Spatial Heterogeneity of the Temporal Dynamics of Arctic Tundra Vegetation

Arctic tundra vegetation has largely been greening in recent decades, resulting in major changes to terrestrial ecosystems, with implications for surface energy balance, permafrost, carbon and water cycling, herbivore populations, and human land use. While general greening trends have been well-studied, more specific vegetation-temperature dynamics are spatially and temporally heterogeneous and currently not well understood. This study uses Normalized Difference Vegetation Index (NDVI) and Summer Warmth Index (SWI) data to investigate patterns of arctic tundra vegetation and temperature dynamics over North American and Eurasian continents and by Arctic bioclimate subzones (essentially latitudinal-based). Relative vegetation increases in northern subzones were muted compared to temperature increases, whereas relative vegetation increases in southern subzones were consistent with, or greater than, relative temperature changes. Detrended, interannual NDVI variances were greatest in middle and southern subzones, whereas interannual SWI variances were greatest in southern subzones. Annual SWI and NDVI relationships were strongest in midlatitude subzones. Plain Language Summary Arctic tundra vegetation has generally been increasing in biomass and productivity in recent decades. This paper uses 34years of satellite data to investigate more thoroughly the relationships between temperature and vegetation in the tundra over time and space. We found that in the southern part of the tundra biome, the vegetation (as indicated by the satellite data) increased at the same rate as, or faster than, temperature, whereas northern tundra vegetation increased more slowly than temperature. The variation in tundra vegetation from year to year was greatest in the middle and southern parts of the Arctic tundra biome, whereas temperature variation from year to year increased from north to south. On an annual basis, the strongest relationships between temperature and vegetation occurred in the midlatitudes of the tundra biome.