Understanding the climate impacts on decadal vegetation change in northern Alaska1

The Arctic is experiencing rapid climate change. This research documents changes to tundra vegetation near Atqasuk and Utqiagvik, Alaska. At each location, 30 plots were sampled annually from 2010 to 2019 using a point frame. For every encounter, we recorded the height and classified it into eight groupings (deciduous shrubs, evergreen shrubs, forbs, graminoids, bryophytes, lichens, litter, and standing dead vegetation); for vascular plants we also identified the species. We found an increase in plant stature and cover over time, consistent with regional warming. Graminoid cover and height increased at both sites, with a 5-fold increase in cover in Atqasuk. At Atqasuk, the cover and height of shrubs and forbs increased. Species diversity decreased at both the sites. Year was generally the strongest predictor of vegetation change, suggesting a cumulative change over time; however, soil moisture and soil temperature were also predictors of vegetation change. We anticipate that plants in the region will continue to grow taller as the region warms, resulting in greater plant cover, especially of graminoids and shrubs. The increase in plant cover and accumulation of litter may negatively impact non- vascular plants. Continued changes in community structure will impact energy balance and carbon cycling and may have regional and global consequences.

Automated summary

The Arctic is undergoing rapid climate change, as evidenced by changes in tundra vegetation in Atqasuk and Utqiagvik, Alaska. This study reveals that plant height and cover are increasing over time, in line with regional warming. However, species diversity is decreasing.