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

Abstract

The appearance and expansion of C-4 plants in the Late Cenozoic was a dramatic example of terrestrial ecological change. The fire hypothesis, which suggests fire as a major cause of C-4 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 C-4 expansion, the 'C-4 maximum period of burned biomass' during the Pliocene to Early Pleistocene, and the collapse of the C-4 in the Late Pleistocene. Records showing the initial expansion of C-4 plants after large fire support the role of fire as a destructive agent of C-3-dominated forest, yet the weak relationships between fire and vegetation after initial expansion suggest that environmental advantages for C-4 plants were necessary to maintain the development of C-4 plants during the late Neogene. Among the various environmental factors, aridity is likely most influential in C-4 expansion.