| 1. |
- Elmberg, Johan, et al.
(författare)
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Climate change-induced shifts in survival and size of the worlds' northernmost oviparous snake : A 68-year study
- 2024
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Ingår i: PLoS ONE. - : Public Library of Science. - 1932-6203. ; 19:3
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Tidskriftsartikel (refereegranskat)abstract
- Because of their dependence on ambient temperature ectothermic animals can serve as sentinels of conservation problems related to global warming. Reptiles in temperate areas are especially well suited to study such effects, as their annual and daily activity patterns directly depend on ambient temperature. This study is based on annual data spanning 68 years from a fringe population of Grass Snakes (Natrix natrix), which is the world's northernmost oviparous (egg-laying) reptile, and known to be constrained by temperature for reproduction, morphology, and behavior. Mark-recapture analyses showed that survival probability was generally higher in males than in females, and that it increased with body length. Body condition (scaled mass index) and body length increased over time, indicative of a longer annual activity period. Monthly survival was generally higher during winter (i.e., hibernation) than over the summer season. Summer survival increased over time, whilst winter survival decreased, especially duringrecent decades. Winter survival was lower when annual maximum snow depth was less than 15 cm, implying a negative effect of milder winters with less insulating snow cover. Our study demonstrates long-term shifts in body length, body condition and seasonal survival associated with a warming climate. Although the seasonal changes in survival ran in opposite directions and though changes were small in absolute terms, the trends did not cancel out, but total annual survival decreased. We conclude that effects of a warming climate can be diverse and pose a threat for thermophilic species in temperate regions, and that future studies should consider survival change by season, preferably in a long-term approach.
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| 2. |
- Elmberg, Johan, et al.
(författare)
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Movements and habitat choice of resident and translocated adult female Grass Snakes (Natrix natrix) during the egg-laying period
- 2019
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Ingår i: Herpetological Journal. - : BRITISH HERPETOL SOC. - 0268-0130. ; 29:4, s. 244-250
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Tidskriftsartikel (refereegranskat)abstract
- We used externally applied transmitters to study movements of female grass snakes (Natrix natrix) during the egg-laying period in a near-urban landscape in Sweden. Half of the studied snakes were residents while the other half were translocated individuals with no previous experience of the area. As predicted, resident females moved more goal-oriented and shorter distances than did translocated individuals. Habitat use did not differ between resident and translocated snakes; they were typically found in bushes, reeds, and tall vegetation. Habitat preference (use in relation to availability) showed that bushy habitats, tall grassy vegetation and reedbeds were over-used in proportion to availability, whereas forest and open grass lawns were used less than expected based on availability. Our study highlights the importance of preserving and restoring linear habitat components providing shelter and connectivity in conservation of grass snakes. We suggest that externally applied transmitters are a better option than surgically implanted ones in movement studies of grass snakes, and that translocation as a conservation method for snakes has drawbacks.
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| 3. |
- Elmberg, Johan, 1960-, et al.
(författare)
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Snokens barnkammare försvinner
- 2013
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Ingår i: Fauna och flora. - 0014-8903. ; 108:1, s. 10-16
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Elmberg, Johan, et al.
(författare)
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Snokens barnkammare försvinner
- 2013
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Ingår i: Fauna och flora populär tidskrift för biologi. - 0014-8903. ; 108:1, s. 10-16
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Hagman, Mattias, et al.
(författare)
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Grass snakes (Natrix natrix) in Sweden decline together with their anthropogenic nesting-environments
- 2012
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Ingår i: Herpetological Journal. - : British Herpetological Society. - 0268-0130. ; 22:3, s. 199-202
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we show that the number of grass snake (Natrix natrix L.) specimens deposited in Swedish museum collections has declined in the last eighty years, and that this is correlated with a dramatic national decrease in the number of livestock holdings. These results support the hypothesis that Swedish grass snakes are declining and that this may be linked to a loss of important nesting-environments provided by open manure heaps in small-scale farming. Our study suggests that information obtained from museum databases potentially may be used to explore population trends for snakes and other reptiles.
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| 6. |
- Hallinger, Martin, et al.
(författare)
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Does it pay to concentrate conservation efforts for dead-wood dependent insects close to existing reserves : a test on conservation planning in Sweden
- 2018
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Ingår i: Insect Conservation and Diversity. - : Wiley. - 1752-458X .- 1752-4598. ; 11:4, s. 317-329
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Tidskriftsartikel (refereegranskat)abstract
- Forestry has significantly changed many boreal forest landscapes with negative effects on biodiversity. Main reasons are habitat loss and deterioration, due to a simplified forest composition, including a reduction in old trees and dead wood. In Sweden, measures to counter the loss of biodiversity are taken at forest harvesting, and include forest harvest retention.Areas of high conservation values (AHCV) have been identified in Sweden to prioritise conservation efforts, but so far these areas have not been used when making decisions about forest harvest retention.In this study, we tested if dead wood from forest harvest retention is used by more dead wood‐dependent insect species (24 beetles and four other insects, redlisted or indicating high biodiversity) on clearcuts within than outside of AHCVs and whether the composition of the surrounding landscape influences species occurrence.There were not more dead wood‐dependent insect species per clearcut within AHCVs than outside. The surrounding landscape had an influence on the species richness on clearcuts, but in several cases the pattern was the opposite of our hypotheses. Increased standing volume of relevant tree species, however, tended to increase the occurrence or number of associated species.The designation of ACHVs in Sweden is not related with occurrence of dead wood or dead wood‐dependent organisms. We also found that landscape context can have effects on species richness. The result urges for better planning so that ACHV areas are designated in landscapes where their potential for conservation of dead wood‐dependent organisms is highest.
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| 7. |
- Hekkala, Anne-Maarit, et al.
(författare)
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Ecological restoration for biodiversity conservation triggers response of bark beetle pests and their natural predators
- 2020
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Ingår i: Forestry: An International Journal of Forest Research. - : Oxford University Press (OUP). - 1464-3626 .- 0015-752X. ; 94, s. 115-126
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Tidskriftsartikel (refereegranskat)abstract
- The restoration of forest structure and function is increasingly being used in boreal forests in order to halt the loss of biodiversity. Often ecological restoration is aimed at increasing the volume of dead and dying trees to enhance the biodiversity of deadwood-dependent organisms, but it may also increase population sizes of pest bark beetle species, even several years following restoration. Herein, we used a large-scale restoration experiment in Northern Sweden to assess the 5 years post-restoration effects of restorative gap cutting and prescribed burning on the populations of a set of economically harmful pest bark beetles (Ips typographus, Polygraphus poligraphus, Tomicus piniperda and Pityogenes chalcographus) and the most important predators of bark beetles, Thanasimus spp. In addition, we assessed the effects of forest stand characteristics at stand and landscape scale on the abundance of I. typographus. Five years post-restoration, gap-cut stands supported the highest abundances of P. poligraphus and contained the highest count of spruce trees newly attacked by bark beetles. By contrast, prescribed burning generally sustained the lowest abundances of pest bark beetles, especially I. typographus and P. poligraphus, and the highest abundance of their natural predators Thanasimus spp. The population abundance of I. typographus was also positively affected by the area of clear cuts within a 500 m radius from the stand. In conclusion, prescribed burning appears to be a safer method for ecological restoration than gap cutting in the long-term. According to our results, a risk of a local bark beetle outbreak still remains 5 years following the initiation of ecological restoration treatments on spruce-dominated mature gap-cut stands.
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| 8. |
- Hekkala, Anne-Maarit, et al.
(författare)
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Habitat heterogeneity is a good predictor of boreal forest biodiversity
- 2023
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Ingår i: Ecological Indicators. - : Elsevier BV. - 1470-160X .- 1872-7034. ; 148
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Tidskriftsartikel (refereegranskat)abstract
- Reliable assessment measures are crucial for tracking changes in biodiversity and for evaluating the state of biodiversity. Two of the main drivers of biodiversity are habitat heterogeneity and resource amount. These drivers are used as proxies of biodiversity but assessing both is costly, limiting their practical use. To test which of the drivers best predicts the number and abundance of sessile species of conservation concern (including macrofungi, lichens, bryophytes, and vascular plants), we assessed forest stand heterogeneity using a method developed in Sweden ('Habitat Heterogeneity Score HHS'), and quantified the resource amount and quality of ecologically important structural variables (deadwood volume, basal area of living trees, proportion of broadleaved trees, and the age of the oldest tree in the stand). We conducted the assessments in 77 boreal coniferdominated forest stands in two regions of Sweden. Despite some group-specific organism differences, HHS was the best predictor of both number and abundance of all species of conservation concern, regardless of the region. Further, HHS was the best predictor of red-listed species number and abundance in the southern region, while a model including the volume of deadwood and the age of the oldest tree performed best in the northern region. Deadwood (CWD) volume was the single best resource amount predictor of the number and abundance of species of conservation concern, emphasizing the critical role that dead trees have for biodiversity. In addition, we calculated threshold values for deadwood volume and HHS depicting the level above which the number of red-listed species is significantly higher, and found this value to be higher in the southern region (22.4 m(3) ha(-1) deadwood and a HSS value of 17) than in the north (20.0 m(3) ha(-1) and 16). These values can be used as guidance when identifying coniferous forests with high enough qualities to support red-listed species. To conclude, the method of assessing habitat heterogeneity presented in this study is a practical and reliable way to identify forests of high biological diversity, and can therefore be part of the toolbox for sustainable forestry in boreal forests.
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| 9. |
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| 10. |
- Kärvemo, Simon, et al.
(författare)
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Beetle diversity in dead wood is lower in non-native than native tree species, especially those more distantly related to native species
- 2023
-
Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 60, s. 170-180
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Tidskriftsartikel (refereegranskat)abstract
- Non-native tree species are widely used in forest plantations. This may have negative consequences for biodiversity. Hitherto, most studies have compared species diversity between native and non-native forest stands, which makes it difficult to separate the impact of tree species per se from stand characteristics. Our study, conducted in the south of Sweden, compares saproxylic beetle diversity across different nutritional groups, in dead wood of two native and four non-native tree species in a block design after one and three seasons. Such an approach allows analysis of the impact of non-native tree species per se. Mean species richness (+/- SD) per log was lower in non-native than in native tree species (non-native trees: lodgepole pine: 10.7 (+/- 5.3); Sitka spruce: 8.5 (+/- 4.3), Douglas fir: 7.1 (+/- 4.3), Japanese larch 9.4 (+/- 4.6); native trees: Norway spruce: 12.0 (+/- 6.0), Scots pine: 12.3 (+/- 5.2)). Sample-based rarefaction revealed that when only native tree species were pooled, the species richness was higher than for all tree species combined. The difference in species composition among tree species was strongly driven by bark and wood consumers in the first season, while for predators and fungivores, the differences were smaller. Species composition differed most in the first season. Dissimilarity in beetle species composition was positively correlated with phylogenetic distances of the tree species. Species richness was lower in non-native tree species that are only remotely related to native trees species. Of the studied non-native tree species, lodgepole pine was more closely related to native tree species and consistently harboured higher species richness. Synthesis and applications. Although non-native tree species also harbour saproxylic beetle communities, the use of non-native tree species, especially those only remotely related to native tree species, reduces local diversity of saproxylic beetles. Thus, for biodiversity conservation, an extensive use of non-native tree species is not recommended as this increases the risk of losing forest biodiversity, especially when they are only distantly related to native tree species.
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| 11. |
- Kärvemo, Simon, 1979-, et al.
(författare)
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Chytrid fungus dynamics and infections associated with movement distances in a red-listed amphibian
- 2020
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Ingår i: Journal of Zoology. - : Wiley. - 0952-8369 .- 1469-7998. ; 311:3, s. 164-174
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Tidskriftsartikel (refereegranskat)abstract
- Amphibians are among the most threatened vertebrate taxa due to anthropogenic habitat change and emerging pathogens. The fungus Batrachochytrium dendrobatidis (Bd) may cause trade‐offs between the immune responses and other important functions, such as mobility. The pool frog (Pelophylax lessonae) is red‐listed in Sweden, and an earlier study conducted in our study area did not detect the fungus. In this study, 67 Swedish pool frogs were tested for Bd. Of these, 28 adults were provided with external radio transmitters and tracked during the summer and autumn to compare movement among infected and non‐infected individuals. Additionally, we tested some individuals for Bd twice during the summer to study intra‐seasonal variation in individual infections. Our results suggest that Bd has recently invaded these pool frog populations. During autumn, movement distances of infected pool frogs were shorter compared to uninfected individuals, and summer movements within ponds were reduced by increasing Bd load. We also found that the frogs can clear (or reduce) Bd infection during their active season. The results from this study increase understanding of the implications of Bd infections in an anuran fringe population, as well as in amphibian metapopulations, and can further guide amphibian conservation planning and management.
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| 12. |
- Kärvemo, Simon, et al.
(författare)
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Different triggers, different stories: Bark-beetle infestation patterns after storm and drought-induced outbreaks
- 2023
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Ingår i: Forest Ecology and Management. - 0378-1127 .- 1872-7042. ; 545
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Tidskriftsartikel (refereegranskat)abstract
- In the recent decades, Norway spruce forests (Picea abies Karst.) in Europe have been subject to large-scale tree mortality caused by the spruce bark beetle (Ips typographus L.). The outbreaks were induced by storm-felling events and periods of drought, which are becoming increasingly frequent due to climate change. Because storms and droughts spatially affect forests differently, the infestation patterns and configuration of the bark beetles might differ between storms and drought. In this study, we examined local and landscape factors associated with bark beetle-caused tree mortality after one storm (2005) and one drought-induced spruce bark beetle outbreak (2018), both occurring in southern Sweden. A total of 13,192 infested one-ha pixels after the storm and 6,425 one-ha pixels after the drought (in total 19,617) were compared regarding differences in infestation occurrence and size and associated forest structures and climate between the two different outbreaks, using a generalized linear model (GLM) approach. Based on our findings, we discovered that the allocation of infestation patch sizes (including four classes: 5-10, 11-25, 26-50 and >50 infested trees) for the two outbreaks were quite similar with a large proportion (>0.6) of small groups (& LE;10 trees). However, the outcomes from this study demonstrate that the drivers behind the spatial configuration of bark beetle infestations can differ considerably between outbreaks triggered by storms and droughts, and the main cause seems to be linked to the spatial distribution of susceptible trees. The most consistent differences for both occurrence and infestation size were that storm-induced infestations increased more with spruce volumes and area of protected forests (nature reserves) in the landscape; whereas for the drought-induced infestations, occurrence and size increased more with clear-cuts in the landscape and spruce heights across spatial scales. Soil moisture and mean drought index (SPEI; May-July) were important for both outbreaks, but generally more important for the infestation sizes after droughts than after storms and may involve a time-lagged effect. The reasoning behind the differences between storms and droughts may be that during storm-induced outbreaks, when the wind-felled trees are removed or not suitable anymore, bark beetles need to find specific susceptible standing trees, while after drought all trees are more or less stressed, which results in a selection of large trees in dry and warm landscapes as they have more resources and favorable reproduction conditions. Finally, we show that the previous infestation size influenced the later infestation size negatively within landscapes of 25 ha and this seems to be related to depletion of susceptible host trees. These results are important for the assessment of more specific outbreak predictions, which should be integrated in future risk mapping of bark beetle outbreaks.
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| 13. |
- Kärvemo, Simon, et al.
(författare)
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Dynamics of spruce bark beetle infestation spots : Importance of local population size and landscape characteristics after a storm disturbance
- 2014
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 334, s. 232-240
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Tidskriftsartikel (refereegranskat)abstract
- The European spruce bark beetle Ips typographus (L) is one of the most important pests of mature Norway spruce in Europe. Outbreaks are often triggered by large-scale storm disturbances, which provide the beetles with a large surplus of suitable breeding material in the form of wind-felled spruces in storm gaps. Due to high reproductive success in storm-felled trees beetle populations may become large enough to overcome defences of living trees in the summers following a storm. From a management perspective, procedures enabling reliable predictions of local tree mortality based on the size of storm gaps would be highly valuable. Thus, in the presented study we recorded tree mortality caused by I. typographus during a five-year period around 35 storm gaps hosting local beetle populations, differing in size with 0-818 colonised wind-felled spruces. We then developed models to address the following questions. How does local population size in wind-felled trees influence tree mortality in the subsequent years? What other storm gap and landscape variables influence tree mortality? How does the tree mortality compare with results of earlier studies? Four gap variables and three landscape variables at four scales (500-2000 m) were included in the models. In total, 21,486 standing spruces were killed by I. typographus around the gaps. Tree mortality started in the second summer after the storm and peaked in the third year around most gaps. The models explained most of the variation in tree mortality around the gaps during the five-year period, accounting for 60-67% of the deviance from null models. The most important variable influencing tree mortality was the number of colonised wind-felled trees (a proxy for the size of local populations), explaining 60-64% of the null deviance. Other gap variables that significantly, and positively, affected tree mortality were the mean diameter of colonised wind-felled trees and basal area of living spruce trees in stands adjacent to the storm gaps. Of the landscape variables, the area of storm gaps in the surrounding landscape explained most of the variation in the models. The area of spruce forest also had a significant positive effect at the largest scales. The finding that the number of colonised wind-felled trees was closely related to the number of killed trees in the forest around the gaps implies that areas with numerous large storm gaps should be harvested first after large-scale storm disturbances. (C) 2014 Elsevier B.V. All rights reserved.
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| 14. |
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| 15. |
- Kärvemo, Simon, 1979-, et al.
(författare)
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Effects of host species and environmental factors on the prevalence of Batrachochytrium dendrobatidis in northern Europe
- 2018
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Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 13:10
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Tidskriftsartikel (refereegranskat)abstract
- The fungal pathogen Batrachochytrium dendrobatidis (Bd) poses a major threat to amphibian populations. To assist efforts to address such threats, we examined differences in Bd host infection prevalence among amphibian species and its relations to both local environmental factors in breeding habitats and landscape variables measured at three scales (500, 2000 and 5000 m radii) around breeding sites in southernmost Sweden. We sampled 947 anurans of six species in 31 ponds and assessed their infection status. We then examined correlations of infection prevalence with canopy cover, pond perimeter and pH (treated as local-scale pond characteristics), and the number of ponds, area of arable land, area of mature forest, number of resident people and presence of sea within the three radii (treated as landscape variables). The Bd infection prevalence was very low, 0.5-1.0%, in two of the six anuran species (Bufo bufo and Rana temporaria), and substantially higher (13-64%) in the other four (Bombina bombina, Bufotes variabilis, Epidalea calamita, Rana arvalis). In the latter four species Bd infection prevalence was positively associated with ponds' pH (site range: 5.3-8.1), and negatively associated with areas of mature forest and/or wetlands in the surroundings. Our results show that the infection dynamics of Bd are complex and associated with host species, local pond characteristics and several landscape variables at larger spatial scales. Knowledge of environmental factors associated with Bd infections and differences in species' susceptibility may help to counter further spread of the disease and guide conservation action plans, especially for the most threatened species.
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| 16. |
- Kärvemo, Simon, et al.
(författare)
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Forest restoration as a double-edged sword: the conflict between biodiversity conservation and pest control
- 2017
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 54, s. 1658-1668
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Tidskriftsartikel (refereegranskat)abstract
- 1. Forestry has markedly changed a large proportion of the world's boreal forests, often with negative effects on biodiversity. As a result, forest restoration is increasingly implemented to counteract the negative effects. However, restoration measures aimed at mimicking natural disturbance regimes could simultaneously increase the risk of unwanted negative effects, such as damage by forest pest species. This study compares the effect of two restoration methods (prescribed burning and gap-cutting), on both biodiversity conservation and pest control, to provide a basis for solutions to this potential conflict.2. Bark beetles are ideal for studying this conflict, as this group is both species-rich and contains notorious pest species. We conducted a unique, large-scale field experiment in which we compared the effect of two different restoration methods on the abundance, species richness and assemblage composition of bark beetles. In addition, we estimated uncontrolled tree mortality by the number of trees that died post-restoration.3. Beetles were divided in two groups, primary and secondary, the former with an ability to kill growing trees. Bark beetle diversity did not differ between treatment groups prior to restoration. However, after restoration, assemblage composition and primary bark beetle abundance differed between the treatments. Furthermore, species richness was higher in burned and gap-cut stands compared to reference stands4. The number of trees that died post-restoration was highest on burned sites, whereas no difference was found between gap-cut and reference stands. The number of dead trees was correlated with the number of primary beetles.5. Synthesis and applications. We demonstrate the potential for a conflict between forest restoration for biodiversity conservation and the potential risk for tree mortality caused by forest pests. This is likely to become a problem in many boreal forests; however, our results suggest that this conflict can be moderated by the choice of restoration method. The restoration method gap-cutting had a similar positive impact on bark beetle species richness as compared to the burning method, but did not as burning, increase tree mortality. Thus, in areas where there is an apparent risk for pest outbreaks, our data suggest that gap-cutting should be the chosen method to avoid an unwanted increase in tree mortality at the stand level.
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| 17. |
- Kärvemo, Simon
(författare)
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Gender differences in seasonal movements of dice snakes in Histria, southeastern Romania
- 2011
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Ingår i: Mertensiella. - 0934-6643. ; 18, s. 245-254
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Tidskriftsartikel (refereegranskat)abstract
- An archaeological excavation site among ancient ruins in Histria, south-eastern Romania, that harbours several thousand dice snakes (Natrix tessellata), is the focus of various ongoing studies. The current work evaluates seasonal variation of gender specific movements. Seasonal movements were estimated from captures of adult snakes over four years. Visible abundance of snakes among the ruins was largest in early spring and autumn. Summed over one entire season, the capture rates were similar for both sexes. During April males were more frequently captured than females. However, the proportion of males decreased later during the mating period in spring and until the end of June, only to rise again in August. Capture rates of gravid females continued to remain high in the vicinity of the ruins throughout vitellogenesis until ovulation, for which they mainly stayed near the hibernation area, which is also favoured for ovipositing. At the onset of hibernation in October, the ratio of males to females was consistently 0.4 across all years of study. We suggest that the skewed sex ratio among captures is due to gender-specific behaviours rather than to a naturally uneven sex ratio or capture artefacts. Males generally emerge earlier from hibernation in order to maximize their chances to reproduce. Consistent with our data, we suggest that in autumn males may be entering hibernation dens over a longer period than do females. Arguably, males do not have the same energy requirements as females, which could be expected to exploit the feeding season maximally, due to their higher-energy reproductive investment
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| 18. |
- Kärvemo, Simon, et al.
(författare)
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Large-scale risk mapping of an eruptive bark beetle – Importance of forest susceptibility and beetle pressure
- 2014
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 318, s. 158-166
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Tidskriftsartikel (refereegranskat)abstract
- Bark beetle outbreaks have increased in Europe and North America. To mitigate damage efficiently during outbreaks, robust models predicting where the risk for tree mortality is highest across forest landscapes and better understanding of the underlying mechanisms are required. Using Boosted Regression Trees, we modelled relative risks of infestation by the spruce bark beetle Ips typographus (L.) across a 130,000ha managed lowland forest landscape in southern Sweden during three years of an outbreak and at a resolution of 100×100m. A second nearby landscape of similar size was used for validation. Both predictors reflecting forest susceptibility and beetle pressure were used. Forest susceptibility predictors included volume per ha of host and non-host trees, tree height and distance to the nearest clear-cut harvested during the last four years, all based on interpretations of satellite images. Bark beetle predictors were based on locations and sizes of previous year infestation spots recorded by helicopter. Model outcomes were similar across years, and there was no major reduction in performance when extrapolating predictions in space or time, indicating the modelled relationships have high reliability. Area under curve (AUC) values varied from 0.729 to 0.818. Including bark beetle predictors increased the AUC value somewhat in one of two years. The most important predictor was volume per ha of the host tree, Norway spruce Picea abies (L.) Karst., which reflects the probability of bark beetles encountering suitable trees. This variable was strongly positively correlated with risk up to 200m3ha-1. Unexpectedly, the volume of the non-host birch was also positively correlated with infestation risk up to 25m3ha-1. Tree height was associated with increased infestation risk above heights of 10m in 2008 and 15m in 2009. In 2007 and 2008 there was a weak negative relationship between infestation risk and distance to the nearest clear-cut. Additionally, our study shows that in managed forest landscapes the I. typographus-killed trees are distributed in many small infestation spots spread out over the landscape. We demonstrate that high-resolution risk-rating maps can be successfully created for large landscapes using easily accessible satellite data of forest characteristics and aerial surveys of infestation spots. The distribution of killed trees in many small infestation spots, poses a challenge for the forest owners to find and remove colonized trees before the new generation emerge. Our results suggest that mitigation efforts in managed lowland forest should focus on high volume spruce stands.
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| 19. |
- Kärvemo, Simon
(författare)
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Life at the edge: The nesting ecology of the world's most northerly oviparous snake and its implications for conservation
- 2013
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Ingår i: Reptiles in research - Investigations of ecology, physiology, and behavior from desert to sea. - 9781628086201 ; , s. 247-264
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Bokkapitel (refereegranskat)abstract
- Temperature imposes a major constraint on reptiles in cold climates. Embryonic development is particularly challenging and oviparous (egg-laying) species may not have access to nesting sites that offer suitable thermal regimes over the duration of the incubation period. Cold-climate reptiles are therefore typically dominated by viviparous (live-bearing) species, because gravid females can regulate their internal temperature behaviorally to maintain high temperatures for the embryos developing inside their bodies. The hypothesis that ambient temperatures restrict the geographic range of oviparous reptiles is strongly supported by correlations between reproductive mode (oviparity versus viviparity) and distributional patterns. The European grass snake (Natrix natrix) is therefore unusual in that it occurs farther north and endures colder climates than any other oviparous snake species in the world. It also is unusual in preferring to nest in anthropogenic environments that function as heat sources, such as compost piles and manure heaps. Oviposition sites of these types are distinctive habitats in the sense that they provide higher temperatures than any other sites in the surrounding landscape. Our work on this system shows that the grass snake’s exploitation of these thermally distinctive man-made microhabitats enables it to colonize areas with much colder climates than can support other types of oviparous reptiles. These microhabitats also serve as a major influence on many aspects of this species life-history, including the incubation period. However, relying on man-made structures for successfully hatching the eggs is a risky strategy if circumstances suddenly change such that the structures decrease or become inaccessible. In this chapter we review the unusual nesting ecology of the grass snake and discuss its implications for conservation.
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| 20. |
- Kärvemo, Simon, et al.
(författare)
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Local colonization-extinction dynamics of a tree-killing bark beetle during a large-scale outbreak
- 2016
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Ingår i: Ecosphere. - : Wiley. - 2150-8925. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Forest pest insects may cause large-scale tree growth reductions and tree mortality during outbreaks. The large-scale development of outbreaks has frequently been studied, while the colonization-extinction dynamics during outbreaks is less known. We study the colonization-extinction dynamics of a severe tree-killing bark beetle, Ips typographus, during an outbreak across a 130000ha forest landscape in southern Sweden. We recorded annual colonization and extinction events in 1ha pixels across the landscape by helicopter surveys during three consecutive years, and modeled colonization and extinction probabilities based on focal pixel quality, local population size, connectivity to surrounding beetle populations, and tree composition in the surrounding landscape. The local populations had a high turnover; 81-93% of all occupied pixels were the result of colonizations in the same year and the annual extinction rates were 84-90%. The colonization probability increased and the extinction probability decreased with increasing spruce (host-tree) volume in focal pixels and the connectivity. The fitted spatial scaling parameter of the connectivity measure suggested that the colonization probability was mainly affected by the number of surrounding occupied pixels within a few hundred meters. The colonization probability also decreased with increasing volume of birch (a nonhost) in the focal pixel, while the extinction probability decreased with increasing local population size. In conclusion, the local population size and quality of the focal pixel explained more of the colonization and extinction probability than the connectivity and composition of surrounding forest. The distribution of tree-killing bark beetles during outbreaks can be patchy and highly dynamic. Two reasons for this are the increased probability of successful attacks when exceeding a critical attack density and the fragmented distribution of large spruce volumes throughout the forest landscape.
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| 21. |
- Kärvemo, Simon
(författare)
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Monitoring a large population of dice snakes at lake Sinoe in Dobrogea, Romania
- 2011
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Ingår i: Mertensiella. - 0934-6643. ; , s. 237-244
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Tidskriftsartikel (refereegranskat)abstract
- Dice snakes (Natrix tessellata) can reach exceptionally large population densities where local conditions permit. Here we report on a study of one large population from Histria, the southern-most area of the Danube Delta in Romania. There the dice snakes forage in the brackish waters of Lake Sinoe. Many snakes are visibly infected by parasitic nematodes, which have piscivorous birds as definitive hosts. The nematode, Eustrongylides excisus, can be fatal to its snake host. In 2005, we began to study the dice snake population at Histria. In 2006 we initiated a monitoring study based on capture-mark-recapture methodology using PIT tag markers. This paper presents general aspects of this population and analyses the results to date in relation to fieldwork effort. We also discuss how external factors may affect the dynamics of the population. Even though it is generally considered that the population was larger in the past, we have not found evidence of a population decline. We estimate that the population has remained at or above 10,000 adult individuals during the three years of PIT tagging
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| 22. |
- Kärvemo, Simon, et al.
(författare)
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Multi-taxon conservation in northern forest hot-spots: the role of forest characteristics and spatial scales
- 2021
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Ingår i: Landscape Ecology. - : Springer Science and Business Media LLC. - 0921-2973 .- 1572-9761. ; 36, s. 989-1002
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Tidskriftsartikel (refereegranskat)abstract
- Context Biodiversity is highly affected by industrial forestry, which leads to the loss and fragmentation of natural habitats. To date, most conservation studies have evaluated associations among a single species group, forest type, or spatial scale. Objective The objective was to evaluate the richness of multiple species groups across various forest types and characteristics at multiple scales. Methods We used the occurrence data for 277 species of conservation interest from 455 stands of high conservation value, including four species groups and four forest types. Results Local, landscape, and regional forest characteristics influenced biodiversity in a non-uniform pattern among species groups and forest types. For example, an increased local spruce basal area in spruce forests was associated with higher vascular plant and bryophyte richness values, whereas macrofungi and lichen richness were positively correlated with deadwood availability, but negatively correlated with the spruce volume in the landscape. Furthermore, landscapes with twice as much mature forest as the average, had more than 50% higher richness values for vascular plants, macrofungi, and lichens. Conclusion Among sessile species groups in northern forests, a uniform conservation strategy across forest types and scales is suboptimal. A multi-faceted strategy that acknowledges differences among species groups and forest types with tailored measures to promote richness is likely to be more successful. Nevertheless, the single most common measure associated with high richness across the species groups and forest types was mature forest in the landscape, which suggests that increasing old forests in the landscape is a beneficial conservation strategy.
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| 23. |
- Kärvemo, Simon
(författare)
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Outbreak dynamics of the spruce bark beetle Ips typographus in time and space
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The European spruce bark beetle Ips typographus (L.) is one of the most important pests of mature Norway spruce Picea abies (Karst.) in Europe. Outbreaks (periods with large-scale beetle-caused tree mortality) are often triggered by large-scale stormfellings or drought, which provide a large surplus of suitable breeding material. The overall aim of the studies in this thesis was to increase knowledge about how forest characteristics and local beetle populations influence tree mortality and bark beetle outbreak dynamics in time and space. We found that the size of infestation spots in general were small (<10 killed trees), that they had high extinction probabilities in the next beetle generation. The main factors increasing the probability of infestation spots in new locations (i.e. colonisations) and decreasing the probability of spot extinction were volume of spruce per ha and to some extent connectivity (i.e. distance and spot size) to neighbouring infestation spots from the previous year. The total number of killed trees during the outbreak in stands surrounding storm gaps increased with the size of the local population of I. typographus initially produced in the storm-felled trees in the storm gaps (measured as number of colonised stormfelled trees). The effect of the previous year’s local population declined as the outbreak progressed due to host tree depletion in the areas with the largest storm gaps. The reproductive success of beetles at the tree level scale was negatively influenced by the colonisation density (as a result of intraspecific competition), which in turn was affected by the trees’ diameter. The reproductive success and colonisation density differed strongly between the outbreak years. A low reproductive success in the final years may have contributed to the ultimate collapse of the outbreak. Increases in the density of natural enemies were lower than expected but may also have contributed somewhat to the outbreak collapse. The results from the different studies demonstrate a large complexity in the bark beetle-host tree interactions that influence the outbreak dynamics of I. typographus in time and space.
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| 24. |
- Kärvemo, Simon
(författare)
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Population dynamics of tree-killing bark beetles - a comparison of the European spruce bark beetle and the North American mountain pine beetle
- 2010
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Rapport (populärvet., debatt m.m.)abstract
- During outbreak periods, the European spruce bark beetle and the North American mountain pine beetle are able to kill millions of coniferous trees. Throughout the 20th century, six outbreaks have occurred in Sweden and four in British Columbia, with about 20-year intervals in both regions. The outbreaks of the mountain pine beetles seem to grow much larger and last longer compared to the outbreaks of the spruce bark beetles. Over the years, the mountain pine beetle has killed about 60 million ha forest or 550 million m3 trees in British Columbia, which is at least one hundred times more than for the Spruce bark beetle in Sweden. Damages of both species have increased markedly in the last forty years. About 750 spruce bark beetles per m2 are necessary to kill a healthy spruce, whereas seven times fewer, i.e., about 110 mountain pine beetles per m2, are needed to kill a healthy pine. Furthermore, twice as many offspring per m2 bark are produced by the spruce bark beetle compared to the mountain pine beetle. An explanation for the large differences in population dynamics between these two beetle species may spring from differences in (1) the availability of host trees, (2) number of specimens required to kill a tree, and (3) reproductive success. The latter is in turn affected by the intraspecific competition, nutrient content, and occurrence of fungi
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| 25. |
- Kärvemo, Simon
(författare)
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Snokens barnkammare försvinner
- 2013
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Ingår i: Fauna och flora. - 0014-8903. ; 108, s. 10-16
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Snoken är en av tre svenska ormarter och världens nordligaste reptil som lägger ägg. I en färsk analys visar vi att det går dåligt för snoken i Sverige. Därför är det alarmerande att man vet så litet om orsakerna. Vi tror att minskningen kan bero på brist på bra äggläggningsplatser, men trots sentida forskning är de obesvarade frågorna många. Hur ser snokens ursprungliga "barnkammare" ut? Och var lägger dagens snokar sina ägg? I denna artikel sammanfattar vi kunskapsläget och vädjar till den naturintresserade allmänheten om hjälp. Vi tycker att det snokas för litet! j
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| 26. |
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| 27. |
- Kärvemo, Simon, 1979-, et al.
(författare)
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Urban environment and reservoir host species are associated with Batrachochytrium dendrobatidis infection prevalence in the common toad
- 2019
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Ingår i: Diseases of Aquatic Organisms. - : INTER-RESEARCH. - 0177-5103 .- 1616-1580. ; 134:1, s. 33-42
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Tidskriftsartikel (refereegranskat)abstract
- Human-induced changes of the environment, including landscape alteration and habitat loss, may affect wildlife disease dynamics and have important ramifications for wildlife conservation. Amphibians are among the vertebrate taxa most threatened by anthropogenic habitat change. The emerging fungal pathogen Batrachochytrium dendrobatidis (Bd) has caused extinctions and population declines in hundreds of anuran species globally. We studied how the urban landscape is associated with the prevalence of Bd infections by sampling 655 anurans of 3 species (mainly the common toad Bufo bufo) in 42 ponds surrounded by different amounts of urban habitat (defined as towns, cities or villages). We also examined the association between Bd infections and a potential reservoir host species (the moor frog Rana arvalis). We found that 38% of the sites were positive for Bd with an infection prevalence of 4.4%. The extent of urban landscape was negatively correlated with Bd infection prevalence. However, the positive association of Bd with the presence of the possible reservoir species was substantially stronger than the urban effects. The body condition index of B. bufo was negatively associated with Bd infection. This Bd effect was stronger than the negative effect of urban landscape on body condition. Our results suggest that urban environments in Sweden have a negative impact on Bd infections, while the presence of the reservoir species has a positive impact on Bd prevalence. Our study also highlights the potential importance of Bd infection on host fitness, especially in rural landscapes.
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| 28. |
- Löwenborg, Kristin, et al.
(författare)
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Agricultural by-products provide critical habitat components for cold-climate populations of an oviparous snake (Natrix natrix)
- 2012
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Ingår i: Biodiversity and Conservation. - : Springer Science and Business Media LLC. - 0960-3115 .- 1572-9710. ; 21:10, s. 2477-2488
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Tidskriftsartikel (refereegranskat)abstract
- Populations of snakes and other reptiles are declining worldwide. Habitat loss and degradation is thought to be a significant factor in these declines, so to improve management strategies it is important to increase our understanding of reptilian habitat requirements. Modern agriculture is abandoning the tradition of gathering compost and manure in large heaps. Consequently these unusually warm environments are disappearing from the landscape. This may imperil populations of grass snakes (Natrix natrix) that rely on these anthropogenic heat sources to incubate their eggs. We conducted a relocation experiment to examine if eggs can develop successfully in other more natural environments that grass snakes potentially could utilize in the absence of manure heaps and compost piles. We found that hatching success was high (71 %) when we placed eggs in manure heaps and non-existent (0 %) when we placed them in potential ‘natural’ nests. Placement in compost piles resulted in intermediate (43 %) hatching success. Eggs in manure heaps hatched earlier than eggs in compost piles and thermal data from the nests showed that temperatures were higher and more stable in manure heaps than in compost piles and potential ‘natural’ nests. Jointly these results suggest that manure heaps generally provide a better nesting habitat than compost piles, attributable to thermal differences between the environments. Our findings facilitate improvement of current management strategies and have implications for conservation of oviparous reptiles in general.
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| 29. |
- Löwenborg, Kristin, et al.
(författare)
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Grass snakes exploit anthropogenic heat sources to overcome distributional limits imposed by oviparity
- 2010
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 24:5, s. 1095-1102
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Tidskriftsartikel (refereegranskat)abstract
- P>1. A lack of warm nest-sites prevents oviparous reptile species from reproducing in cool climates; such areas are dominated by viviparous species because sun-seeking pregnant females can maintain high temperatures for their developing offspring. 2. Our field and laboratory studies show that one oviparous species (the grass snake, Natrix natrix) escapes this cold-climate constraint (and hence, extends much further north in Europe than do other oviparous taxa) by ovipositing in a thermally distinctive man-made microhabitat (manure heaps on farms). 3. In the field, temperatures inside manure heaps averaged 30 center dot 7 degrees C, much higher than compost heaps (20 center dot 6 degrees C) or potential natural nest-sites under logs and rocks (15 center dot 5 degrees C). 4. In the laboratory, higher incubation temperatures not only hastened hatching, but also increased hatching success and modified the body sizes, colours, and locomotor abilities of hatchlings. Incubation temperatures typical of manure heaps (rather than alternative nest-sites) resulted in larger, faster offspring that hatched earlier in the season. 5. Thus, anthropogenic activities have generated potential nest-sites offering thermal regimes not naturally available in the region; and grass snakes have exploited that opportunity to escape the thermal limits that restrict geographic distributions of other oviparous reptile taxa.
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| 30. |
- Löwenborg, Kristin, et al.
(författare)
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Snokens vanor kartläggs
- 2009
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Ingår i: Fauna och Flora. - 0014-8903. ; 104:2, s. 42-45
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 31. |
- Meurling, Sara, et al.
(författare)
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Occurrence of Batrachochytrium dendrobatidis in Sweden : higher infection prevalence in southern species
- 2020
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Ingår i: Diseases of Aquatic Organisms. - : Inter-Research Science Center. - 0177-5103 .- 1616-1580. ; 140, s. 209-218
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Tidskriftsartikel (refereegranskat)abstract
- The chytrid fungus Batrachochytrium dendrobatidis (Bd) has caused worldwide declines in amphibian populations. While Bd is widespread in southern and central Europe, its occurrence and distribution in northernmost Europe is mostly unknown. We surveyed for Bd in breeding anurans in Sweden by sampling 1917 amphibians from 101 localities and 3 regions in Sweden (southern, northern and central). We found that Bd was widespread in southern and central Sweden, occurring in all 9 investigated species and in 45.5% of the 101 localities with an overall prevalence of 13.8%. No infected individuals were found in the 4 northern sites sampled. The records from central Sweden represent the northernmost records of Bd in Europe. While the proportion of sites positive for Bd was similar between the southern and central regions, prevalence was much higher in the southern region. This was because southern species with a distribution mainly restricted to southernmost Sweden had a higher prevalence than widespread generalist species. The nationally red-listed green toad Bufotes variabilis and the fire-bellied toad Bombina bombina had the highest prevalence (61.4 and 48.9%, respectively). Across species, Bd prevalence was strongly positively, correlated with water temperature at the start of egg laying. However, no individuals showing visual signs of chytridiomycosis were found in the field. These results indicate that Bd is widespread and common in southern and central Sweden with southern species, breeding in higher temperatures and with longer breeding periods, having higher prevalence. However, the impact of Bd on amphibian populations in northernmost Europe remains unknown.
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| 32. |
- Mihalca, A.D., et al.
(författare)
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Severe Granulomatous Lesions in Several Organs from Eustrongylides Larvae in a Free-ranging Dice Snake, Natrix tessellata
- 2007
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Ingår i: Veterinary Pathology. - : SAGE Publications. - 0300-9858 .- 1544-2217. ; 44:1, s. 103-105
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Tidskriftsartikel (refereegranskat)abstract
- During an extensive study regarding the epidemiology of larval Eustrongylides infestation in a free-ranging endangered population of dice snakes (Natrix tessellata) from Histria, Romania, an adult female was euthanized to evaluate pathologic changes. Parasites appeared as nodules at various locations: in subcutaneous connective tissues, on the serosae of the intestines and liver. Histologic sections revealed nematode larvae surrounded by a capsule, forming a parasitic granuloma with 3 layers: macrophage layer, lymphocyte layer, and fibrous capsule. Differences between newly formed and mature granulomas consisted mainly in the eosinophilic infiltration. Other types of parasitic granulomas of reptiles are discussed in comparison with our findings.
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| 33. |
- Persson, Henrik, et al.
(författare)
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Large-scale wall-to-wall mapping of bark beetle damage and forest practices using the distance red swir index and operational harvester data
- 2024
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Ingår i: Ecological Indicators. - 1470-160X .- 1872-7034. ; 162
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Tidskriftsartikel (refereegranskat)abstract
- Satellite-based inventories of bark beetle attacks are increasingly used for detecting and monitoring infested forest at the landscape scale. The Normalized Distance Red & SWIR index is one of few indices that have shown higher accuracies than commonly used vegetation indices. In this study, the temporal changes of the distance red swir (Delta DRS) index were analyzed, validated and applied to multi-temporal Sentinel-2 images covering one tile of 110 x 110 km(2). The main purpose was to assess the applicability of a new Delta DRS vegetation index to detect spruce forest after bark beetle (Ips typographus) attacks. Harvester data from a private forest company were used to validate the method. The normalized DRS index has previously been developed and tested at test site level, while this study explored and demonstrated the use of Delta DRS in an applied context on a larger scale. Water and chlorophyll induced changes and different disturbances were effectively identified across the landscape. A linear-discriminant analysis was used to classify 274 clusters as attacked and healthy forest, with an overall accuracy of 78%. The largest Delta DRS values in our study (>0.06) corresponded well to clear-cuts, and all 172 clear-cuts were correctly classified. We conclude that the Delta DRS index has a potential to map vegetation changes related to water and chlorophyll changes in the Scandinavian forests and that it can be useful to identify bark beetle-infested forest within 1 year after the attacks and clear-cuts.
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| 34. |
- Rödin Mörch, Patrik, et al.
(författare)
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Small-scale population divergence is driven by local larval environment in a temperate amphibian
- 2021
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Ingår i: Human Heredity. - : Springer Science and Business Media LLC. - 0001-5652 .- 1423-0062. ; 126:2, s. 279-292
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Tidskriftsartikel (refereegranskat)abstract
- Genomic variation within and among populations is shaped by the interplay between natural selection and the effects of genetic drift and gene flow. Adaptive divergence can be found in small-scale natural systems even when population sizes are small, and the potential for gene flow is high, suggesting that local environments exert selection pressures strong enough to counteract the opposing effects of drift and gene flow. Here, we investigated genomic differentiation in nine moor frog (Rana arvalis) populations in a small-scale network of local wetlands using 16,707 ddRAD-seq SNPs, relating levels of differentiation with local environments, as well as with properties of the surrounding landscape. We characterized population structure and differentiation, and partitioned the effects of geographic distance, local larval environment, and landscape features on total genomic variation. We also conducted gene-environment association studies using univariate and multivariate approaches. We found small-scale population structure corresponding to 6-8 clusters. Local larval environment was the most influential component explaining 2.3% of the total genetic variation followed by landscape features (1.8%) and geographic distance (0.8%), indicative of isolation-by-environment, -by-landscape, and -by-distance, respectively. We identified 1000 potential candidate SNPs putatively under divergent selection mediated by the local larval environment. The candidate SNPs were involved in, among other biological functions, immune system function and development. Our results suggest that small-scale environmental differences can exert selection pressures strong enough to counteract homogenizing effects of gene flow and drift in this small-scale system, leading to observable population differentiation.
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| 35. |
- Schroeder, Martin, et al.
(författare)
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Ny kunskap om skaderisker
- 2015
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Ingår i: Skogseko. - 0346-0495. ; , s. 15-15
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 36. |
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