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Bergqvist G.,Swedish Association for Hunting and Wildlife Management | Bergstrom R.,Forestry Research Institute of Sweden | Wallgren M.,Forestry Research Institute of Sweden
Silva Fennica | Year: 2014

Moose browsing damage from the winter preceding the study (recent damage) on Scots pine, birch and aspen was examined in relation to forage availability, an index of moose population density and site productivity in young forests in the hemiboreal zone. Recent damage was observed for 4.1 ± 0.54% (mean ± SE; Scots pine), 16.8 ± 1.89% (birch) and 67.6 ± 13.76% (aspen) of the trees. A multiple regression with five independent variables explained 19% (Scots pine) 14% (birch) and 33% (aspen) of the variation in recent damage. Cover of Scots pine browse was the most important variable for predicting damage to Scots pine and accounted for 44% of the explained variation. When birch was overtopping pine there was a significant increase in damage to pine. Moose index was the only significant variable to explain recent damage to birch, and accounted for 64% of the explained variation. For aspen, damage was negatively correlated to coverage of Scots pine and birch browse, each variable accounting for 38% of the explained variation. For Scots pine, increasing the number of pines ha-1 and performing pre-commercial thinning in such a way that pines are not overtopped may be efficient ways of reducing damage proportions, whereas birch needs to be protected from moose (by a reduction of the moose population or otherwise) in order to escape damage. Increased amounts of Scots pine browse and birch browse may also reduce damage levels to aspen, according to this study.

Elmhagen B.,University of Stockholm | Hellstrom P.,University of Stockholm | Angerbjorn A.,University of Stockholm | Kindberg J.,Swedish Association for Hunting and Wildlife Management
Annales Zoologici Fennici | Year: 2011

Cyclic dynamics with extensive spatial synchrony has long been regarded as characteristic of key herbivores at high latitudes. This contrasts to recent reports of fading cycles in arvicoline rodents in boreal and alpine Fennoscandia. We investigate the spatiotemporal dynamics of boreal red fox and alpine arctic fox in Sweden as a proxy for the dynamics of their main prey, voles and Norwegian lemming, respectively. We analyse data from five decades, 1960-2008, with wavelets and autocorrelation approaches. Cyclic dynamics were identified with at least one method in all populations (arctic fox n = 3, red fox n = 6). The dynamics were synchronous between populations, or coupled with a 1-yr lag, in 8 of 13 pairwise comparisons. Importantly though, the dynamics were heterogeneous in space and time. All analytical approaches identified fading cycles in the three arctic fox populations and two northern red fox populations. At least one method identified similar patterns in three southern red fox populations. Red fox dynamics were cyclic in the 1970s primarily, while arctic fox dynamics was cyclic until the late 1980s or early 1990s. When cyclic, 4-yr cycles dominated in arctic fox and northern red fox, whilst 3-4-yr cycles was found in southern red foxes. Significant cyclic regimes reappeared in the 1990s or 2000s in two red fox populations and one arctic fox population. Cycles and regionally coupled dynamics appeared associated in northern arctic and red foxes. This study supports accumulating evidence which suggests that cyclic and synchronous patterns in the dynamics of lemmings and voles are nonstationary in space and time. Furthermore, the similar patterns of change in both fox species indicate that persistence of cycles is governed by similar mechanisms in lemmings and voles. © Finnish Zoological and Botanical Publishing Board 2011.

Bergqvist G.,Swedish Association for Hunting and Wildlife Management | Bergstrom R.,Forestry Research Institute of Sweden | Wallgren M.,Forestry Research Institute of Sweden
Scandinavian Journal of Forest Research | Year: 2013

Moose (Alces alces L.) browse Scots pine (Pinus sylvestris L.) mainly during the winter. There is a growing concern also regarding summer browsing by moose on Scots pine. We studied summer browsing on Scots pine during two consecutive years. In a survey of 47 stands in 2003, current summer browsing was found for 20.4% of the Scots pine main stems, and on almost half of them (9.8%) the top shoot was browsed. This indicates that the pine damage causing reduced wood quality was as serious during summer as during the preceding winter. There was significantly more summer browsing on previously browsed pines, compared to a random use, both at tree and stand level, and summer browsing was also spatially clumped within stands. Browsing on top shoots occurred up to a height of 2.8 m, whereas side shoot browsing was recorded for pines with a height up to 4.8 m. In 2004, 11 of the 47 stands were randomly selected for a more detailed study of pines browsed during that summer. The summer browsed trees contained, on average, 114 current shoots tree-1, and 10.5 shoots tree-1 (9.2%) were browsed. In this area, summer browsing may explain a considerable part of the moose-related forest damage recorded. The proportion of pines subjected to summer browsing did not change with availability of pines. Hence, increasing the number of Scots pine trees in young stands may be a way to increase the number of unbrowsed pine trees at a given moose population density. © 2013 Copyright Taylor and Francis Group, LLC.

Bergqvist G.,Swedish Association for Hunting and Wildlife Management | Bergstrom R.,Forestry Research Institute of Sweden | Wallgren M.,Forestry Research Institute of Sweden
Scandinavian Journal of Forest Research | Year: 2012

Food selection by large herbivores occurs at a hierarchy of scales, for example landscape, patch or plant. Several hypotheses regarding food plant selection on patch or plant level have been developed. In this cafeteria-type design field experiment, conducted during one winter immediately after planting, we tested the effect of species mixture on browsing by large herbivores (mainly roe deer) on Scots pine seedlings in mixture with seedlings of ash (highly preferred) or silver birch (less preferred). Browsing on Scots pine was not affected by species mixture, neither in terms of the number of browsed pines nor browsing intensity. Instead, browsed biomass was positively and significantly correlated to the total biomass available for browsing. Also, there were differences due to species, with ash being most browsed (44.6%), followed by Scots pine (18.9%) and silver birch (11.6%). Browsed biomass per browsed seedling, however, was largest for Scots pine. In addition, browsed seedlings were initially taller compared to unbrowsed seedlings for all species. The main management implication in this study is that the species mixture did not influence large herbivore browsing on Scots pine seedlings. Hence, removing or discouraging more (or less) attractive browse species in early stages of pine regeneration activities seems unnecessary from the point of large herbivore browsing. © 2012 Copyright Taylor and Francis Group, LLC.

Carlsson N.O.L.,The County Administrative Board | Carlsson N.O.L.,Cary Institute of Ecosystem Studies | Jeschke J.M.,Cary Institute of Ecosystem Studies | Jeschke J.M.,Ludwig Maximilians University of Munich | And 3 more authors.
Biological Invasions | Year: 2010

Studies of the effects and population dynamics of invasive species typically cover only short time periods. However, populations of invasive species interact with native species, and these interactions may have strong effects on invaders' populations and effects over time. We present and analyze long-term data on invasive American mink (Neovison vison), native red fox (Vulpes vulpes), and mountain hare (Lepus timidus) in Sweden. The mink's population dynamics followed a pattern of logistic growth from the late 1930s to the late 1970s. In the early 1980s, however, the population tripled, then declined sharply. We suggest that the mink's population tripling was caused by a drastic decline in red fox populations, which caused terrestrial prey to increase. Later recovery of the fox population reversed the trend and caused the mink population's recent decline. Our study shows that species interactions between native and invasive species, and therefore biotic resistance, can change dramatically over time. © 2009 Springer Science+Business Media B.V.

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