The stability of the Pinus sylvestris treeline in the Cairngorms, Scotland over the last millennium

Abstract

Background: Changes in climate and recent land use have been related to treeline advances in many alpine and arctic regions. Short-term (<50 years) observations on treeline dynamics are available for many parts of the world; we present here millennium-scale data for a Pinus sylvestris treeline in the Cairngorms, Scotland, where a natural treeline at ca. 650 m is thought to exist at Creag Fhiaclach.Aim: We demonstrate that treeline position can be determined from an altitudinal sequence of quotients of treeline tree pollen and dwarf-shrub pollen and therefore past treeline dynamics can be deduced from quotients of the same pollen types determined from dated peat strata.Methods: Modern pollen was extracted from moss cushions and replicate peat cores were taken for pollen analysis at each of six elevations, from below the treeline at 606 m to about 100 m above the treeline at 758 m. Ratios of Pinus sylvestris to Calluna vulgaris pollen were calculated after complete pollen analysis of each of the cores and radiocarbon dating.Results: In the modern pollen most palynomorphs (96%) were either of Pinus or Calluna. The pollen analysis extracted and identified 26 palynomorphs from peat. The ratios of Pinus/(Pinus+Calluna) pollen in the sampled elevation belts suggested a relative stability of today's treeline for about the last 1000 years.Conclusions: The observed stability of treeline elevation is likely to have been caused by site conditions and land-use history (windiness, fire and grazing) that overruled a simple climate-elevation relationship. © 2013 Copyright 2013 Botanical Society of Scotland and Taylor & Francis.