After 8 years of annual pollen trapping across the tree line in western Norway: are the data still anomalous?
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The modern pollen production of local sub-alpine and alpine vegetation has been monitored over 8 years by using pollen traps situated along an elevational transect crossing the Pinus sylvestris and Betula pubescens elevational limits and continuing into the mid- and high-alpine vegetation in western Norway. The aim of the study is to monitor annual variation in the pollen production and hence the representation of common taxa found at or near the tree-line. The results can be used to derive critical pollen values that can be used to infer the presence of these taxa in the past, and to reconstruct past changes in tree line positions. Nine modified Tauber pollen traps were critically positioned in the vegetation from 663 to 1,347 m a.s.l. Three sub-aquatic traps were located in a small lake at 800 m a.s.l. just above the present-day B. pubescens tree-line. The traps have been sampled from 2004 to 2012. The results display large variations in pollen percentages and pollen accumulation rates from year to year, as well as great differences between the traps placed in the vegetation and in the lake, suggesting that further pollen trapping is needed to get a solid long-term average. The vegetation traps follow the vegetation distribution better and, as expected, give a more local signal than the lake traps.
KeywordsMonitoring Pollen Pollen accumulation rates Pollen traps Concentrations Tree-line ecotone
This paper is dedicated to Hilary H. Birks on the occasion of her 70th birthday and as recognition of all her work, efforts and contributions to palaeoecology! I am very grateful to Hilary for developing the DOORMAT project together with me. I am also grateful to all the fieldwork assistants who have helped setting out and collecting the traps from 2004 until today, and to Trond Brattelid for designing and making the traps! I am also grateful to Vivian A. Felde for help in making the box plots used in this paper, to John Birks for help in the field, ideas and input along the way and also for helpful comments and suggestions improving this manuscript. And to Sheila Hicks for showing the importance of pollen monitoring and encouraging me to continue. I thank Pim van der Knaap and one anonymous reviewer for valuable comments helping to improve this manuscript. This work has been funded by Bergen Myrdyrkningsfond (in 2004) and from the Olaf Grolle Olsens legat til UiB med tilførsel av arv etter Miranda Bødtker (Olaf Grolle Olsen’s Legacy to the University of Bergen with the addition of the bequest of Miranda Bødtker) of the University of Bergen from 2004 to 2012. This is publication no. A441 from the Bjerknes Centre for Climate Research.
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