Estimation of pollen deposition time-span in moss polsters with the aid of annual pollen accumulation values from pollen traps

Abstract

The length of the pollen deposition period covered by an individual moss sample is a matter of discussion. Here we evaluate (1) how many years of pollen deposition are contained in individual moss samples, (2) which factors (i.e. moss type, geographical location and thickness of sample) affect the pollen content, and (3) whether the time span of the pollen deposited in the moss is related to the pollen type. The pollen deposition period covered by 20 individual moss samples adjacent to pollen traps was estimated using the accumulation method. The investigated moss samples usually contain pollen from a period of two to five years. The length of the time period covered by the moss depends on the thickness of the moss cushion and, therefore, we recommend estimating the time period over which the moss has been growing by the increment method. Compared to pollen traps, mosses tend to accumulate more Poaceae and bisaccate grains (especially Picea) but less Cyperaceae pollen. Betula and pollen tetrads tend to be equally represented in mosses and traps. This study demonstrates that moss samples may contain sufficient pollen to be a reliable modern analogue for Quaternary peat and sediment samples but cannot be used to calculate pollen accumulation rates.

Keywords:

• pollen deposition period
• modern pollen deposition
• northern Fennoscandia
• pollen trap
• moss sample
• bisaccates
• pollen tetrads

Acknowledgements

The authors express their profound gratitude to Satu Räsänen for data contribution. This study is a contribution to the ESF EUROCLIMATE programme project DECVEG (Dynamic European Climate–Vegetation Impacts and Interactions). Financial support to OVL came from the Academy of Finland, the Ella and Georg Ehrnrooth Foundation, Oulun läänin talousseuran maataloussäätiö, OY Luonnontieteenllinen tiedekuntan työskentelyapurahat, ThuleEdu apurahat and Oulun Yliopiston Apteekin Rahasto. Much of the pollen trap data was collected during the course of the three EU projects FOREST (ENV4-CT95-0063), PINE (EVK2-CT-2002-00136) and Millennium (FP 6: SUSTDEV-20043.1.4.1. Contract No. 017008).