Pollen representation in surface samples of the Juniperus, Picea and Juglans forest belts of Kyrgyzstan, central Asia

Abstract

Surface pollen deposition at five sites (Kichikol, Karakol, Nishneye and Verkhneye Ozero, and Bakaly) in four different forest types ( Juniperus , Picea, Juglans and mixed forests) in Kyrgyzstan have been investigated to assess the relationship between modern vegetation and pollen composition in order to calibrate the pollen representation. Vegetation surveys with an estimation of the tree-crown cover (%) were made in 10 m × 10 m plots to relate the vegetation to surface pollen of moss polsters. Correlation calculations show a close relationship between vegetation (tree-crown cover) and pollen for the Juniperus site (eg, r2 = 0.76 between crown cover and arboreal pollen, AP) and the Picea site ( r2 = 0.85), whereas the linkage is weaker at the Juglans site ( r 2 = 0.35) and in mixed forests ( r2 = 0.32). The results of the surface samples of moss polsters are compared and discussed with surface samples of lake sediments that were taken at the same locations. We use vegetational maps from around the lakes to discuss the link between vegetation and pollen at extra-local scales (800 m around the sites). These comparisons show that AP underestimates the effective tree cover around all sites, with in extreme cases densely forested areas corresponding to AP values as low as <60; 30%. We explain this finding by the prevalent background pollen load that derives from the dry lowland and slope steppes ( Artemisia, Chenopodiaceae, Poaceae). Our investigation may improve the reconstruction of Quaternary vegetation and climate history of these forest belts in Kyrgyzstan (Central Asia) on the basis of fossil pollen assemblages from mire and lake sediments. It provides new insights into the pollen reflection of forest isles (eg, on humid slopes or mountain tops) that are surrounded by continental steppes; a vegetational situation that may be used as an analogue for the conditions during the full glacial in Eurasia and Northern America.