Phytolith evidence for C4-dominated grassland since the early Holocene at long pocket, northeast Queensland, Australia

摘要

Preliminary phytolith analysis of ephemeral lake fill sediment at Long Pocket, near Toomba, northeast Queensland, Australia, indicates that a C4-dominated grassland with a minor woody component has been present in the region since ca. 8000 cal yr B.P. Based on the modem distribution of C4 and C3 native grasses in Australia, this suggests that mean summer temperatures of at least 14 degreesC (ca. 10 degreesC cooler than present) were maintained since the early Holocene. This interpretation is comparable with previous studies, which together imply that the establishment of C4-dominated grasses in central and northeast Australia occurred between the last glacial maximum (most likely after ca. 16,000 C-14 yr B.P.) and ca. 7200 C-14 yr B.P. (ca. 8000 cal yr B.P.). Taxonomic composition of the grassland appears relatively consistent since the early Holocene at Long Pocket and includes phytoliths comparable with those from modem Arundinoideae, Panicoideae, and Chloridoideae. Rare non-grass phytoliths are also present. A gradual decrease in abundance of saddle phytolith forms (attributed to Chloridoideae grasses) from the base of the record at ca. 6500-7000 cal yr B.P. suggests decreasing aridity throughout the Holocene. This trend could reflect a locally drawn out effect of the end of the postglacial and period due to the well-drained basalt flow catchment maintaining a local and habitat for the Chloridoideae grasses. (C) 2004 University of Washington. All rights reserved.