Clearcut Edges Research Articles

BRYOPHYTE RESPONSES TO MICROCLIMATIC EDGE EFFECTS ACROSS RIPARIAN BUFFERS

Although riparian buffers are an important aspect of forest management in the boreal forest of Canada, little is known about the habitat conditions within buffers, due in part to complex edge effects in response to both the upland clearcut and the stream. We investigated microclimatic conditions and bryophyte growth and vitality in seven locations between the stream edge and 60 m into the upland undisturbed conifer forests and at the clearcut sites with riparian buffer 30 km northwest of Thunder Bay, Ontario, Canada. We hypothesized that the growth and vitality of a pleurocarpous moss, Hylocomium splendens, and an acrocarpous moss, Polytrichum commune, would be directly related to the microclimatic gradients detected. We further hypothesized that sensitivity of the bryophytes to environmental factors will vary depending on their life form type, i.e., pleurocarpous moss will respond differently than the acrocarpous moss. Both bryophyte species were transplanted in pots and placed at 10-m intervals along 60-m transects perpendicular to the stream across the buffer and undisturbed sites. Bryophyte growth, cover, and vitality, as well as microclimatic parameters and plant cover, were measured over the summer in 2003. The riparian buffers were simultaneously affected by microclimatic gradients extending from both the clearcut edge and the riparian-upland ecotonal edge. Both bryophyte species responded to changes in the microclimatic conditions. However, vapor pressure deficit (VPD) was the most important factor influencing the growth of H. splendens, whereas for P. commune growth soil moisture was most important. Our study confirms earlier findings that interior forest bryophytes such as H. splendens can be used as indicators to monitor edge effects and biodiversity recovery following forest harvesting. We demonstrate that growth and vitality of these bryophytes reflect the prevailing near-ground microclimatic conditions at the forest edges. Abundance estimates of such bryophytes can be used to determine the depth of edge effects across both ecotonal edges (e.g., riparian-upland forest edge) and anthropogenically created edges (e.g., clearcut edge). Forest management practices must consider depth of edge in determining the appropriate width of riparian buffers that would be necessary to sustain biodiversity and associated values at the land/water interface.

Predictive value of 99mTc-sestamibi scintigraphy for healing of extremity amputation

Although various non-invasive procedures have been proposed to determine the optimal level of amputation of limbs in patients who have vascular disease, currently there are no consistent criteria that can be applied before surgery. The purpose of this study was to determine whether (99m)Tc-sestamibi imaging can accurately predict the healing of amputation sites. In a prospective study in 26 patients (21 men, 5 women; age range 23-94 years) presenting with ulcers or gangrene of the foot and hand, (99m)Tc-sestamibi imaging was performed preoperatively. The indications for amputation included gangrene (23 patients), electrical injury (2 patients) and trauma (1 patient) of extremities. Although the amputation levels were chosen according to clinical criteria and scintigraphic results, the final amputation level was defined by scintigraphic results. Two below-knee, one above-knee, 12 toe, 11 transmetatarsal, two phalanx, one finger and one thumb amputations and one shoulder disarticulation were performed. In four cases, the amputation defect was not suitable for coverage using a local dermal flap; rather, it was covered with free tissue transfer. Patients had clinical follow-up for 6-36 months (mean 11.69 months) to assess healing of the stump. Scan results were compared with clinical outcome to assess prediction of healing. There was healing in all amputations at the end of the follow-up period. When evaluated regarding preoperative (99m)Tc-sestamibi uptake pattern, there was no perfusion to the lesion site in 21 patients and perfusion to an area smaller than the extent of skin necrosis in four patients; thus, in these 25 patients, (99m)Tc-sestamibi scintigraphy suggested non-viable tissue in the extremities with clear-cut edges of perfused muscle tissue. Diffusely decreased uptake was seen below the left knee in one case. How scintigraphy changed management was analysed. The amputation levels proposed before scintigraphy were divided into two groups, "definite" (n=14) and "indefinite" (n=12), based on visual examination and Doppler findings. In nine patients in the definite group, the proposed amputation level before scintigraphy was not altered by the scintigraphic data. However, (99m)Tc-sestamibi scan enabled unnecessarily high amputation levels to be avoided in 12 patients in the indefinite group and in five patients in the definite group. Therefore, there was change in management of 65% of cases based on scintigraphic findings. Since healing of the stump was seen in all cases, outcome was correctly predicted by scintigraphy. This preliminary study supports the use of (99m)Tc-sestamibi scan in selecting the optimal amputation level consistent with subsequent stump healing.

The radiance contrast of forest‐to‐clearcut edges on a medium resolution Landsat Enhanced Thematic Mapper satellite winter image

Forest logging results in decreased and fragmented forest area and the increased appearance of edge habitats. The monitoring of forest area and particularly, the detection of changes over the years relies on correctly determined forest edge locations. Radiance contrast of forest clearcut edges Our objective was to characterize the radiance contrast at the sharp forest edges of recently created clearcuts of boreal and boreo‐nemoral forests in Estonia. Radiance data were derived from a medium resolution Landsat Enhanced Thematic Mapper (ETM+) satellite image taken in late winter, in March. In the winter image there is a high radiance contrast at the forest to clearcut boundary area. This radiance contrast was investigated in the visible and near infrared spectral regions (ETM+ bands 1–4) with 30m‐pixel‐size resolution in the spectral bands and 15m‐pixel‐size in the ETM+ panchromatic band. The analyses of radiance contrast at clearcut to forest edges reveal the effects of stand parameters, clearcut age and azimuthal exposure. The results of the analyses show that the radiance contrast between forest and clearcut area depends on the stand height and stem volume of coniferous trees in the first and the second tree layer. The stem volume of deciduous trees had no statistically significant effect on the variation of radiance contrast at the forest edge. A significant non‐linear effect of the edge exposure to sun was found, indicating a shade length effect. Shade and forest structure affect edge detection on medium resolution satellite images.

In Vivo Corneal Confocal Microscopy Comparison of Intralase Femtosecond Laser and Mechanical Microkeratome for Laser In Situ Keratomileusis

To assess and compare corneal modifications induced by IntraLase PulsionFS femtosecond laser and mechanical microkeratome Hansatome for laser in situ keratomileusis (LASIK) using the new-generation Heidelberg Retina Tomograph II (HRT II)/Rostock Cornea Module confocal microscope. In this case-control study, 24 eyes of 12 patients were examined with the HRT II in the follow-up of IntraLase femtosecond laser for LASIK myopic surgery. Twenty eyes of 10 patients were also examined after microkeratome Hansatome-LASIK surgery. In both groups, the patients underwent the first follow-up examination on day 7 and the last 12 months after surgery. Morphologic modifications of corneal architecture were evaluated, and comparisons were made between the two flap-formation techniques. Evaluation of both groups on day 7 showed keratocyte transformation, most likely related to cellular activation beneath the interface. The flap margin after the IntraLase technique appeared microscopically as a clear-cut edge that included the epithelial plug. At month 2, secondary fibrosis, adjacent to the still well-defined IntraLase flap edge, was observed. This reaction diminished with time, leaving a fibrotic scar adjacent to a wound constriction originating from the surrounding stroma. The flap margin of the mechanical microkeratome had the appearance of a less clearly identified fibrotic scar with no epithelial plug. This study reveals morphologic similarities between the interfaces obtained by femtosecond laser and mechanical microkeratome, probably because the same excimer laser performed the photoablation. However, the IntraLase flap margin showed greater fibrotic scarring than that induced by the mechanical microkeratome.

Functional Bowel Disorders

Employing a consensus approach, our working team critically considered the available evidence and multinational expert criticism, revised the Rome II diagnostic criteria for the functional bowel disorders, and updated diagnosis and treatment recommendations. Diagnosis of a functional bowel disorder (FBD) requires characteristic symptoms during the last 3 months and onset > or =6 months ago. Alarm symptoms suggest the possibility of structural disease, but do not necessarily negate a diagnosis of an FBD. Irritable bowel syndrome (IBS), functional bloating, functional constipation, and functional diarrhea are best identified by symptom-based approaches. Subtyping of IBS is controversial, and we suggest it be based on stool form, which can be aided by use of the Bristol Stool Form Scale. Diagnostic testing should be guided by the patient's age, primary symptom characteristics, and other clinical and laboratory features. Treatment of FBDs is based on an individualized evaluation, explanation, and reassurance. Alterations in diet, drug treatment aimed at predominant symptoms, and psychotherapy may be beneficial.

Edge type defines alien plant species invasions along Pinus contorta burned, highway and clearcut forest edges

Forest edges have been long recognized as the first landscape elements to be invaded by alien plant species in forest ecosystems. However, little is known about the role of forest edge type in invasive species patterns. In the Northern Rocky Mountains of the United States, disturbance-caused forest edges are a common feature in the landscape with anthropogenic (e.g. roadside, clearcut) and natural (e.g. burned, windthrown) edge types. In this paper we examine patterns of alien species invasion and native community structure across three forest edge types in Pinus contorta forests including contrasts between undeveloped landscapes in Yellowstone National Park (YNP), and developed (roaded and logged) portions of the adjacent Gallatin National Forest (GNF). Six sets of transects were located in each of five study sites, including clearcut, burn and highway edge types. When burn and highways edges were compared between GNF and YNP, landscape matrix did not have a significant effect on either alien species richness or cover. In both landscapes, highway edges had higher alien species richness and cover than burn edges. For burn and highway edges, alien species richness and cover were significantly related to edge type, distance from edge and the interaction between both variables. In Gallatin NF, alien species were concentrated along highway edges, while burn and clearcut edges are significantly less invaded. Overall, alien species richness was negatively correlated with native species richness in plots with at least one alien species ( R 2 = 0.30, p < 0.001). We were able to explain from 23 to 68% of the variation in alien species richness from simple measures of vegetation structure within each of the edge types. Our study suggests that at least for high elevation conifer ecosystems such as West Yellowstone, alien plant invasion into interior forest is significantly enhanced by disturbance edges only along roadsides. Further studies are needed to determine causal mechanisms that explain the high degree of invisibility of roadside edges. Our results highlight the need for careful planning and management of roads, as they may become a primary conduit of alien plant invasions.

Association of common brown froglets, Crinia signifera, with clearcut forest edges in Tasmania, Australia

We examined the response of the common brown froglet, Crinia signifera, to recently clearcut forest edges in Tasmanian wet Eucalyptus obliqua forest. We established transects of pitfall traps crossing coupe edges, within coupes, and within mature forest interiors (riparian and non-riparian) at three study sites. Pitfall captures of C. signifera were greatest at the immediate logged forest edge (which corresponded with a firebreak constructed as part of standard clearfell, burn and sow silvicultural practices in Tasmania). Capture rates were lower in both the coupe interior and the immediate unlogged forest edge and declined to negligible numbers in the unlogged forest interior. Edge penetration was estimated to be generally 50–100 m. We suggest that Tasmania’s current management of wet forest may provide additional habitat for C. signifera by changing the age structure of the forest and providing additional forest edge/firebreak habitat. However, C. signifera is common and disturbance tolerant, and thus these findings should not be extrapolated to other Australian frog species that may be disadvantaged by current logging practices.

Edge influence on forest structure in large forest remnants, cutblock separators, and riparian buffers in managed black spruce forests

:Remnants of old forests left on the landscape following forest harvesting, especially corridors, provide benefits of connectivity and facilitation of movement or dispersal, which may be hindered by the presence of edges. Our objective was to determine the extent of edge influence on forest structure in these forest remnants in black spruce boreal forest. We sampled canopy cover and the density of trees, snags, and logs along clearcut edge–forest gradients in large forest patches, cutblock separators, and riparian buffers. The distance-of-edge influence was determined by comparing values at different distances from the edge to values in interior forest using randomization tests. Forest remnants had lower live tree density and canopy cover and higher mortality and windthrow than interior forest. Distance-of-edge influence on forest structure extended 10–30 m from the edge, and was slightly more extensive into cutblock separators where two edges are in close proximity, but was less extensive in riparian buffers, possibly due to the presence of stable internal edges near the stream. Because of edge influence, structure near the edges of forest remnants and across narrow corridors is modified; wider corridors would be required to provide a core habitat of interior forest conditions.

Movement of forest birds across river and clearcut edges of varying riparian buffer strip widths

The ability to move across and perhaps exploit resources in adjacent habitats may also allow a species to persist in marginal habitats until a better territory is found. Understanding how animals respond to the distribution of forest remnants may be useful in combining conservation efforts with landscape harvest designs. Studies have examined movements of birds within permanently fragmented habitats, but movement patterns may differ in temporarily fragmented landscapes. I examined the frequency of movements across river and forest-clearcut edges for several habitat and nesting guilds and individual species. Movements were almost four times higher at clearcut edges than river edges and were dominated by forest generalists, open-edge and ubiquitous species across both edges particularly those nesting in deciduous trees. Forest interior species were rarely observed crossing either boundary. Movements were positively related to abundances in buffers and negatively related to buffer width for deciduous tree nesters and those species associated with open-edge habitats. High movements in the narrow buffers suggests that these species incorporate this edge habitat as part of their territories. For forest specialists that are unwilling to cross-habitat boundaries, retaining wide buffers may provide valuable connections between unlogged patches in addition to breeding habitat. Narrow buffers that do not provide suitable habitat to support most forest-dwelling species may function as foraging sites or travel corridors that offer more protection from predators than flying across open spaces.

Edge effect on ground vegetation in clear-cut edges of pine-dominated forests

This study investigated the spatial and temporal patterns of edge effect following forest harvesting in pine-dominated hemiboreal forests. The aim of the study was to determine how the edge influenced ground vegetation and how it changed over successional time. The chronosequence approach was used for the description of the succession by taking sites in similar environments but in different periods after cutting. Five transects were established in each type of edge. All ground vegetation was recorded and the percentage cover of each species was estimated. The impact of edge effect to overall species composition was evaluated by canonical correspondence analysis. The variety of species composition along the distance from the edge was highest in clear-cut–mature stand edges. The highest species richness was found at the edges of older clear-cuts. The cover of herb layer was highest in older clear-cuts and young stands. The cover of moss layer was lower in clear-cutting areas than in nearby standing mature stands. Edge influence was still detectable up to 40 years after clear-cutting, when forest interior conditions have not yet formed.

Optical recording characteristics of WO3 films grown by pulsed laser deposition method

W O 3 films were deposited on the glass substrate (Corning No. 7059 with an area of 26×38mm) by the pulsed laser deposition method using an ArF excimer laser. It was found that after annealing at 500°C for 10min, the film thickness became 1.8 times compared with that (approximately 40nm) in the as deposited state. At this time, the difference in the transmittance, ΔT, between the annealed state and the as deposited state was about 40% at the wavelength of 400nm. From x-ray diffraction spectra and x-ray photoelectron spectroscopy spectra, it was considered that the ratio of the peak values of W6+ 4f5∕2 (tungsten oxide) versus W 4f5∕2 (metal tungsten) increased steeply after the annealing process. From this, it was considered that oxygen was absorbed into the WO3 films through the annealing process. From the revolution test for the sample without the protection layer in which the WO3 films were deposited upon the digital versatile disk disk substrate, a write peak-power dependence of carrier to noise ratio (CNR) (at λ=406nm, NA=0.65) of 3T signal (58.5MHz) was measured at a linear velocity of 5m∕s and a read power of 0.6mW. It was confirmed that the values of CNR obtained at the write peak-power 5–6mW were near 50dB (the region A) and the ones obtained at the write power 7–10mW were more than 60dB (the region B). From scanning electron microscopy observation, it was recognized that bits with 0.16–0.25μm size, having the fine-shaped dots with clear-cut edge, were made in the region A. This corresponded to the maximal storage capacity of 25GB in the “Blu-ray disk” specification. However, it was also identified that holes were formed in the region B and the film materials were scattered by receiving a train of high write power impulses. Next, it was found that the write power corresponding to region A for the structures with the WO3 layer sandwiched between a Al2O3 or ZnS–SiO2 protection layer increased or decreased, respectively. Larger values of the CNR will be obtained if the film thickness of each layer including the active layer were optimized.

Portability of stand-level empirical windthrow risk models

Wind damage to stand edges recently exposed by harvesting is a significant management problem. Large datasets were assembled for clearcut edges in three coastal and three continental locations in British Columbia. The datasets were produced by dividing cutblock boundaries into 25 m deep by 25 m long edge segments. The sample was restricted to cutblocks that had been harvested between 1 and 10 years prior to the most recent aerial photography and further restricted to produce equal sample sizes of 6700 segments per location. Each dataset was then randomly partitioned into 80% for model building and 20% for model testing. Forest cover, ecosystem, wind speed and elevation data were compiled within a geographic information system. Additional topographic variables were derived from digital elevation models. The orientation and exposure of each edge segment was derived with customized scripts. Windthrow polygons were mapped using stereo-photographs. Logistic regression models were fit for each location and were then tested in each other location. Datasets were pooled to enable fitting and testing of generic models. Models correctly predicted outcomes 67–83% of the time for the model building locations. Portability of local models to other locations varied from excellent to poor. The models built for continental locations were the least portable. Calibration by multiplying predictions by the ratio of local mean observed damage to the mean predicted damage substantially improved local model portability. Well-fitting models were produced with pooled coastal, interior and provincial datasets. The similarity between models in the contribution of geographic wind exposure, boundary wind exposure and stand stability factors indicate an underlying consistency in the factors leading to windthrow across the province. The methods are applicable to other forest regions where synoptic weather systems produce damaging winds.

Évaluation en microscopie confocale des modifications morphologiques cornéennes induites après LASIK et découpe du volet stromal par laser femtoseconde IntraLase ®

To assess stromal modifications occurring after IntraLase femtosecond laser for laser in situ keratomileusis (LASIK) using the Heidelberg retina tomograph II/Rostock cornea module.Twelve eyes from six patients were examined using the Heidelberg retina tomograph II cornea module after IntraLase femtosecond laser: ten eyes were examined at 1 week and 2 months after laser surgery, including four eyes examined at day 1, and two eyes examined at day 2. Morphological modifications of the corneal stroma, flap interface, and flap margin were evaluated at these different times and compared with the mechanical microkeratome interfaces of five patients (ten eyes), using the same technique at the same periods after the surgical intervention.Evaluations at days 1 and 7 showed simultaneous depletion and activation of keratocytes on both sides of the interface. We also observed some brightly reflecting particles together with scattered, less bright dots, from day 7 and increasing after 2 months. Some clinically visible deposits at the level of the interface were observed at the periphery of the flap at day 1 and could represent cell-degradation products. With confocal microscopy, they appeared as homogeneous reflective deposits with a larger size than that of particles; they had decreased at month 2. The flap margin appeared microscopically as a very clear-cut edge, including epithelial cells, while those performed with a mechanical microkeratome appeared more like a poorly limited fibrotic scar. We also observed a secondary fibrotic reaction at month 2, adjacent to the still well-defined IntraLase flap edge.This study showed substantial morphological similarity between the interfaces obtained with femtosecond laser and mechanical microkeratome. The discovery of brightly reflecting particles in the IntraLase interface goes against the hypothesis of the metallic origin of these deposits. The flap margin microscopically looked extremely well delimited, but seemed to provoke an adjacent secondary fibrotic reaction, both microscopically and macroscopically, greater at 2 months than after a mechanical microkeratome cut.

To what extent do forest herbs recover after clearcutting in beech forest?

We studied the occurrence of 22 plant functional groups and the distribution patterns of 12 forest herbs in four clear-felled areas of different ages, and across ecotones between the forest and clearcuts in a 4383 ha beech forest in central Belgium. The main goal was to improve our knowledge on the clearcut harvesting system and its possible influence on herb vegetation. Within each study site, the herbaceous vegetation was sampled along a north–south and an east–west transect with points at 20 or at 10 m intervals. We studied a total of 82 vegetation relevés (4 m 2) on 18 transects according to the Braun–Blanquet method. Around the study sites, the abundance of each species present was noted according to a grid-map with cells of 50 m × 50 m, up to a distance of 150 m from the clearcut edges. Differences in species’ cover percentage and frequency between the clearcuts and the surrounding matrix were tested. The colonisation rate for each species was calculated and possible effect of clearcut age on the plant composition was examined. Results of this study show that plant functional groups with a high conservation value, such as ancient-forest species, stress-tolerant species and autochorous species showed a progressive decrease in time after clearcutting. Most of the studied forest herbs had a lower frequency and/or cover in the clearcut areas than in the surrounding forest matrix. For some of these species, we found a progressive abundance decrease along a 150 m-gradient within the forest towards the clearcut (e.g. Dryopteris dilatata, Luzula pilosa, L. sylvatica, Oxalis acetosella). Others, such as Anemone nemorosa and Circaea lutetiana, are characterised by a regular cover in the forest which suddenly drops at the edge and sustains a very low level throughout the clearcut. If some forest herbs recover better than others, data collected so far indicate that most of the studied species are not able to recover such disturbed sites within a few years. We conclude that silvicultural systems should be adapted to the dispersal and recruitment limitations of forest herbs in order to enable their long-term conservation. To achieve this goal, management without large clear fellings and harvesting methods that never leave the ground completely bare are proposed as alternatives to the clearcutting system.

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 (&gt;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. &amp; 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 (&lt;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.

Analytical methods for defining stand–clearcut edge effects demonstrated for N mineralization

Edge effects are becoming an important forest management consideration, but information regarding the influence of edges on N cycling variables has not been well documented. In addition, the quantification of edge effects can benefit from the application of complementary spatial analysis methods. Forest floor N mineralization and environmental variables were intensively measured 5 years after harvest along transects crossing the north and south edges of a 1-ha clearcut, in a high-elevation Engelmann spruce – subalpine fir forest. Wavelet analysis and depth-of-edge influence (DEI) methods were used to locate and measure the spatial extent of edge effects on N mineralization. Then variance partitioning (partial redundancy analysis) was used to examine the influence of edges on N mineralization relative to the influence of other environmental factors. Initial NO3-N content and net nitrification markedly increased in the opening within 2–6 m of each edge. Net ammonification did not exhibit obvious edge-related spatial patterns. Spatial patterns of nitrification appeared to be more closely related to spatial changes in substrate quality than to soil temperature and moisture. Results of the wavelet and DEI analyses provided quantification of locations and functional extents of edge effects.

Forest structure and composition at young fire and cut edges in black spruce boreal forest

We compared structure and composition at forest edges created by wildfire and clear-cutting in black spruce (Picea mariana (Mill.) BSP) dominated boreal forest in northwestern Quebec. Forest structure and plant species composition were sampled along transects perpendicular to eight 3- to 4-year-old fire edges and eight 2- to 5-year-old cut edges. Significance of edge influence was assessed by comparing mean values at different distances from the edge to the range of variation in interior forest. The influence of clearcut edges was minimal, generally extending only 5 m from the edge, and included greater log density and different species composition, compared with interior forest. At fire edges, prominent responses to edge creation included increased snag density and lower moss cover, compared with interior forest, extending up to 40 m into the forest. This initial structural change was likely due to partial burning extending into the forest. Overall, fire edges had more snags and a different species composition than cut edges. Our hypothesis that edge influence is more extensive at fire edges than at cut edges was supported for overstory and understory structure, but not for species composition. We suggest that there is a need for management to consider the cumulative effect of the loss of fire edges on the landscape.

Factors limiting the early survivorship ofThuja plicataon northern Vancouver Island, British Columbia

Western redcedar (Thuja plicata Donn ex D. Don), a late successional species on northern Vancouver Island, has a low seedling survival in mature hemlock (Tsuga heterophylla (Raf.) Sarg.) – amabilis fir (Abies amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes) (HA) stands. Shade, moss competition, and substrate were tested as causes of low cedar establishment. Cedar seeds were sown on reference and local soils isolated from surrounding soil, on nonisolated local soil, and on forest floor with moss removed. Western hemlock, amabilis fir, and cedar seeded on forest floor acted as controls. Treatments were implemented in the HA interior and the HA–clearcut edge, with soil treatments also implemented in clearcuts. Germinants and very young seedlings of cedar have a low leaf area of needle-like primary foliage. Cedar development of secondary foliage (the scale foliage normally associated with this species) was correlated with greater vigour and growth. Secondary foliage developed in the rankings forest edge and clearcut &gt; forest interior, and reference isolated soil &gt; local isolated soil &gt; nonisolated local soil. Seedling survival rankings were edge &gt; interior, and amabilis fir &gt; hemlock &gt; cedar on soil and with moss removed &gt; cedar on forest floor. Cedar and amabilis fir showed a smaller growth response to light than hemlock. The results indicate that cedar, normally considered a late successional species, needs disturbance for early seedling establishment and survival and thus has some characteristics of an early seral species.

Occurrence of Moths in Boreal Forest Corridors

Abstract: We studied the utility of riparian corridors in boreal forest landscapes as habitats and dispersal routes for forest‐associated noctuid and geometrid moths in northern Finland. We collected moths with baited traps to investigate their occurrence and abundance in four habitat types—forest interior, forest edge, forested corridors, and clearcuts—along riparian zones. This was done with a sampling design in which the four habitat types were nested within four riparian systems. Corridors were strips of forest 30–70 m wide surrounded by clearcuts and sapling stands. Trap sites in forest interior were more than 100 m away from the nearest forest edge within large ( &gt;50 ha ) patches of mature ( timber volume&gt; 100 m 3/ha ), spruce‐dominated forests. Forest ‐ edge trap sites were in the same forest patches within 25 m from the nearest clearcut edge, and clearcut trap sites were in recent ( &lt;10 ‐year‐old ) clearcuts&gt;50 m away from the nearest mature forest. A total of 6485 specimens, representing 57 moth species, were captured during the 6‐week trapping period in late June–August 1999. The number of species and total number of individuals did not differ among the forested habitats ( interior, edge, corridor ) but were significantly lower in clearcuts. A consistent pattern across the nine species we examined in more detail was the low number of individuals captured in clearcuts. In general their abundance in corridors was equal to that observed in forest interiors and edges. Two species tended to occur in corridors in higher numbers than in forest‐interior habitats. Our results suggest that corridors in boreal forest landscapes serve as breeding habitats or dispersal routes for the moths and may direct the movements of these forest‐associated species. Results from studies showing positive effects of corridors on dispersal or population persistence should not, however, be used to justify more habitat destruction.

Siberian flying squirrel responses to high- and low-contrast forest edges

We examined responses of Siberian flying squirrels ( Pteromys volans ) to edges between nesting habitat (mature spruce forests), movement habitat (other forests, pine bogs), and open areas within their home ranges in southern Finland in 1996-2000. Radio-tracked squirrels (n=146) were generally associated to edges when they were ac tive at night. Compared to distances expected from the habitat pattern of their home range, squirrels occurred closer to high-contrast edges (of open areas) and low-contrast edges (nesting or movement forest types). Asso ciation with edges of open areas was more pronounced when squirrels were in movement habitat than in nesting habitat, possibly because of stronger channeling of movements in the former habitat. When in nesting habitat, squirrels responded more strongly to field edges than to recent clearcut edges, probably as a result of the pres ence of more deciduous trees on field edges, unlike clearcut edges. Responses to open areas were independent of spatial scale. However, responses to movement habitat from nesting habitat, and vice versa, were more pronounced over hundreds than tens of meters. Nesting cavities and dreys were generally located at random with respect to edges. We conclude that squirrel responses to edges of landscape attributes are diverse and depend both on spatial scale and edge contrast.