Decadal high-resolution multi-proxy analysis to reconstruct natural and human-induced environmental changes over the last 1350 cal. yr BP in the Altai Tavan Bogd National Park, western Mongolia

Abstract

The ‘Altai Tavan Bogd’ National Park in the north-western part of the Mongolian Altai, Central Asia, is located in a forest-steppe ecosystem. It occurs under the influence of extreme continental and montane climate and is sensitive to natural and anthropogenic impacts. High-resolution (<20 years per sample) multi-proxy data of pollen, non-pollen palynomorphs (NPPs), macro-charcoal, diatoms, and XRF scanning from radiocarbon-dated lacustrine sediments reveal various environmental changes and the impact of different settlement periods for the late-Holocene. From 1350 to 820 cal. yr BP (AD 600–1130), the distribution of grass steppe indicates a climate similar to present-day conditions. Rapid improvements of climatic conditions (e.g. increased rainfall events) possibly favored a recovery of forest-steppe encouraging nomadic movements into alpine areas. In the period from 820 to 400 cal. yr BP (AD 1130–1550), the decline of forested areas suggests an increasingly drier and possibly colder climate. Some political shifts during the Mongol Empire (744–582 cal. yr BP; AD 1206–1368) favored variations in nomadic grazing habits. After 400 cal. yr BP (AD 1550), moisture and temperature increased slightly, and from ca. 40 cal. yr BP (AD 1910) to present, annual temperature continued to increase more markedly favoring an additional water availability due to permafrost degradation. Diatom data suggest several intervals of increased water availability in all periods which might have caused erosion due to heavier rainfall events or increased snow melt. Immediately after most of these high-water intervals, NPP data reveal periods of increased grazing activities in the area.