Signals of tree volume and temperature in a high-resolution record of pollen accumulation rates in northern Finland

Abstract

Pollen accumulation rates (PARs) provide a potential proxy for quantitative tree volume (m3 ha 1) reconstruction with reliable absolute pollen productivity estimates (APPEs). We obtained APPEs for pine, spruce and birch at their range limits in northern Finland under two temperature periods ('warm' and 'cold') based on long-term pollen trap and tree volume records within a 14-km radius of each trap. APPEs (mean SE; 108 grains m 3 a 1) tend to be higher for the 'warm' periods (pine 123.8 24.4, birch 528.0 398.4, spruce 434.3 113.7) compared with the 'cold' periods (pine 95.5 37.3, birch 317.3 282.6, spruce 119.6 37.6), although the difference is only significant for spruce. Using an independent temperature record and the APPEs obtained, we reconstruct a low-frequency record of pine volume changes over the last 1000 years at Palomaa mire, where a high-resolution record of Pinus PARs is available. Five phases are distinguished in the reconstruction: moderate pine volume, AD 1080-1170; high volume, AD 1170-1340; low volume, AD 1340-1630; very low volume, AD 1630-1810; and rising pine volume, AD 1810- 1950. These phases do not coincide with periods of high or low June-July-August temperatures, and thus appear to reflect regional variations in tree volume, while high-frequency changes within each time-period block show variations in PARs in response to temperature