The Arctic is viewed as most sensitive to climate warming and subject to a
general greening. Yet, summer weather conditions, which differ greatly among years, are
believed to have little direct effect on arctic plant productivity. The dominant view is that
between-year variation in aboveground plant biomass is small and poorly related to weather
conditions in the same year in the Arctic. Here, we test this view based on a 12-year
investigation of peak plant biomass among habitats, plant functional types, and species in
high-arctic Svalbard.
Our study revealed twofold variation (range 23–46 g/m2) in plant biomass between years,
this being strongly related to summer temperature (r ¼ 0.92). Importantly, we found strong
plant biomass–summer temperature relationships across habitats, plant functional types, and
species, and little evidence for a lagged effect of previous year’s biomass. Responses were of
similar orders of magnitude, indicating that summer weather conditions were the key driver of
plant productivity at all three levels of investigation.
We propose three key factors behind such tight relationships between summer temperature
and plant biomass in the same year. First, our methodological approach, a combination of
nondestructive shoot density estimates in small, permanent plots and destructive shoot mass
estimates outside these plots, allowed us to overcome the otherwise overwhelming small-scale
spatial heterogeneity in aboveground plant biomass typical for high-arctic tundra vegetation.
Second, the high-latitude location (788 N) makes the vegetation most susceptible to
temperature differences due to their influence on process rates. Third, Svalbard’s oceanic
nature dictates prevalent cloud cover, making summer temperature a good proxy for light
availability and thus an index of photosynthetic activity required for plants to produce
biomass.
The present study challenges the prevailing notion that relationships between summer
weather and vascular plant performance in the Arctic are weak and highly variable among
plant species. This has important implications for our understanding of how and at which
temporal scales future climate change will shape arctic plant productivity and, in turn, the
dynamics of other ecosystem components in the low-productivity, bottom-up regulated
ecosystems of the High Arctic.
climate change; high-arctic Spitsbergen; July temperature; long-term study; permanent
plots; plant community biomass; plant functional type; Svalbard; tundra ecosystem; vegetation.
