Intermediate Decay Stages Research Articles

Microhabitat diversity – A crucial factor shaping macrofungal communities and morphological trait expression in dead wood

The majority of studies exploring the ecology of saprotrophic fungi have worked with individual logs as homogenous sampling units, neglecting the presence of microhabitats and inner complexity. Based on close to 7000 sporocarp records of more than 450 fungal taxa from 134 decaying beech logs we investigated microhabitat preferences in macrofungi and linked these to sporocarp traits. The respective microhabitats were defined by the local wood decay stage, vertical position on the fallen log and special habitat features (hollows, fracture surfaces, woody material fallen from the log). We found microhabitat associations to be non-random in relation to fungal community composition and sporocarp morphology, indicating an evolutionary link between dead wood niche and sporocarp morphology. While log-level fungal species richness peaked at intermediate decay stages, taxa with significant indicator values were skewed towards early and late decay stages, when defined at microhabitat decay level. This suggests that the commonly found peak in fungal species richness on dead logs in intermediate decay stages expresses a peak in niche diversity rather than a peak in taxa decay stage preferences.

Landscape context and substrate characteristics shape fungal communities of dead spruce in urban and semi-natural forests.

SummaryUrban green areas are becoming increasingly recognized for their biodiversity potential. However, little is known about how urbanization shapes cryptic species communities, such as those residing in deadwood. In this study, we investigated downed Norway spruce trunks at intermediate stages of decay, in urban and semi‐natural forests in southern Finland. To understand the interconnections between landscape context, deadwood characteristics and wood‐inhabiting fungal communities, we studied structural characteristics, surface epiphyte cover and internal moisture and temperature conditions of the tree trunks, and fungal communities residing in the wood. Our findings showed that urban tree trunks had less epiphyte cover and lower moisture than trunks in semi‐natural forests. Overall, urban forests provide less favourable habitats for a majority of the dominant wood‐inhabiting fungal species and for red‐listed species as a group. Yet, 33% of urban trunks hosted at least one red‐listed species. While these landscape‐scale effects may be driven by local climatic conditions as well as contingencies related to available species pools, our results also highlight the significance of substrate‐scale variability of deadwood in shaping wood‐inhabiting fungal communities. We show that epiphyte cover is a significant driver or indicator of these small‐scale dynamic processes in deadwood.

Dead wood quality influences species diversity of rare cryptogams in temperate broadleaved forests

Dead wood is one of the most important indicators of forest naturalness and the most important manageable habitat for biodiversity in forests. Standing and lying dead wood, and especially coarse woody debris, plays an important part in creating habitats for many highly specialized organisms, e.g., insects, fungi, lichens and bacteria. Temperate mixed deciduous forests, rich in species, have been studied only to a small extent from the point of view of the ecology of wood-related cryptogams. Our study aimed at the reduction of the gap in knowledge about the ecological characteristics of dead wood-dependent organisms by focusing on species of cryptogams developing on various dead wood structures typical of temperate non-beech forests. Studies were performed in forests located in Lithuania, Poland, Belarus and Russia. We recorded 48 species of cryptogams: 18 species of bryophytes, 24 species of fungi and 6 species of lichens developing on dead wood. Our study stresses the importance of all types of dead wood as a substrate for the development of rare cryptogam species. Logs were the most important substratum type for cryptogams, followed by snags, dead trees and stumps. The cryptogam species richness on logs was several times higher than on the three other types of substrata. Coarse logs of intermediate decay stages hosted the highest number of cryptogams, followed by freshly fallen logs and, finally, well decayed logs. Assessing the importance of dead wood quality for the studied cryptogams, we found that intermediate decay stages are extremely important for fungi, while bryophytes or lichens do not show a clear preference. The highest number of cryptogams was found on Fraxinus excelsior, Quercus robur and Picea abies, while other tree species had less than half cryptogam species.

Succession of saproxylic beetles associated with decomposition of boreal white spruce logs

We reared saproxylic beetles from 54 white spruce [Picea glauca (Moench) Voss] logs collected in northwestern Alberta, Canada. Logs represented six decay classes, ranging from freshly dead to well decayed. Beetle assemblages were indicated mainly by phloeophagous and predaceous species in early decay stages, although indicator species were mainly predaceous in later stages of decay. No indicator species were identified for intermediate decay stages. Larvae from rearings were disproportionately predaceous. Thus, movement of juveniles within and among coarse woody debris (CWD) substrates is likely an important aspect of the life history for these species. Beetle assemblages changed progressively with increasing stages of decomposition. Assemblages of adjacent decay classes were highly similar, although similarity decreased with increasing difference in decay classes. Therefore, the retention of all decay classes of white spruce downed CWD on post-harvest landscapes is necessary to conserve the associated saproxylic beetle fauna. Retention of CWD in advanced decay stages, which contains species not found in earlier decay classes, presents a particular challenge in forest management because of the long times required to develop CWD in the later stages of decomposition.

Loss of diversity in wood-inhabiting fungal communities affects decomposition activity in Norway spruce wood

Hundreds of wood-inhabiting fungal species are now threatened, principally due to a lack of dead wood in intensively managed forests, but the consequences of reduced fungal diversity on ecosystem functioning are not known. Several experiments have shown that primary productivity is negatively affected by a loss of species, but the effects of microbial diversity on decomposition are less studied. We studied the relationship between fungal diversity and the in vitro decomposition rate of slightly, moderately and heavily decayed Picea abies wood with indigenous fungal communities that were diluted to examine the influence of diversity. Respiration rate, wood-degrading hydrolytic enzymes and fungal community structure were assessed during a 16-week incubation. The number of observed OTUs in DGGE was used as a measure of fungal diversity. Respiration rate increased between early- and late-decay stages. Reduced fungal diversity was associated with lower respiration rates during intermediate stages of decay, but no effects were detected at later stages. The activity of hydrolytic enzymes varied among decay stages and fungal dilutions. Our results suggest that functioning of highly diverse communities of the late-decay stage were more resistant to the loss of diversity than less diverse communities of early decomposers. This indicates the accumulation of functional redundancy during the succession of the fungal community in decomposing substrates.

Fungal community dynamics in relation to substrate quality of decaying Norway spruce (Picea abies [L.] Karst.) logs in boreal forests

Decaying wood plays an important role in forest biodiversity, nutrient cycling and carbon balance. Community structure of wood-inhabiting fungi changes with mass loss of wood, but the relationship between substrate quality and decomposers is poorly understood. This limits the extent to which these ecosystem services can be effectively managed. We studied the fungal community and physico-chemical quality (stage of decay, dimensions, density, moisture, C : N ratio, lignin and water or ethanol extractives) of 543 Norway spruce logs in five unmanaged boreal forest sites of southern Finland. Fungi were identified using denaturing gradient gel electrophoresis and sequencing of DNA extracted directly from wood samples. Macroscopic fruiting bodies were also recorded. Results showed a fungal community succession with decreasing wood density and C : N ratio, and increasing moisture and lignin content. Fungal diversity peaked in the most decayed substrates. Ascomycetes typically colonized recently fallen wood. Brown-rot fungi preferred the intermediate decay stages. White-rot fungi represented approximately one-fifth of sequenced species in all decay phases excluding the final phase, where ectomycorrhizal (ECM) fungi became dominant. Lignin content of logs with white-rot fungi was low, and ECM fungi were associated with substrates containing abundant nitrogen. Macroscopic fruiting bodies were observed for only a small number of species detected with molecular techniques.

Effect of deadwood position on saproxylic beetles in temperate forests and conservation interest of oak snags

Abstract.1. Intensive forestry has drastically reduced the volume of standing deadwood, even more than total deadwood volume. It has been demonstrated in boreal forests that snags have a high conservation value for many saproxylic species and that the lying or standing aspect of the deadwood makes a difference. The conservation of saproxylic beetles in the changing deadwood landscape of temperate managed forests depends on a deeper understanding of the ecological value of forest stand legacies.2. Our study questioned whether the retention of oak snags is an important conservation concern in European temperate forests. We analysed the differences in saproxylic beetle fauna between oak snags and logs and explored the diameter effect on log–snag differences. We compared the species composition and richness of saproxylic beetle assemblages in a temperate deciduous forest. Emergence traps were set in a balanced sampling design of 22 ground‐lying logs and 22 oak snags with a range of intermediate decay stages and 2 diameter classes.3. Oak snags yielded more individuals per volume unit and supported more species than logs, and exhibited significantly dissimilar assemblages from logs and hosted original species. Snags, especially large snags, were more interesting for rare beetle species conservation than logs. The feeding guild structure slightly differed between snags and logs. Overall, log–snag differences depended on the diameter class.4. We confirm that saproxylic biodiversity would significantly benefit from forestry measures favouring oak snag retention (especially large snags), even though further multi‐scale studies are necessary to develop quantitative retention guidelines.

Availability of standing trees for large cavity-nesting birds in the eastern boreal forest of Québec, Canada

Large cavity-nesting birds depend on large-diameter trees for suitable nest sites. The increased spatial extent of commercial timber harvesting is modifying forest structure across the land base and may thus compromise the availability of large trees at the landscape scale. In this study, our objectives were to (1) characterize the availability of large living and dead trees in old-growth stands dominated by different tree species and surficial deposits that encompass the range of natural cover types of eastern Québec's boreal forest; (2) analyze the distribution of trees among decay-classes; and (3) compare the availability of large trees in unharvested, remnant, and harvested stands for the entire range of decay-classes. A total of 116 line transects were distributed across unharvested forests, remnant linear forests, and cutblocks in cutover areas. Unharvested forest stands (black spruce [ Picea mariana], balsam fir [ Abies balsamea]–black spruce, balsam fir–white spruce [ Picea glauca] and balsam fir) reflected a gradient of balsam fir dominance. The remnant forests selected were isolated for 5–15 years. Analyses were performed at two diameter cut-off values. Trees with DBH ≥20 cm were considered for availability of total trees whereas trees with DBH ≥30 cm were considered for availability of large trees. Forest stands comprised high proportions of standing dead trees (33% of all stems, 8% were large dead stems). Availability of total and large standing trees increased with the dominance of balsam fir in stands. Forest stands located on thick surficial deposits showed higher densities of large dead trees for every stand type suggesting a higher productivity on those sites. Availability of stems according to decay-classes showed a dome-shaped distribution with higher densities of snags in intermediate decay stages. However, for large stems, black spruce stands showed a significantly lower availability that was consistent across all decay-classes. In linear remnant forests, pure balsam fir stands were absent. Remnant stands thus showed a much lower availability in large trees when compared with unharvested balsam fir stands. Clearcuts had the lowest densities of dead trees across sampled stands. Current even-aged management practices clearly affect availability and recruitment of large trees, therefore forest-dwelling wildlife relying on these structures for breeding is likely to be affected by large-scale harvesting in coniferous boreal forests.

Intra- and interspecific patterns of day roost selection by three species of forest-dwelling bats in Southern British Columbia

We examined intra- and interspecific patterns of roost-site selection by females of three species of forest-dwelling bats (silver-haired, Lasionycteris noctivagans; big brown, Eptesicus fuscus; and California, Myotis californicus) in the Pend d’Oreille Valley in southern British Columbia. Roost-sites were located by outfitting reproductive and non-reproductive female bats with radio-transmitters and tracking them during the daytime. The tree and site characteristics of roost trees used by each bat species were then compared to those of randomly available trees with cavities, as well as to each other, using logistic regression. All three bat species selected roosts that were taller than cavity trees, and the majority of roost trees were emergent or canopy trees. In addition, tree species and the type of cavity were important predictors of whether trees were used as roosts in both intra- and interspecific analyses. The majority of silver-haired and big brown bat roost trees were in hollows in live trembling aspen trees ( Populus tremuloides), but both species used small numbers of roosts on conifer snags. In contrast, the majority of California bat roosts were beneath loose bark on conifer snags, particularly Douglas-fir ( Pseudotsuga menziesii), in intermediate stages of decay. In general, site characteristics were only weak predictors of differences between roost and random trees, and roost trees used by the three bat species, but roost trees were found in patches with lower percent canopy closure and greater density of available trees. These results suggest that while all three species of forest-dwelling bats use large trees, within this restricted range of trees there is considerable variation among species in the types of cavities and the tree species used. Maintaining stands containing mature trembling aspen is necessary to provide silver-haired and big brown bats with suitable roosting opportunities, but to meet the needs of California bats, areas rich in conifer snags must be protected. Thus, unique management strategies or silvicultural practices may be required to maintain suitable habitat for all bat species in a given area.

Cavity tree occurrence in hardwood forests of central Ontario

Forest managers seek to retain and promote cavity trees because they provide habitat for a wide range of wildlife species. However, it is difficult to identify cavity trees, or predict which trees are likely to develop cavities, because the factors associated with cavity presence are not well quantified. In this study we, developed models for predicting the occurrence of three cavity types (nest, escape and feeding) in live and dead trees in northern hardwood forests. We also quantified the reduction in cavity abundance after selection harvesting. For all three cavity types, the probability of occurrence increased substantially with size in both live and dead trees, and in live trees all cavity types were most likely to be present in trees of the intermediate crown class. The majority of nest and escape cavities occurred in live trees, while most feeding cavities were in snags. However, nest cavities were nearly twice as likely to occur in snags as in live trees. Nest cavities were also more likely to occur in snags at intermediate stages of decay, while escape and feeding cavities were more likely to occur in snags at later stages of decay. Harvesting removed or knocked down 63% of snags and 55% of the associated feeding cavities. In contrast, harvesting only removed 27% of live trees, significantly lower than the snag removal rate. Harvesting also removed 31–33% of nest and escape cavities, but this was not significantly higher than the live tree removal rate. Results of this study will allow managers to better predict the occurrence of cavity trees, and provide guidance on which trees to retain as cavity trees during harvest operations. Additionally, this study suggests that selection silviculture had a greater effect on the availability of feeding cavities than on nest cavities. As a result, forest managers may need to place a greater priority on retaining and promoting feeding cavities in selection-managed stands.

Effects of management on coarse woody debris volume and composition in boreal forests in northern Sweden

Forest management practices have led to a reduction in the volume and a change in the composition of coarse woody debris (CWD) in many forest types. This study compared CWD volume and composition in reserves and two types of managed forest in the central boreal zone of Sweden. Ten areas were surveyed, each containing clear-cut, mature managed and old-growth stands, to determine the volume of standing and lying CWD in terms of species composition, decay class and size class. Volumes of CWD on clear-cuts and in mature managed forests were high compared with previous studies. Old-growth forests (72.6 m3 ha−1) contained a greater volume of CWD than mature managed forests (23.3 m3 ha−1) and clear-cuts (13.6 m3 ha−1). Differences were greatest for the larger size classes and intermediate decay stages. Despite stand ages being up to 144 years, CWD volume and composition in managed forests was more similar to clear-cuts than to old-growth forests.

Effects of Forest Edges on the Distribution, Abundance, and Regional Persistence of Wood‐Rotting Fungi

Abstract: Designing reserves and management practices to contribute to the persistence of old‐forest specialized species in fragmented landscapes requires data on plant and animal species responses to edges. We studied 15 edges between Picea abies [L. Karsten] dominated old‐growth forests and young clearcuts (6–23 years), old clearcuts (25–39 years), and natural peatlands in eastern Finland. All fallen spruce logs (>10‐cm diameter; 10,679 logs) in old‐forest fragments (13–85 ha) were located by GPS positioning system. Environmental variables and occurrences of old‐forest indicator fungi (Phlebia centrifuga P. Karsten, Amylocystis lapponica [Romell] Singer, Fomitopsis rosea [Alb. & Schwin.: Fr] P. Kartsen, Phellinus ferrugineofuscus [P. Kartsen] Bourdot); a light‐adapted fungus (Gloeophyllum sepiarium [Wulfen: Fr] P. Karsten); and a pathogen and saprophyte fungus (Fomitopsis pinicola [SW.: Fr] P. Karsten) were investigated. The frequency of G. sepiarium was higher and the frequencies of old‐forest indicator fungi and F. pinicola were lower near (<25 m) young clearcut edges in comparison with interiors. Frequencies of some indicator fungi, however, were highest at intermediate distances (10–25 m) from old clearcut and peatland edges. Indicator fungi preferred thick logs of intermediate decay stages in moist biotopes, and their incidence patterns in old‐growth forest stands were aggregated. We applied a geographic information system (GIS)‐based edge model to calculate edge‐interior area relationships of 2,698 old‐forest fragments with three values for depth of edge effect: 25 m, 2*(height of old forest), and 2*(differences between the heights of old and adjacent forests). Interior area was reduced to 55–71% of the original with different depth‐of‐edge values. Total numbers of separate interior areas increased, although interior areas disappeared from the smallest fragments. The results showed that the edge effect is complex and also that it changes when the edge matures because of interactions among several factors. We suggest that sequential management of forests adjacent to reserves and the formation of larger reserves would increase the capacity of the reserves to maintain edge‐sensitive species.

Roost site selection by forest-dwelling male Myotis in central Ontario, Canada

We used radiotelemetry and random exit counts to determine roost site selection by male northern long-eared bats ( Myotis septentrionalis) and unidentified Myotis, either northern long-eared or little brown bats ( M. lucifugus) in a conifer-dominated, mixedwood forest landscape in central Ontario, Canada. We compared the characteristics of snags used as roosts ( n = 26), with randomly located snags and random points ( n = 52 and 50, respectively), at three spatial scales: focal tree, surrounding forest, and landscape. Snags used as roost sites by these bats differed from random snags for 19 of the 23 variables measured ( P < 0.05). Logistic regression models were derived which suggested that the bats selected large snags, in open canopies, of intermediate stages of decay, that were located in upland areas, but away from water bodies. Bats may have selected roost sites for their thermal advantage in the mornings, as most used cavities or bark on the south and east sides of snags. To ensure that snags of appropriate characteristics persist for these two species of Myotis, forest managers in the northern Great Lakes forest region should retain, and manage for, large white pine ( Pinus strobus) and trembling aspen ( Populus tremuloides) snags at sites in forests that meet these criteria. Such a regime is possible under a selection harvest that is normally practiced in these mixedwood forest types.

Macroinvertebrate-wood associations during decay of plantation pine in New Zealand pumice-bed streams: stable habitat or trophic subsidy?

AbstractExtensive areas of production pine forest in New Zealand have been planted in the North American native Pinus radiata. We investigated the use of pine large woody debris (LWD) by aquatic invertebrates in central North Island spring-fed streams with pumice beds to provide an improved basis for managing LWD inputs following logging. Invertebrate faunas in early summer were dominated by Ephemeroptera and Diptera on inorganic substrates, and by these groups and Trichoptera (predominantly Pycnocentria funerea; Conoesucidae) on wood. Densities of total invertebrates and P. funerea, Eukiefferiella sp. (Diptera), and the ephemeropterans Coloburiscus humeralis (Coloburiscidae), Zephlebia dentata, and Austroclima sepia (both Leptophlebiidae) were significantly higher on wood than on inorganic substrates in summer. These dominant species showed varying preferences for wood at different stages of decay. Austroclima sepia appeared to prefer wood at early to intermediate stages of decay, P. funerea and Z. denta...

Day-Roosts of Female Long-Eared Myotis in Western Oregon

Roosts are a critical habitat component for bats and may influence their survival and fitness. We used radiotelemetry to investigate characteristics of day-roosts of female long-eared myotis (Myotis evotis) in watersheds characterized by different forest conditions and the spatial relationships between day-roosts and available water. We tracked 21 bats to 73 roosts (n = 102 occasions) from June to August 1996 and 1997 on the western slope of the Cascade Mountains, Oregon. Bats primarily used conifer stumps as day-roosts in watersheds dominated by younger forests and used conifer snags, and to a lesser extent conifer stumps, in watersheds with greater proportions of older forests. Individual long-eared myotis used different types of structures as day-roosts, and type of structure used did not differ with reproductive condition. Day-roosts were primarily located in upslope habitat and averaged 0.59 ± 0.03 km from available water and 0.66 ± 0.02 km from capture sites. Roosts were not located closer to available water than random points, but were closer than random points to captures sites. Conifer snags used as day-roosts averaged 34 ± 5 m in height and 93 ± 12 cm diameter at breast height (dbh); snags in intermediate stages of decay had highest use. Use of conifer snags was positively associated with the number of snags within 20 m and negatively associated with distance from stand edge. Conifer stumps used as day-roosts averaged 133 ± 9 cm in height and 59 ± 4 cm dbh. Western hemlock and Douglas-fir stumps were used more often than western redcedar stumps as day-roosts. Odds of a stump being used as a day-roost increased with increasing height of the stump (downhill side) and whether it was situated in a gap in vegetation. We contend that management of day-roosts for forest-dwelling bats should focus on maintaining large conifer snags across landscapes through space and time. In landscapes where there are relatively few large conifer snags, stumps appear to provide important, but ephemeral, roosts for long-eared myotis.

Wood-inhabiting cryptogams on dead Norway spruce (Picea abies) trees in managed Swedish boreal forests

We surveyed the quantity and quality of dead Norway spruce (Picea abies (L.) Karst.) trees and wood-inhabiting cryptogams in a managed boreal forest landscape in northern Sweden. Size and decay of dead trees was related to substrate utilization by wood-inhabiting species. Coarse woody debris (CWD) was surveyed along 34 strip transects. CWD and wood-inhabiting cryptogams were surveyed in eight circular plots at each site. A total of 6195 spruce CWD units occurred along strip transects and 809 spruce CWD units in circular plots. On average 2.2 m3/ha spruce CWD was found on the plots. The majority (63%) of the transect CWD units were &lt;10 cm diameter and in early to intermediate decay stages. Sixty-eight wood-specific species of fungi, lichens, mosses, and hepatics occurred on the plots. Of these, 13 occurred on [Formula: see text]5% of the 809 CWD units surveyed for wood-inhabiting species. Eight species occur on the Swedish red lists, indicating that such species are indeed uncommon in managed forests. Red-listed species showed strong preferences for large diameter CWD and CWD in late decay stages, i.e., substrates that are poorly represented in managed forests. Frequently occurring species, however, showed utilization patterns that correspond with the distribution of the substrate types.

Wood-inhabiting cryptogams on dead Norway spruce (&lt;i&gt;Picea abies&lt;/i&gt;) trees in managed Swedish boreal forests

We surveyed the quantity and quality of dead Norway spruce (Picea abies (L.) Karst.) trees and wood-inhabiting cryptogams in a managed boreal forest landscape in northern Sweden. Size and decay of dead trees was related to substrate utilization by wood-inhabiting species. Coarse woody debris (CWD) was surveyed along 34 strip transects. CWD and wood-inhabiting cryptogams were surveyed in eight circular plots at each site. A total of 6195 spruce CWD units occurred along strip transects and 809 spruce CWD units in circular plots. On average 2.2 m3/ha spruce CWD was found on the plots. The majority (63%) of the transect CWD units were <10 cm diameter and in early to intermediate decay stages. Sixty-eight wood-specific species of fungi, lichens, mosses, and hepatics occurred on the plots. Of these, 13 occurred on 5% of the 809 CWD units surveyed for wood-inhabiting species. Eight species occur on the Swedish red lists, indicating that such species are indeed uncommon in managed forests. Red-listed species show...

Roost-site selection and roosting ecology of forest-dwelling bats in southern British Columbia

We used radiotelemetry to examine the roost-site preferences of four species of tree-roosting bats (Eptesicus fuscus, Lasionycteris noctivagans, Myotis evotis, and M. volans) in southern British Columbia, Canada, by radio-tracking bats to their day roosts. We found a total of 21 roost trees: 14 roosts were beneath loose bark, 5 were in cavities excavated by woodpeckers, and 2 were in natural cavities. Entrance height increased with tree height, but roost entrances tended to be situated below the level of the canopy. Of the 22 tree and site variables examined, only 3 significantly discriminated between roost trees and available trees: tree height, distance to the nearest available tree, and percent canopy closure. Bats preferred tall trees associated with low percent canopy closure and a short distance to the nearest available tree. Bats roosted in western white pine, and to a lesser extent ponderosa pine and western larch, in intermediate stages of decay more often than would be expected at random. Bats switched roosts frequently. The distance between subsequent roost trees was short, suggesting a degree of fidelity to a particular group of trees or area of forest. The number of days of rain during the roosting period significantly influenced the number of days spent in a particular roost, and thus ambient conditions may restrict the frequency with which bats can switch roosts.

The relationship between cavity-nesting birds and snags on clearcuts in western Oregon

Relationships between cavity-nesting birds (CNB) and density and characteristics of snags were investigated on 13 clearcuts in central coastal Oregon. Species richness and density of CNB were positively ( P<0.05) related to snag density and were still increasing at the maximum snag density evaluated. Cavity-nesting birds selected ( P<0.05) snags taller than 6.4 m and greater than 78–102 cm in diameter, and avoided ( P<0.05) snags less than 28 cm in diameter. Snags of intermediate decay stages were used for nesting more ( P<0.05) than snags of early and advanced stages of decay. Cavity-nesting birds selected snags with more ( P<0.05) bark cover (greater than 11%) than the average cover found on available snags. Individual CNB species exhibited significantly different ( P<0.05) selections for snag height, diameter, hardness and bark cover. To optimize density and richness of CNB, forest managers should provide ≥ 14 snags ha −1 between 28 and 128 cm diameter at breast height (dbh), between 6.4 and 25 m tall, with at least 10% bark cover, and with a majority in hardness stages 3 and 4.

The occurrence of epixylic bryophyte and lichen species in an old natural and a managed forest stand in Northeast Sweden

An old natural spruce stand and a managed spruce stand were compared with regard to occurrence of epixylic bryophyte and lichen species and amount of decaying wood in different size classes and decay stages. Epixylic hepatics occurred more frequently in the natural stand while Cladonia species were predominant in the managed stand. This difference is explained by differences in humidity regimes, with the managed stand exposed to drought more often than the natural stand. The managed stand also had a more uneven supply of logs in different decay stages with some stages almost missing. Wood in advanced stages of decomposition was scarce and occurred mostly as stumps in the managed stand. These two factors, substrate shortage and humidity regimes, may explain why only the most drought-resistant of the epixylic species preferring well-decayed wood were found. It is concluded that drought-sensitive bryophytes growing on logs in intermediate stages of decay are among the species most threatened by modern forest management.