Data from: The role of migration in the change of Northern Hemisphere vegetation for the past 50,000 years

Our primary aim was to assess how dispersal limitation affected forest
changes in the Northern Hemisphere during the last glacial cycle, and
especially after the last deglaciation. We used the LPJ-GM 2.0 dynamic
global vegetation model to simulate the vegetation dynamics of the
Northern Hemisphere over the past 50,000 years. We compared two dispersal
modes by allowing establishment as soon as suitable environmental
conditions were realised (free dispersal), or by additionally constraining
establishment based on potential migration speed and maturation time
(dispersal limitation). For both dispersal modes, we inferred
(mega-)biomes and calculated the fraction of forest cover, earliest
post-glacial forest establishment, and the difference between dispersal
modes (dispersal lag). To evaluate our results, we compared simulated tree
cover with pollen-based reconstructions of European Holocene vegetation
and of North American vegetation since the Last Glacial Maximum. We
simulated multi-millennial dispersal lags in post-glacial establishment of
temperate forests in Europe, boreal forests in Central Siberia, and
scattered forest areas close to mountain chains (Rocky Mountains and north
of Himalaya). Overall, the simulation with limited dispersal had lower
forest extents compared to the free-dispersal simulation, especially after
the Last Glacial Maximum, with greater mismatches following intervals of
rapid warming, notably the onsets of GI-1 and the Holocene. Comparisons
with pollen-based reconstructions showed that the simulation with limited
dispersal better captured both the expansion of European temperate trees
and the distribution of broadleaved and needleleaved trees in North
America during the early Holocene. The lag in response of forests to rapid
climate change has implications for past ecosystems and projections of
future ecosystem services.