Black carbon as a tracer of terrestrial biome distribution in the late Neogene

Abstract

The evolution and expansion of C4 plants in the late Cenozoic was a dramatic example of terrestrial ecological changes. Fire hypothesis is gaining support as the cause of C4 grassland development in Africa, yet the role of fire in C4 grassland development in other continents still needs to be proved. We present the proportion and stable carbon isotope records of black carbon (BC) of a sediment core from the northeastern equatorial Pacific, covering the past 14.3 million years. Content record of BC in sediment indicates changes in atmospheric circulation and paleoclimate aridity. Stable carbon isotope record of BC reveals not only early expansion of C4 vegetation, but also the C4 maximum period during the Pliocene to Early Pleistocene, and the collapse of C4 dominance in the Late Pleistocene. Records showing expansion of C4 plants after large disturbance of fire support the role of fire as a destructing agent of C3-dominated forest, yet the weak relations between fire and vegetation after C4 expansion event suggest that environmental advantage for C4 plants were necessary factors to keep the dominance of C4 plants during the Late Neogene. Also, comparison between regional data shows that consideration of specific climate event is necessary to interpret BC as a fire-vegetation tracer.and development in other continents still needs to be proved. We present the proportion and stable carbon isotope records of black carbon (BC) of a sediment core from the northeastern equatorial Pacific, covering the past 14.3 million years. Content record of BC in sediment indicates changes in atmospheric circulation and paleoclimate aridity. Stable carbon isotope record of BC reveals not only early expansion of C4 vegetation, but also the C4 maximum period during the Pliocene to Early Pleistocene, and the collapse of C4 dominance in the Late Pleistocene. Records showing expansion of C4 plants after large disturbance of fire support the role of fire as a destructing agent of C3-dominated forest, yet the weak relations between fire and vegetation after C4 expansion event suggest that environmental advantage for C4 plants were necessary factors to keep the dominance of C4 plants during the Late Neogene. Also, comparison between regional data shows that consideration of specific climate event is necessary to interpret BC as a fire-vegetation tracer.