Response of Pinus sibirica and Larix sibirica to climate change in southern Siberian alpine forest-tundra ecotone

A warming climate provides competitive advantages to Siberian pine (Pinus sibirica Du Tour) in areas with sufficient precipitation. The warmer temperatures observed in central Siberia over the past three decades appear to have had a noticeable effect on growth of Siberian pine and larch (Larix sibirica Ledeb.) in the south Siberian Mountain forest-tundra ecotone. Larch is more tolerant of harsh climates and exhibits an arboreal growth form, whereas Siberian pine is in krummholz form. Larch also has an advantage at the upper tree limit and in areas with low precipitation. Since the mid-1980s there have been measurable increases in growth increments, stand densification, regeneration propagation into the alpine tundra and transformation of krummholz into arboreal forms. Warming winter temperatures have been sufficient for increased survival of regeneration. Regeneration responded to temperature increase of 1°C by migration to areas 10-40 m higher in elevation. Regeneration has propagated into the alpine tundra at the rate of ~1.0-2.0 m year-1. Siberian pine and larch regeneration surpassed their upper historical limit by 10-80 m in elevation. While increased tree growth and migration into alpine tundra areas affect the regional carbon balance, it will also decrease albedo, which may increase warming at the regional level.