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1. Although anthropogenic edges are an important consequence of timber harvesting, edges due to natural disturbances or landscape heterogeneity are also common. Forest edges have been well studied in temperate and tropical forests, but less so in less productive, disturbance-adapted boreal forests. 2. We synthesized data on forest vegetation at edges of boreal forests and compared edge influence among edge types (fire, cut, lake/wetland; old vs. young), forest types (broadleaf vs. coniferous) and geographic regions. Our objectives were to quantify vegetation responses at edges of all types and to compare the strength and extent of edge influence among different types of edges and forests. 3. Research was conducted using the same general sampling design in Alberta, Ontario and Quebec in Canada, and in Sweden and Finland. We conducted a meta-analysis for a variety of response variables including forest structure, deadwood abundance, regeneration, understorey abundance and diversity, and non-vascular plant cover. We also determined the magnitude and distance of edge influence (DEI) using randomization tests. 4. Some edge responses (lower tree basal area, tree canopy and bryophyte cover; more logs; higher regeneration) were significant overall across studies. Edge influence on ground vegetation in boreal forests was generally weak, not very extensive (DEI usually < 20 m) and decreased with time. We found more extensive edge influence at natural edges, at younger edges and in broadleaf forests. The comparison among regions revealed weaker edge influence in Fennoscandian forests. 5. Synthesis. Edges created by forest harvesting do not appear to have as strong, extensive or persistent influence on vegetation in boreal as in tropical or temperate forested ecosystems. We attribute this apparent resistance to shorter canopy heights, inherent heterogeneity in boreal forests and their adaptation to frequent natural disturbance. Nevertheless, notable differences between forest structure responses to natural (fire) and anthropogenic (cut) edges raise concerns about biodiversity implications of extensive creation of anthropogenic edges. By highlighting universal responses to edge influence in boreal forests that are significant irrespective of edge or forest type, and those which vary by edge type, we provide a context for the conservation of boreal forests.

Although forest edges surrounding lakes and wetlands are common in many heterogeneous landscapes, there are few studies on patterns of vegetation across these natural landscape boundaries. We investigated forest structure, understorey composition and bryophytes at bog and lakeshore edges in spruce and old-growth hemlock forests. Our objectives were to estimate edge width for vegetation across lake and bog edges, and to examine patterns across the bog-forest edge. We sampled canopy cover, trees, deadwood, structural diversity, species diversity, saplings, and understorey vegetation along transects across four bog and four lakeshore edges in spruce forests and five lakeshore edges in hemlock forests. We used randomization tests to determine the distance of edge and forest influence into adjacent interior forest and bog, respectively. Patterns were assessed using wavelet analysis to determine locations of abrupt changes. Edge influence extended only 5 m into the forest for most variables with notable results of fewer bryophytes, more shrubs and greater tree and shrub diversity at lakeshore edges in hemlock forests. Forest influence at bog edges resulted in a wider approx. 40 m transition zone within the bog in which tree density, graminoid cover, Sphagnum spp. cover, and herb diversity were greater than both adjacent bog and forest. Varying edge width and responses to edge influence between forest types emphasizes the need for site-specific studies. Lakeshore and bog-forest edges harbor greater diversity and unique vegetation structure on heterogeneous landscapes in Nova Scotia, particularly in bog margins, and are key areas to consider for conservation.

QUESTIONS: What factors control broad‐scale variation in edge length and three‐dimensional boundary structure for a large region extending across two biomes? What is the difference in structure between natural and anthropogenic edges? LOCATION: Temperate and boreal forests across all of Sweden, spanning latitudes 55–69° N. METHODS: We sampled more than 2000 forest edges using line intersect sampling in a monitoring programme (National Inventory of Landscapes in Sweden). We compared edge length, ecosystem attributes (width of adjacent ecosystem, canopy cover, canopy height, patch contrast in canopy height, forest type) and boundary attributes (profile, abruptness, shape) of natural edges (lakeshore, wetland) with anthropogenic edges (clear‐cut, agricultural, linear disturbance) in five regions. RESULTS: Anthropogenic edges were nearly twice as abundant as natural edges. Length of anthropogenic edges was largest in southern regions, while the abundance of natural edges increased towards the north. Edge types displayed unique spectrums of boundary structures, but abrupt edges dominated, constituting 72% of edge length. Anthropogenic edges were more abrupt than natural edges; wetland edges had the most gradual and sinuous boundaries. Canopy cover, canopy height, patch contrast and forest type depended on region, whereas overall boundary abruptness and shape showed no regional pattern. Patch contrast was related to temperature sum (degree days ≥ 5 °C), suggesting that regional variability can be predicted from climate‐controlled forest productivity. Boundary abruptness was coupled with the underlying environmental gradient, land use and forest type, with higher variability in deciduous than in conifer forest. CONCLUSIONS: Edge origin, land use, climate and tree species are main drivers of broad‐scale variability in forest edge structure. Our findings have important implications for developing ecological theory that can explain and predict how different factors affect forest edge structure, and help to understand how land use and climate change affect biodiversity at forest edges.

Vegetation structure, defined by the height, cover, and types of plants, is an important component of habitat suitability for plant species or communities. The identification of potential habitat is a crucial knowledge gap for endangered Atlantic Coastal Plain Flora (ACPF), a group of taxonomically unrelated plants that share common habitat types and are mostly found on lakeshores and wetlands in the Atlantic coastal region of North America. Our objectives were to assess spatial patterns and relationships of ACPF richness and structural diversity indices at different scales and positions along the lakeshore-to-forest gradient. We sampled 16 sites at 7 lakes in southwestern Nova Scotia using contiguous 20 × 20 cm quadrats along 20 m transects, perpendicular to the waterline, and in 5 × 5 m grids, between the lake and the forest edge. We measured the cover of 19 ACPF species and structural elements at different heights and calculated structural diversity indices using the Shannon index. Spatial patterns were assessed using one - and two-dimensional wavelet variance and covariance. The edge of the zone of high ACPF richness coincided with greater structural diversity at the lakeshore edge. Herbaceous ACPF richness was positively associated with structural diversity at finer scales and on lakeshores, but negatively associated at coarser scales and farther from the waterline. A strong association of structural diversity with ACPF richness suggests it could be used as a habitat indicator for ACPF on lakeshores, which could help the identification and conservation of potential suitable shorelines for ACPF populations in Nova Scotia.

Riparian ecotones at lakeshore edges are prominent features on the heterogeneous boreal forest landscape. We introduce a new method (the critical values approach), which incorporates inherent variability in interior forest, to quantify distance of edge influence at lakeshore forest edges. We use this method to examine the variation in forest structure and composition along the lakeshore forest edge-to-interior gradient in the mixed-wood boreal forest. Our objectives were: (1) to quantify distance of edge influence for forest structure and composition at lakeshore forest edges; and (2) to investigate spatial pattern in vegetation along the edge-to-interior gradient. Trees, coarse woody material, saplings, shrubs, and herbs were sampled in plots at varying distances along 200-m transects established perpendicular to lakeshore forest edges. Distance of edge influence was determined by comparing mean values at different positions along the transect to critical values established from a randomization test of interior forest data. The spatial pattern of four selected species along the edge-to-interior gradient was assessed using split moving window analysis and wavelet analysis. The results suggest that a distinct lakeshore forest edge community exists. This community was ∼40 m wide and was characterized by greater structural diversity, larger amounts of coarse woody material, and more saplings and mid-canopy trees than interior forest. Distance of edge influence for understory composition was generally greater than for forest structure. Patterns of response for different species along the edge-to-interior gradient were related to shade tolerance. Lakeshore forest edges are distinct landscape elements, but their prominence depends on the reference forest, species, and scale.

The simultaneous influence from multiple edges on remnant forest patches (such as wildlife corridors, protection buffers, small unharvested remnants or corners of larger patches) in harvested forest landscapes could impair, or possibly enhance, their effectiveness. When multiple edges are in close proximity, there may be interactions of edge influence such that the observed response is greater or less than would result from the influence of either edge alone. We examined possible ways in which two nearby forest edges of similar or different types might interact in terms of their influence on forest structure. We present an 'edge interaction' model for three possible types of interaction of edge influence: (1) no interaction, edge influence is limited to the strongest influence from either edge, (2) positive interaction, observed edge influence is greater than from either edge alone; (3) negative interaction or resistance, the influence from both edges is less than from a single edge (e.g., an older edge is resistant to effects from a younger edge). Empirical data for forest structure at the edges of cutblocks (harvested areas) and water bodies were entered into the models to predict edge influence in narrow forest corridors assuming the null hypothesis of no interaction. Randomization tests were used to compare predictions to observed edge influence on recently-fallen logs and Populus spp. (P. tremuloides Michx. and P. balsamifera L.) sapling density in lakeshore buffers in boreal mixedwood forest as well as on canopy cover and log, tree and snag abundance in riparian buffers and forested corridors separating cutblocks in Picea mariana (Mill.) BSP. forest. In lakeshore buffers, there was evidence of both positive and negative interaction at different locations within the buffer or at different times since buffer creation for both the abundance of logs and Populus sapling density. Trends suggested positive interaction for canopy cover and live tree density in riparian buffers and cutblock separators, and for snag density near the cut edges of riparian buffers. Testing hypotheses arising from our model of interaction of edge influence could lead to a clearer understanding of edge influence in fragmented landscapes.

We experimentally tested the hypothesis that nest predation rate in hole-nesting birds, especially the common goldeneye Bucephala clangula, was related to the edge between aquatic and terrestrial habitats. We also studied whether nest predation rate was related to habitat patch (lake) size. In three study areas nest-boxes were erected in pairs: one nest-box was erected at the shoreline and the other one inside the forest at a varying distance (range from 14 to 140 m) from the shoreline. One chicken egg was placed in each nest-box (dummy nest). Overall predation rate on dummy nests varied from 34.6% to 52.6% depending on the study area. The pine marten Martes martes was the primary nest predator in all study areas. Daily predation rates did not differ between natural and dummy nests. Predation rate on dummy nests was not related to the distance of the nest-box from the shoreline in any study area. Predation rate was not related to lake size in two study areas but in one area predation rate on dummy nests was lower around largest lakes. However, the result may be accidental and not because of lake size per se because the proportion of forest was exceptionally low in that part of the study area.

Habitat edges affect several ecological phenomena, usually known as the edge-effect concept. One of its basic principles is the ecological trap hypothesis which assumes that birds are attracted to nest near habitat edges where food supplies may be greater but nest predation is higher. We studied nest-site selection in relation to the lake shore/forest habitat edge in the Common Goldeneye Bucephala clangula, a hole-nesting duck, using two types of experiment. First, we examined nest-site prospecting by erecting nest boxes with traps at the shoreline and inside the forest at varying distances from the shoreline. Secondly, we examined nest-site selection in three study areas by erecting nest boxes in pairs: at the shoreline and at varying distances inside the forest. In addition we experimentally measured nest predation rate in shore and forest boxes using artificial nests. Goldeneye females prospected shore and forest boxes equally. However, the final decision was in favour of shore boxes: within a box pair, the shore box was occupied first in all three study areas. There was no difference in nest predation rate between shore and forest boxes, except in one study area where predation rate was lower, not higher, in shore boxes. Thus, while Goldeneye females clearly exhibit a pattern of nest-site selection in relation to habitat edge, the ecological trap hypothesis is not supported so far as the risk of predation is considered. Increased predation risk associated with the period of getting hatched young out of the nest to a brood-rearing lake may be the reason for the rejection of forest boxes.

We examined nocturnal roosting and diurnal perching habitat used by nonbreeding bald eagles (Haliaeetus leucocephalus) in North Carolina during 1986 and 1987. Eagles used roost areas that were less dense, had less canopy cover, were closer to forest edges, and had larger trees than randomly selected areas, and they used trees that were larger than random trees for roosting and perching. Suitable perch trees were the most important attribute of perching habitat. Eagles used loblolly pines (Pinus taeda) and trees with leafless crowns, probably because these crowns were most accessible for perching. Eagles perched in the bottom of tree crowns during summer, but they perched in tree tops during fall and winter. Eagle did not use perches that were different from forest stand characteristics within 20 m of perch trees, forest cover types in 1-ha blocks surrounding perches, or habitat disturbances. Roosting habitat should receive primary management emphasis because of its apparent low occurrence in central North Carolina. Perch trees were plentiful, but long-term management is desirable.