Correspondence between growth, branching and NDVI
Annual variation in C. tetragona shoot-length growth and
branching frequency positively related to fluctuations in
satellite-observed vegetation greenness over the research area. This
suggests that there is, at least to some degree, correspondence in
annual variation in community-level vascular plant biomass. This is in
line with , who found that annual growth of this species represents
annual above-ground tundra vegetation productivity at the local scale.
Moreover, the same climate variables, i.e. summer and winter
temperatures, as observed for the evergreen dwarf shrub C.
tetragona drove year-to-year satellite-observed variation in greenness.
The same climate parameters determine growth rates of the co-dominant
deciduous dwarf shrub B. nana in the research area in the
Blæsedalen valley on Disko Island . Such similarity in climatic drivers
of growth patterns between shrub species with contrasting life
strategies and NDVI was earlier observed over Arctic-alpine areas in
northwest North America . The lack of a link between branch mortality
and NDVI may be due to increased branching after winter warming events .
Satellite-observed vegetation productivity in the research area did not
correlate with early summer precipitation, but there were positive
relations with late winter and spring precipitation. Growth and
productivity of the shrub-dominated vegetation in the Blæsedalen valley
may thus be increasingly moisture-limited. It is, however, not in
decline, as observed for B. nana and S. glauca in a warmer
and drier area on the mainland of Greenland , approx. 270 km
south-southeast of Disko Island. While there was a slight increasing
trend in late summer NDVI, there was no trend in
NDVImax, which is in line with the widespread vegetation
stability observed over large parts of the Arctic .