PyC is generally resistant to decomposition, and upon extraction from sediments can be used not only to document the frequency and intensity of past fire activity, but also changes in the relative contributions of C 4 and C 3 plants in combusted biomass 15 , 16 , 23 – 25 . Similarly, long chain n -alkanes (≥ n- C 27 ), which are important building blocks of lipids forming the protective waxy cuticle covering leaf and stem tissue, are resistant to diagenetic alteration 26 .…”