Younger Dryas Larix in eastern Siberia: A migrant or survivor?

Knowledge of past forest change serves for a better understanding of the climate system, carbon cycle and genetic diversity, and can inform current predictions and conservation strategies (Prentice et al., 1992; Tarasov et al., 2007; Petit et al., 2008). Botanical records from high-latitude regions of Europe and North America indicate that boreal forests “became established during the Holocene interglacial (the past 11.6 ka) as a result of population invasion from southern glacial refugia and local expansion of small tree populations that survived the Last Glacial Maximum interval (LGM: ~25-17 ka) in cryptic refugia” (Petit et al., 2008). An extensive dataset of radiocarbon-dated macrofossils from northern Asia provides evidence that boreal trees advanced close to the current arctic coastline between 9 and 7 ka (MacDonald et al., 2000). Due to a lack of wood macrofossils older than 10 ka from the ~2000×2500 km2 region of eastern Siberia between 108° and 145°E (Fig. 1a), there is no agreement on whether trees could persist there during the coldest phases of the last glacial period (Johnsen et al., 2001), including the Younger Dryas (YD: ~12.7-11.6 ka) and the LGM (Brubaker et al., 2005; Tarasov et al., 2007; Binney et al., 2009 and references therein).