Past changes in the vegetation density of the Chinese Loess Plateau revealed by variations in the size of Artemisia pollen grains

Abstract

We reconstructed paleovegetation changes on the Chinese Loess Plateau by applying concepts in palynology and pollination biology to the statistical analysis of the size of Artemisia pollen grains from 26 surface samples, four loess paleosoil profiles, and extant Artemisia species. We found that the size of Artemisia pollen grains varied in different plant communities, and was positively correlated with local habitat quality and population density of local Artemisia communities. The Mean Artemisia Pollen Size (MAPS), which has changed significantly since Marine Isotope Stage 3 (MIS3), reflects integrated ecological changes, including compositional changes and shifts in population density. During MIS3, the high MAPS values indicate that high population densities of Artemisia grassland covered the northern and southern Loess Plateau. During the Last Glacial Maximum (LGM), with much less favorable growing conditions, a low MAPS value indicates that lower-density short grass steppe covered the Loess Plateau at that time. Overall, the results demonstrate that a statistical analysis of the size of fossil pollen grains at genus level can provide useful ecological information, e.g., on changes in the composition and population density of local communities, and thus can lead to a better understanding of the evolution of terrestrial ecosystems.