Author: isabel

This paper highlights the strong relationship between forage phenology in alpine areas and the dynamics of plant consumption by alpine herbivores.

In this study, Johan Espunyes and colleagues assessed the seasonal changes in diet composition of Pyrenean chamois (Rupicapra p. pyrenaica) and its relationship to primary production trends in a Mediterranean alpine environment. Moreover, the diet composition in two populations with contrasting livestock pressure was compared in order to study the effect of sheep flocks on the feeding behaviour of chamois. Using monthly sampling during three consecutive years, they showed an intra-annual variation in the diet composition of Pyrenean chamois and demonstrated a strong relationship between plant consumption dynamics and phenology in alpine areas. This study could not detect differences between both chamois populations despite the presence of sheep flocks in only one area. However, the detection of a shift in the diet of chamois in both areas after the arrival of high densities of multi-specific livestock suggest a general livestock effect. In conclusion, Pyrenean chamois are well adapted to the variations in the seasonal availability of plants in alpine habitats but could be disturbed by the seasonal presence of livestock. Due to the key plants in their diet, it is suggested that population management programmes should focus on the preservation of mixed grasslands composed of patches of shrubs and herbs. The effects of climate change and shrub expansion should be studied as they may potentially affect chamois population dynamics through changes in habitat composition and temporal shifts in forage availability.

Reference: Espunyes, J., Bartolomé, J., Garel, M., Gálvez-Cerón, A., Fernández Aguilar, X., Colom-Cadena, A., et al. (2019) Seasonal diet composition of Pyrenean chamois is mainly shaped by primary production waves. PLoS ONE 14(1): e0210819

https://doi.org/10.1371/journal.pone.0210819

You can read the full article here.

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Picture: Pyrenean chamois (Rupicapra p. pyrenaica) (photo: Johan Espunyes)

This paper highlights the impacts that hyperabundant herbivores can have on tundra habitats and sympatric-nesting species.

In this study Scott Flemming and colleagues examined how grazing and grubbing by a lesser snow (Chen caerulescens) and Ross’ goose (Chen rossii) colony influenced the availability and quality of habitats selected by eight different shorebird species in the eastern Canadian Arctic.

During randomly selected habitat surveys conducted at three study sites that varied in goose presence and influence (High, Moderate, Low), they estimated the proportional contribution of difference habitat types, amount of lateral concealment provided, and measured the height of various cover types (e.g. grasses, rock, willow). They also searched for shorebird nests at plots situated within each study site and conducted habitat surveys at all shorebird nests. At random sites, the availability of sedge meadow was negatively related to increasing goose influence while the availability of exposed sediment was positively related. The amount of lateral concealment provided by cover types was also negatively related to increasing goose influence and this trend was largely driven by changes in sedges and grasses. The densities of cover-nesting shorebirds (species that prefer nesting in sedge meadow habitat that provides high concealment) were lowest at the High goose influence site and highest at the Low goose influence site. Furthermore, cover-nesting shorebirds at the Moderate goose influence site selected nest sites with less sedge meadow and concealment than those at the Low goose influence site. Many shorebirds select nesting habitats that provide them with high concealment from predators; the authors therefore suggest that goose-induced habitat alteration may not only be influencing shorebird nest site selection, but also nest survival probability and recommend more research in this field.

This study demonstrates how habitat alteration by hyperabundant populations of geese can influence nest site selection of Arctic shorebirds at multiple scales and highlights the importance of goose population management.

Reference: Flemming, S.A., Nol, E., Kennedy, L.V., Smith, P.A. (2019) Hyperabundant herbivores limit habitat availability and influence nest site selection of Arctic‐breeding birds. Journal of Applied Ecology
https://doi.org/10.1111/1365-2664.13336

You can read the full article here.

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Picture: Foraging Lesser snow goose (Chen caerulescens) in Nunavut (photo credit: Scott Flemming, Trent University)

This paper highlights the key role arctic herbivores play in arctic vegetation and nutrient dynamics, and reveal the potential strong ecosystem responses that may happen if changes in large herbivore abundances occur. In this study the authors examined the impacts of a large dominant herbivore in the tundra ecosystem, the muskox, Ovibos moschatus, using exclosures established in a fen in high Arctic Greenland. Using weekly sampling throughout the growing season, they quantified the effects of muskox exclusion on aboveground plant biomass, and on concentrations and pools of carbon and nitrogen, and explored the timing of peak biomass and nutrient pools. Excluding muskoxen profoundly changed plant abundances and dynamics of the fen, with more than a doubling of aboveground plant biomass and carbon and nitrogen pool sizes. Specifically, large increases in mosses and litter were observed, while graminoid biomass did not change significantly with exclusion of muskoxen. Excluding muskoxen advanced the peak of plant biomass, but also led to a more rapid decline, resulting in an earlier and shorter period of maximal plant biomass inside the exclosures. The largest impact of muskoxen on the arctic fen ecosystem seems to be through their trampling effects on the moss layer, which likely mediated most of the observed changes. This study demonstrates how quickly an ecosystem may respond to changes in the abundance of large herbivores, and highlights their pivotal role in modifying vegetation dynamics and nutrient cycling in tundra ecosystems.

Reference: Mosbacher, J.B., Michelsen, A., Stelvig, M., Hjermstad-Sollerud, H., Schmidt, N.M. (2018) Muskoxen modify plant abundance, phenology and nitrogen dynamics in a High Arctic fen. Ecosystems https://doi.org/10.1007/s10021-018-0323-4

You can read the full article here.

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Picture: Tundra ecosystems can respond rapidly to changes in the abundance of large herbivores (photo credit: Lars Holst Hansen, Aarhus University)