Natural treeless areas in the Krkonoše mountains: insights from two decades of pollen monitoring

Abstract Understanding past landscapes through sedimentary pollen records relies on precise knowledge of modern pollen–vegetation relationships. In mountain environments, however, altitudinal gradients, geomorphological complexity and prevailing air currents affect pollen deposition and make reconstructions of vegetation dynamics harder. This study investigates whether pollen assemblages can effectively differentiate between open habitats above and below the timberline (forest limit) in the Krkonoše mountains, or whether the effects of strong atmospheric circulation outweigh the diverging characteristics of these sites. We used 23 years of annual pollen trap data and vegetation surveys from 19 open sites distributed across an altitudinal gradient. Pollen deposition patterns were analysed using hierarchical clustering, ordination and dissimilarity analyses. Pollen assemblages from above and below the forest limit were statistically distinct, with differences driven mainly by quantitative variation rather than qualitative changes in composition of pollen types. The primary gradient was expressed by the proportion of long-distance transported pollen types, which dominated alpine and subalpine areas. Arboreal taxa formed a major component of background pollen, accompanied by low but consistent levels of wind pollinated herbs commonly interpreted as indicators of human impact. Other herbaceous taxa generally reflected their local presence, except for Vaccinium -t., which was under-represented. For sites above and below the upper forest limit, we characterised pollen composition in terms of percentages and accumulation rates, and established presence/absence thresholds for Pinus , Picea , Fagus , Abies , Betula , Corylus , Alnus , Quercus , Cerealia and Urtica . These findings improve our understanding of the role of long-distance pollen transport in high mountain treeless areas and provide baseline data for interpreting fossil pollen records from high elevation sites in Central Europe.