Eight years of trapping modern pollen gives a good possibility to study the relationship between presence of plants in the current vegetation and how they are represented in pollen samples. Knowledge of this relationship is important to be able to reconstruct past plant presence and abundance, as well as changes in past tree line positions.
For eight years Anne E. Bjune at the Bjerknes Centre and Uni Research has collected pollen deposited in small bottles placed at different elevations at Upsete and Finse. The study is now published in Vegetation History and Archaeobotany and shows that there are large variations in both pollen percentages and pollen accumulation rates (PAR) from year to year, but shows that the amounts of pollen from trees are decreasing with distance from the source vegetation. Pollen traps placed in the vegetation reflects a more local signal than traps placed in a small lake at Upsete. It is suggested that further pollen trapping is needed to get a solid long-term average.
A well-known fact in palaeoecology is that the relationship between vegetation cover and the amount of pollen that will be deposited in lake sediments or peat is not 1:1, but is dependent on factors such as pollen productivity, pollen transport, and sedimentary processes. As a result of these factors, the interpretation of the presence of species and of past vegetation on the basis of pollen assemblages is complex.
To gain a better knowledge and understanding of the processes affecting pollen deposition a network of pollen traps has been set out over a large area especially in northern Europe – including Norway. It is easy and simple, and does not require heavy and expensive equipment. The traps have proven to be efficient traps, and the results show that it is important to keep on trapping pollen within the same geographical region as a palaeoecological or palaeoclimatological study is being performed.
In this study, the modern pollen production of local forest and mountain vegetation has been monitored over eight years by using pollen traps situated along an elevational transect crossing the pine (Pinus sylvestris) and birch (Betula pubescens) elevational limits and continuing into the open alpine vegetation near Upsete, along the Bergen-Oslo railway.
Full reference:
Bjune, A.E. 2014. After 8 years of annual pollen trapping across tree line in western Norway – are the data still anomalous? Vegetation History and Archaeobotany, 23: 299-308.
http://link.springer.com/article/10.1007/s00334-013-0428-9