Vegetation change in the northwestern Putorana Plateau (North Siberia, Russia) during the Late Holocene inferred from pollen spectra
Northern Siberia is well suited as a source for different climatic archives, due to its isolation and therefore minor, anthropogenic influences. It is common that even small global temperature changes could cause the highest impacts in sensitive arctic ecosystems. Changes like the shifting of treeline, the ratio of tree and shrub vegetation compared to grasses and herbs, as well as the presence of certain species in the area, provide important information regarding environmental changes of the past. In this study a pollen data set was generated and statistically analyzed. The results from palynological and statistical analyses were used to generate five pollen assemblage zones (PAZ). Each PAZ has a different pollen composition, pointing out various changes of the local vegetation around the lake during a specific period. The results of the principal component analysis confirm these indications and allow taking conclusions on changes in temperature and the local ecosystem. The oldest part (PAZ 1) covers a period from 420 BC until 812 AD and characterizes the Roman Warm Period and the following epoch of the Dark Ages. The composition of this zone is dominated by tree and shrub pollen with a decreasing trend at the end of the period, which is a result of colder conditions. The second PAZ reaches from 868 AD – 1484 AD, describes the Medieval Warm Period (MWP). Trees like Larix and Alnus are indicator plants for warmer conditions. They show an increase around 1200 AD, which is known as the warmest stage during the MWP. From 1500 AD to 1624 AD the vegetation signal showed a significant decrease in pollen arrangement, which is visible in a decrease of tree pollen grains, except from cold tolerant Betula, assigned to the Little Ice Age (LIA). The following fourth zone describes the transition period after the Little Ice Age until 1953 AD and the beginning of modern Global Warming. The PAZ 4 has the lowest proportion of total tree and shrub pollen grains in relation to herbaceous plants. After 1978 AD a signifi-cant increase of tree species and a decrease of herbaceous plants indicate higher temperatures and therefore the period of modern Global Warming. Overall, the single proxy approach has generated good results. The data shows a continuing cooling trend with more or less stable stages of warm and cold events, over the last 2500 years. Since 1978 AD the mean cooling is interrupted and the composition of the vegetation reached a level that indicates conditions like in the period of the Roman Climatic Optimum.
Helmholtz Research Programs > PACES II (2014-2020) > TOPIC 3: The earth system from a polar perspective > WP 3.1: Circumpolar climate variability and global teleconnections at seasonal to orbital time scales