Small-mammal abundance differs between pipelines, edges, and interior boreal forest habitat

Oil and gas development alters boreal forests by creating early-successional habitat and an increased amount of edge. We evaluated which small-mammal species used pipeline rights of way, the influence of vegetation recovery on pipelines, and edge effects in the adjacent forest. Meadow voles (Microtus pennsylvanicus (Ord, 1815)) were the most common species on pipelines, whereas adjacent forest was dominated by southern red-backed voles (Myodes gapperi (Vigors, 1830)), northern red-backed voles (Myodes rutilus (Pallas, 1779)), and North American deer mice (Peromyscus maniculatus (Wagner, 1845)). Deer mouse abundance was greater along pipeline transects with greater vegetation recovery. Within the forest, irrespective of vegetation recovery on pipelines, meadow voles and deer mice increased near edges. Red-backed voles showed a mixed (i.e., neutral or positive) response to edge. Vegetation variables (i.e., canopy type and cover, ground cover, stem counts, and volume of downed woody material) were important predictors of small-mammal abundance in the forest, but they could not fully account for observed edge effects. Altered small-mammal communities on and adjacent to pipelines may have implications for boreal forest management and conservation through potential changes in predator–prey dynamics and boreal food webs; these implications require further study.

Edge effects in fire-prone landscapes: Ecological importance and implications for fauna

Edges are ecologically important environmental features and have been well researched in agricultural and urban landscapes. However, little work has been conducted in flammable ecosystems where spatially and temporally dynamic fire edges are expected to influence important processes such as recolonization of burnt areas and landscape connectivity. We review the literature on fire, fauna, and edge effects to summarize current knowledge of faunal responses to fire edges and identify knowledge gaps. We then develop a conceptual model to predict faunal responses to fire edges and present an agenda for future research. Faunal abundance at fire edges changes over time, but patterns depend on species traits and resource availability. Responses are also influenced by edge architecture (e.g., size and shape), site and landscape context, and spatial scale. However, data are limited and the influence of fire edges on both local abundance and regional distributions of fauna is largely unknown. In our conceptual model, biophysical properties interact with the fire regime (e.g., patchiness, frequency) to influence edge architecture. Edge architecture and species traits influence edge permeability, which is linked to important processes such as movement, resource selection, and species interactions. Predicting the effect of fire edges on fauna is challenging, but important for biodiversity conservation in flammable landscapes. Our conceptual model combines several drivers of faunal fire responses (biophysical properties, regime attributes, species traits) and will therefore lead to improved predictions. Future research is needed to understand fire as an agent of edge creation; the spatio-temporal flux of fire edges across landscapes; and the effect of fire edges on faunal movement, resource selection, and biotic interactions. To aid the incorporation of new data into our predictive framework, our model has been designed as a Bayesian Network, a statistical tool capable of analyzing complex environmental relationships, dealing with data gaps, and generating testable hypotheses.

Responses of red-backed voles (Myodes gapperi) to windrows of woody debris along forest–clearcut edges

Context Southern red-backed voles (Myodes gapperi) disappear from clearcuts within the first year or two after harvest, at least in studies in coniferous and mixed forests of western North America. Post-harvest woody debris arranged in large piles and windrows supports populations of M. gapperi on clearcuts and may extend their persistence there. Aims To test the hypotheses (H) that for M. gapperi, (H1) population parameters of abundance, reproduction, and survival would be higher in windrow–forest than isolated windrow sites, and higher or similar to those in interior old forest sites; (H2) connectivity provided by windrow-forest structures will mitigate potential negative effects of clearcuts and abundance of M. gapperi will remain similar at the abrupt edge between forest and new clearcuts; and (H3) connectivity provided by windrow–forest structures will allow increased movements between both habitats. Methods Study areas were located in three forest ecological zones in southern British Columbia, Canada. Populations of M. gapperi were sampled from 2010 to 2012 in three types of habitats on new clearcuts: isolated windrows of woody debris, windrows attached to uncut old forest, and in uncut old forest. Key results Higher mean values of abundance and number of juvenile recruits of M. gapperi in the isolated windrow and windrow–forest sites than forest sites was contrary to our prediction for H1. In support of H2, we could not detect any differences in the mean number of captures among forest, edge and windrow sections of the windrow–forest sites, nor in the mean range length among the three habitat types. For H3, connectivity provided by windrow–forest structures may mitigate potential negative effects on abundance for M. gapperi at the abrupt edge between forest and new clearcuts. Conclusions and Implications Voles did not commonly move between the forest and windrow habitats, but did move readily within forest and within windrows. Substantial movement by M. gapperi within windrows suggested that this microtine will move along windrows and potentially use these paths of connectivity to cross clearcuts. If the prey base is present, windrow connectivity may enhance these open areas for small mustelids and other carnivores and help maintain abundance and diversity of some forest mammals on clearcuts.

Ecotones: Marginal or central areas of transition?

Areas of environmental transition, where ecological communities coincide, are sometimes termed ecotones. These regions often correspond with sharp environmental gradients. Ecotones occur at multiple spatial scales, ranging from transitions between biomes to local small-scale transitions. In recent years ecotones have received increasing scientific attention after being neglected for years, as studies historically often focused on distinct communities. However, it is still debatable whether these transitional regions are speciation and biodiversity hotspots that deserve special conservation interest or are actually areas that hold marginal populations that depend on other parts of the range for the maintenance of their biodiversity and therefore should not deserve primary investment. This paper discusses some of the recent advancements in our understanding of the role of ecotones in ecology, evolution, and conservation.