Re-defining the natural range of Scots Pine (Pinus sylvestris L.): a newly discovered microrefugium in western Ireland

Aim Native Pinus sylvestris became extirpated in Ireland, during a massive population decline experienced throughout Europe. It was extensively replanted in Ireland during the 18th century from Scottish stock. We test the hypothesis that P. sylvestris in Rockforest Co. Clare did not become extirpated during the P. sylvestris decline, and persisted to present day independent of 18th century plantations. Location Rockforest, Co. Clare in Ireland. Methods Fossil pollen was counted from a terrestrial core. Radiocarbon dates and age-depth modelling was used to ascertain the core chronology. Loss-onignition was carried out to investigate sediment accumulation history. Pollen was also counted from moss polster pollen traps to explore the deposition of P. sylvestris pollen in the surrounding landscape. Historical maps were consulted to investigate the longevity of other nearby P. sylvestris populations. Results A continuous record of P. sylvestris is reported. The core extends through the last two millennia, and reports a clear decline of P. sylvestris at c.1550 cal bp. The P. sylvestris pollen curve recovers quickly after the decline event and persists at high levels up until the present day. The loss-on-ignition data reveal a stable accumulation of sediment with no major erosion events. The moss polster pollen traps show the core site is a suitable location for collecting pollen from the Rockforest P. sylvestris population. Historical maps demonstrate that none of the other nearby P. sylvestris populations extends further back than plantations in the early 18th century. Main conclusions The population of P. sylvestris in Rockforest Co. Clare survived the regional P. sylvestris decline, recovered and persisted right up to the present day, independent of introduction by human agency. Hence, we identify this microrefugium population of native Irish stock outside of the current understanding of the native range for this tree species.