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. While of higher plant origin, a specific source assignment ofsedimentary leaf wax n-alkanes remains difficult. In addition, it isunknown how fast a changing catchment vegetation would be reflected insedimentary leaf wax archives. In particular, for a quantitativeinterpretation of n-alkane C and H isotope ratios in terms ofpaleohydrological and paleoecological changes, a better understanding oftransfer times and dominant sedimentary sources of leaf wax n-alkanes isrequired. In this study we tested to what extent compositional changes in leaf waxn-alkanes can be linked to known vegetation changes by comparison withhigh-resolution palynological data from the same archive. We analyzed leafwax n-alkane concentrations and distributions in decadal resolution from asedimentary record from Trzechowskie paleolake (TRZ, northern Poland),covering the Late Glacial to early Holocene (13 360–9940 yr BP). Asan additional source indicator of targeted n-alkanes, compound-specific carbonisotopic data have been generated in lower time resolution. The resultsindicated rapid responses of n-alkane distribution patterns coinciding withmajor climatic and paleoecological transitions. We found a shift towardshigher average chain length (ACL) values at the Allerød–Younger Dryas (YD) transition between 12 680 and 12 600 yr BP, coevaled with a decreasingcontribution of arboreal pollen (mainly Pinus and Betula) and a subsequently higherabundance of pollen derived from herbaceous plants (Poaceae, Cyperaceae,Artemisia), shrubs, and dwarf shrubs (Juniperus and Salix). The termination of the YD wascharacterized by a successive increase in n-alkane concentrations coincidingwith a sharp decrease in ACL values between 11 580 and 11 490 yr BP,reflecting the expansion of woodland vegetation at the YD–Holocenetransition. A gradual reversal to longer chain lengths after 11 200 yr BP,together with decreasing n-alkane concentrations, most likely reflects theearly Holocene vegetation succession with a decline of Betula. These results show that n-alkane distributions reflect vegetation changesand that a fast (i.e., subdecadal) signal transfer occurred. However, ourdata also indicate that a standard interpretation of directional changesin biomarker ratios remains difficult. Instead, responses such as changes inACL need to be discussed in the context of other proxy data. In addition, wefind that organic geochemical data integrate different ecologicalinformation compared to pollen, since some gymnosperm genera, such asPinus, produce only a very low amount of n-alkanes and for this reason theircontribution may be largely absent from biomarker records. Our resultsdemonstrate that a combination of palynological and n-alkane data can be usedto infer the major sedimentary leaf wax sources and constrain leaf waxtransport times from the plant source to the sedimentary sink and thus pavethe way towards quantitative interpretation of compound-specific hydrogenisotope ratios for paleohydrological reconstructions.

climate of the past

Leaf wax &amp;lt;i&amp;gt;n&amp;lt;/i&amp;gt;-alkane distributions record ecological changes during the Younger Dryas at Trzechowskie paleolake (northern Poland) without temporal delay