Sources of carbon isotope variation in kangaroo bone collagen and tooth enamel

详细信息	查看全文 | 推荐本文 |

• 作者：Brett P. Murphy ; David M.J.S. Bowman ; Michael K. Gagan
• 关键词：intertidal ; saltmarsh ; mangrove ; foraminifera ; taphonomy ; infauna ; fossil assemblage
• 刊名：Geochimica et Cosmochimica Acta
• 出版年：2007
• 期刊代码：27_00167037
• 类别：ear
• 出版时间：1 August 2007
• 卷：71
• 期：15
• 页码：3847-3858
• 文件大小：626 K

摘要

The stable carbon isotopic composition (expressed as δ¹³C) of herbivore remains is commonly used to reconstruct past changes in the relative abundance of C₄ versus C₃ grass biomass (C₄ relative abundance). However, the strength of the relationship between herbivore δ¹³C and C₄ relative abundance in extant ecosystems has not been thoroughly examined. We determined sources of variation in δ¹³C of bone collagen and tooth enamel of kangaroos (Macropus spp.) collected throughout Australia by measuring δ¹³C of bone collagen (779 individuals) and tooth enamel (694 individuals). An index of seasonal water availability, i.e. the distribution of rainfall in the C₄ versus C₃ growing seasons, was used as a proxy for C₄ relative abundance, and this variable explained a large proportion of the variation in both collagen δ¹³C (68%) and enamel δ¹³C (68%). These figures increased to 78%and 77%, respectively, when differences between kangaroo species were accounted for. Vegetation characteristics, such as woodiness and the presence of an open forest canopy, had no effect on collagen or enamel δ¹³C. While there was no relationship between collagen δ¹³C and kangaroo age at death, tooth enamel produced later in life, following weaning, was enriched in ¹³C by 3.5‰ relative to enamel produced prior to weaning. From the observed relationships between seasonal water availability and collagen and enamel δ¹³C, enrichment factors (ε^*) for collagen-diet and enamel-diet (post-weaning) were estimated to be 5.2‰ ± 0.5 (95%CI) and 11.7‰ ± 0.6 (95%CI), respectively. The findings of this study confirm that at a continental scale, collagen and enamel δ¹³C of a group of large herbivores closely reflect C₄ relative abundance. This validates a fundamental assumption underpinning the use of isotopic analysis of herbivore remains to reconstruct changes in C₄ relative abundance.