Vegetation Changes in the Nordic Mountain Birch Forest: the Influence of Grazing and Climate Change

Abstract

The study focuses on vegetation changes in the Nordic mountain birch forest in northern Norway, covering a period of more than 40 yr. The study area comprises the municipalities of Kautokeino and Karasjok on Finnmarkskvidda; it is predominantly covered by lichen and dwarf shrub vegetation. Sizes of various vegetation classes were estimated by the use of remote-sensing techniques and ground surveys. A significant change in vegetation cover during the study period was registered in the whole study area. Vegetation types dominated by bilberry (Vaccinium myrtillus), wavy hair-grass (Deschampsia fleuxuosa), the dwarf cornel (Cornus suecica), and mosses have tripled in abundance compared to 40 yr ago. In contrast, lichen-dominated heaths and woodland (forests), preferred by the reindeer stocks intensively utilizing these areas of Finnmarksvidda, have decreased by approximately 80% in abundance during the same period. Correspondingly, there has been a significant increase in the extent of birch forests especially in Kautokeino (90% increase). The reason for the steep decline in lichen-dominated areas appears to be a direct consequence of the intensive grazing by the increasing reindeer population in the period 1961-1987, but climate change (increased precipitation), caterpillar attacks, and long-transported air pollution (e.g., nitrogen) may also have accentuated the increase of forests and other vegetation types.

Modelling Tundra Vegetation Response to Recent Arctic Warming

“…The underlying mechanism in the model is an increase in light attenuation, favouring taller plants to the detriment of the ground vegetation they shade. Shrub expansion and densification has been reported in numerous studies and related to recent warming trends (Kullman 2002;Jia et al 2003;Tømmervik et al 2004;Tape et al 2006;Hedenås et al 2011;Rundqvist et al 2011). A popular hypothesis is that increased microbial activity in warmer soils enhances the availability of nutrients, particularly nitrogen, and that this lends a competitive advantage to shrubs relative to other types of tundra plants (Chapin et al 1995;Tape et al 2006).…”

“…Changes in Arctic plant communities may already be taking place in response to warming over recent decades. Important lines of evidence include positive trends in surface greenness and photosynthetic activity inferred from satellite data (Tucker et al 2001;Bunn and Goetz 2006;Bhatt et al 2010;Beck and Goetz 2011), advancement of elevational and latitudinal treelines (Sonesson and Hoogesteger 1983;Kullman 2002;Harsch et al 2009;Van Bogaert et al 2010, 2011, and an increased cover, abundance and stature of shrubs in tundra areas (Kullman 2002;Jia et al 2003;Tømmervik et al 2004;Tape et al 2006;Hedenås et al 2011;Rundqvist et al 2011). Despite numerous local exceptions, the weight of evidence from observational studies suggests that, in general, Arctic vegetation is responding to rising temperatures through increases in productivity, density, cover and stature of vegetation and, in many areas, an increase in woody biomass and the representation of trees and shrubs (Post et al 2009;Callaghan et al 2011;Elmendorf et al 2012).…”

Human land-use, forest dynamics and tree growth at the treeline in the Western Italian Alps

“…The hypothesis attempting to explain these processes are focused on changes in climate, CO 2 concentration, fire regimes and, in the mountains where humans have social or economical interests, land-use change and, particularly, the grazing of domestic animals [6,7,15,34,57,65].…”

Ecology of the Gyrfalcon in Finnmark Based on Data from Two 11-Year Periods 150 Years Apart.

“…Global warming and increased forestation (Tømmervik et al 2004) may affect ptarmigan numbers, hunting areas, and cliffs suitable for Gyrfalcon nesting, the latter because many of the cliffs in the area are so small that increased size and number of trees in front of them will obstruct them to varying degrees ( Figure 7). …”

“…Human residence, presence of roads, use of fossil fuels, hunting pressure on game-birds, Reindeer (Rangifer tarandus) numbers, and eco-tourism have all increased. In addition, the vegetation of the area has become increasingly forested (Tømmervik et al 2004). In contrast to previous assessments (Tømmeraas 2002), the Golden Eagle (Aquila chrysaetos) now breeds regularly in the area.…”