Deadwood as a surrogate for forest biodiversity: Meta-analysis of correlations between deadwood volume and species richness of saproxylic organisms

Deadwood is an important component of forest ecosystems on which many forest dwelling species depend. Deadwood volume is therefore widely used as an indicator of forest biodiversity, notably throughout Europe. However, using deadwood as an indicator has mostly been based on boreal references, and published references for temperate forests are scarce. As a result, the magnitude of the relationship between deadwood volume and species richness remains unclear for saproxylic species. We used meta-analysis to study the correlation between deadwood volume and the species richness of saproxylic beetles and fungi relative to several predictors at the forest stand level: biome, type of deadwood (log, snag, and stump) and decay class (fresh vs. decayed). We showed that the correlation between deadwood volume and species richness of saproxylic organisms was significant but moderate (r = 0.31), and that it varied only slightly between logs and snags or between decay stages. However, we found a strong biome effect: deadwood volume and species richness were more correlated in boreal forests than in temperate forests. This could be attributed both to differences in the history of forest management between biomes and to varying landscape patterns. Finally, we conclude that total deadwood volume is probably not a sufficient indicator of saproxylic biodiversity, and those additional variables (notably at the landscape level) such as type of deadwood or decay class should be integrated in deadwood monitoring. In addition, further forest research is needed to better assess the quantitative relationship between deadwood and saproxylic biodiversity, and in order to build indicators adapted to different biome contexts.     

In search of the best local habitat drivers for saproxylic beetle diversity in temperate deciduous forests

Deadwood-associated species are increasingly targeted in forest biodiversity conservation. In order to improve structural biodiversity indicators and sustainable management guidelines, we need to elucidate ecological and anthropogenic drivers of saproxylic diversity. Herein we aim to disentangle the effects of local habitat attributes which presumably drive saproxylic beetle communities in temperate lowland deciduous forests. We collected data on saproxylic beetles in 104 oak and 49 beech stands in seven French lowland forests and used deadwood, microhabitat and stand features (large trees, openness) as predictor variables to describe local forest conditions. Deadwood diversity and stand openness were consistent key habitat features for species richness and composition in deciduous forests. Large downed deadwood volume was a significant predictor of beetle species richness in oak forests only. In addition, the density of cavity- and fungus-bearing trees had weak but significant effects. We recommend that forest managers favor the local diversification of deadwood types, especially the number of combinations of deadwood positions and tree species, the retention of large downed deadwood and microhabitat-bearing trees in order to maximize the saproxylic beetle diversity at the stand scale in deciduous forests. To improve our understanding of deadwood-biodiversity relationships, further research should be based on targeted surveys on species-microhabitat relationships and should investigate the role of landscape-scale deadwood resources and of historical gaps in continuity of key features availability at the local scale.     

Diameter of downed woody debris does matter for saproxylic beetle assemblages in temperate oak and pine forests

Deadwood is widely recognized to be an important issue for biodiversity conservation in forest ecosystems. Establishing guidelines for its management requires a better understanding of relationships between woody debris characteristics and associated species assemblages. Although deadwood diameter has been identified as an important factor predicting occurrence of many saproxylic species, the boundary between small and large diameter has not yet been precisely defined. In commercial forests, it is also of critical importance to know which diameter is large enough to host the beetle species associated with large logs in order to ensure cost-effectiveness of biodiversity conservation measures. We investigated the differences in saproxylic beetle assemblages among four different diameter classes of downed woody oak and maritime pine debris, in France. Beetles were sampled using in situ emergence traps. The diameter of deadwood pieces ranged from 1 to 40 cm. No patterns of nestedness associated with the gradient of diameter size were identified for either tree species. More indicator saproxylic species were observed in large logs and branches than in small logs. A clear distinction appeared in assemblage composition around the 5-cm diameter threshold whereas no similar pattern occurred around the 10 cm value, i.e. the classical threshold used in forestry to distinguish fine woody debris from coarse woody debris. For both tree species, the mean body length of beetles increased with the diameter of deadwood suggesting that the quantity of available resources per piece may constitute a limiting factor for large beetle species. This study confirms that not only large deadwood pieces are relevant for saproxylic biodiversity conservation but also the smallest pieces. Therefore, forest managers would be well advised to maintain a high diversity of deadwoods to maintain saproxylic biodiversity.     

Are biodiversity patterns of saproxylic beetles shaped by habitat limitation or dispersal limitation? A case study in unfragmented montane forests

Understanding the processes that shape biodiversity patterns is essential for ecosystem management and conservation. Local environmental conditions are often good predictors of species distribution and variations in habitat quality usually positively correlate to species richness. However, beside habitat limitation, species presence-absence may be constrained by dispersal limitation. We tested the relative importance of both limitations on saproxylic beetle diversity, using forest continuity as a surrogate for dispersal limitation and stand maturity as a surrogate for habitat limitation. Forest continuity relies on the maintenance of a forest cover over time, while stand maturity results in the presence of old-growth habitat features. Forty montane beech-fir forests in the French pre-Alps were sampled, under a balanced sampling design in which forest continuity and stand maturity were crossed. A total of 307 saproxylic beetle species were captured using flight-interception traps and Winkler–Berlese extractors. We explored the response of low- versus high-dispersal species groups to forest continuity and stand maturity. Saproxylic beetle diversity increased significantly with stand maturity and was mostly influenced by variables related to deadwood diversity at the stand scale and suitable habitat availability at the landscape scale. Surprisingly, no evidence of dispersal limitation was found, as diversity patterns were not influenced by forest continuity and associated variables, even for low-dispersal species. Our study demonstrates that in an unfragmented forest landscape, saproxylic beetles are able to colonize recent forests, as long as local deadwood resources are sufficiently diversified (e.g. tree species, position, diameter and/or decay stage).     

Effect of deadwood management on saproxylic beetle richness in the floodplain forests of northern Italy: some measures for deadwood sustainable use

Saproxylic beetles may act as bio-indicators of high-quality mature woodlands, and their conservation is strongly linked to the quality and quantity of deadwood in a biotope. We tested the effect of deadwood accumulation and habitat variables on saproxylic species richness by investigating six sampling sites under different deadwood management practices that belong to both alluvial and riparian mixed forests of the Po plain, Italy. We sampled 43 obligate saproxylic species. The main factor predicting saproxylic species richness was the amount of deadwood measured by both log diameter and volume. We found a threshold of 0.22 m diameter (confidence interval CI 0.18–0.37 m) and 32.04 m³/ha volume (CI 16.09–64.09 m³/ha) below which saproxylic beetle richness would be significantly reduced and a threshold of 35 m³/ha dead wood volume (CI 33–40 m³/ha) over which species richness increases by <5 %. The other deadwood and environmental components influenced saproxylic beetle richness to a lesser extent; some of them, however, should still be considered for proper management. Forest structure variables describing forest density such as large trees and basal areas have a negative effect on species richness. According to the results of our study, stumps and advanced decaying class are positively correlated, while small logs are negatively correlated to species richness. Thus, in extensively managed forests, the regular cutting of trees should be implemented to create artificial stumps, in order to assure a continuity of deadwood and, in the meantime, increase the number and width of openings in the forest. Moreover, prolonging rotation times can assure the presence of deadwood at intermediate/later stages of decay.     

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.     

Linking taxonomical and functional biodiversity of saproxylic fungi and beetles in broad‐leaved forests in southern Italy with varying management histories

Abstract

The fundamental ecological significance of deadwood decomposition in forests has been highlighted in several reviews, some conclusions regarding silviculture being drawn. Old‐growth forests are natural centres of biodiversity. Saproxylic fungi and beetles, which are vital components of these ecosystems, occupy a variety of spatial and trophic niches. Fungal and beetle diversity on coarse woody debris (CWD) was analysed in 36 forest sites in the Cilento and Vallo di Diano National Park, Italy. The data were analysed by DCA and Spearman’s rank correlation. The results provide empirical evidence of the existence of a pattern of joint colonization of the woody substrate by fungi and beetles, which includes an assemblage of reciprocal trophic roles within fungal/beetle communities. These organisms act together to form a dynamic taxonomical and functional ecosystem component within the complex set of processes involved in wood decay. The variables most predictive of correlations between management‐related structural attributes and fungal/beetle species richness and their trophic roles for old‐growth forest are: number of logs, number of decay classes and CWD total volume. Deadwood spatio‐temporal continuity should be the main objective of forest planning to stop the loss of saproxylic fungal and insect biodiversity.     

Ecologie des coléoptères saproxyliques dans les forêts de l’étage montagnard des Alpes du nord françaises

Ecology of the saproxylic beetles in mountain forests of the northern French Alps. Both saproxylic beetles and deadwood stocks were studied in order to detect special deadwood features important for these organisms, and to better understand their ecology. A total of 37 window traps were used in ten stations covering four mountain forests in the French northern Alps. In the same time, the deadwood stocks were inventoried in the ten stations. 181 m³ of deadwood (1219 fragments) were measured and 4268 individuals belonging to 235 saproxylic species were trapped. The deadwood volume ranges from 21.1 to 233.6 m³/ha and the number of beetle species from 27 to 113. A positive relation was observed between the stand age, the whole volume of deadwood and the species richness of saproxylic beetles. However, in some deadwood rich sites the beetle diversity is not as high as expected. This was explained by the negative influence of the management history of the forest. The compositions of saproxylic communities depend also of some characteristics of the deadwood stocks. Xylophagous and zoophagous species prefer “not lying and recently dead softwood” while the mycophagous and saproxylophagous species are strongly dependent on fungi growing on hardwood, respectively under “large surfaces of barks” and in “large woody debris”. Surprisingly, the majority of the saproxylic beetles living on softwood does not depend on the most represented resinous deadwood type: the “decayed and lying softwood”.     

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.     

One taxon does not fit all: Herb-layer diversity and stand structural complexity are weak predictors of biodiversity in Fagus sylvatica forests

Since adequate information on the distribution of biodiversity is hardly achievable, biodiversity indicators are necessary to support the management of ecosystems. These surrogates assume that either some habitat features, or the biodiversity patterns observed in a well-known taxon, can be used as a proxy of the diversity of one or more target taxa. Nevertheless, at least for certain taxa, the validity of this assumption has not yet been sufficiently demonstrated.We investigated the effectiveness of both a habitat- and a taxa-based surrogate in six European beech forests in the Apennines. Particularly, we tested: (1) whether the stand structural complexity and the herb-layer species richness were good predictors of the fine-scale patterns of species richness of five groups of forest-dwelling organisms (beetles, saproxylic and epigeous fungi, birds and epiphytic lichens); and (2) the cross-taxon congruence in species complementarity and composition between herb-layer plants and the target taxa.We used Generalized Linear Mixed Models (GLMMs), accumulation curves and Procrustes analysis to evaluate the effectiveness of these surrogates when species richness, complementarity and composition were considered, respectively.Our results provided a limited support to the hypothesis that the herb-layer plants and the stand structural complexity were good surrogates of the target taxa. Although the richness of the herb-layer plants received a stronger support from the data than structural complexity as a predictor for the general patterns of species richness, the overall magnitude of this effect was weak and distinct taxa responded differently. For instance, for increasing levels of herb-layer richness, the richness of lichens showed a marked increase, while the richness of saproxylic fungi decreased. We also found significantly similar complementarity patterns between the herb-layer plants and beetles, as well as a significant congruence in species composition between herb-layer plants and saproxylic fungi. Finally, when different stand structural attributes were considered singularly, only the total amount of deadwood received support from the data as a predictor of the overall species richness.At the fine scale of this study, herb-layer plants and stand structural complexity did not prove to be effective surrogates of multi-taxon biodiversity in well-preserved southern European beech forests. Rather than on weak surrogates, these results suggest that sound conservation decisions should be supported by the information provided by comprehensive multi-taxonomic assessments of forest biodiversity.     

Identifying practical indicators of biodiversity for stand-level management of plantation forests

Identification of valid indicators of biodiversity is a critical need for sustainable forest management. We developed compositional, structural and functional indicators of biodiversity for five taxonomic groups—bryophytes, vascular plants, spiders, hoverflies and birds—using data from 44 Sitka spruce (Picea sitchensis) and ash (Fraxinus excelsior) plantation forests in Ireland. The best structural biodiversity indicator was stand stage, defined using a multivariate classification of forest structure variables. However, biodiversity trends over the forest cycle and between tree species differ among the taxonomic groups studied. Canopy cover was the main structural indicator and affected other structural variables such as cover of lower vegetation layers. Other structural indicators included deadwood and distances to forest edge and to broadleaved woodland. Functional indicators included stand age, site environmental characteristics and management practices. Compositional indicators were limited to more easily identifiable plant and bird species. Our results suggest that the biodiversity of any one of the species groups we surveyed cannot act as a surrogate for all of the other species groups. However, certain subgroups, such as forest bryophytes and saproxylic hoverflies, may be able to act as surrogates for each other. The indicators we have identified should be used together to identify stands of potentially high biodiversity or to evaluate the biodiversity effects of silvicultural management practices. They are readily assessed by non-specialists, ecologically meaningful and applicable over a broad area with similar climate conditions and silvicultural systems. The approach we have used to develop biodiversity indicators, including stand structural types, is widely relevant and can enhance sustainable forest management of plantations.     

Co-variation and indicators of species diversity: Can richness of forest-dwelling species be predicted in northern boreal forests?

Design and establishment of ecologically good networks of conservation areas often requires quick assessments of their biodiversity. Reliable indicators would be useful when doing such assessments. In order to explore the potential indicators for species richness in boreal forests, we studied (1) the co-variation of species richness and composition of species assemblages among beetles, polypores, birds and vascular plants, (2) the relationships between species richness and four boreal forest site types, (3) the relationship between species richness and forest physical structure and (4) the suitability of potential indicator groups within the four taxa to predict the species richness generally. The data show that there are probably not a single taxonomic or forest structural characteristic to be used as a general biodiversity indicator or surrogate for all the species. The correlations in species richness among the four taxa studied were low. However, group-specific indicators were obvious: forest site type was a good surrogate for vascular plant richness, and quantity and quality of dead wood predicted the species richness of polypores. The results support the view that different indicators shall be used for different forest types and taxonomic groups. These indicators should facilitate relatively rapid methods to assess biodiversity patterns at the forest stand level.     

The importance of substrate type, shading and scorching for the attractiveness of dead wood to saproxylic beetles

Modern forestry management has reduced the amount of dead wood in forest ecosystems and this has become a serious threat to flora and fauna. Efforts are therefore being made to reverse this trend but one problem is that we still lack detailed knowledge regarding the substrate requirements of many saproxylic species. In a field experiment, conducted in three forest types (forest reserve, mature managed forest and clear-cut), we evaluated the value, from a conservation perspective, of different substrate types (logs, snags and tops) of Norway Spruce, Picea abies, and if the quality of spruce logs as saproxylic habitats can be improved by simple log treatments (scorching and shading). We collected 9982 individuals representing 262 saproxylic beetle species in window traps. Both substrate type and, to a lesser extent, log treatment had a significant effect on the abundance and species richness of saproxylic beetles attracted to the different dead wood substrates. However, more importantly, the composition of the beetle assemblages differed significantly between both substrates and log treatments. Snags, logs and tops all attracted significantly different beetle assemblages and scorched logs differed from untreated control logs. Sixteen red listed species were trapped, with the highest number (11 species) being found on scorched logs. We found strong evidence that some species preferred a specific substrate type, mainly logs, in some cases treated logs (scorched or shaded), but not snags, the substrate commonly provided for conservation purposes on e.g. clear-cuts. This stresses the importance of conducting forestry in such a way that a multitude of both forest habitats and dead wood substrates are available continuously in the forest landscape to maintain biodiversity.     

浙江天目山种植林管理历史及粗死木残体特征影响柳杉腐木甲虫多样性（英文）

不合理的森林管理是导致腐木甲虫多样性丧失的重要原因。在中国亚热带地区, 多样性较高的天然林已被大面积的人工种植林取代, 然而, 这些人工林对腐木甲虫多样性的影响还研究甚少。本研究对浙江天目山自然保护区人工幼龄林（30~40年）、 人工老熟林（80~100年）和半天然混合林（>200年）中柳杉枯立木上的腐木甲虫群落及多样性进行比较。结果表明： 半天然混合林腐木甲虫个体数量（97.4±66.7）显著高于幼龄林（39.9±16.3）和老熟林（21.9±5.9）, 但半天然林混合林(27.9±11.2)与幼龄林(24.1±3.7)腐木甲虫物种数差异并不显著(P>0.05), 而幼龄林的腐木甲虫物种数和个体数量则显著高于老熟林(P<0.05)。腐木甲虫物种数和个体数量与样地粗死木残体体积相关性显著(P<0.05)。典范对应分析和多响应置换过程分析表明腐木甲虫群落特征在不同林型间差异显著(P<0.001)。柳杉枯立木直径、 粗死木残体的直径和数量以及林冠盖度均对腐木甲虫物种组成具有显著影响(P<0.05)。腐木甲虫营养级组成分析也表明, 半天然混合林菌食性甲虫数量显著高于种植林(P<0.001)。结果提示, 提高种植林粗死木残体的数量和质量可以增加腐木甲虫的物种丰富度, 但种植林腐木甲虫多样性可能在随后的演替阶段有所下降, 而且种植林与天然林在腐木甲虫群落组成上差异十分明显。     

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.     

The Influence of Habitat Variables on Bird Communities in Forest Remnants in Costa Rica

This study examined the effects of forest structure (tree species richness, canopy height, percent canopy cover, understory density, tree density and DBH) and avian species traits (nest type and indicator list status) on the diversity, abundance and dissimilarity of bird communities in forest remnants and reforestation areas adjacent to Costa Rican banana plantations. Bird species richness and abundance were significantly related to tree species richness, canopy height and canopy cover in multiple linear regressions, the latter two forest structure variables being the best statistical predictors. Stratification of analyses by bird species indicator categories improved fits of regressions, because correlations with environmental variables differed in sign for different guilds of birds, a result likely to hold for other avifaunas. Analysis of avifauna dissimilarities among sites demonstrated that the species composition of bird communities was highly correlated with forest structure and tree species composition. Logistic regressions indicated that birds making protected (cavity, burrow, pendant, sphere and covered) nests were 2–6 times more likely to be present in the study avifauna than birds making open (cup, saucer, platform and scrape) nests and indicators of disturbed habitats were 11 times more likely to be present than indicators of primary forest. The forest structure data used were simple and inexpensive to collect, and data on avian traits were drawn from the literature. Thus, these methods could easily be replicated at other locations and would be valuable management aids and biodiversity assessment tools for conservation planning.     

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.     

Beetle families as indicators of Coleopteran diversity in forests: a study using Malaise traps in the central mountainous region of Japan

The conservation of biodiversity is an important goal of most forest management efforts, and proper monitoring of biodiversity requires immediate attention. Coleoptera, the largest order of organisms on Earth, should be monitored as a crucial part of overall biodiversity. To facilitate monitoring of Coleopteran diversity, indicators at the family level that adequately represent the beetle diversity were investigated. One Malaise trap was placed in each of 52 forest stands in the central mountainous region of Japan; all captured beetles were identified to species. Pearson’s correlation coefficients were calculated between the number of species in each family and the total number of species in all families combined. The relationship between the species composition of each family and the overall composition of all families was examined using Mantel tests. Families with high correlation coefficients for species richness included Cerambycidae, Cleridae, Curculionidae, Lycidae, Elateridae. Families exhibiting strong similarity in composition to the composition of all families were Scolytidae, Elateridae, Curculionidae, Cerambycidae, and Staphylinidae and the Cerambycidae, Curculionidae, and Elateridae were determined to be useful surrogates for Coleopteran diversity. All significant pairwise correlations between each of these three families and other Coleopteran families were positive, indicating that each was appropriate as a competent surrogate. Thus, this study identified adequate diversity indicators in Coleoptera that can be caught by Malaise traps. The accumulation of data on indicators obtained through different methods or in different climates is necessary to ensure the selection of widely applicable indicator families as stable surrogates of beetle diversity.     

Increased openness around retained oaks increases species richness of saproxylic beetles

The decrease of old deciduous trees in northern Europe is a threat to the saproxylic fauna. In northern Europe, oak sustains the highest richness of saproxylic invertebrates, among which beetles is a large group. In order to preserve species associated with old trees, it has become common practice in commercial forestry to retain such trees at final felling. However, to create beneficial conditions for species associated with retained trees, the surrounding plantation has to be managed with regard to their specific demands. In the case of oak-associated species, including many red-listed species, several studies have shown that light is an important factor. The aim of this study was to analyze the effects of increased openness around oaks (Quercus robur) in spruce plantations (Picea abies) on species richness and abundance of oak-associated saproxylic beetles. The study was performed in nine spruce plantations located in southern Sweden, with mature oaks standing in a gradient of canopy openness. Beetles were collected from 54 oaks from May to September during two seasons, using window traps. The analyses revealed that increased openness around oaks increases species richness and abundance of oak-associated beetles. By including insolation angle in the analysis, we found that it is mainly the degree of openness directed south from the oak that has positive effects on beetle richness. These findings imply that it is desirable to maintain an open area around retained oaks, and that this area should be placed on the southern side of the oak to maximize the biodiversity benefit in relation to costs for the forest owner.     

Multi‐taxon and forest structure sampling for identification of indicators and monitoring of old‐growth forest

Abstract

The most commonly used old‐growth forest indicators are structural attributes; nevertheless, they do not necessarily represent the biodiversity value of old‐growth forests. The aim of this study is to analyse the relationships between species richness data of different taxa and structural indicators of old‐growth and to identify taxonomic/functional groups, species and structural attributes that may be used as indicators of old‐growth. To achieve this goal we sampled forest structure, vascular plants, lichens, bryophytes, fungi, saproxylic beetles and birds in mature and old‐growth stands in southern Italy. We calculated Spearman’s correlation coefficients between species richness data and structural attributes. Analyses of indicator species, co‐occurrences and two‐way clusters were performed on the multi‐taxonomic list. The group of vascular plants most significantly correlated with other groups in terms of species richness; furthermore, it displays the highest proportion of between‐group co‐occurrences. The resulting multi‐taxonomic list of potential indicators may serve as an effective means of detecting and monitoring forest ecosystems; however, for this goal, structure‐based indicators, such as forest structural attributes and vascular plant species composition, are of primary importance.