δ13Corg and n-alkane evidence for changing wetland conditions during a stable mid-late Holocene climate in the central Tibetan Plateau

This study has examined bulk and compound specific organic carbon isotopes (δ13Corg) and lipid n-alkanes of modern plants and a wetland sediment sequence from the central Tibetan Plateau and explores the usefulness of these two methods for palaeoenvironmental reconstructions. Results show that a combination of δ13Corg values and n-alkane indices can help differentiate organic matter from C3 terrestrial plant, C4 terrestrial plant and submerged macrophytes, the three main sources of organic matter in the study area. The analyses of total organic carbon, δ13Corg values and n-alkane indices for the sediment sequence imply that a wetland habitat was established about 8000 years ago, and the wetland conditions were largely stable with dominantly C3 wetland herbs covering the wetland. However, small fluctuations in the dominant organic matter supply between vascular and aquatic plants are revealed, suggesting short duration changes in the extent of open water area within the wetland or variations in the productivity of submerged macrophytes and aquatic plants within the wetland ecosystem, which reflects variations in the strength of precipitation and evaporation.