Nicklas Jansson

The influence of forest regrowth, original canopy cover and tree size on saproxylic beetles associated with old oaks

Abandoned management has caused many sites with free-standing, large oaks (Quercus robur) to become more shaded. This study shows how forest regrowth affects beetle species associated with old oaks in south-eastern Sweden. Beetles were trapped by pitfall traps placed in hollows and window traps placed near hollows in oak trunks in pasture woodlands. We assessed the influence of forest regrowth, tree size and original canopy cover on the species richness of saproxylic beetles (a total of 120 species identified) and the occurrence of 68 saproxylic beetle species in particular. Species richness was greatest in stands with large, free-standing trees. Large girth as well as low canopy cover increased frequency of occurrence for several species. Forest regrowth was found to be detrimental for many beetle species. As most localities with endangered beetles living in old oaks are small and isolated, ongoing management and the restoration of abandoned pasture woodlands should have a high priority in nature conservation.

A comparison of three methods to survey saproxylic beetles in hollow oaks

One of the most endangered assemblages of species in Europe is insectsassociated with old trees. For that reason there is a need of developing methodsto survey this fauna. This study aims at comparing three methods – windowtrapping, pitfall trapping and wood mould sampling – to assess speciesrichness and composition of the saproxylic beetle fauna in living, hollow oaks.We have used these methods at the same site, and to a large extent in the sametrees. Useful information was obtained from all methods, but they partiallytarget different assemblages of species. Window trapping collected the highestnumber of species. Pitfall trapping collected beetles associated with treehollows which rarely are collected by window traps and therefore it isprofitable to combine these two methods. As wood mould sampling is the cheapestmethod to use, indicator species should preferably be chosen among specieswhich are efficiently collected with this method.

An indicator system for identification of sites of high conservation value for saproxylic oak (Quercus spp.) beetles in southern Sweden.

The saproxylic beetle fauna on old oaks was sampled in four regions of southern Sweden using two methods: window and pitfall trapping. The aim was to test a way of finding indicator species which can be used to identify sites with high species number or that scored high on a conservation priority species index, based on occurrence of red-listed species. From 92 sites surveyed, in total 164 species of saproxylic beetles were identified. Different sets of indicator species were selected based upon 22 sites from a centrally located region. Predictions of species number and the index for 30 other sites from the same province were made. The correlation between observed and predicted species number and the index increased with increasing number of indicators. When comparing different treatment of species indata, the explanatory power of predictions was strongest for presence/absence data. Indicator sets of species effectively caught with pitfall traps gave overall the best predictions of both species number and the index. Predictions of species number and the index worked well within the same regions but gave varied result for the three other regions which shows that transferability of indicators between regions may be doubtful.

Using Sex Pheromone and a Multi-Scale Approach to Predict the Distribution of a Rare Saproxylic Beetle.

The European red click beetle, Elater ferrugineus L., is associated with wood mould in old hollow deciduous trees. As a result of severe habitat fragmentation caused by human disturbance, it is threatened throughout its distribution range. A new pheromone-based survey method, which is very efficient in detecting the species, was used in the present study to relate the occurrence of E. ferrugineus to the density of deciduous trees. The latter data were from a recently completed regional survey in SE Sweden recording >120,000 deciduous trees. The occurrence of E. ferrugineus increased with increasing amount of large hollow and large non-hollow trees in the surrounding landscape. Quercus robur (oak) was found to be the most important substrate for E. ferrugineus, whereas two groups of tree species (Carpinus betulus, Fagus sylvatica, Ulmus glabra, vs. Acer platanoides, Aesculus hippocastanum, Fraxinus excelsior, Tilia cordata) were less important but may be a complement to oak in sustaining populations of the beetle. The occurrence of E. ferrugineus was explained by the density of oaks at two different spatial scales, within the circle radii 327 m and 4658 m. In conclusion, priority should be given to oaks in conservation management of E. ferrugineus, and then to the deciduous trees in the genera listed above. Conservation planning at large spatial and temporal scales appears to be essential for long-term persistence of E. ferrugineus. We also show that occurrence models based on strategic sampling might result in pessimistic predictions. This study demonstrates how pheromone-based monitoring make insects excellent tools for sustained feedback to models for landscape conservation management.

Low host-tree preferences among saproxylic beetles: a comparison of four deciduous species

Many wood‐dwelling beetles rely on old hollow trees. In Europe, oaks are known to harbour a species‐rich saproxylic beetle fauna, while less is known regarding other broad‐leaved tree species. Furthermore, the extent to which saproxylic insect species have specialised on different tree species remains unknown. In this study, we sampled beetles through pitfall traps and window traps in four different tree species in a landscape with many old oaks. We recorded 242 saproxylic beetle species of which 27 were red‐listed. After eliminating the species recorded only on a single tree, few cases among the 171 remaining species in the data set were confined to a single tree species. Using odds ratios, we showed that 19 of the 171 beetle species showed significant associations with Quercus robur in at least one of the two trap types. For Acer platanoides, Fraxinus excelsior and Tilia cordata, the corresponding numbers were 6, 2 and 5, respectively. One species showed a negative association with Q. robur. Using meta‐analysis, we quantified the degree of association between the beetle species and the tree species. The associations were most profound among species classified as obligate saproxylic rather than facultative in lifestyle. Overall, a significant association was only found with Q. robur. We conclude that the saproxylic fauna is dominated by non‐specialist species but includes a small proportion of truly host‐tree‐specific species. Furthermore, other broad‐leaved trees can be important as supporting habitats for many saproxylic organisms that have had presumed associations with oaks to date.

Specialists in ancient trees are more affected by climate than generalists.

Abstract Ancient trees are considered one of the most important habitats for biodiversity in Europe and North America. They support exceptional numbers of specialized species, including a range of rare and endangered wood‐living insects. In this study, we use a dataset of 105 sites spanning a climatic gradient along the oak range of Norway and Sweden to investigate the importance of temperature and precipitation on beetle species richness in ancient, hollow oak trees. We expected that increased summer temperature would positively influence all wood‐living beetle species whereas precipitation would be less important with a negligible or negative impact. Surprisingly, only oak‐specialist beetles with a northern distribution increased in species richness with temperature. Few specialist beetles and no generalist beetles responded to the rise of 4°C in summer as covered by our climatic gradient. The negative effect of precipitation affected more specialist species than did temperature, whereas the generalists remained unaffected. In summary, we suggest that increased summer temperature is likely to benefit a few specialist beetles within this dead wood community, but a larger number of specialists are likely to decline due to increased precipitation. In addition, generalist species will remain unaffected. To minimize adverse impacts of climate change on this important community, long‐term management plans for ancient trees are important.

Surrogate tree cavities: boxes with artificial substrate can serve as temporary habitat for Osmoderma barnabita (Motsch.) (Coleoptera, Cetoniinae)

Abstract Many saproxylic insects have declined or became extinct, mainly due to habitat loss and fragmentation, and their survival increasingly depends on active conservation. Efforts to achieve this goal may be supported by the introduction of new methods, including creation of artificial habitats. Here we present results of studies on the use of wooden boxes mimicking tree cavities for an endangered saproxylic species, Osmoderma barnabita. Boxes were filled with the feeding substrate for larvae and installed on trees. Second and third-instar O. barnabita larvae were introduced in half of the boxes; the remaining ones were left uninhabited. Later inspection of boxes showed a high survival rate of introduced larvae, as well as successful breeding of a new generation inside the boxes. At the same time boxes were not colonized by the local population of O. barnabita, although other cetoniids did so. The co-occurring larvae of other cetoniids did not affect O. barnabita larvae. Thermal conditions inside boxes and natural tree cavities were almost identical and based on the results of our studies we conclude that wooden boxes may serve as temporary habitat for O. barnabita. They may be particularly useful in cases of destruction of species’ natural habitat, in restoration programs, and have the potential to act as a ‘stepping stones’ in cases of a lack of habitat continuity.

Assemblages of saproxylic beetles on large downed trunks of oak.

Abstract Old living oaks (Quercus robur) are known as a very species‐rich habitat for saproxylic beetles, but it is less clear to what extent such veteran trees differ from an even rarer feature: downed trunks of large oaks. In this study, we set out to sample this habitat, using window traps, with two aims: (1) to describe the variation of assemblages among downed trunks of different type and (2) to compare beetles on downed oaks with data from veteran standing trees. The results showed that trunk volume and sun exposure better explained assemblages as well as species numbers on downed trunks than did decay stage. Furthermore, species classified as facultative saproxylic species showed weak or no differentiation among downed trunks. Species with different feeding habits showed no apparent differentiation among downed trunks. Furthermore, species composition on dead, downed oak trunks differed sharply from that of living, veteran oaks. Wood or bark feeders were more common on veterans than downed trunks, but there was no difference for those species feeding on fungi or those feeding on insects and their remains. In conclusion, for a successful conservation of the saproxylic beetle fauna it is important to keep downed oak trunks, and particularly large ones, in forest and pastures as they constitute a saproxylic habitat that differs from that of living trees.

Saproxylic beetles on old hollow oaks (Quercus spp.) in a small isolated area in southern Turkey: (Insecta: Coleoptera)

Abstract Old oaks (Quercus spp.) and their fauna are rare and threatened all over Europe including Turkey. Preliminary results are presented from a study in Turkey using window traps in a cemetery with old hollow oaks. In total, 87 beetle species were identified and the number of beetle species was the highest from the families Elateridae, Anobiidae and Tenebrionidae. Several of the species are considered to be very rare in Europe and one of the species will be described as new to science (Mycetochara sp.). Species composition was surprisingly high when compared to similar studies in the region.

Attributes of trees used by nesting and foraging woodpeckers (Aves: Picidae) in an area with old pollarded Oaks (Quercus spp.) in the Taurus Mountains, Turkey

We used three woodpecker species as umbrella species for old deciduous forests, and analysed their preferences in an area with old pollarded oaks in the Taurus Mountains, Turkey. Using plot inventories, we physically characterised trees utilised for nesting and foraging amongst woodpeckers in general and the Middle Spotted Woodpecker (Leiopicus medius) in particular. Trees more frequently visited by foraging woodpeckers differed from randomly chosen trees by being taller, having a larger circumference, greater bark furrow depth and shorter distance to neighbouring trees. Nesting trees were taller, had a higher proportion of dead wood but a lower surface area of natural cavities. Our results suggest that the woodpeckers in the study area rely upon woodlands containing mature trees, thus have the potential to function as suitable umbrella species’ to highlight the conservation value of oak forest habitats in southern Turkey.