Russian Arctic warming and ‘greening’ are closely tracked by tundra shrub willows

Abstract

Growth in arctic vegetation is generally expected to increase under a warming climate, particularly among deciduous shrubs. We analyzed annual ring growth for an abundant and nearly circumpolar erect willow (Salix lanata L.) from the coastal zone of the northwest Russian Arctic (Nenets Autonomous Okrug). The resulting chronology is strongly related to summer temperature for the period 1942-2005. Remarkably high correlations occur at long distances (41600 km) across the tundra and taiga zones of West Siberia and Eastern Europe. We also found a clear relationship with photosynthetic activity for upland vegetation at a regional scale for the period 1981-2005, confirming a parallel 'greening' trend reported for similarly warming North American portions of the tundra biome. The standardized growth curve suggests a significant increase in shrub willow growth over the last six decades. These findings are in line with field and remote sensing studies that have assigned a strong shrub component to the reported greening signal since the early 1980s. Furthermore, the growth trend agrees with qualitative observations by nomadic Nenets reindeer herders of recent increases in willow size in the region. The quality of the chronology as a climate proxy is exceptional. Given its wide geographic distribution and the ready preservation of wood in permafrost, S. lanata L. has great potential for extended temperature reconstructions in remote areas across the Arctic.

Changes in Tree Growth, Biomass and Vegetation Over a 13-Year Period in the Swedish Sub-Arctic

“…There were significant transitions in the cover of vegetation types; the cover of ''Meadow with low herbs M(lh)'' and ''Birch forest of heath type with mosses BFo(m)'' increased significantly, while the cover of ''Moderate snowbed vegetation SB(mod)'' decreased significantly. Our study concurs with the results of other studies which suggest that there has been a general increase in cover and biomass of trees and shrubs in sub-Arctic and Arctic areas (e.g., Sturm et al 2001;Tape et al 2006;Danby and Hik 2007;Tømmervik et al 2009;Forbes et al 2010;Hallinger et al 2010;Van Bogaert et al 2011;Rundqvist et al 2011, this issue). Tree biomass increased on average 1.5% per year from 3.5 t ha -1 in 1997 to 4.2 t ha -1 in 2010.…”

“…However, it could also be suspected that heaths dominated by dwarf shrubs may be converted to heaths dominated by graminoids or larger shrubs, as experiments suggest that shrubs and graminoids may increase following warming (e.g., Walker et al 2006). Indeed, comparison of old and new photographs has revealed an expansion of large shrubs throughout the Arctic (Sturm et al 2001;Tape et al 2006;Forbes et al 2010).…”

Longitudinal changes of clavarioid funga (Basidiomycota) diversity in the tundra zone of Eurasia

“…″Greening″ of many sectors of the Arctic has been noted, and it is reflected in significant changes of the biodiversity level of the ecosystems situated in the cryolithozone (Shiyatov and Mazepa 2007; Forbes et al 2010). The biota is restructured, which is indicated by ″forest″ boreal species that were not present in the tundra zone before or those that can be found solely in the intro-zonal bottomland biotopes.…”

Long-Term Effects of Grazing and Global Warming on the Composition and Carrying Capacity of Graminoid Marshes for Moulting Geese in East Greenland

“…A variety of tundra manipulative experiments and observations suggest vegetation productivity is increasing with rising temperatures (e.g. Hollister et al 2005;Walker et al 2006;Hudson and Henry 2009;Bhatt et al 2010;Forbes et al 2010). Even though the ecological responses to climate change may be complex and non-linear (Post et al 2009), it may be expected that increased vegetation productivity will provide herbivores with richer food supplies, resulting in increased population densities.…”