Tree and Shrub Expansion Over the Past 34 Years at

Authors: Sara Rundqvist Henrik Hedenås Anneli Sandström Urban Emanuelsson Håkan Eriksson Christer Jonasson Terry V Callaghan

Publish Date: 2011/08/24

Volume: 40, Issue: 6, Pages: 683-

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Abstract

Shrubs and trees are expected to expand in the subArctic due to global warming Our study was conducted in Abisko subarctic Sweden We recorded the change in coverage of shrub and tree species over a 32– to 34year period in three 50 × 50 m plots in the alpinetreeline ecotone The cover of shrubs and trees 35 cm diameter at breast height were estimated during 2009–2010 and compared with historical documentation from 1976 to 1977 Similarly all tree stems ≥35 cm were noted and positions determined There has been a substantial increase of cover of shrubs and trees particularly dwarf birch Betula nana and mountain birch Betula pubescens ssp czerepanovii and an establishment of aspen Populus tremula The other species willows Salix spp juniper Juniperus communis and rowan Sorbus aucuparia revealed inconsistent changes among the plots Although this study was unable to identify the causes for the change in shrubs and small trees they are consistent with anticipated changes due to climate change and reduced herbivoryThe authors would like to acknowledge NilsÅke Andersson for providing them with unpublished data and photographs from 1976–1977 Craig Tweedie and an anonymous reviewer for valuable comments The authors also sincerely thank the staff on Abisko Arctic Scientific Research Station for their logistic support The project was financed by a grant from the Swedish Research Council Vetenskapsrådet 3272007833

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