Long-term Impacts of Contrasting Management of Large Ungulates in the Arctic Tundra-Forest Ecotone: Ecosystem Structure and Climate Feedback
The arctic forest-tundra ecotone (FTE) represents a major transition zone between contrasting ecosystems, which can be strongly affected by climatic and biotic factors. Expected northward expansion and encroachment on arctic tundra in response to climate warming may be counteracted by natural and anthropogenic processes such as defoliating insect outbreaks and grazing/browsing regimes. Such natural and anthropogenic changes in land cover can substantially affect FTE dynamics, alter ground albedo (index of the amount of solar energy reflected back into the atmosphere) and provide important feedbacks into the climate system. We took advantage of a naturally occurring contrast between reindeer grazing regimes in a border region between northern Finland and Norway which was recently defoliated by an outbreak of the geometrid moth. We examined ecosystem-wide contrasts between potentially year-round (but mainly summer) grazed (YRG) regions in Finland and mainly winter grazed (WG) regions in Norway. We also used a remotely sensed vegetation index and albedo to quantify effects on local energy balance and potential climate feedbacks. Although differences in soil characteristics and ground vegetation cover were small, we found dramatic differences in the tree layer component of the ecosystem. Regeneration of mountain birch stands appears to have been severely hampered in the YRG regime, by limiting regeneration from basal shoots and reestablishment of individual trees from saplings. This has led to a more open forest structure and a significant 5% increase in spring albedo in the summer grazed compared to the winter grazed regions. This supports recent suggestions that ecosystem processes in the Arctic can significantly influence the climate system, and that such processes must be taken into account when developing climate change scenarios and adaptation strategies.
Key words:Arctic vegetation climate change insect defoliation grazing climate feedback reindeer husbandry
This study is a contribution from Work Package 4 (WP4) of the Nordic Centre of Excellence—How to preserve the tundra in a warming climate (NCoE-Tundra) funded by the Norden Top-Level Initiative “Effect studies and adaptation to climate change.” Additional funding was obtained from FRAM—High North Research Centre for Climate and the Environment, the Norwegian Research Council, the Norwegian Institute for Nature Research, the University of Tromsø, and the Academy of Finland (Project #138309). We thank Maja S. Kvalvik, Lauri Kapari, Sabrina Schultze, Jakob Iglhaut, Moritz Klinghardt, Elina Vainio, Ilkka Syvänperä and Marianne Iversen for assistance during field work, and Tuulikki Pakonen and Tarja Törmänen for assistance with nutrient analyses.
- Bates D, Maechler M, Bolker B. 2012. lme4: Linear mixed-effects models using S4 classes. R package version 0.999999-0. http://CRAN.R-project.org.
- Bohner A, Starlinger F, Koutecky P. 2012. Vegetation changes in an abandoned montane grassland, compared to changes in a habitat with low-intensity sheep grazing - a case study in Styria, Austria. Eco Mont 4(2):5–12.Google Scholar
- CAFF. 2010. Arctic biodiversity trends 2010—selected indicators of change. Akureyri: CAFF International Secretariat.Google Scholar
- Callaghan TV, Crawford RMM, Eronen M, Hofgaard A, Payette S, Rees WG, Skre O, Sveinbjornsson J, Vlassova TK, Werkman BR. 2002. The dynamics of the tundra-taiga boundary: an overview and suggested coordinated and integrated approach to research. AMBIO 12:3–5.Google Scholar
- Caporaso JG, Lauber CL, Walters WA, Berg-Lyons D, Lozupone CA, Turnbaugh PJ, Fierer N, Knight R. 2011. Microbes and Health Sackler Colloquium: Global patterns of 16S rRNA diversity at a depth of millions of sequences per sample [Microbiology]. Proc Natl Acad Sci 108(Suppl 1):4516–22.PubMedCentralPubMedCrossRefGoogle Scholar
- Chapin FS, Sturm M, Serreze MC, McFadden JP, Key JR, Lloyd AH, McGuire AD, Rupp TS, Lynch AH, Schimel JP, Beringer J, Chapman WL, Epstein HE, Euskirchen ES, Hinzman LD, Jia G, Ping CL, Tape KD, Thompson CDC et al. 2005. Role of land-surface changes in Arctic summer warming. Science 310(5748):657–60.PubMedCrossRefGoogle Scholar
- Christensen RHB. 2012. Ordinal—regression models for ordinal data. R package version 2013.9-30. http://CRAN.R-project.org.
- Duffey E, Morris MG, Sheail J, Ward LK, Wells DA, Wells TCE. 1974. Grassland ecology and wildlife management. London: Chapman and Hall.Google Scholar
- Hämet-Ahti L. 1963. Zonation of the mountain birch forests in northernmost Fennoscandia: Selostus. Annales Botanici Societatis Zoologicæ 4(34):1–360.Google Scholar
- Hausner VH, Fauchald P, Tveraa T, Pedersen E, Jernsletten JL, Ulvevadet B, Ims RA, Yoccoz NG, Brathen KA. 2011. The ghost of development past: the impact of economic security policies on Saami pastoral ecosystems. Ecol Soc 16(3):4.Google Scholar
- Klein DR. 1990. Variation in quality of caribou and reindeer forage plants associated with season, plant part, and phenology. Rangifer Spec Issue 3:123–30.Google Scholar
- Kumpula J, Tanskanen A, Colpaert A, Anttonen M, Törmänen H, Siitari J, Siitari S. 2008. Pasture survey of northern reindeer herding area in Finland—results from 2005–2008 and changes in the condition of pastures. Loppuraportti: Riista- ja porotutkimuslaitos.Google Scholar
- Lundberg A, Beringer J. Albedo and snowmelt rates across a tundra-to-forest transition. In: Proceedings of the 15 northern research basins international symposium and workshop. Department of Water Resources Engineering, Lund University; 2005. pp. 1–10.Google Scholar
- Moen J, Aune K, Edenius L, Angerbjorn A. 2004. Potential effects of climate change on treeline position in the Swedish mountains. Ecol Soc 9(1):16.Google Scholar
- Muga DA. 1986. A commentary on the historical transformation of the Sami communal mode of production. J. Ethnical Stud 14:111–21.Google Scholar
- Myers-Smith IH, Forbes BC, Wilmking M, Hallinger M, Lantz T, Blok D, Tape KD, Macias-Fauria M, Sass-Klaassen U, Levesque E, Boudreau S, Ropars P, Hermanutz L, Trant A, Collier LS, Weijers S, Rozema J, Rayback SA, Schmidt NM et al. 2011. Shrub expansion in tundra ecosystems: dynamics, impacts and research priorities. Environ Res Lett 6(4):045509.CrossRefGoogle Scholar
- Neuvonen S, Ruohomäki K, Bylund H, Kaitaniemi P. 2001. Insect herbivores and herbivory effects on mountain birch forest dynamics. In: Wielgolaski F, Ed. Nordic mountain birch ecosystems. Man and the biosphere series, Vol. 27. New York: Paris and Parthenon Publishing. p 207–22.Google Scholar
- Oksanen J, Blanchet FG, Kindt R, Legendre P, Minchin PR, O’Hara RB, Simpson GL, Solymos P, Stevens MHH, Wagner H. 2011. R package version 2.0-5. http://CRAN.R-project.org.
- Pajunen A, Virtanen R, Roininen H. 2008. The effects of reindeer grazing on the composition and species richness of vegetation in forest-tundra ecotone. Polar Biol 31:1233–44.Google Scholar
- R Development Core Team. 2011. R: a language and environment for statistical computing. Vienna: R Development Core Team.Google Scholar
- Reindriftsforvaltningen. 2008. Ressursregnskap for reindriftsnæringen. Reindriftsforvaltningen.Google Scholar
- Skaug H, Fournier D, Nielsen A, Magnusson A, Bolker B. 2012. Generalized Linear Mixed Models using AD Model Builder. R package version 0.7.3. http://CRAN.R-project.org.
- Skjenneberg S, Slagsvold L. 1968. Reindriften og dens naturgrunnlag. Oslo: Universitetsforlaget.Google Scholar
- Skogland T. 1994. Villrein: fra urinnvåner til miljøbarometer. Oslo: Teknologisk Forlag.Google Scholar
- Sturm M, Douglas T, Racine C, Liston GE. 2005a. Changing snow and shrub conditions affect albedo with global implications. J Geophys Res 110(G1):G01004.Google Scholar
- Tenow O, Bylund H. 1989. A survey of winter cold in the mountain birch/Epirrita autumnata system. Memoranda Societatis Pro Fauna Et Flora Fennica 65:67–72.Google Scholar
- Vorren Ø. 1946. Reindrift og nomadisme i Varangertraktene. Tromsø Museums Årshefter 69(2):145.Google Scholar
- WMO. 2006. Systematic observation requirements for satellite-based products for climate. Geneva: World Meteorological Organization/Global Climate Observing System.Google Scholar
- Zeileis A, Kleiber C, Jackman S. 2008. Regression models for count data in R. J Stat Softw 27(8):1–25.Google Scholar