INTEGRATION OF PLANT LIPID BIOMARKERS BY STREAMS IN THE AREGUNI MOUNTAINS, ARMENIAN HIGHLANDS

Sedimentary records of lipid biomarkers, such as leaf wax n-alkanes, are not only influenced by ecosystem turnover and physiological changes in plants, they are also influenced by earth surface processes integrating these signals. We collected both soil and stream sediments between 1500 and 2500 m.a.s.l. from the Areguni Mountains, a subrange of the Lesser Caucasus Mountain system in the Armenian Highlands. We measured a shift in soil average chain length (ACL) values associated with the transition from deciduous forest (mean ACL=29.2) to alpine grasses (mean ACL=30.5) between 2200 and 2100 m.a.s.l. Soils from other mountains in the Armenian Highlands without a treeline, Mt. Hatis and Mt. Ara, do not show ACL shifts over similar elevation ranges, demonstrating in the Areguni Mountains this ACL shift is driven by ecosystem turnover rather than plant physiological changes. Stream sediments above treeline have similar ACL values to grassy soils, however, immediately below treeline stream samples have ACL values which match those of the deciduous soils without an area of transitional values between the two. This suggest that despite comprising a significant amount of the watershed, the biomarkers from alpine grasses are not quantitatively integrated into the stream sediment. These results suggest that alpine grasses may be under-represented in sedimentary biomarker records in this area, and caution should be taken when using biomarkers to attempt quantitative environmental reconstruction in similar depositional environments.