Abstract
It is widely believed that deciduous tundra-shrub dominance is increasing in the pan-Arctic region, mainly due to rising temperature. We sampled dwarf birch (Betula nana L.) at a northeastern Siberian tundra site and used dendrochronological methods to explore the relationship between climatic variables and local shrub dominance. We found that establishment of shrub ramets was positively related to summer precipitation, which implies that the current high dominance of B. nana at our study site could be related to high summer precipitation in the period from 1960 to 1990. The results confirmed that early summer temperature is most influential to annual growth rates of B. nana. In addition, summer precipitation stimulated shrub growth in years with warm summers, suggesting that B. nana growth may be co-limited by summer moisture supply. The dual controlling role of temperature and summer precipitation on B. nana growth and establishment is important to predict future climate-driven vegetation dynamics in the Arctic tundra.
Highlights
Global climate change has markedly affected the ecosystems on Earth (ACIA 2005; IPCC 2013)
We found that establishment of shrub ramets was positively related to summer precipitation, which implies that the current high dominance of B. nana at our study site could be related to high summer precipitation in the period from 1960 to 1990
The chronology of B. nana was characterized by a reasonable common signal represented by rbar (0.351) and expressed signal (EPS) (0.933)
Summary
Global climate change has markedly affected the ecosystems on Earth (ACIA 2005; IPCC 2013). The Arctic region is experiencing dramatic air temperature increase and more extreme precipitation events (Hinzman et al 2005; McGuire et al 2006). During the last four decades, surface air temperature increased on average 0.4 °C per decade over the Arctic (Anisimov et al 2007). Local vegetation composition has changed in the North American and Scandinavian Arctic (ACIA 2005). Deciduous shrubs have been observed to increase in Arctic tundra. Experimental studies in tundra ecosystems (Shaver et al 2001; Mack et al 2004; Walker et al 2006; Bret-Harte et al 2008; Nowinski et al 2010) suggested that deciduous shrubs, especially Betula nana L. The observed shrub expansion could reduce tundra albedo, leading to additional
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