Partial cutting as a conservation alternative for oak (Quercus spp.) forest—Response of bryophytes and lichens on dead wood

Semi-open oak-rich forests may support many species adapted to large trees and coarse woody debris. Currently many oak-rich forests in northern Europe have more or less closed canopies due to lack of natural and cultural disturbances. In these forests, conservation oriented partial harvesting of biofuel may restore a desired forest structure and light regime that potentially may favour many species that have declined during the last century. We quantified effects of such cutting on lichens and bryophytes living on dead wood in southern Sweden, using a design with paired cutting and control plots (each 1 ha) in 15 forests. In each plot we surveyed the same five logs and three stumps before and after harvest (25% of the tree basal area removed). The epixylic species composition shifted towards a flora typical for dryer dead wood. The mean species number of lichens per stump increased (clear effect) and the mean number of bryophytes per stump decreased (nearly significantly) due to harvesting. The species composition, but not species richness, on logs was affected. No increases or decreases in species of conservation concern could be detected. Since the overall negative effects were weak, we suggest that partial harvesting of dense oak forests is compatible with maintenance of the diversity of lichens and bryophytes on dead wood. However, the amount of such forest harvested needs to be carefully assessed in relation to demands of other taxa.     

Bryophytes and decaying wood in Hepatica site-type boreo-nemoral Pinus sylvestris forests in Southern Estonia

The aim of the study was to establish the amount of decaying wood (logs and stumps) in various groups of Hepatica site-type pine forests of different age and management intensity and to analyse the composition of bryophytes in dependence of these factors. The average volume of CWD in old unmanaged forests was 47.5 m³/ha, which is rather well comparable with respective estimations from Fennoscandia. Reduced human impact contributes positively to the amount of CWD. Diversity of log diameter classes and decay stages is larger in old forests. Altogether 73 bryophyte species were recorded, 65 species on logs and 55 on stumps. Species richness on stumps was higher in managed forests than in unmanaged ones. At the same time, the species having high indicator value for man-cut stumps are very common species in boreal forests and grow on other substrata as well. Species composition and ecological conditions differed between stumps and logs. Logs are more humid microhabitats than stumps, therefore the occurrence of hepatics is more frequent on them. According to species composition on decaying wood the old unmanaged forests distinguished from others. As the differences of substratum characteristics were notable between old and young forests, the stand age described a considerable part of species variance on logs.     

Legacies from natural forest dynamics: Different effects of forest management on wood-inhabiting fungi in pine and spruce forests

The species composition of wood-inhabiting fungi (polypores and corticoids) was investigated on 1138 spruce logs and 992 pine logs in 90 managed and 34 natural or near-natural spruce and pine forests in SE Norway.Altogether, the study included 290 species of wood-inhabiting fungi. Comparisons of logs with similar properties (standardized tree species, decay class, dimension class) in natural and managed forests showed a significant reduction in species number per log in managed spruce forests, but not in managed pine forests. The species number per log in managed spruce forests was 10-55% lower than on logs from natural spruce forests. The reduction was strongest on logs of large dimensions. A comparison of 200-400 spruce logs from natural and managed forests showed a 25% reduction in species richness corresponding to a conservative loss of ca. 40 species on a regional scale.A closer inspection revealed that species confined to medium and very decayed spruce logs were disfavored in managed forests, whereas species on early decay classes and decay generalists were unaffected. Similarly, species preferring large spruce logs were disfavored in managed forests. Forest management had strongest impact on low-frequent species in the spruce forests (more than 50% reduction), whereas common species were modestly affected. Corticoid fungi were more adversely affected than polypore fungi.These results indicate that wood-decaying fungi in pine forests are more adapted to forest disturbances than spruce-associated species. Management measures securing a continuous supply of dead wood are more important in spruce forests than in pine forests.     

Saproxylic beetle assemblages on low stumps,high stumps and logs: Implications for environmental effects of stump harvesting

The aim of this study was to evaluate how future harvesting of spruce low stumps as a renewable energy source, might influence the saproxylic (wood living) beetle fauna. Species richness, abundance and assemblages of saproxylic beetles were compared on low stumps, high stumps and logs of spruce on 10 clear-cuts in northern Sweden. The sampling was conducted with emergence traps and a total of 929 individuals and 120 species were collected. No significant differences in beetle abundance or species richness were detected between substrate types. However, there were clear differences in assemblage composition between all substrate types. Our results suggest that low stumps created at final felling support as many species and individuals per volume dead wood as other dead wood substrates and that they are therefore overlooked as substrates for wood living organisms. Consequently, harvesting of low stumps might have negative effects on the diversity of saproxylic beetles, as up to 80% of the dead wood remaining on clear-cuts is in the form of low stumps. Future studies should evaluate if compensatory measures can be performed to minimize negative impacts.     

Immediate Effects of Logging,Mounding, and Removal of Logging Residues on Epixylic Species in Managed Boreal Norway Spruce Stands in Southern Finland

The immediate effects of bioenergy harvesting methods on epixylic species were studied in mature managed Norway spruce dominated forests in southern Finland. The treatments included logging, residue harvesting, and soil preparation as either mounding or mounding combined with stump harvesting. Altogether, 110 logs and 440 species sample plots on logs were inventoried before and after logging, and after soil preparation treatments. Logging decreased the cover and species richness in all epixylic species groups. The soil preparation decreased the cover of macrolichens, while stump harvesting was significantly most devastating both for cover and richness in bryophytes. We suggest that bioenergy harvesting critically affects the epixylic species, and therefore the use of less devastating methods and compensation for the loss of coarse woody debris is recommended on a landscape level.     

Habitat associations of saproxylic beetles in the southeastern United States: A comparison of forest types,tree species and wood postures

Saproxylic beetles are highly sensitive to forest management practices that reduce the abundance and variety of dead wood. However, this diverse fauna continues to receive little attention in the southeastern United States even though this region supports some of the most diverse, productive and intensively managed forests in North America. In this replicated three-way factorial experiment, we investigated the habitat associations of saproxylic beetles on the coastal plain of South Carolina. The factors of interest were forest type (upland pine-dominated vs. bottomland hardwood), tree species (Quercus nigra L., Pinus taeda L. and Liquidambar styraciflua L.) and wood posture (standing and downed dead wood, i.e., snags and logs). Wood samples were taken at four positions along each log and snag (lower bole, middle bole, upper bole and crown) ∼11 months after the trees were killed and placed in rearing bags to collect emerging beetles. Overall, 33,457 specimens from 52 families and ≥250 species emerged. Based on an analysis of covariance, with surface area and bark coverage as covariates, saproxylic beetle species richness differed significantly between forest types as well as between wood postures. There were no significant interactions. Species richness was significantly higher in the upland pine-dominated stand than the bottomland hardwood forest, possibly due to higher light exposure and temperature in upland forests. Although L. styraciflua yielded more beetle species (152) than either Q. nigra (122) or P. taeda (125), there were no significant differences in species richness among tree species. There were also no relationships evident between relative tree abundance and observed or expected beetle species richness. Significantly more beetle species emerged from logs than from snags. However snags had a distinct fauna including several potential canopy specialists. Our results suggest that conservation practices that retain or create entire snags as opposed to high stumps or logs alone will most greatly benefit saproxylic beetles in southeastern forests.     

Red-listed wood-inhabiting fungi in natural and managed forest landscapes adjacent to the timberline in central Sweden

Many wood-inhabiting fungi are today threatened as modern forestry practices drastically reduce the amount of dead wood available in various forest ecosystems. We investigated whether the occurrence of red-listed wood-inhabiting fungi differed between natural and managed forest landscapes adjacent to the timberline in the middle part of Sweden. We assessed whether environmental variables such as the degree of human impact, length of forest roads, dead wood volume and quality affected species richness and abundance. The effects of forestry on wood-inhabiting fungi have been assessed in several studies in lowland Swedish forests. Few studies have, however, been conducted in forest landscapes adjacent to the timberline in Sweden. This is potentially important since forests close to the Swedish mountains have been pointed out as one of few intact forest landscapes in Fennoscandia and they are subjected to increasing logging pressure. Similar to other studies, species numbers and abundances were positively correlated with larger volumes of logs in various decay stages. However, never shown previously, the length of forest roads was negatively correlated with species abundance and occurrence of red-listed species. We suggest that a low amount of forest roads can be used as a conservation indicator to localize still-intact forest landscapes.     

Saproxylic beetles in high stumps and residual downed wood on clear-cuts and in forest edges

Abstract

This study evaluates how the placement and the different possible outcomes of a spruce retention tree affected species richness and assemblages of spruce-associated saproxylic beetles. In a field experiment in the boreal zone of central Norway, high stumps were created and compared with residual wood pieces (i.e. top boles with branches), in clear-cuts versus in forest edges. Flight interception traps were mounted close to the substrate. The results were analysed using rarefaction techniques, ordination (DCA) and anova. It was found that the placement of retention trees of spruce does matter: beetle assemblages were significantly different in stumps in the four treatments. For all species pooled, the species richness was higher in stumps in clear-cuts than in stumps or boles in the forest edge. Four red-listed species were more abundant near stumps than boles, and two red-listed species were more abundant in clear-cuts than forest edge. To cater for the variety of habitat preferences among forest beetles in managed forest, managers should leave both standing spruce trees (many of which will end up as windthrown, downed boles) and some high stumps (to secure some upright dead wood), in both exposed clear-cut and semi-shaded forest edge.     

Aspen-inhabiting Aphyllophoroid fungi in a managed forest landscape in Estonia

Abstract

In northern Europe, the biologically rich European aspen (Populus tremula) tends to disappear both from intensively managed and strictly protected forests, thus representing a biodiversity conservation challenge. This study describes the distribution of Aphyllophoroid fungi inhabiting aspen in a hemiboreal mixed-forest landscape where clear-cutting was usually followed by natural regeneration. In a 4-km² area in Estonia, 181 individual forest stands and cut areas were surveyed. Sixty-one percent of the 2831 live aspen trees found were concentrated in 11% of the area. Thirty-six polypore species were recorded on aspen, with old stands and naturally created deadwood hosting most species. Among the records of 14 pre-defined aspen-specific basidiomycetes, Phellinus tremulae comprised about 95%. Six species (Ceriporiopsis aneirina, Clavicorona pyxidata, Funalia trogii, Phellinus populicola, Rigidoporus corticola, Steccherinum pseudozilingianum) were infrequent to rare, but widely distributed, inhabiting various stand-age classes, and mostly occurring outside “key habitats”. All the seven species absent are of conservation concern and frequent in Estonian old-growth forests. Thus, rotational management with natural aspen regeneration only provided habitat for some aspen-specific species. For sustaining all species, such landscapes should probably be complemented with stands managed using modified thinning and partial harvesting techniques in aspen-containing mixed stands.     

Local spatial pattern in the occurrence of two congeneric wood-decaying fungi in an old-growth boreal forest

Abstract

This paper characterizes spatial patterns in the occurrence of two congeneric wood-decaying fungi (Aphyllophorales: Polyporaceae) in an old-growth boreal forest in eastern Finland. The spatial patterns are used to evaluate indirectly the short-distance dispersal ability of the species. Fomitopsis rosea is a specialist on Picea abies occurring mainly in forests with large amounts of dead wood, whereas Fomitopsis pinicola is a substrate generalist and also abundant in managed forests. Within a forest reserve, a 25 ha study area was divided into 25 m×25 m grid (n=400), and all dead trees and fruiting bodies of the two polypore species were recorded. Spatial patterns were analysed with Spatial Analysis by Distance IndicEs methodology (SADIE). Downed spruce logs were highly aggregated within the study area. After this distribution was accounted for, the spatial pattern of F. pinicola and F. rosea on logs was random. The lack of spatial aggregation suggests that within old-growth forest stands dispersal of the two fungal species is not a limiting factor for their occurrence.     

Epiphytic lichen diversity in late-successional Pinus sylvestris forests along local and regional forest utilization gradients in eastern boreal Fennoscandia

Pinus sylvestris-dominated forests have been heavily utilized across all of boreal Fennoscandia and the remaining natural forests are generally highly fragmented. However, there are considerable local and regional differences in the intensity and duration of past forest utilization. We studied the impact of human forest use on the diversity of epiphytic and epixylic lichens in late-successional Pinus sylvestris-dominated forests by assessing species richness and composition along both local and regional gradients in forest utilization. The effects of local logging intensity were analysed by comparing three types of stands: (i) near-natural, (ii) selectively logged (in the early 20th century) and (iii) managed stands. The effects of regional differences in duration and intensity of past forest use were analysed by comparing stands in two contrasting regions (Häme and Kuhmo–Viena). The species richness of selectively logged stands was as high as that of near-natural stands and significantly higher in these two stand categories than in managed stands. Species richness increased with the density of small understorey Picea, which correlated strongly with decreasing intensity of local forest use and increasing structural complexity of selectively logged and near-natural stands. Stands in the Häme region hosted a lower number of species, and were less likely to host many old-growth indicator species than the Kuhmo–Viena region, suggesting that species have been lost from stands in the Häme region due to a longer history of intensive forest use. We conclude that selectively logged stands, along with near-natural stands, are valuable lichen habitats particularly for species confined to old-growth structures such as coarse trees and deadwood. In landscapes where natural forests have become fragmented, the management or restoration of the remaining late-successional Pinus-dominated forests, e.g. through the use of fire, should be carefully planned to avoid adverse effects on lichen species richness.     

A lack of large-diameter logs and snags characterises dead wood patterns in Irish forests

Dead wood is an important component of forest ecosystems and volumes vary depending on forest age, management intensity and productivity. This is the first large-scale study to quantify dead wood in Irish forests and to compare them to forests in other locations. We measured the volume and size distribution of logs, the density and size distribution of snags and the volume of dead wood contained in stumps in Oak (Quercus spp.) and Ash (Fraxinus excelsior) forests and in Sitka spruce (Picea sitchensis) plantations throughout Ireland. We also assigned each log, snag and stump to one of three decay classes (intact, part-rotted and well-rotted). We found no significant difference in log volume between any of the forest types. The majority (>90%) of logs were less than 20 cm in diameter, and large logs (>40 cm diameter) were scarce. We found a relatively high density of snags in all forest types but, as in the case of logs, over 90% of snags were <20 cm DBH and large snags (>40 cm DBH) were rare. The volume of dead wood contained in stumps was significantly higher in plantations than in Oak or Ash forests as a result of thinning and harvesting. Most logs and snags were moderately decayed but, in plantations, most stumps were intact. Log volume and the size of logs and snags were considerably lower than in old-growth forests in other regions. These patterns may reflect historical use of Irish forests for coppice and timber production. Management for biodiversity should aim to accelerate dead wood accumulation to increase the frequency of large-diameter logs and snags. Although management seeking to replicate the dead wood volumes of old-growth forests is ideal, it may be unrealistic in the short term.     

Effects of forest-fuel harvesting on the amount of deadwood on clear-cuts

Forest residue left after clear-cutting is increasingly being used as biofuel in Sweden. Deadwood is an important habitat for many species and a crucial resource for forest biodiversity. On eight clear-cuts in eastern central Sweden, the amount of Picea abies (L.) Karst. deadwood left on the ground was compared with the amount collected in piles for fuelwood extraction. It was found that 65% of the volume, 77% of the surface area and 84% of the pieces of slash were to be extracted. In another study on 23 clear-cuts in the same region, it was found that 36% of the logs left outside piles after clear-cutting were later removed. These studies indicate that a considerable amount of potential substrate is lost during slash extraction.     

The effects of burning and dead-wood creation on the diversity of pioneer wood-inhabiting fungi in managed boreal spruce forests

The loss of natural forest habitats due to forestry is the main reason for the decline in boreal forest biodiversity of the Nordic countries of Europe. Ecological rehabilitation may provide means to recover and sustain biodiversity. We analyzed the effects of controlled burning and dead-wood creation (DWC) on the diversity of pioneer wood-inhabiting fungi in managed Norway spruce (Picea abies) forests in southern Finland. Altogether 18 stands were first subjected to a partial cutting with ordinary logging residues in form of cut stumps and treetops left on site. The subsequent rehabilitation treatments consisted of a controlled burning applied in half of the stands and three levels of dead-wood creation (5, 30 and 60 m³ ha⁻¹). The DWC involved creation of logs; felling of whole trees to mimic downed logs formed by natural disturbance processes. Each treatment was replicated three times. Inside each stand, substrates were sampled in two different biotopes; one on mineral soil and one on mineral soil with a thin peat layer. We surveyed the fungal flora on the logs (n = 364) and the ordinary residue stumps (n = 1767) and tops (n = 845) five years after the treatments.When comparing different stands, controlled burning had a significant effect on species composition; certain species were significantly more frequent on substrates in burned stands than in unburned stands, indicating that these species were favored by controlled burning. By contrast, we found no significant effects of DWC levels or biotope on species composition or richness. When comparing different substrates, 99% of the logs hosted at least one species and the occurrence probability of certain species was significantly higher on logs than on ordinary residue stumps and tops. Yet, volume-based rarefaction analyses showed that residues were more species dense than the logs, indicating that ordinary logging residues constitute important resources for many pioneer species.We conclude that controlled burning combined with DWC have strong effects on biodiversity; it modifies the composition of the pioneer wood-inhabiting fungal species found in managed forests and may thereby also influence the further succession and diversity of the secondary fungal flora.     

Effects of forest management on the amount of deadwood in Mediterranean oak ecosystems

Context

Deadwood is an important habitat for vertebrate and invertebrate species, a key factor in the nutrient cycle and a valuable carbon pool. Difference in the deadwood C stock depends on many variables such as forest type, microclimate and forest management.

Aims

We investigated the relationship between C stock in deadwood and forest management in oak stands of southern Italy.

Methods

Deadwood C stock was quantified in 74 forest stands under intensive, extensive or multifunctional management. The relationship between management and C stock in deadwood was assessed taking into account the decay class and the type of deadwood (snags, stumps and logs).

Results

Intensively managed forests are characterized by significantly lower mean levels of deadwood C than the other forms of management. Multifunctional management resulted in the highest level of C, mainly in logs and snags, while extensive management resulted in high levels of C storage concentrated in snags.

Conclusion

Results of the research highlight that forest management practices greatly influence the quantitative and qualitative presence of deadwood in forests.     

Diversity of polyporous fungi (Polyporaceae) in northern boreal forests: effects of forest site type and logging intensity

The effects of forest site type and logging intensity on polyporous fungi were studied in subxeric, mesic and herb-rich forests and spruce mires in northern Finland. The species richness of polypores did not follow the fertility gradient of the site types, but was connected with the amount and diversity of coarse woody debris (CWD). The total number of species, and the numbers of indicator and threatened species were equal in subxeric pine forests and in more fertile spruce-dominated stands. The species composition of pine-dominated forests differed conspicuously from that of spruce-dominated site types. The total number of species was not affected by logging intensity, but no virgin forest species or threatened species were found on the sites where the number of cut stumps exceeded 150 stumps ha^?1. Increasing logging intensity decreased the number of polypore observations, indicating reduced substrate availability. The results stress the importance of protecting not only fertile spruce-dominated stands, but also poorer, pine-dominated forests, and sites with high and diverse CWD content.     

Silviculture as a disturbance regime: the effects of clear-cutting,planting and thinning on polypore communities in mixed forests

The structure of modern forest landscapes is profoundly affected by human-caused disturbances, particularly forest management; however, the effects and prospects of individual silvicultural techniques are insufficiently understood. This study distinguishes the effects of clear-cutting, planting and thinning on species richness and community composition of polypore fungi. In 2008–2009, 181 forest compartments (ranging from naturally regenerated deciduous stands to planted Picea abies stands and 0–137 years post clear-cutting) were explored in a hemiboreal landscape subjected to even-aged management. Altogether 104 polypore species were recorded. For species richness, time since clear-cutting was the most influential factor at both stand and landscape scales, followed by thinning. Clear-cuts had distinct polypore communities (including several red-listed species) whose species richness declined in time. Following 20 years post clear-cutting, species richness started to increase along different community–composition pathways determined by regeneration type. The communities developed after planting were moderately species rich at stand scale but homogeneous over larger areas. Thus, at landscape scale, mature unmanaged naturally regenerated stands hosted most species; thinning reduced species richness by approximately 15%, and among thinned stands, planted areas had a further 9–22% fewer species than naturally regenerated areas. In such variably managed landscape, silviculture appeared to create particularly distinct communities in young stands on nutrient-rich soils, which naturally provide polypores with a rich supply of small deciduous snags absent from stands artificially planted with P. abies and intensively thinned.     

Spatial distribution of dead wood and the occurrence of five saproxylic fungi in old-growth timberline spruce forests in northern Finland

Abstract

Adequate understanding of the factors that determine the establishment and survival of dead-wood-dependent species in natural forests is a prerequisite to the successful maintenance of these species in managed forests. This study investigated the factors affecting the occurrence of five wood-inhabiting polypores in old-growth timberline spruce forests in northern Finland, including the substrate availability and the spatial arrangement of large-diameter logs. The volume of coarse woody debris (CWD) varied significantly between the sites (range 15–30 m³ ha^?1), large-diameter logs comprising on average 35% of the total CWD volume. However, the within-site variation in CWD volume was 10–15 times larger than the between-site variation. The spatial distribution of large-diameter logs was aggregated or initially aggregated on four sites and random on one site, creating local patches of high CWD volume. An individual target species occurred on average on 8% of all large-diameter logs, and on 11% of optimal logs (as determined by the decay stage). The characteristics of the logs and stand variables explained partly the occurrence of the target species; furthermore, the mortality pattern of trees (stem breakage versus uprooting) and the presence of primary decomposers also significantly affected the occurrence of the target species. The results indicate that besides substrate availability and quality, local habitat factors and species interactions also play a role in the occurrence of wood-inhabiting fungi in boreal timberline forests.     

Torque required to twist and cut loose Scots pine stumps

Abstract

Stump wood is a possible source of renewable energy, but before its potential as a fuel can be utilised to a high degree, new harvesting techniques should be developed to reduce the environmental impact (notably ground disturbance) of harvesting stumps. The forces required to lift and drag stumps out of the soil are known. In this study, two unknown and important parameters were addressed: the torque required to uproot stumps by twisting them and the torque required to cut lateral roots around stumps. A new, improved stump-twisting rig was designed and used in trials with 28 Scots pine (Pinus sylvestris) trees (breast-height diameter over bark, 153–427 mm). The measured torque requirements ranged from 10 to 50 kNm. Twisting stumps required more torque than cutting lateral roots around stumps and the required torque increased with increases in stump size. The results indicate that a wrist on a big feller-buncher, but not a conventional rotator used on forest machines, should be able to generate sufficient torque to cut the roots around stumps such as those used in this study.     

The regeneration characteristics of Picea jezoensis and Abies sachalinensis on cut stumps in the sub-boreal forests of Hokkaido Tokyo University Forest

The regeneration characteristics of Picea jezoensis Carr. and Abies sachalinensis Masters on cut stumps in natural forest under selection cutting and natural regeneration were studied in a sub-boreal forest of the Hokkaido Tokyo University Forest. The following points were investigated: (1) what decay class of cut stumps are suitable for regeneration of the two conifer species; (2) what part, either a root collar or a cut surface, of a cut stump is suitable for regeneration; and (3) what percentages of cut stumps support conifer seedlings. The percentages of cut stumps that supported conifer seedlings increased as the decay class advanced, but slightly decreased in the latest stage of decay class, V. Both P. jezoensis and A. sachalinensis seedling densities per cut stump and per square meter of cut stumps increased as the decay class advanced. Some root collars in decay class IV supported A. sachalinensis seedlings, but few supported P. jezoensis. Densities of P. jezoensis per cut surface and per square meter of cut surface in decay class IV were higher than those of A. sachalinensis. On the other hand, densities of A. sachalinensis per root collar and per square meter of root collar in decay class IV were higher than those of P. jezoensis. Cut stumps in advanced decay classes are more suitable for regeneration of P. jezoensis and A. sachalinensis than those in early decay classes. Whereas a cut surface is more suitable for regeneration of P. jezoensis, a root collar is more suitable for regeneration of A. sachalinensis. Cut stumps are not sufficient to ensure enough conifer regeneration because not all conifer cut stumps in advanced decay classes support conifer seedlings.