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1.
New conservation-oriented forestry aims to maintain intact populations of forest organisms by improving the conservation value of managed forests and providing protected areas. We tested the conservation value of treatments of dead wood for assemblages of early successional saproxylic beetles. In nine areas in northern Sweden, we selected one clear-cut, one mature managed forest and one reserve. In 2001-2002, we placed three blocks of spruce logs, each containing control, burned and shaded logs and a high stump (“snag”) at each site. Saproxylic beetles emerging from the dead wood were collected using emergence traps and beetles flying close to it were collected using flight-intercept traps. After one year of exposure, assemblage composition was examined, with respect to nutritionally-defined functional groups, red-listed species and fire-favoured species. Experimental snags were most complementary to control logs, supporting different assemblages of cambium consumers and fungivores and supporting more red-listed individuals. Burned logs supported depauperate assemblages, particularly with respect to cambium consumers, while shading of logs affected assemblages of fungivores, but only on clear-cuts. Despite containing less dead wood, managed forests provided valuable habitat, supporting similar assemblages of saproxylic beetles to reserves. Most functional groups were less abundant on clear-cuts than in older forests, but fire-favoured species were more common on clear-cuts, suggesting that clear-cuts may support assemblages of species associated with natural disturbances, if suitable substrates are available. Utilization of logs by saproxylic beetles changes over time, so long-term monitoring of our experimental logs will determine their lifetime conservation value.  相似文献   

2.
Global conventions on biological diversity force governments to develop region-wide conservation strategies. Such strategies are difficult to design for all taxa because little is known about the important spatial scales. Here we applied additive partitioning of the diversity of saproxylic beetles in Bavarian forests in Southern Germany using a nested hierarchical design of five increasingly broader spatial levels: trap, strata, forest stand, forest site, and ecoregion. We consistently found a significantly higher percentage than expected by chance of between ecoregion diversity and significantly lower α diversity within traps. A significant proportion of β diversity was also found between stands. Analysis of species represented by <0.005% of all specimens in our samples and of species classified as threatened revealed similar results. Critical spatial scales for threatened species encompassed the critical levels of common species. Within habitat substratum guilds, the proportion of β diversity increased from species associated with fresh wood to those associated with rotten wood to those associated with fungi. Our results suggest that the most effective way to ensure saproxylic beetle diversity in a state-wide strategy is to add new conservation sites within different ecoregions and to establish new conservation areas in additional forest stands, rather than to enlarge reserves. Our findings further suggest that monitoring of saproxylic beetle diversity on a broader scale in European temperate forests can be restricted to “monitoring species”, i.e. a subgroup of families easy to identify, and that canopy sampling can be neglected without a substantial loss of information.  相似文献   

3.
In a study of the effect of forest clear-cutting on the saproxylic beetle fauna in aspen in Norwegian boreonemoral forest, we find that both sun exposure and substrate are important structuring factors for the community of saproxylic beetles. Even though the species number and abundance is rather similar across the gradient of sun exposure, there is a major turnover in species composition in decaying aspen from mature forest to clear-cuttings. Our results confirm that aspen is an important element for beetle biodiversity both because of a generally species-rich community and a high number of rare and threatened (red-listed) beetles. There is a higher probability of presence of red-listed beetle species in snags than in logs. Sun exposure increases the probability of presence of red-listed species, but this was largely an effect of one dominating species. We conclude that retention of trees when clear-cutting is an important means for safeguarding the fauna of saproxylic beetles in aspen.  相似文献   

4.
Increasing demands for firewood owing to rising energy costs have accelerated discussions about the amount of dead wood needed for conservation. A sharp increase in dead wood caused by bark beetles in a German national park provides lessons for management of commercial and protected forests. We investigated the effects of dead wood due to bark beetle infestation as well as tree senility on abundance and richness of saproxylic species of beetles. Increasing amounts of spruce dead wood and opening of the canopy by bark beetles had positive effects on the abundance of host-generalist, conifer-specialist, and red-listed saproxylic beetles. Broadleaf specialists were positively associated with the amount of broadleaf dead wood and negatively associated with canopy openness. Gradient analysis of beetle assemblages revealed two major environmental axes: canopy openness and amount of dead wood. We found a threshold for community divergence at a canopy openness of 23% (confidence interval CI: 11-49) and at an amount of dead wood of 64 m3 ha−1 (CI: 35-160). Critically endangered species served as indicators of dense and open forests, but only when the amount of dead wood was high. Our results suggest that, to maintain saproxylic beetle assemblages, the amount of dead wood in commercial montane forests (at present ≈15 m3 ha−1) needs to be tripled, with a focus on broadleaf wood in dense stands and spruce wood in open stands. For large protected areas in Europe, our data suggest that bark beetle infestation and senescence without active forest management improves habitat conditions for saproxylic beetles.  相似文献   

5.
The appropriate management of forest reserves is debated; two major alternatives are succession to ‘wild’ state, or management to produce semi-open stands. For temperate conservation stands, there are no strong experiments replicated at landscape level. In each of 22 forests rich in oaks (Quercus spp.) in Sweden, we set up a closed-canopy wild plot (1 ha), and a cutting plot (1 ha) to produce semi-open conditions, studying them before and after cutting. About 25% of the tree basal area was cut (large trees and dead wood retained) and harvested as bio-fuel, a CO2 - neutral energy source. We examined the response of beetles and trapped 59,000 individuals (1174 species; 100 red-listed species). For both the guild of herbivorous beetles (222 species) and of saproxylic beetles connected to oak wood (267 species), species richness increased by about 35% in the harvested plots, relative to the wild reference plots. Species composition within the groups changed, though not strongly. Thirteen saproxylic species of 50 analysed, and three herbivores of 12 increased in cutting plots. For red-listed saproxylic beetles, species richness did not change significantly. Regression analyses suggest that more open cutting plots disfavour the red-listed beetles of this forest type. Thus, partial cutting increased species diversity of two beetle groups, probably due to changed microclimate and increase in herbaceous plants, but some red-listed saproxylic beetles may be disfavoured. A hands-off alternative may through storms and other disturbances produce open patches, more dead wood, and favour some species. Combinations of these alternatives, carefully planned at the landscape level, need to be considered.  相似文献   

6.
Saproxylic Coleoptera are diverse insects that depend on dead wood in some or all of their life stages. In even-aged boreal forest management, remnant habitats left as strips and patches contain most of the dead wood available in managed landscapes and are expected to act as refuges for mature forest species during the regeneration phase. However, use of remnant habitats by the saproxylic fauna has rarely been investigated. Our objective was to characterize the saproxylic beetle assemblages using clearcuts and forest remnants in western Québec, Canada, and to explore the effects of forest remnant stand characteristics on saproxylic beetle assemblages. We sampled both beetle adults and larvae, using Lindgren funnels and snag dissection, in five habitat locations (clearcuts, forest interiors of large patches, edges of large patches, small patches and cut-block separators) from three distinct landscapes. Adult saproxylic beetles (all feeding guilds combined) had significantly higher species richness and catch rates in small patches compared to forest interiors of large patches; the phloeophagous/xylophagous group had significantly higher species richness only. Small patches, cut-block separators and edges of large patches also had the highest snag density and basal area, increasing habitat for many saproxylic beetles. No significant differences in density of saproxylic larvae were found between habitat patches, but snag dissection nevertheless suggests that snags in forest remnants are used by comparable densities of insects. Saproxylic beetles appear to readily use habitat remnants in even-aged managed landscapes suggesting that forest remnants can insure the local persistence of these species, at least in the timeframe investigated in our study.  相似文献   

7.
The influence of environmental factors on species richness and species composition may be manifested at different spatial levels. Exploring these relationships is important to understand at which spatial scales certain species and organism groups become sensitive to fragmentation and changes in habitat quality. At different spatial scales we evaluated the potential influence of 45 factors (multiple regression, PCA) on saproxylic oak beetles in 21 smaller broadleaved Swedish forests of conservation importance (woodland key habitats, WKH). Local amount of dead wood in forests is often assumed to be important, but two landscape variables, area of oak dominated woodland key habitats within 1 km of sites and regional amount of dead oak wood, were the main (and strong) predictors of variation in local species richness of oak beetles. The result was similar for red-listed beetles associated with oak. Species composition of the beetles was also best predicted by area of oak woodland key habitat within 1 km, with canopy closure as the second predictor. Despite suitable local quality of the woodland key habitats, the density of such habitat patches may in many areas be too low for long-term protection of saproxylic beetles associated with broadleaved temperate forests. Landscapes with many clustered woodland key habitats rich in oak should have high priority for conservation of saproxylic oak beetles.  相似文献   

8.
It is important that measures to maintain biodiversity are taken in a way that is cost-effective for the landowner. We analyzed the cost-effectiveness of silvicultural measures that aim at increasing the substrate availability for red-listed (species that are threatened, near threatened or where species probably are threatened but data is deficient) saproxylic (wood-inhabiting) organisms. We modelled stands of Norway spruce (Picea abies) in three regions of Sweden by using computer simulations and a database with substrate requirements of saproxylic beetles and cryptogams on the Swedish Red-List. Conclusions concerning cost-effectiveness of silvicultural measures depend on the extinction thresholds of the species they are intended to conserve; measures that generate only small amounts of coarse woody debris (CWD) may provide too little substrate to be useful for species with high extinction thresholds. In northern Sweden, forestland is relatively inexpensive, so a cost-effective strategy to increase the amount of spruce CWD was to set aside more forests as reserves. In central and southern Sweden, more emphasis should instead be given to increasing the amount of CWD in the managed forest. The regulations by the Forest Stewardship Council (FSC) could be made more cost-effective by prescribing creation of more high stumps and retention of larger amounts of naturally dying trees. Large-sized CWD, CWD from slow-growing trees, and CWD in late decay stages are substrate types that were particularly rare in managed forest in relation to unmanaged forests. Manual soil scarification and retention of living trees are measures that can increase the proportion of these underrepresented CWD types.  相似文献   

9.
Intensive forest management in Scandinavia has decreased the amount of dead wood required by saproxylic (wood-living) organisms. To reduce this problem, some dead wood is now retained during forest operations, often in the form of man-made high stumps (ca. 4 m high). Most often these stumps are cut with a harvester, although the stumps in this study were made with explosives. The aims of this study were to determine whether such stumps of aspen (Populus tremula) and birch (Betula spp.) could be used by red-listed saproxylic beetles (Coleoptera), and to examine how the fauna of man-made high stumps differs from that of natural stumps. We also studied how tree species, sun-exposure, stage of decay and trunk diameter influenced the fauna. In 169 samples of bark from high stumps 116 saproxylic species were found, of which 21 were red-listed. Many species, including red-listed ones, were more associated with man-made stumps than with natural stumps. However, in total, more species were found in the natural than in the man-made stumps. This is probably because man-made stumps provide a more homogeneous type of wood substrate than natural ones. Among the other variables the difference between aspen and birch was the most important. We conclude that man-made high stumps are valuable habitats for many saproxylic beetle species.  相似文献   

10.
Saproxylic organisms are among the most threatened species in Europe and constitute a major conservation problem because they depend on the most important forestry product - dead wood. Diversity of fungal and bryophyte communities occurring on dead beech trees was analyzed in five European countries (Slovenia, Hungary, The Netherlands, Belgium and Denmark) considering tree level species richness (TLSR), country level species richness (CLSR), frequency distributions of species, occurrence of threatened species and relations between TLSR and decay stage, tree size and countries. Altogether 1009 trees were inventoried in 19 beech dominated forest reserves.The number of fungi in the full dataset was approximately three times larger (456 versus 161 species) and the proportion of low frequent species was higher than among bryophytes. The species richness of bryophytes and fungi was significantly different among countries considering both TLSR and CLSR. In addition the diversity patterns deviated considerably between the two groups of organisms. Slovenian sites appeared to be biodiversity hotspots for bryophytes characterized by high TLSR and CLSR and a high fraction of threatened species. Hungarian sites had somewhat lower bryophyte diversity, while the Atlantic region had deteriorated assemblages. Fungal species richness was very high in Denmark, but the Hungarian and Slovenian sites were richer in threatened and low frequency species. Tree size was better able to explain variation in TLSR in both organism groups than decay stage. TLSR was found to vary significantly between countries but the difference was most considerable in the case of bryophytes.The diversity patterns of both organism groups along the investigated geographical gradient appear to be influenced by both climatic and management related factors (forest history, dead wood availability and continuity, habitat fragmentation). There is no doubt that an increase in the abundance of dead wood in European beech forests will benefit diversity of saproxylic fungi and bryophytes, especially if a continuous presence of large diameter logs are secured within individual stands.  相似文献   

11.
The effort of boreal forest conservation has emphasised the preservation of old-growth forests while the role of young successional stages in maintaining biodiversity has remained largely unstudied. We compared the richness of beetle species and composition of species assemblages between managed and seminatural forests in five stages of forest succession. The sites were in boreal sub-xeric pine-dominated forests in eastern Finland. Seminatural study sites, especially the recently burned sites, were important habitats for threatened and near-threatened species. We propose that young stages of natural succession should be included in the network of protected forest areas. On the other hand, the composition of saproxylic species assemblages in seminatural forests differed from the assemblages in managed forests, indicating also the need to improve the forest management guidelines so that they better address the requirements of species protection. Regeneration methods applied should resemble or mimic the natural disturbances more closely.  相似文献   

12.
Fragmentation of old-growth forests and greatly reduced amounts of coarse dead wood in managed forests threat the persistence of many saproxylic species in boreal Fennoscandia. Individual old-growth forest remnants may lose species over time as they pay off their extinction debt. We tested this by comparing the observed site occupancy of individual wood-inhabiting fungal species in isolated old-growth stands (i.e. woodland key habitats; WKHs) with statistical predictions of their occupancy assuming potential extinction debt had already been paid off. The occupancy of species was analysed in two sets of WKHs differing in time since isolation (i.e. recent and old isolates).Few species occurred more frequently than expected in WKHs. However, patterns across species and across all WKHs masked important differences among species in their risk of facing future extinction. The site occupancy decreased significantly between recent and old isolates for a group of annual, red-listed specialist fungal species, suggesting that an extinction debt in WKHs may exist among specific species confined to coarse dead wood and old-growth forest habitat. Generalist species that also occur in the surrounding matrix showed no negative trends, or actually increased in site occupancy, making future extinctions less likely. Thus, continuing loss of threatened species are likely if not preservation of WKHs are combined with other conservation efforts in managed forest landscapes. Natural forest landscapes may serve as important references when aiming to identify species in risk of future extinction but more detailed knowledge about the biology of the most vulnerable species is also required.  相似文献   

13.
In this study we compared ground beetles (Carabidae) from a range of different forest fragments along an urbanization gradient in Brussels, Belgium. We address the following questions: (i) How does the degree of urbanization in the surrounding habitat affect forest beetles, and does it interact with the effects of patch size and distance to forest edge? (ii) Do these factors have a different effect at the level of individual species, habitat affinity groups or total community? During 2002 we sampled 13 forest plots in 10 forest patches, ranging in size from 5.27 to 4383 ha. The beetles were captured using transects of pitfall traps from the edge to a distance of 100 m into each woodland and identified to species level. Effects of urbanization, forest size and forest edge were evaluated on total species number, abundance and habitat affinity groups and ten abundant, widespread model carabid species. Overall, the effects of urbanization, forest size and edge effects slightly influenced total species richness and abundance but appeared to have a major effect on ground beetle assemblages through species specific responses. More urbanized sites had significantly fewer forest specialists and more generalist species. Large forest fragments were favoured by forest specialist species while generalist species and species frequently associated with forest (forest generalists) dominated the smaller forests. Forest edges mainly harboured generalist species while forest specialist species were more frequent into the forests if the forest patches were large enough, otherwise they disappeared due to the destruction or impoverishment of their habitat. Our results show the importance of differentiating between habitat affinity, especially habitat generalists versus specialists, the latter having a higher value in nature conservation, and merely the quantity of species represented in human-dominated areas.  相似文献   

14.
Forest management in temperate and boreal regions is often based on a strong foundation of applied ecological research. Increasingly, this has allowed the needs of saproxylic (dead wood associated) insects to be addressed. However, there has been very little equivalent research in tropical forests, where saproxylic insect faunas are likely to be much richer and where forestry is usually subject to weaker environmental controls. This study compares the saproxylic beetle fauna of old-growth, selectively logged and regrowth rainforest in the Daintree lowlands of northeastern Queensland, Australia. Old-growth levels of abundance, species richness, assemblage composition and guild structure were not maintained in logged and regrowth forest, suggesting that intact assemblages may not survive in the long-term in managed tropical rainforest. However, retaining a continuous supply of commercially overmature trees in the managed stand may prevent a repeat of the widespread extinctions of saproxylic insects witnessed in temperate and boreal forest regions.  相似文献   

15.
Polypore communities were compared between mature managed, overmature managed, and old-growth spruce-dominated forests in southern Finland. A total of 85 polypore species, with 6000 records, were found in 16 sample plots, each 4 ha in size. Old-growth stands had on average 80% more species than mature stands, and 38% more species than overmature managed stands. Variation in polypore species richness was best explained by diversity of dead wood and the number and volume of dead trees. The best predictor for the number of threatened polypore species was the number of cut stumps. Threatened species were practically confined to old-growth forests and to stands in which the amount of dead wood exceeded 20 m3/ha. This figure appears to represent a stand-level threshold value for the amount of dead wood, below which the persistence of threatened species becomes unlikely. Our results suggest that a significant increase in the amount of dead wood (e.g. by leaving large retention trees and even by killing trees) is needed in managed forests before they become suitable habitats for threatened polypores.  相似文献   

16.
We sampled the carabid beetles in 22 forests managed by six different silvicultural systems, defined by treatment and tree species composition: even-aged conifer, even-aged beech, even-aged oak, uneven-aged conifer, uneven-aged beech and group mixed (beech + conifer). In each of these forests, we placed pitfall traps in young, medium-aged and mature stands (3 stages). We evaluated the effect of treatment, tree species composition, silvicultural system, stage and habitat type (silvicultural system + stage) on indicators of community conservation value and ecological structure. The species composition and the ecological structure of carabid beetles of the managed stands were then compared to that of nine unmanaged stands (without tree exploitation). In the managed forests, species richness was highest in large young stands (3-10 years old) and in forests managed by even-aged systems (with large clear-cuts), mainly due to eurytopic and opportunist carabid species with high dispersal abilities. Oak and beech, uneven-aged, and mature stands were mainly inhabited by typical forest species, and even-aged conifer stands mainly by ubiquitous species. Several typical forest species recorded in unmanaged stands were lacking from the managed forests. Large scale clear-cutting allows open-habitat species to enter the forest, which increases the species richness at a landscape level but can disfavour typical forest species by competition. Long rotations should be implemented and more areas left unmanaged in Belgium, in order to help typical forest species to re-colonise managed forests.  相似文献   

17.
The habitat requirements and effects of forest management on insects belonging to higher trophic levels are relatively unknown in forest ecosystems. We tested the effect of forest successional stage and dead wood characteristics on the saproxylic parasitoid (Hymenoptera, Ichneumonoidea) assemblage in boreal spruce-dominated forests in northern Sweden. Within each of nine areas, we selected three sites with different management histories: (1) a clear-cut (2) a mature managed forest and (3) an old-growth forest. Parasitoids were collected in 2003 using eclector traps mounted on fresh logs, which were either untreated (control), burned, inoculated with fungi, or naturally shaded, and on artificially-created snags.Both forest type and dead wood characteristics had a significant effect on parasitoid assemblages. Grouped idiobionts and some species, such as Bracon obscurator and Ontsira antica, preferred clear-cuts, while others, such as Cosmophorus regius (Hym., Braconidae) and other koinobionts, were associated with older successional forest stages. No single dead wood substrate was sufficient to support the entire community of parasitoids in any forest type, even when the regular host was present. In particular, snags hosted a different assemblage of species from other types of dead wood, with parasitoids of Tetropium spp. such as Rhimphoctona spp. (Hym., Ichneumonidae) and Helconidea dentator (Hym., Braconidae) being abundant. These results indicate that a diversity of dead wood habitats is necessary to support complete assemblages of beetle-associated parasitoids from early successional stages of dead wood and that parasitoids may be more sensitive to habitat change than their hosts.  相似文献   

18.
The increasing demand for biofuel may decrease the dead wood supply in managed forests, and hence the amount of substrate available for dead wood dependent species. Slash is already being harvested for biofuel purposes, and stumps are an even bigger potential source of wood fuel. Both substrates constitute a major component of dead wood in managed forests, but have been poorly studied in terms of lichen diversity. We compared lichen species diversity between the lateral surface of slash and the cut surface of stumps of Norway spruce in planted boreonemoral Swedish forests of four age classes; 4-5, 8-9, 12-13, and 16-18 years. We also estimated the amounts of the two substrates, and discriminated between slash with bark and decorticated slash. There were no differences in species number per surface area, but slash had more species when equal volumes were compared. We found compositional differences between slash and stumps throughout the decay process. The majority of species found on both substrates were more frequent on stumps, which also had a higher number of unique species and species in the literature indicated as nationally rare or uncommon. The volume per hectare of stumps was ten times greater than that of slash but conversely, the lateral surface area of slash was five times greater than the cut surface area of stumps. Few dead wood specialist lichen species were, however, strictly associated with slash, whereas stumps offer a more heterogeneous environment and may provide important habitats for rare lichens in the managed forest landscape.  相似文献   

19.
In European temperate forests, changes in the compositional similarity among local plant communities (beta diversity) have rarely been studied due to the lack of adequate baseline data. Several studies, however, report the spread of common, generalist species or a decline in specialized, rare species. Both processes may lead to increased similarity among communities, i.e., biotic homogenization.To quantify changes in beta diversity, we resampled the herb layer composition of ancient broadleaf forests at 175 semi-permanent plots distributed across the Weser-Elbe region in NW Germany 20 years after first sampling. We hypothesized that beta diversity would have decreased on average as a result of a spread of habitat generalists and a decline in habitat specialists.After two decades, the forest communities did not yet exhibit severe biotic impoverishment, although there was a broad trend towards homogenization. The actual magnitude of change depended on which beta diversity measure was applied. The downward trend was primarily the result of the spread of native species that are able to tolerate broad pH and moisture ranges. A distinction between forest specialists (closely tied to forest habitats) and generalists (also found in open habitats) did not help explain changes in beta diversity. The study shows that on the regional scale and in habitats not yet threatened by the invasion of alien species, shifts in native species can promote biotic homogenization.  相似文献   

20.
A consequence of isolation is increased susceptibility to catastrophe. Insect damage to fragmented and isolated forests has the potential to serve as a catastrophic force; such damage has increased worldwide due to climate change and fire suppression policies. We examined the response of endangered endemic Mt. Graham red squirrels to catastrophic insect damage due to moths, beetles, and introduced aphids. Insects changed the forest environment significantly for the endemic squirrel by reducing basal area and stem densities of live stems, while increasing number and basal area of standing dead stems. Availability of two major foods, fungi and tree seeds, declined in insect-damaged forests relative to trends in undamaged forests. Numbers of Mt. Graham red squirrels declined precipitously in insect-damaged forests suggesting a catastrophe. Conservation options are limited in such situations. Forest-insect induced catastrophes are likely to become more common in the near future as forest health declines due to past management tactics and climate change. Prudent conservation measures include the anticipation of insect outbreaks and effective forest treatments to decrease likelihood of such catastrophes to species of precarious conservation status, while avoiding abrupt changes to critical habitat.  相似文献   

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