Plant succession on glacial moraines in the Arctic Brooks Range 2017-2018.

Widespread glacial retreat is now occurring in many Arctic mountain ranges, yet little is known about primary succession following deglaciation in these settings. Newly created habitats could provide refugia for flora and fauna whose ranges are threatened elsewhere by rapid warming. To assess vegetation responses to glacial retreat in an arctic-alpine setting, we first describe plant-community development on two recently deglaciated moraines in the Brooks Range. We then compare these recent communities with communities developed along a moraine chronosequence that spans more than 125,000 years and ranges in altitude between 800 and 1700 meters above sea level. Results show: (1) Within 22-36 years following deglaciation, primary succession begins with the assembly of small communities of 8-13 vascular and non-vascular plant species. (2) Species turnover is low with many pioneer taxa, particularly lichens, persisting at the oldest sites and across all altitudes. (3) Overall, succession is directional and slow, with species richness increasing for up to 25,000 years, and percent vegetation cover reaching 100% on the oldest glacial deposits. This is the first vegetation study on primary succession in the high, central Brooks Range, and it supplies a previously missing alpine element within a vegetation transect across northern Alaska’s bioclimatic gradient.