Molecular-isotopic stratigraphy of long-chain n-alkanes in Lake Baikal Holocene and glacial age sediments

Spatial and temporal variations of C3/C4 relative abundance in global terrestrial ecosystem since the Last Glacial and its possible driving mechanisms

“…When environmental temperature is below the "threshold value", especially during the growing seasons, C 4 plants will be absent in local ecosystem, such as the reconstructed paleovegetation in the high-latitudes since the Last Glacial [53,56,59] and that during the Last Glacial on the western edge of the CLP [35]. When environmental temperature is higher than the "threshold value", extremely arid, especially during the growing seasons, could also be adverse to the growth of C 4 plants, such as the modern vegetation in the Mediterranean climate zone (Pasadena in California and Seville in Spain [5] in Figure 1).…”

“…However, sediments from Lake Baikal (Figure 1), Russia provides excellent materials for the reconstruction of paleo-C 3 /C 4 changes. Although the total organic   13 C values of the lake sediment are more positive during the Last Glacial than in the Holocene, n-alkanes of leaf waxes derived from terrestrial plants show remarkably uniform   13 C values that consistent with those from modern C 3 -plants throughout the entire core spanning the last 20 ka, indicating the predominance of C 3 vegetation in this highlatitude region occurred not only during the Last Glacial but also during the Holocene [53]. Although the loess region in the northwestern Europe is close to the mid-latitudes, its Figure 2 Comparison of the representative C 3 /C 4 records since the Last Glacial from the low-latitudes (a) [13], mid-latitudes (b) [19], high-latitudes (c) [53] and records of atmospheric CO 2 concentration (d) [54] and global mean temperature since the Last Glacial (e) [55].…”

“…All of these indicate that C 4 plants never become significant components of the local biomass in the high-latitudes during both the Last Glacial and Holocene.   13 C record from Lake Baikal [53] is selected as a representative of C 3 /C 4 variation since the Last Glacial in high-latitudes (Figure 2(c)).…”

Late Quaternary environmental and climatic changes in central Europe as inferred from the composition of organic matter in annually laminated maar lake sediments

“…This shift in the vegeta- tion is also obvious from the distribution of lipid biomarkers. As illustrated in Figures 8b and 8c, an increase in the abundance of n-C 27 alkane relative to n-C 31 in samples from the Lateglacial indicates a change toward dominant forest vegetation in the catchment of MFM [Brincat et al, 2000;Fischer, 2004]. Increasing amounts of low reflecting huminite/vitrinite particles and terrigenous liptinite have been found in samples and kerogen concentrates from the Lateglacial compared to Pleniglacial (Figures 3 and 7) which points to a larger amount of relatively fresh plant material from shrubs and/ or trees close to the investigated sites and thus corroborates the above findings.…”

“…This confirms a major contribution of herbaceous plants to the sedimentary OM during the Pleniglacial [cf. Brincat et al, 2000].…”