Spatial patterns and dynamic responses of arctic food webs corroborate the exploitation ecosystems hypothesis (EEH).

According to the exploitation ecosystems hypothesis (EEH), productive terrestrial ecosystems are characterized by community-level trophic cascades, whereas unproductive ecosystems harbor food-limited grazers, which regulate community-level plant biomass. We tested this hypothesis along arctic-alpine productivity gradients at the Joatka field base, Finnmark, Norway. In unproductive habitats, mammalian predators were absent and plant biomass was constant, whereas herbivore biomass varied, reflecting the productivity of the habitat. In productive habitats, predatory mammals were persistently present and plant biomass varied in space, but herbivore biomass did not. Plant biomass of productive tundra scrublands declined by 40% when vegetation blocks were transferred to predation-free islands. Corresponding transfer to herbivore-free islands triggered an increase in plant biomass. Fertilization of an unproductive tundra heath resulted in a fourfold increase in rodent density and a corresponding increase in winter grazing activity, whereas the total aboveground plant biomass remained unchanged. These results corroborate the predictions of the EEH, implying that the endotherm community and the vegetation of the North European tundra behaves dynamically as if each trophic level consisted of a single population, in spite of local co-occurrence of >20 plant species representing different major taxonomic groups, growth forms, and defensive strategies.

Herding conditions related to infectious keratoconjunctivitis in semi-domesticated reindeer: a questionnaire-based survey among reindeer herders.

BACKGROUND: Infectious keratoconjunctivitis (IKC) in Eurasian semi-domesticated reindeer (Rangifer tarandus tarandus) is a multifactorial disease, associated to infectious agents such as Cervid herpesvirus 2 (CvHV2) and various species of bacteria, but environmental factors may also be necessary to initiate the disease. Little effort seems to have been invested in addressing the herder`s experience with this disease. An information letter with a link to an online questionnaire was sent to 410 herding community representatives in Norway and Sweden. RESULTS: Sixty-three herders responded, 76 % of these having reindeer in Norway and 24 % in Sweden. Thirty-three herders (55 %) responded that they had seen this disease during the preceding year (2010) and 23 (38 %) that they had seen it in previous years (2009 or earlier). The majority (67 %) claimed that only 1-5 animals in their herd were affected at one time, whereas three herders (7 %) responded that more than 30 animals had been affected. No environmental factor could be singled out as significantly associated with the appearance of IKC, but when categorizing the number of contact herds for each herd (i.e. sharing pastures, corrals etc.), IKC was observed more often in herds with many (>25) contact herds. The questionnaire revealed that a veterinarian is not always available for reindeer herders, but also that a veterinarian seldom is contacted for this disease. None of the herders practiced isolation of a diseased animal from the rest of the herd when IKC was observed. Slaughter was the action most commonly initiated by the herders in response to IKC, whereas the veterinarian usually prescribed antibiotics, usually an ophthalmic ointment, alone or combined with systemic treatment. The herders claimed that IKC and other diseases had less importance than predators concerning loss of animals. CONCLUSIONS: IKC is to be considered a common disease, observed in 55 % of the herds (2010), typically affecting 1-5 animals, although larger outbreaks (>30 animals) occur. The herders usually slaughtered affected animals rather than consulting a veterinarian for medical treatment.

Where do the treeless tundra areas of northern highlands fit in the global biome system: toward an ecologically natural subdivision of the tundra biome.

According to some treatises, arctic and alpine sub-biomes are ecologically similar, whereas others find them highly dissimilar. Most peculiarly, large areas of northern tundra highlands fall outside of the two recent subdivisions of the tundra biome. We seek an ecologically natural resolution to this long-standing and far-reaching problem. We studied broad-scale patterns in climate and vegetation along the gradient from Siberian tundra via northernmost Fennoscandia to the alpine habitats of European middle-latitude mountains, as well as explored those patterns within Fennoscandian tundra based on climate-vegetation patterns obtained from a fine-scale vegetation map. Our analyses reveal that ecologically meaningful January-February snow and thermal conditions differ between different types of tundra. High precipitation and mild winter temperatures prevail on middle-latitude mountains, low precipitation and usually cold winters prevail on high-latitude tundra, and Scandinavian mountains show intermediate conditions. Similarly, heath-like plant communities differ clearly between middle latitude mountains (alpine) and high-latitude tundra vegetation, including its altitudinal extension on Scandinavian mountains. Conversely, high abundance of snowbeds and large differences in the composition of dwarf shrub heaths distinguish the Scandinavian mountain tundra from its counterparts in Russia and the north Fennoscandian inland. The European tundra areas fall into three ecologically rather homogeneous categories: the arctic tundra, the oroarctic tundra of northern heights and mountains, and the genuinely alpine tundra of middle-latitude mountains. Attempts to divide the tundra into two sub-biomes have resulted in major discrepancies and confusions, as the oroarctic areas are included in the arctic tundra in some biogeographic maps and in the alpine tundra in others. Our analyses based on climate and vegetation criteria thus seem to resolve the long-standing biome delimitation problem, help in consistent characterization of research sites, and create a basis for further biogeographic and ecological research in global tundra environments.

Climate and environmental change drives Ixodes ricinus geographical expansion at the northern range margin.

BACKGROUND: Global environmental change is causing spatial and temporal shifts in the distribution of species and the associated diseases of humans, domesticated animals and wildlife. In the on-going debate on the influence of climate change on vectors and vector-borne diseases, there is a lack of a comprehensive interdisciplinary multi-factorial approach utilizing high quality spatial and temporal data. METHODS: We explored biotic and abiotic factors associated with the latitudinal and altitudinal shifts in the distribution of Ixodes ricinus observed during the last three decades in Norway using antibodies against Anaplasma phagocytophilum in sheep as indicators for tick presence. Samples obtained from 2963 sheep from 90 farms in 3 ecologically different districts during 1978 - 2008 were analysed. We modelled the presence of antibodies against A. phagocytophilum to climatic-, environmental and demographic variables, and abundance of wild cervids and domestic animals, using mixed effect logistic regressions. RESULTS: Significant predictors were large diurnal fluctuations in ground surface temperature, spring precipitation, duration of snow cover, abundance of red deer and farm animals and bush encroachment/ecotones. The length of the growth season, mean temperature and the abundance of roe deer were not significant in the model. CONCLUSIONS: Our results highlight the need to consider climatic variables year-round to disentangle important seasonal variation, climatic threshold changes, climate variability and to consider the broader environmental change, including abiotic and biotic factors. The results offer novel insight in how tick and tick-borne disease distribution might be modified by future climate and environmental change.