Author: isabel

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)

Posted on

Herbivory Network: An international, collaborative effort to study herbivory in Arctic and alpine ecosystems

This paper summarizes the need for herbivory studies and presents the protocols designed by the Herbivory Network.

Plant-herbivore interactions are central to the functioning of tundra ecosystems, but their outcomes vary over space and time. Accurate forecasting of ecosystem responses to ongoing environmental changes requires a better understanding of the processes responsible for this heterogeneity. To effectively address this complexity at a global scale, coordinated research efforts, including multi-site comparisons within and across disciplines, are needed. The Herbivory Network was established as a forum for researchers from Arctic and alpine regions to collaboratively investigate the multifunctional role of herbivores in these changing ecosystems. One of the priorities is to integrate sites, methodologies, and metrics used in previous work, to develop a set of common protocols and design long-term geographically-balanced, coordinated experiments. The implementation of these collaborative research efforts will also improve our understanding of traditional human-managed systems that encompass significant portions of the sub-Arctic and alpine areas worldwide. A deeper understanding of the role of herbivory in these systems under ongoing environmental changes will guide appropriate adaptive strategies to preserve their natural values and related ecosystem services.

Reference: Barrio, I.C., Hik, D.S., Jónsdóttir, I.S., Bueno, C.G., Mörsdorf, M.A., Ravolainen, V.T. (2016) Herbivory Network: An international, collaborative effort to study herbivory in Arctic and alpine ecosystems. Polar Science 10: 297-302.

Link to publication / request a copy

Posted on

Sea ice, rain-on-snow and tundra reindeer nomadism in Arctic Russia

frozen reindeer

According to oral histories collected among fully nomadic tundra Nenets on Yamal Peninsula in West Siberia, extreme weather (rain-on-snow) events resulting in significant mortality within tundra herds have occurred roughly once per decade during the past century.

The extreme weather events of November 2006 and 2013 caused mass reindeer starvation that we were able to track in detail using state-of-the-art satellite sensors. The most recent rain-on-snow event of November 2013 resulted in ca. 61,000 reindeer deaths, about 22% out of 275,000 reindeer on the Yamal Peninsula at the time. Empirical data and modelling efforts for the events in 2006 and 2013 found that the likely trigger was brief periods of significant Barents and Kara sea ice retreat during early November. Relatively warm, open water and fragmented ice allowed high levels of atmospheric humidity to develop, while onshore winds combined with anomalously high November air temperatures led to eventual rainfall over extensive continental areas in the Nenets and Yamal-Nenets Autonomous Okrugs.

Socio-economic and ecological implications of the 2013-14 event will play out for years to come. The herders who lost their reindeer through starvation have resorted to full-time fishing in situ, while also borrowing breeding stock to rebuild their herds. In the meantime, northern Yamal pastures that are normally subject to intense grazing pressure in summer will likely experience less grazing and trampling.

Reference: Forbes, B.C., Kumpula, T., Meschtyb, N., Laptander, R., Macias-Fauria, M., Zetterberg, P., Verdonen, M., Skarin, A., Kim, K.Y., Boisvert, L.N. and Stroeve, J.C. (2016) Sea ice, rain-on-snow and tundra reindeer nomadism in Arctic Russia. Biology Letters 12(11):20160466.

Link to publication

Picture: Reindeer frozen into the snowpack in Spring 2014 (photo: Roma Serotetto)

Posted on

Herbivores affect the distribution of rare plants in alpine and Arctic tundra

Domestic sheep in Norway

Herbivores influence many aspects of ecosystems in Arctic and alpine tundra, from plant population dynamics and community composition to soil carbon storage and nutrient cycling. Herbivory is a multi-scale process, herbivores select their food at small spatial scales, but also at large spatial scales in terms of their ranges and distributions.

We have a good understanding of how herbivores affect site level dynamics, but not larger scale dynamics. Indeed, while climatic variables have been successfully used to model species distributions, biotic interactions including herbivory have been notably absent from such approaches. However, a recent study seeks to change this.

Herbivory Network members James Speed and Gunnar Austrheim from the NTNU University Museum at the Norwegian University of Science and Technology have published a paper in the journal Biological Conservation where they use a national-level data set mapping densities of all large herbivores to predict the distribution of rare plant species within Norway. The study focussed on seven arctic and alpine tundra plant species on the Norwegian Red List for species, and the main herbivores grazing in these ecosystems – domestic sheep along with both wild and semi-domestic reindeer.

Although climatic variables were the most important factor in controlling the distribution of all seven species, there was a clear signal of herbivore densities influencing the distributions. This was most notable for Primula scandinavica (Scandinavian primrose). Low densities of herbivores were associated with low habitat suitability for this species. Speed and Austrheim mapped the regions of Norway where herbivore density was the factor most limiting the distribution of each rare plant species. There was little overlap in these areas between the seven plant species. This suggests that the management of herbivore populations for the conservation of rare plant species needs to be specific for each location and plant species.

Reference: Speed, J.D.M. & Austrheim, G. (2017) The importance of herbivore density and management as determinants of the distribution of rare plant species. Biological Conservation, 205:77-84. http://dx.doi.org/10.1016/j.biocon.2016.11.030

Picture: Domestic sheep in Norway (photo: Atle Mysterud)

Posted on

HN meeting – Iceland, 2016

We had a successful meeting in Reykjavik, Iceland in September, 2016. A total of 34 HN members joined us from Scandinavia, England, Russia, Canada, and the U.S. The agenda of the meeting was to launch new collaborative projects, to strengthen the ongoing ones, and to form strategies for steering and research collaboration within the network.

During the meeting, we discussed the following projects:

  • An assessment of the functional diversity of herbivore assemblages across the Arctic led by James Speed. This work follows from the Barrio et al. (2016) data material and aims to summarize the functional groups and phylogenetic diversity of arctic herbivores.
  • A systematic review on the effects of herbivores on tundra soils led by the soil working group (Maria Väisänen, Guillermo Bueno, Maria Tuomi and Francis Brearley). This work will revise the current knowledge on the impacts of herbivores on tundra soils through literature search. A report of this workshop will be soon uploaded to the HN website.
  • Identification of data gaps in tundra herbivory research led by Eeva Soininen, James Speed and Jennifer Forbey. Eeva and James are developing a systematic protocol that aims to create a systematic map of the conducted herbivory research. Jennifer will lead a review on what kind of paradigms have been prominent in herbivory research for the last decades.
  • The assessment on the effects of historical grazing within tundra sites led by Martin Mörsdorf. In the workshop discussion on the methods in defining historical grazing effects within tundra study sites was initiated, which could be developed into a protocol during the next meetings.

At the end of the meeting we concluded that the Herbivory Network should continue to be an open, active network, where members are encouraged to take active roles in developing new initiatives and networking opportunities.

You can find the workshop report here.

Funding for this workshop was provided by:

Posted on

Experimental warming increases herbivory by leaf‐chewing insects in an alpine plant community

caterpillar

Tone Birkemoe and collaborators have recently published a paper on the effects of experimental warming on insect herbivory. Here’s Tone’s summary of their paper:

Climate warming is predicted to affect species and trophic interactions worldwide, and alpine ecosystems are expected to be especially sensitive to changes. In this study, we used two ongoing climate warming (open-top chambers) experiments at Finse, southern Norway, to examine whether warming had an effect on herbivory by leaf-chewing insects in an alpine Dryas heath community.

We recorded feeding marks on the most common vascular plant species in warmed and control plots at two experimental sites at different elevations and carried out a brief inventory of insect herbivores. Experimental warming increased herbivory on Dryas octopetala and Bistorta vivipara. Dryas octopetala also experienced increased herbivory at the lower and warmer site, indicating an overall positive effect of warming, whereas B. vivipara experienced an increased herbivory at the colder and higher site indicating a mixed effect of warming.

The Lepidoptera Zygaena exulans and Sympistis nigrita were the two most common leaf-chewing insects in the Dryas heath. Based on the observed patterns of herbivory, the insects life cycles and feeding preferences, we argue that Z. exulans is the most important herbivore on B. vivipara, and S. nigrita the most important herbivore on D. octopetala. We conclude that if the degree of insect herbivory increases in a warmer world, as suggested by this study and others, complex interactions between plants, insects, and site-specific conditions make it hard to predict overall effects on plant communities.

A popular version of the paper is available in Norwegian from this web-page: http://blogg.nmbu.no/insektokologene/2016/09/spiser-insekter-mer-planter-i-en-varmere-verden/

Reference: Birkemoe T, Bergmann S, Hasle TE, Klanderud K. (2016) Experimental warming increases herbivory by leaf‐chewing insects in an alpine plant community. Ecology and Evolution 6(19):6955-6962

Link to the publication

Posted on

Biotic interactions mediate patterns of herbivore diversity in the Arctic

herbivore diversity map

Understanding the forces that shape biodiversity is essential for improving our ability to predict the responses of ecosystems to rapid, ongoing environmental change.  In the Arctic, herbivores often play a key role in the functioning of terrestrial ecosystems.  The diversity of herbivores varies across the Arctic, and until now, no one knew whether this was shaped by physical environmental factors, like temperature, or biotic factors, such as plant productivity.

We collected information on the distribution of all 73 species of vertebrate herbivores that occur in the Arctic.  Vertebrate herbivores are particularly important as they affect the structure and dynamics of plant communities and provide food for higher trophic-level predators.  The results of this study showed that herbivore diversity in the Arctic is higher in areas with greater plant productivity and with higher diversity of predators.  The interactions between plants, herbivores and predators, occurred over large spatial scales across the Arctic, in ecosystems where patterns of biodiversity were supposed to be affected mainly by temperature variation.

Reference: Barrio, I.C., Bueno, C.G., Gartzia, M., Soininen, E.M., Christie, K.S., Speed, J.D., Ravolainen, V.T., Forbes, B.C., Gauthier, G., Horstkotte, T., Hoset, K.S., Høye, T.T., Jónsdóttir, I.S., Lévesque, E., Mörsdorf, M.A., Olofsson, J., Wookey, P.A. and Hik, D.S. (2016) Biotic interactions mediate patterns of herbivore diversity in the Arctic. Global Ecology and Biogeography 
25(9):1108-1118

Link to publication

Proudly powered by WordPress