Micro and macro-habitat associations in saproxylic beetles: implications for biodiversity management

Restoration of habitats is critically important in preventing full realization of the extinction debt owed as a result of anthropogenic habitat destruction. Although much emphasis has been placed on macrohabitats, suitable microhabitats are also vital for the survival of most species. The aim of this large-scale field experiment was to evaluate the relative importance of manipulated microhabitats, i.e., dead wood substrates of spruce (snags, and logs that were burned, inoculated with wood fungi or shaded) and macrohabitats, i.e., stand types (clear-cuts, mature managed forests, and forest reserves) for species richness, abundance and assemblage composition of all saproxylic and red-listed saproxylic beetles. Beetles were collected in emergence traps in 30 forest stands in 2001, 2003, 2004 and 2006. More individuals emerged from snags and untreated logs than from burned and shaded logs, but species richness did not differ among substrates. Assemblage composition differed among substrates for both all saproxylics and red-listed saproxylic species, mainly attributed to different assemblage composition on snags. This suggests that the practise of leaving snags for conservation purposes should be complemented with log supplementation. Clear-cuts supported fewer species and different assemblages from mature managed forests and reserves. Neither abundance, nor species richness or assemblage composition differed between reserves and mature managed forests. This suggests that managed stands subjected to selective cutting, not clear-felling, maintain sufficient old growth characteristics and continuity to maintain more or less intact assemblages of saproxylic beetles. Thus, alternative management methods, e.g., continuity forestry should be considered for some of these stands to maintain continuity and conservation values. Furthermore, the significantly higher estimated abundance per ha of red-listed beetles in reserves underlines the importance of reserves for maintaining viable populations of rare red-listed species and as source areas for saproxylic species in boreal forest landscapes.     

Restoration of Young Forests in Eastern Finland: Benefits for Saproxylic Beetles (Coleoptera)

Effective fire suppression in combination with intensive forestry has caused a large number of dead wood‐dependent (saproxylic) species to become threatened in Fennoscandia. In order to return the fire disturbance dynamics and to increase the amount of dead wood, restoration actions are urgently needed. We studied the effects of restoring young (under 30 years old) pine‐dominated (Pinus sylvestris L.) forest stands on saproxylic beetle assemblages in eastern Finland, focusing especially on rare, red‐listed, and pyrophilous (RRLP) species. Our experiment included a restoration treatment including two tree felling levels for fuel load (10 or 20 m³/ha) followed by burning, and an untreated control. We sampled beetles before restoration in 2005, during the year of restoration in 2006, and in two post‐treatment years in 2007 and 2011. Both restoration treatments increased the number of saproxylic and RRLP species. The species richness increased most in the year of restoration in 2006 and this trend continued in the following year 2007, but no differences in species assemblages were detected between the two fuel load levels. By 2011, however, the species richness and abundance had declined back to the pre‐treatment level. We suggest that restoration burning can also be directed to young forests where biodiversity values are initially low. On the basis of the observed decline in the species richness, we suggest that fire could be introduced in neighboring areas in approximately 5‐year intervals to maintain populations of the most demanding pyrophilous species .     

Mimicking natural disturbances of boreal forests: the effects of controlled burning and creating dead wood on beetle diversity

The young successional stages of boreal forests are an important habitat for many saproxylic species. These habitats are formed by disturbances such as forest fires and they are characterized by large volumes of dead wood and sun-exposed conditions. Today, young successional stages of natural origin are very rare in Fennoscandia and there is need for restoration. We constructed a large-scale field experiment in which we studied the effects of two restoration practices on beetle diversity: controlled burning and partial harvesting with creating different volumes of dead wood. We sampled beetles with flight-intercept traps recording a total of 56,031 individuals and 755 species. The species richness and abundance of both saproxylic and non-saproxylic beetles were increased by burning and harvesting but the volume of dead wood created on harvested sites had no short-term effect on species richness or abundance. Rare species, especially saproxylic ones, preferred burned sites and a similar trend was observed among red-listed and pyrophilous species. Burning and harvesting also resulted in different species assemblages and there were some additional differences according to the volume of dead wood. We conclude that fire can be successfully used in restoration of managed boreal forests to increase species diversity and to facilitate the recovery of declined species. However, long-term monitoring is needed to clarify the effects of the restoration practices, in particular those of creating dead wood without using fire.     

Does selective logging change ground‐dwelling beetle assemblages in a subtropical broad‐leafed forest of China?

Selective logging with natural regeneration is advocated as a near‐to‐nature strategy and has been implemented in many forested systems during the last decades. However, the efficiency of such practices for the maintenance of forest species are poorly understood. We compared the species richness, abundance and composition of ground‐dwelling beetles between selectively logged and unlogged forests to evaluate the possible effects of selective logging in a subtropical broad‐leafed forest in southeastern China. Using pitfall traps, beetles were sampled in two naturally regenerating stands after clearcuts (ca. 50 years old, stem‐exclusion stage: selectively logged 20 years ago) and two mature stands (> 80 years old, understory re‐initiation stage: selectively logged 50 years ago) during 2009 and 2010. Overall, selective logging had no significant effects on total beetle richness and abundance, but saproxylic species group and some abundant forest species significantly decreased in abundance in selectively logged plots compared with unlogged plots in mature stands. Beetle assemblages showed significant differences between selectively logged and unlogged plots in mature stands. Some environmental characteristics associated with selective logging (e.g., logging strategy, stand age, and cover of shrub and moss layers) were the most important variables explaining beetle assemblage structure. Our results conclude that selective logging has no significant impacts on overall richness and abundance of ground‐dwelling beetles. However, the negative effects of selective logging on saproxylic species group and some unlogged forest specialists highlight the need for large intact forested areas for sustaining the existence of forest specialist beetles.     

Can 'continuity indicator species' predict species richness or red-listed species of saproxylic beetles?

This study investigates the relationship between the abundance of wood-rotting fungus suggested as 'continuity indicator species' and environmental variables for the assemblage of saproxylic (wood-living) beetles associated with Fomitopsis pinicola fruiting bodies in a mature spruce forest in southeastern Norway. The presence of species thought to indicate continuity in old growth is one of the criteria used when finding and delineating small protected areas ('woodland key habitats') in Scandinavian forestry. Although it is clear that remnants of old-growth forest are important for many taxa, documentation as to which entities or species the indicator species indeed indicate is scarce. If stands with a continuous and unbroken input of dead wood have a unique assemblage of wood-rotting fungi, it seems relevant to ask if these stands also have a unique assemblage of rare saproxylic beetles. I find that the indicator species exhibit no significant correlations with beetle species richness or with the presence of red-listed saproxylic beetles as a group. The different characteristics of dead wood conditions are the most important environmental variables that explain both the species richness and the presence of red-listed beetles. Single-species analyses reveal contrasting relationships. The red-listed beetle Atomaria alpina shows a significant and positive association to the abundance of indicator species. Contrary, a group of three red-listed species with similar ecology in the family Cisidae exhibits a significant and negative association to indicator species abundance. This indicates that important patterns are concealed when considering general measures such as overall presence of red-listed beetles. Single-species studies are necessary in order to correctly understand how rare beetles respond to forestry activities and to develop a policy that can secure their continuing existence in the boreal forest.     

Effects of different tree harvesting intensities on saproxylic beetle diversity in coniferous and broad-leaved mixed forest in the Changbai Mountain,Northeast, China

1. Saproxylic beetles have gained increasing attention due to their role in the decomposition of rotting wood in forests. Studying the response of saproxylic beetles to tree harvesting is important for developing harvesting strategies that consider conservation of saproxylic beetle diversity.
2. We report results from a case study in which we designed four treatment stands to test the effects of forest harvesting intensity on saproxylic beetle diversity, harvest intensities of 0% untreated control (CK), 17.2% light harvest (LT), 34.7% moderate harvest (MT) and 51.9% high harvest (HT). Flight intercept traps were used to collect specimens of saproxylic beetles in each stand at 2, 3 and 4 years post-harvest.
3. The richness and abundance of saproxylic beetles were higher in MT and HT than in CK. Twelve of the 15 indicator species were significantly associated with MT or HT, whereas only three species were significantly associated with CK.
4. We found that moderate and high intensity harvesting affected the composition and increased beetle abundance and richness of saproxylic beetles, and light intensity harvesting had no effect on the beetle community in years 2, 3 and 4 post-harvest. There was no difference in the beetle community composition between moderate and high harvest stands.

     

Different effects of coarse woody material on the species diversity of three saproxylic beetle families (Cerambycidae, Melandryidae, and Curculionidae)

The relationships between coarse woody material (CWM) and the diversity of three saproxylic beetle families (Cerambycidae, Melandryidae, and Curculionidae) were investigated. These three families responded differently toward the quality and quantity of CWM. The species richness of cerambycid beetles increased in forests with more CWM in the early stage of decomposition. The richness of saproxylic curculionids increased in stands with more tree species. No clear trend was evident for melandryid diversity. The CWM differed in quality and quantity among three forest types [middle-aged larch (Larix kaempferi [Lamb.] Carrière) plantation, secondary forest, and old-growth forest] and between two forest-management practices (thinning and long rotation). Forest type and management practices affected CWM and the number of tree species, and CWM and the number of tree species influenced the diversity of saproxylic families differently. Because each decomposition stage is considered to be important for saproxylic beetles at the species level, a constant supply of CWM is necessary to maintain a suitable balance of CWM through these decomposition stages in forests to maintain the diversity of saproxylic beetles.     

Saproxylic beetle assemblages related to silvicultural management intensity and stand structures in a beech forest in Southern Germany

Compared to agricultural land and spruce plantations, central European beech-oak forests are often relatively close to natural conditions. However, forest management may alter these conditions. In Steigerwald, southern Germany, a large beech-dominated forest area, three management intensities were applied during the past 30–70 years. Here, we examined the influence of management intensity on saproxylic beetles in >100-year old mature stands at 69 sampling plots in 2004. We sampled beetles using flight-window traps and time standard direct searches. The community structure based on presence/absence data changed remarkably along the gradient from unmanaged to low-intensity to high-intensity management, but these differences were not evident using abundance data from flight interception traps. Saproxylic species richness decreased in intensively managed forests. Elateridae and threatened species richness peaked in unmanaged forests and in forests under low-intensity management. Saproxylic species richness was dependent on certain micro-habitat factors. These factors were (1) the amount of dead wood for Elateridae, overall and threatened saproxylic beetle richness; (2) the amount of flowering plants for Cerambycidae; (3) the richness of wood-inhabiting fungi for Staphylinidae, Melandryidae and overall saproxylic beetle richness; and (4) the frequency of Fomes fomentarius for threatened species. Species richness was better explained by plot factors, such as dead wood or fungi, than by management intensity. These results suggest that the natural variation of dead wood niches (decay stages, snag sizes, tree cavities and wood-inhabiting fungi species) must be maintained to efficiently conserve the whole saproxylic beetle fauna of beech forests. Also, intensive management may alter the specialised saproxylic beetle community even if the initial tree-species composition is maintained, which was the case in our study. For monitoring the ecological sustainability of forest management we must focus on threatened species. If structures alone are sampled then the amount of dead wood is the best indicator for a rich saproxylic beetle fauna.     

Evaluation of window flight traps for effectiveness at monitoring dead wood-associated beetles: the effect of ethanol lure under contrasting environmental conditions

1 Subsequent to the diversity of saproxylic beetles being proposed as a management tool in forestry, more explicit knowledge about the efficiency and selective properties of beetle sampling methods is needed.
2 We compared saproxylic beetle assemblages caught by alcohol-baited or unbaited window traps in different forest contexts. Considering that trap attractiveness depends on kairomone concentrations, we appraised whether the trap efficiency was influenced by trap environment (openness and local supply of fresh dead wood).
3 Saproxylic beetles were sampled using 48 cross-vane window flight traps, arranged in paired designs (alcohol-baited/unbaited), in eight ancient and eight recent gaps (open stands), and eight closed-canopy control stands in an upland beech forest in the French Pyrenees.
4 Baited traps were more efficient than unbaited traps in terms of abundance and richness in our deciduous forests. The ethanol lure did not have any repellent effect on the individual response of saproxylic taxa.
5 The influence of local environmental conditions on trap attractiveness was observed. Openness had a significant moderate effect on species richness. Trap attractiveness was slightly reduced in the alcohol-saturated environment of recent gaps probably due to a disruption by local fresh dead-wood concentrations of the kairomonal response of saproxylic beetles to baited traps ('alcohol disruption').
6 Because the ethanol lure enhanced the probability of species detection, it may be useful in early-warning surveillance, monitoring and control of wood borers, despite slight influences of local conditions on baited trap efficiency.     

Saproxylic beetle diversity in a managed boreal forest: importance of stand characteristics and forestry conservation measures

Saproxylic beetles constitute a significant proportion of boreal forest biodiversity. However, the long history of timber production in Fennoscandia has significantly reduced the availability of dead wood and is considered a threat to the conservation of saproxylic beetle assemblages. Therefore, since the mid‐1990s dead wood retention in harvested stands has formed an integral part of silvicultural practices. However, the contribution of this biodiversity‐orientated management approach to conserving saproxylic beetle assemblages in boreal forest landscapes that include production forestry remains largely untested. We examined differences in resident saproxylic beetle assemblages among stands under different management in a boreal forest landscape in Central Sweden, and in particular stands managed according to new conservation‐orientated practices. We also investigated the relationship between beetle diversity and forest stand characteristics. Bark of coarse woody debris (CWD) was sieved for beetles in old managed stands, unmanaged nature reserves, and set‐aside areas, and clear‐cut stands harvested according to certification guidelines [new forestry (NF) clear‐cuts]. All stand types contributed significantly to the total diversity of beetles found. While stand size, position, and distance to nearest reserve were unimportant, both the quality and the quantity of CWD in stands contributed significantly to explaining beetle abundance and species richness. This extends the previous findings for red‐listed invertebrates, and shows that heterogeneous substrate quality and a range of management practices are necessary to maintain saproxylic beetle diversity in boreal forest landscapes that include production forestry. The unique abiotic conditions in combination with the abundant and varied CWD associated with NF clear‐cuts form an important component of forest stand heterogeneity for saproxylic beetles. It is thus essential that sufficient, diverse, CWD is retained in managed boreal landscapes to ensure the conservation of boreal saproxylic beetle assemblages.     

Saproxylic Beetles in Standing Dead Wood Density in Relation to Substrate Sun-exposure and Diameter

Species-specific densities of saproxylic beetles in cut 4-m high, medium to large diameter stumps of spruce, birch, aspen and oak were monitored for 7 years after cutting, by trapping emerging insects within seasonally applied net enclosures. A total of 47,038 individuals, representing 316 saproxylic beetle species including 40 red-listed species, were recorded. Densities of 86 species were modelled in relation to stump diameter and measured levels of sun-exposure. Two thirds of the species favoured semi- or fully exposed substrates, while one third performed better in shade. Few species seemed to be specifically adapted to semi-exposed conditions. Diameter was generally of less importance than exposure, and similar numbers of species favoured medium and large diameter substrates. Group mean diameter and exposure calculated from means per individual and species were similar for groups of modelled and non-modelled species, and for groups of red-listed and non-red-listed species, respectively. This indicates that the proportions found in the models are representative for the diverse regional fauna of saproxylic beetles that utilise high stumps of spruce, birch, aspen and oak in early stages of decay. The results suggest that sun-exposed dead wood substrates generated and retained in managed forest landscapes are potentially important for many species. However, stands of unmanaged self-thinning successions of deciduous trees, as well as substantial areas of old-growth spruce-forests are also necessary to address the wide spectrum of saproxylic beetles.     

How will low-intensity burning after clear-felling affect mid-boreal insect assemblages?

Intensive forest management and fire protection programs have dramatically reduced the frequency of fires and this is believed to have negative effects on biodiversity. As a result, fire is used as a restoration tool to improve conditions for fire adapted/favoured species. The aim of our study was to determine how burning of clear-felled areas (i.e. those typical of real-world management in Fennoscandinavia) influenced beetle assemblages, and to identify taxonomic and functional groups and individual species that are favoured by burning as it is currently practiced. We studied five sites, each consisting of one burned and one unburned clear-cut. Beetles were collected in sixteen pitfall traps per site for three consecutive years. Regardless of whether beetles were divided into taxonomic or functional groups, abundance was generally higher on burned clear-cuts, with the exception of Staphylinidae which showed indications of an opposite response. The species assemblages differed significantly between burned and control clear-cuts in all years. The species contributing most to the difference included Corticaria ferruginea, Pterostichus adstrictus, Corticaria rubripes, Atomaria pulchra and Hylobius abietes (all more common on burned clear-cuts), and Drusilla canaliculata and Atomaria peltata (more common on controls). We also found a succession of species, i.e. Otiorhynchus nodosus and Anthicus ater became dominant species on burned clear-cuts the third year after burning whereas C. ferruginea and A. pulchra became scarce. In conclusion, clear-cut burning clearly changed the assemblage composition of beetles and seems to benefit at least some species associated with natural fires. Thus, although clear-cut burning cannot exactly emulate the effect of natural fires it could be used as a restoration tool for improving the quality of the matrix outside protected areas and in particular to create habitats for disturbance-associated species, including species associated with fire.     

Effects of landscape composition and substrate availability on saproxylic beetles in boreal forests: a study using experimental logs for monitoring assemblages

Intensive forestry practises in the Swedish landscape have led to the loss and fragmentation of stable old‐growth habitats. We investigated relationships between landscape composition at multiple scales and the composition of saproxylic beetle assemblages in nine clear‐cut, mature managed and old‐growth spruce‐dominated forest stands in the central boreal zone of Sweden. We set out fresh spruce and birch logs and created spruce snags in 2001–2002 to experimentally test the effects of coarse woody debris (CWD) type and forest management on the composition of early and late successional, and red‐listed saproxylic beetle assemblages. We examined effects of CWD availability at 100 m, and landscape composition at 1 and 10 km on saproxylic beetle abundances. Additionally, we tested whether assemblage similarity decreased with increasing distance between sites. We collected beetles from the experimental logs using eclector and window traps in four periods during 2003. CWD was measured and landscape composition data was obtained from maps of remotely sensed data. The composition of saproxylic beetles differed among different CWD substrates and between clear‐cuts and the older stand types, however differences between mature managed and old‐growth forests were significant only for red‐listed species. Assemblage similarities for red‐listed species on clear‐cuts were more different at greater distances apart, indicating that they have more localised distributions. CWD availability within 100 m of the study sites was rarely important in determining the abundance of species, suggesting that early successional saproxylic beetles can disperse further than this distance. At a larger scale, a large area of suitable stand types within both 1 and 10 km resulted in greater abundances in the study sites for several common and habitat‐specific species. The availability of suitable habitat at scales of 1–10 km is thus likely to be important in the survival of many saproxylic species in forestry‐fragmented areas.     

The diversity of beetle assemblages in different habitat types in Sabah, Malaysia

The diversity of beetle assemblages in different habitat types (primary forest, logged forest, acacia plantation and oil palm plantation) in Sabah, Malaysia was investigated using three different methods based on habitat levels (Winkler sampling, flight-interception-trapping and mist-blowing). The overall diversity was extremely high, with 1711 species recorded from only 8028 individuals and 81 families (115 family and subfamily groups). Different degrees of environmental changes had varying effects on the beetle species richness and abundance, with oil palm plantation assemblage being most severely affected, followed by acacia plantation and then logged forest. A few species became numerically dominant in the oil palm plantation. In terms of beetle species composition, the acacia fauna showed much similarity with the logged forest fauna, and the oil palm fauna was very different from the rest. The effects of environmental variables (number of plant species, sapling and tree densities, amount of leaf litter, ground cover, canopy cover, soil pH and compaction) on the beetle assemblage were also investigated. Leaf litter correlated with species richness, abundance and composition of subterranean beetles. Plant species richness, tree and sapling densities correlated with species richness, abundance and composition of understorey beetles while ground cover correlated only with the species richness and abundance of these beetles. Canopy cover correlated only with arboreal beetles. In trophic structure, predators represented more than 40% of the species and individuals. Environmental changes affected the trophic structure with proportionally more herbivores (abundance) but fewer predators (species richness and abundance) in the oil palm plantation. Biodiversity, conservation and practical aspects of pest management were also highlighted in this study.     

Biodiversity conservation in old-growth boreal forest: black spruce and balsam fir snags harbour distinct assemblages of saproxylic beetles

Biodiversity conservation of forest ecosystems strongly relies on effective dead wood management. However, the responses of saproxylic communities to variations in dead wood characteristics remains poorly documented, a lack of knowledge that may impede the development of efficient management strategies. We established the relationship between saproxylic beetles—at the species and community levels—and attributes of black spruce and balsam fir in old-growth boreal forests. The relationship was first evaluated for individual snag bole segments, and then for forest stands. A total of 168 bole sections were collected in summer 2006 along a compositional gradient ranging from black spruce-dominated stands to balsam fir-dominated ones, in a boreal forest dominated by >90-year-old stands. A total of 16,804 beetles belonging to 47 species emerged from bole segments, with 21% of the species being found exclusively in black spruce snags and 36% exclusively in balsam fir snags. Black spruce and balsam fir snags thus contributed differently to forest biodiversity by being inhabited by different saproxylic communities. Wood density was an important attribute in the host-use patterns for several species of saproxylic beetles, but no relationship was found between snag availability within stands and abundance of beetles strongly linked to either black spruce or balsam fir. Our study outlines the relative contribution of tree compositional diversity to saproxylic species, while highlighting the contribution of black spruce and balsam fir to animal diversity in old-growth boreal forests.     

Species richness of saproxylic beetles in woodlands is affected by dispersion ability of species,age and stand size

This study examines the occurrence of saproxylic beetles in woodlands of different size and age and their potential to leave woodland areas and cross open grassland in northern Germany. The beetles were recorded by emergence traps and flight-intercept-traps. The investigated sites were dominated by beech, oak and alder, but other tree species also occurred in low abundance. Species richness showed a positive relation to stand size and age of woods. Both total and rarefaction species richness were the lowest in small and young woods and highest in old and large woods. Species richness decreased asymptotically from the inner-wood habitat to a distance greater than 80 m from the wood margin. 80 species were classified into 46 low mobile species found at a distance <30 m from wood margins and 34 high mobile species found >30 m from wood margins. The most mobile species were found the most frequently in all woods; but they contributed less to species richness in wood stands than did the species with low mobility. The contribution of the least mobile species to species richness in wood stands increased with the age and size of the stands, with the effect of stand size being the greater. We conclude that in our study region woods larger than 100 ha are necessary to maintain the highest richness of the least mobile saproxylic beetles.     

Short-term development of ambrosia and bark beetle assemblages following a windstorm in French broadleaved temperate forests

Abstract: In most temperate deciduous forests, windstorm is the main source of dead wood. However, the effects of this natural disturbance on ambrosia and bark beetle communities are poorly known. In managed oak‐hornbeam forests storm‐damaged in France in 1999, we sampled ambrosia (and second bark beetles) by ethanol‐baited window‐flight traps in 2001. By comparing uncleared gaps, undisturbed closed‐canopy controls and seedling‐sapling stands, we investigated the short‐term effects of gap formation, gap size and surrounding landscape to provide a snapshot of scolytid response. Contrary to expectations, neither the abundance nor the richness of ambrosia beetle species was significantly higher in gaps than in undisturbed stands. Few responses in abundance at the species level and only a slight difference in assemblage composition were detected between gaps and closed‐canopy controls. Gaps were more dissimilar from seedling‐sapling stands, than from closed‐canopy controls. More scolytid individuals and species were caught in gaps than in seedling‐sapling stands. Mean local and cumulative richness peaked in mid‐size gaps. Only mid‐size gaps differed from closed‐canopy controls in terms of species composition. We identified generalist gap species (Xyleborus saxesenii, X. cryptographus), but also species significantly more abundant in mid‐size gaps (Platypus cylindrus, Xyloterus signatus). The faunistic peculiarity of mid‐size gaps seemed to be partly related to a bias in oak density among gap size classes. Few landscape effects were observed. Only the scolytids on the whole and X. dispar were slightly favoured by an increasing density in fellings at the 78 ha scale. We did not find any correlation between scolytid abundance and the surrounding closed‐forest percentage area. We confirmed that temperate, deciduous, managed stands did not come under threat by ambrosia and bark beetle pests after the 1999 windstorm. Nonetheless, our data stressed the current expansion in Western Europe of two invasive species, X. peregrinus and especially X. germanus, now the predominant scolytid in the three oak forests studied.     

Effects of forest continuity on flying saproxylic beetle assemblages in small woodlots embedded in agricultural landscapes

Ancient forests are of considerable interest for strategies for biodiversity conservation. However, in European forest landscapes fragmented and harvested for a long time forest continuity might be no longer a key driver for flying organisms such as saproxylic beetles. In a study based on paired samples (n = 60 stands, p = 180 traps) of ancient and recent forests, we investigated the effects of forest continuity on saproxylic beetle assemblages in two French regions. Mean species richness was significantly related with deadwood volume in ancient forests, but not in recent forests. This loss of relationship between assemblages and their environment suggests that dispersal limitation is at work, at least for some species. Forest continuity had a significant effect on mean species richness and on the mean number of common species, but not on rare species. Forest continuity had a significant effect on assemblage composition in one out of the four cases tested. In both regions, we identified species associated with either recent or ancient forests. Finally, mean body size of species was significantly smaller in recent forests compared with ancient ones, as was their tree diameter preference, despite a higher volume of large deadwood in recent forests. These results lend support to using forest continuity as a criterion to identify sites of conservation importance, even in highly fragmented landscapes.     

Effects of Clearfell Harvesting on Lucanid Beetles (Coleoptera: Lucanidae) in Wet and Dry Sclerophyll Forests in Tasmania

The effects of commercial forestry harvest and regeneration practices (clearfelling and slash-burning) on the lucanid fauna of the wet sclerophyll forests of southern Tasmania and the dry sclerophyll forests of eastern Tasmania were examined using pitfall catches. Lucanids are saproxylic beetles, dependent on dead, moribund and decaying wood. Samples taken from old-growth forest and from a chronosequence of sites regenerating after logging, in each forest type, were used to compare the species richness and abundance of the lucanid assemblages. In both forest types, species richness and abundance was highest in the youngest regeneration sites (1–3 year), reflecting the species richness of the original and adjacent unlogged forest, lowest in the older (20–25 year) sites, and variable in the old-growth sites. TWINSPAN cluster analysis showed no clear distinction between regeneration and old-growth forest. The post-harvest slash and stump residue provided an important refugium and initial habitat, but our research indicates that some species may not maintain populations in the long term. Our results suggest that most species of lucanids will find a continuous supply of suitable habitat only in old-growth forests; and such species may become less common as clearfell harvesting leads to a replacement of heterogeneous old-growth forest with single-aged monospecific stands. Continuity of supply of wood in all decay stages, the maintenance of sufficient source areas, and biological connectivity between old-growth stands to enable dispersal, are all likely to be essential to maintain lucanid beetle community integrity. If similar principles apply to other saproxylic species of invertebrate, then clearfelling and slash-burning may cause a gradual extinction of an important element of the forest biota.     

Diversity distribution of saproxylic beetles in Chilean Mediterranean forests: influence of spatiotemporal heterogeneity and perturbation

Mediterranean ecosystems have been recognized as a priority for biodiversity conservation due to their high levels of species richness and endemism. In South America, these environments are restricted to central Chile and represent a biodiversity hotspot. The study of saproxylic beetles in this area is an unexplored topic, despite the ecological role they play in these ecosystems and their potential usefulness for monitoring the degree of forest conservation. We investigated the diversity distribution of trophic guilds of saproxylic beetles in Chilean Mediterranean forests, to identify the main environmental variables that influence their distribution. We also analyzed seasonal dynamics as a key factor influencing insect communities and the effect of human disturbance on their diversity and composition. We identified characteristic species of perturbation degree as bioindicators for habitat monitoring. A total of 40 window traps were used to survey three Mediterranean forest types in the Río Clarillo National Reserve and the adjacent non-protected areas. We found that the diversity, abundance and composition of saproxylic beetles varied significantly spatiotemporally among the studied forest types and among perturbation degrees, showing different patterns depending on the trophic guild. Results indicated that conservation decisions should include the preservation of a larger range of different vegetation types and the nearby zones that have suffered low levels of disturbance or fragmentation and where actions promoting the presence of old native trees would have a significant conservation value.