Pinus and Betula pollen accumulation rates from the northern boreal forest as a record of interannual variation in July temperature

Abstract

AbstractFossil Pinus and Betula pollen accumulation rates (PARs, grains cm−2 a−1) from a peat profile in Nellim, northern Finland, were compared to a 20‐year annually resolved record of monitored pollen deposition data of both taxa from 2.5 km away, in order to determine the boundaries in the fossil pollen record. The smoothing inherent in the fossil PAR data is about 5 years compared with the annually monitored PARs but, while year‐to‐year variation in PARs is lost, the overall trend is retained. The fossil PARs were then calibrated with the appropriately smoothed temperature record for northern Finland. Betula pollen accumulation rates are much lower in the fossil record compared to the monitored ones. The correlation between fossil Betula PARs and July mean temperatures is much higher than the correlation between fossil Pinus PARs and temperature, probably because the subspecies Betula pubescens ssp. pubescens is at its northern limit in the area. The temperature signal in this dataset was disturbed during the period when the forests in the area were heavily cut and when regenerating trees were reaching maturity. Copyright © 2009 John Wiley & Sons, Ltd.