Author: isabel

Posted on

Cervid exclusion alters boreal forest properties with little cascading impacts on soils

fence in boreal forest

This paper sheds new light on how moose affects forests. In a recently published article in the journal Ecosystems, Kolstad et al. showed the impact moose browsing has on boreal forest structure, tree species composition, and soil temperature and processes. Understanding the effect moose have on forest ecosystems is crucial for guiding how we manage their populations, as moose have no natural predators in most of Scandinavia. The article showed that chronic moose browsing has caused developing forest to become more open and considerably warmer. The researchers did not find any change in belowground parameters such as soil nutrient dynamics, in contrast to previous studies which showed that the conifer dominated forest associated with larger moose presence also comes with a reduction in soil fertility. This discrepancy may be a product of soils generally taking a long time to change in response to pressures, which makes way for exciting research in the future. We hope the large experimental infrastructure underpinning this study can continue for many more years so that we can increase our understanding of the functional role that moose has in the forest.

Reference: Kolstad, A.L., Austrheim, G., Solberg, E.J., Venete, A.M.A., Woodin, S.J., Speed, J.D.M. (2018) Cervid exclusion alters boreal forest properties with little cascading impacts on soils. Ecosystems 21(5):1027-1041

Picture: Moose exclosure 8 years after it was built on a recent boreal forest clear cut site in Trondheim, central Norway (Photo: Audun Hageskal)

Posted on

Multiple feedbacks contribute to a centennial legacy of reindeer on tundra vegetation

The article explores long-term stability of reindeer-induced vegetation shifts by addressing “Historical Milking Grounds” (HMGs): patches in the Scandinavian tundra that were subject to high reindeer concentrations until 100 years ago,but still show a striking similarity to actively grazed areas. Next to providing a detailed description in terms of vegetation, soil and reinvasion rate of the surrounding tundra, the study reveals that several ecological drivers, such as increased nutrient turnover rates and a preference of rodents to feed on shrubs inside the HMGs, contribute to the stability of this vegetation type.

You can access the full publication here. This paper is the first chapter of Dagmar’s PhD thesis to be published. She defended her PhD thesis, called ‘Long-Lasting Ecological Legacies of Reindeer on Tundra Vegetation’ recently. Please find here a link to the PhD thesis, or email Dagmar if you are interested in the full PDF or a paper copy.

Reference: Egelkraut, D., Aronsson, K.-A., Allard, A., Åkerholm, M., Stark, S., Olofsson, J. (2018) Multiple Feedbacks Contribute to a Centennial Legacy of Reindeer on Tundra Vegetation. Ecosystems 21: 1545–1563

Posted on

Wildlife species benefitting from a greener Arctic are most sensitive to shrub cover at leading range edges

Ground squirrel, reindeer and shrub encroachment

Through meta-analysis of existing literature we investigated the evidence for links between shrub cover and indicators of population performance in arctic and sub-arctic wildlife. Species from greener habitats (higher NDVI) were more likely to respond positively to shrub cover indicators demonstrating the potential for boreal species to expand northward.Populations at leading edges of species ranges with respect to greenness (low NDVI relative to species range) were more likely to respond positively to shrub cover, showing how shifts at leading edges of species ranges may be particularly rapid. To date, few studies assess how arctic specialists might respond to shrub change. The study also highlights the complexities of discriminating between herbivore responses to shrub and herbivore effects on vegetation and the need for further research to evaluate the relative influence of these two processes on shrub-wildlife associations.

Reference: Wheeler, H.C., Høye, T.T., Svenning, J-C. (2018) Wildlife species benefitting from a greener Arctic are most sensitive to shrub cover at leading range edges. Global Change Biology 24:212–223.

Link to publication

Picture: Different herbivores will respond differently to changes in shrub cover (photos: Helen Wheeler)

Posted on

HN get-together at Nordic Oikos 2018

meeting in Trondheim

Quite the number of HN members attended the Nordic Oikos conference in Trondheim in 19-22 February 2018, so we decided to have a brief meet-up. After a short introduction round and welcoming some new faces, we discussed several plans and highlights for the coming year.

We planned on organizing a HN one-day workshop at the Arctic Biodiversity Congress October 9-11, in Rovaniemi, Finland and a session during the conference, to present some of the ongoing work. Isa and Eeva made a little reminder that the HN would be happy with more people actively engaged in the organizing and managing of the newsletter, meetings, workshops, etc. Any help is welcome!

Posted on

MSc thesis: Invertebrate herbivory in tundra

Sarah Rheubottom
Sarah Rheubottom defended her MSc on invertebrate herbivory at the University of Alberta in January 2018

Sarah Rheubottom defended her MSc at the University of Alberta in January 2018, on measuring invertebrate herbivory in tundra. Her work was based on the sampling that was coordinated in summer 2015 and to which many HN members contributed. Sarah spent hours on end behind the magnifier glass, looking at leaves of 46 species of tundra plants from 22 sites across the tundra. Sarah’s work contributes a basic understanding of the occurrence and intensity of invertebrate herbivory at different tundra sites, and will help develop a more general protocol to measure invertebrate herbivory in tundra. If you are interested in getting a copy of Sarah’s thesis, please contact her! 

Posted on

Assessing the Ecological Impacts of Extensive Sheep Grazing in Iceland

Icelandic sheep

This paper compiles available information on the effects of sheep grazing on vegetation, soil properties and other organisms in the rangelands of Iceland. While the scarcity of studies prevented drawing general conclusions, there were some consistent trends. The extent of bare ground was significantly higher in grazed areas and grazing affected plant community structure. This indicates that sheep grazing increases the potential for soil erosion in Icelandic rangelands. A better understanding of the ecological impacts of sheep grazing is required to inform sustainable grazing practices adapted to the local conditions of this region. You can access the full publication here.

Reference: Marteinsdóttir, B., Barrio, I.C. and Jónsdóttir, I.S. (2017) Assessing the ecological impacts of extensive sheep grazing in Iceland. Icelandic Agricultural Sciences 30:57-72.

Posted on

Invertebrate herbivory in the tundra is prevalent and sensitive to climate change

Recent studies have shown that biotic interactions influence macroecological patterns and global dynamics, stressing the need to consider them outside local or regional scales. In the context of global changes affecting the dynamics and fate of whole biomes, we still know little about the role of key biotic interactions. In this study, the intensity of invertebrate background herbivory (low intensity but chronic herbivory) on one common tundra plant (Betula nana-glandulosa complex) is investigated across the tundra biome in relation to latitude and climate. Samples were collected from 56 locations across the tundra biome in the first coordinated effort to measure invertebrate herbivory in tundra, outside the well-studied effects of insect outbreaks. Background herbivory was detected at nearly all tundra sites. The intensity of background herbivory, although low, was mainly associated with higher temperatures. As such, invertebrate herbivory is likely to increase in a warmer Arctic. This paper represents the first coordinated effort combining two international research networks in the tundra: the Herbivory Network and the
Network for Arthropods of the Tundra (NeAT).

You can access the paper here.

Reference: Barrio, I.C., Lindén, E., TeBeest, M., Olofsson, J., Rocha, A., Soininen, E.M., Alatalo, J.M., Andersson,T., Asmus, A., Boike, J., Bråthen, K.A., Bryant, J.P., Buchwal, A., Bueno, C.G., Christie, K.S., Denisova, Y.V., Egelkraut, D., Ehrich, D., Fishback, L., Forbes, B.C., Gartzia, M., Grogan, P., Hallinger, M., Heijmans, M.M.P.D., Hik, D.S., Hofgaard, A., Holmgren, M., Høye, T.T., Huebner, D.C., Jónsdóttir, I.S., Kaarlejärvi, E., Kumpula, T., Lange, C.Y.M.J.G., Lange, J., Lévesque, E., Limpens, J., Macias-Fauria, M., Myers-Smith, I., van Nieukerken, E.J., Normand,S., Post, E.S., Schmidt, N.M., Sitters, J., Skoracka, A., Sokolov, A., Sokolova, N., Speed, J.D.M., Street, L.E., Sundqvist, M.K., Suominen, O., Tananaev, N., Tremblay, J.-P., Urbanowicz, C., Uvarov, S.A., Watts, D., Wilmking, M., Wookey, P.A., Zimmermann, H.H., Zverev, V., Kozlov, M.V. (2017) Background invertebrate herbivory on dwarf birch (Betula glandulosa-nana complex) increases with temperature and precipitation across the tundra biome. Polar Biology 40, 2265–2278

  

Posted on

Not only mosses: lemming winter diets as described by DNA metabarcoding

The temporal dynamics of most tundra food webs are shaped by the cyclic population dynamics of lemmings. While processes during winter may be behind the recent disruptions of lemming cycles, lemming winter ecology is poorly known. We present here the first DNA metabarcoding data on the winter diet of Norwegian lemmings (Lemmus lemmus), based on feces collected after a winter of population increase. Prostrate willows, mosses, and graminoids dominated the species winter diet, indicating that the conventional idea of lemmings as moss-specialists should be revised. The behavior of lemming-plant models in theoretical studies is conditional on the assumptions of mosses being their main winter food item. As shrubs have been excluded from the framework of these models, incorporating them in future modeling studies should nuance our understanding on how plants affect lemmings. We also sampled diet of a few individuals found dead on top of the snow. These individuals had relatively empty stomachs and had, prior to death, relied heavily on mosses. This apparent lack of abundant good quality indicates spatial heterogeneity in local food availability during the population increase phase.

Reference: Soininen, E.M., Zinger, L., G. Ludovic, Yoccoz, N.G., Henden, J-A., Ims, R.A. (2017) Not only mosses: lemming winter diets as described by DNA metabarcoding. Polar Biology 40(10):2097-103. DOI:10.1007/s00300-017-2114-3.

Posted on

Lunch get-together at CSEE 2017

Some of us met at the Canadian Society for Ecology and Evolution meeting in May 2017 in Victoria, BC. The (herbivory) highlight of the conference was the session “Ecology of Plant-Herbivore Interactions in Cold Places”, where we listened to very interesting presentations by Jen Forbey, Greg Henry, John Serafini, Michel P Laforge, Peter Tarleton and Peter Kotanen. We also had a lovely HN lunch get-together, discussing some science while enjoying the sun!

Posted on

Expansion of deciduous tall shrubs but not evergreen dwarf shrubs inhibited by reindeer in Scandes mountain range

exclosure

One of the most palpable effects of warming in Arctic ecosystems is shrub expansion above the tree line. However, previous studies have found that reindeer can influence plant community responses to warming and inhibit shrubification of the tundra.

 In this study, we revisited grazed (ambient) and ungrazed study plots (exclosures), at the southern as well as the northern limits of the Swedish alpine region, to study long-term grazing effects and vegetation changes in response to increasing temperatures between 1995 – 2011, in two vegetation types (shrub heath and mountain birch forest).

We found that shrub expansion is occurring rapidly in the Scandes mountain range, both above and below the tree line. But although tall, deciduous shrubs had benefitted significantly from grazing exclosure, both in terms of cover and height, which in turn lowered summer soil temperatures, the overriding vegetation shift across our sites was a striking increase in evergreen dwarf shrubs, which were not influenced by grazing. Since the effects of an increase in evergreen dwarf shrubs and more recalcitrant plant litter may to some degree counteract some of the effects of an increase in deciduous tall shrubs, herbivore influence on shrub interactions is potentially of great importance for shaping arctic shrub expansion and its associated ecosystem effects.

Reference: Vowles, T., Gunnarsson, B., Molau, U., Hickler, T., Klemedtsson, L., Björk, R.G. (2017) Expansion of deciduous tall shrubs but not evergreen dwarf shrubs inhibited by reindeer in Scandes mountain range. Journal of Ecology 105(6):1547-61. DOI: 10.1111/1365-2745.12753.

Picture: Reindeer exclosures in the Scandes mountains (photo: Tage Vowles, University of Gothenburg)

Proudly powered by WordPress