Expansion of shrub species is widely reported in northern regions, although its extent varies across the landscape. In subarctic Québec (Canada), where dwarf birch (Betula glandulosa Michx) is the main species responsible for shrub expansion, little is known about the causes and consequences of this phenomenon. This study aims to identify the drivers of dwarf birch densification heterogeneity at the landscape level and to evaluate its influence on other shrub species. We used model selection with Akaike's information criterion to rank ecologically relevant models including topographic, historical and edaphic variables. The influence of dwarf birch densification was evaluated through regression analysis. We found that the best model explaining the heterogeneity in dwarf birch densification in western Nunavik includes factors related to both historical conditions (initial shrub cover, time elapsed since last wildfire) and topography (type of environment). Among these factors, only the initial shrub cover had a significant positive influence on the shrub densification. Increase in dwarf birch cover was found to negatively influence the cover of other shrub species. However, no relation was found between dwarf birch densification and other shrub species richness, suggesting that the densification did not yet lead to the exclusion of less competitive species.

Floodplain wetlands in the upper Columbia River valley are governed by the flood pulse. Water flows from the river into adjacent wetlands through channels incised through levees or over the top of the levees. This floodplain is relatively pristine with few road crossings restricting the flow of water in a 110 km length of the floodplain. We describe the floodplain vegetation at three points over 60 years to detect natural vegetation changes and contrast that with changes downstream of roads transecting the wetlands. We mapped eight landscape cover types within 40 floodbasins and four 2 km sections downstream of road crossings at three dates, over 60 years, using historical aerial photographs. Over 60 years the area of open water increased by 77% within the wetlands, and there was a decrease of 14.5%and 40%of marsh and shrub vegetation, respectively. During this time, floodbasins became more connected to the river. We observed greater change within the natural wetlands than in sections downstream of the road crossings. Since floodplain ecosystems are inherently complex due to their highly dynamic nature, isolating specific causes of trends is difficult. However, large-scale loss of vegetation and increase in open water has dramatically changed the wetlands.

Whatever their size and the ecosystem they live in, all organisms may disperse at some stage of their life cycle. Dispersal dynamics are to a varying extent dependent on organismal size, life history, ecological niche, survival capacities and phylogeny. Moves towards a synthesis in dispersal ecology have focused primarily on vertebrates and higher plants, yet recent studies suggest that the dispersal of microorganisms and macroorganisms has much more in common than previously assumed. The dispersal of one organism enables co-dispersal for many others, smaller in size. There is an increasing need for a more integrated approach to study dispersal within the context of organismal interactions and their environments. Such an approach is facilitated by recent developments of powerful indirect techniques that enable tracking of microorganisms and macroorganisms over multiple spatial and temporal scales. Likewise, dispersal modelling and theoretical models of the consequences of dispersal can inspire empirical studies across the entire size spectrum. Simultaneously studying the relationships between dispersal of microorganisms and macroorganisms, and accounting for dispersal through time and space, will allow us to better understand the functioning and dynamics of communities and ecosystems, and to make better predictions of future dispersal patterns, changes in biodiversity and connectivity.

Two structural-diversity and two biodiversity indexes and carbon stocks were determined at eight humid and sub-humid tropical forest sites 20–120 years old in southeastern Mexico. All trees >10 cm at diameter breast height were measured and species identified in 131 randomly located plots. The number of species (S), Shannon (H′), biomass-species (BS) and abundance-biomass-species (ABS) indexes were related to Mg C ha^-1 and the age of the sites. Values were: S, 27–109; H′, 3.9–5.31; BS, 7.39–16.0; ABS, 9.87–18.2; Mg C ha^-1, 39.7–130.7. The relationships between BS and ABS to carbon and the site age were linear and positive, showing that stand structure directly influenced carbon storage. The relationship between site age and carbon was remarkably high (R² = 0.79). Humid forests showed higher values of carbon than sub-humid forests (104.4 vs. 70.6, t = 2.07, p = 0.04) but their structural diversity was similar (BS, 11.25 vs. 8.3, p = 0.134; ABS, 13.9 vs. 10.6, p = 0.135). It is concluded that forestry management of tree diameter may be a factor that can favor more carbon storage in secondary forest regrowth as it starts to reach maturity.

Forming the majority of plant diversity in boreal forests, understory communities are important drivers of nutrient cycling and overstory succession. In western Canadian boreal forests, fire is the primary mechanism of natural disturbance, with oil sands mining a substantial anthropogenic disturbance in north-eastern Alberta. An operational reclamation trial, at an oil sands mine, was established the same year as a nearby forest fire, allowing for direct comparison of plant community development between reclaimed and naturally regenerated fire-origin and mature stands. This work reflects a case study with large, but unreplicated, areas of both fertilized and unfertilized reclamation treatments on forest floor-mineral mix (FFMM) and peat-mineral mix (PMM) capping materials. After three years, reclamation sites are compositionally distinct from post-fire and mature natural stands, with more non-native species in reclamation treatments than in natural stands. Communities developing on FFMM are more similar to post-fire successional communities than those on PMM, with high species richness and diversity on FFMM comparable with post-fire stands. Cover soil had a stronger impact on plant community development than fertilization, with fertilization effects dependent on cover soil. A standard dose of fertilizer lowered richness and diversity on FFMM and is not recommended for use with that soil.

Black-backed woodpecker is known to be a disturbance-associated species, being more abundant in disturbed forest stands than in undisturbed habitats, but its demography and population dynamic still need to be clarified. The present study was conducted in central Quebec within coniferous forests shaped largely by timber harvest and wildfire. The objectives were to compare the age composition of breeding black-backed woodpeckers, nest survival rate and productivity in both disturbed and undisturbed habitats (respectively recently burned and unburned habitats). In addition, we evaluated the general productivity of both habitat types in a simulated boreal landscape. There was a positive relationship between nest age and daily survival rates. Older woodpeckers were the most abundant breeders in unburned habitats and younger birds in oneyear-old burns. Although nests in recently burned forests produced more nestlings per successful nest, our simulation of a boreal forest landscape showed that unburned habitat produced about two-thirds more fledglings per year than burned habitat. Globally, unburned habitat may provide woodpeckers more temporally stable resources. Population dynamics of the black-backed woodpecker, at least in our study area, may be explained by resource pulse interactions where populations benefit opportunistically from short-term high-quality habitat, and rely on unburned habitats for long-term persistence.

The aggressive behaviour of Anochetus ghilianii (Spinola, 1851) was estimated in the laboratory by observing the outcome of individual confrontations between workers belonging to 17 colonies according to the geographical distance between these colonies. This study aimed to better understand the social organization of this species and its mode of reproduction and colony foundation. Three categories of behaviours were exhibited by the opponent ants: aggressive, low-aggressive and non-aggressive. The latter category was the most prevalent with an average percentage of 82.56%, and prevailed in eight colonies. Conversely, aggressive behaviours represented only 9.61% of the records on average and appeared only when distance between colonies exceeded 1500 m. In addition, the percentage of aggressive behaviours considerably increased in relation to the geographical distance between the colonies. There was a significant positive correlation for aggressive behaviours, and negative for non-aggressive behaviours. This low level of aggressive behaviour suggests a short genetic distance between colonies which could have arisen through colony fission reproduction (dependent colony foundation).

Chinese cordyceps (or caterpillar fungus, Cordyceps sinensis), an expensive medicinal organism, is collected intensively every spring. It is concluded that over-collection has caused vegetation and soil degradation. However, most descriptions of the ecological impact of collection were qualitative and the impact on plant communities has not been quantified precisely. Collection plots and control plots were established in three counties on the Tibetan Plateau in order to measure impacts of collection on plant community composition. The results showed that due to Chinese cordyceps collection, species diversity expressed as the Shannon—Wiener indices significantly decreased by 10–13%, community dominance expressed as the Berger—Parker indices significantly increased by 17–32%, vegetation cover significantly decreased by 11–19% and aboveground biomass significantly decreased by 21–46%. However, root biomass did not change significantly, and only a few soil physical and chemical indicators in some plots changed significantly. Although Chinese cordyceps collection caused ecological degradation, the undisturbed plant roots and soil guarantee vegetation recovery. Aboveground biomass was the most sensitive variable to Chinese cordyceps collection, and could be used as the evaluation indicator in efforts of ecological protection and recovery.