Understanding the drivers of extensive plant damage in boreal and Arctic ecosystems: Insights from field surveys in the aftermath of damage

Jarle W Bjerke; Rachael Treharne; Dagrun Vikhamar-Schuler; Stein R Karlsen; Virve Ravolainen; Stef Bokhorst; Gareth K Phoenix; Zbigniew Bochenek; Hans Tømmervik

doi:10.1016/j.scitotenv.2017.05.050

Understanding the drivers of extensive plant damage in boreal and Arctic ecosystems: Insights from field surveys in the aftermath of damage

Sci Total Environ. 2017 Dec 1:599-600:1965-1976. doi: 10.1016/j.scitotenv.2017.05.050. Epub 2017 May 23.

Authors

Jarle W Bjerke¹, Rachael Treharne², Dagrun Vikhamar-Schuler³, Stein R Karlsen⁴, Virve Ravolainen⁵, Stef Bokhorst⁶, Gareth K Phoenix², Zbigniew Bochenek⁷, Hans Tømmervik⁸

Affiliations

¹ Norwegian Institute for Nature Research (NINA), FRAM - High North Research Centre for Climate and the Environment, PO Box 6606, Langnes, NO-9296 Tromsø, Norway. Electronic address: jarle.bjerke@nina.no.
² Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK.
³ Norwegian Meteorological Institute, NO-0313 Oslo, Norway.
⁴ Northern Research Institute - Tromsø, Science Park, NO-9294 Tromsø, Norway.
⁵ Norwegian Polar Institute, FRAM - High North Research Centre for Climate and the Environment, PO Box 6606, Langnes, NO-9296 Tromsø, Norway.
⁶ Norwegian Institute for Nature Research (NINA), FRAM - High North Research Centre for Climate and the Environment, PO Box 6606, Langnes, NO-9296 Tromsø, Norway; Department of Ecological Science, VU University Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands.
⁷ Institute of Geodesy and Cartography, 02-679 Warsaw, Poland.
⁸ Norwegian Institute for Nature Research (NINA), FRAM - High North Research Centre for Climate and the Environment, PO Box 6606, Langnes, NO-9296 Tromsø, Norway.

PMID: 28558420
DOI: 10.1016/j.scitotenv.2017.05.050

Abstract

The exact cause of population dieback in nature is often challenging to identify retrospectively. Plant research in northern regions has in recent decades been largely focussed on the opposite trend, namely increasing populations and higher productivity. However, a recent unexpected decline in remotely-sensed estimates of terrestrial Arctic primary productivity suggests that warmer northern lands do not necessarily result in higher productivity. As large-scale plant dieback may become more frequent at high northern latitudes with increasing frequency of extreme events, understanding the drivers of plant dieback is especially urgent. Here, we report on recent extensive damage to dominant, short, perennial heath and tundra plant populations in boreal and Arctic Norway, and assess the potential drivers of this damage. In the High-Arctic archipelago of Svalbard, we recorded that 8-50% of Cassiope tetragona and Dryas octopetala shoots were dead, and that the ratios of dead shoots increased from 2014 to 2015. In boreal Norway, 38-63% of Calluna vulgaris shoots were dead, while Vaccinium myrtillus had damage to 91% of shoots in forested sites, but was healthy in non-forested sites. Analyses of numerous sources of environmental information clearly point towards a winter climate-related reason for damage to three of these four species. In Svalbard, the winters of 2011/12 and 2014/15 were documented to be unusually severe, i.e. insulation from ambient temperature fluctuation by snow was largely absent, and ground-ice enforced additional stress. In boreal Norway, the 2013/14 winter had a long period with very little snow combined with extremely low precipitation rates, something which resulted in frost drought of uncovered Calluna plants. However, extensive outbreaks of a leaf-defoliating geometrid moth were identified as the driver of Vaccinium mortality. These results suggest that weather and biotic extreme events potentially have strong impacts on the vegetation state of northern lands.

Keywords: Cryosphere; Extreme events; Pest; Plant mortality; Tundra; Winter climate change.