Immediate facilitation and engineering legacy of beavers: 54 years of patch dynamics in a boreal landscape.

Beavers are powerful ecosystem engineers that transform terrestrial areas into aquatic systems. Beaver-induced disturbances create a dynamic mosaic of wet and dry successional habitats across the landscape, yet the long-term impacts of beavers on biodiversity remain poorly understood. We used unique long-term data on beaver floods to study how the return of the beaver-induced patch disturbances affects habitat suitability and connectivity, which serve as proxies for biodiversity, in a boreal landscape over a 54-year period.

Chemical responses of small boreal lakes to atmospheric and catchment drivers over four decades.

During the last few decades organic matter concentrations and water colour values have increased in a large number of lakes and rivers in Eurasia and North America. The upward shift in colour, often called water browning, and shortage of mobile cations have been linked to the recovery of catchments and lakes from acid deposition and increased precipitation. Here, long-term water chemistry responses of 33 boreal forest lakes to atmospheric and catchment scale drivers were studied in a small drainage basin in southern Finland.

Anthropogenic bottom-up and top-down impacts on boreal breeding waterbirds.

Wetland habitats are changing under multiple anthropogenic pressures. Nutrient leakage and pollution modify physico-chemical state of wetlands and affect the ecosystem through bottom-up processes, while alien predators affect the ecosystems in a top-down manner. Boreal wetlands are important breeding areas for several waterbird species, the abundances of which potentially reflect both bottom-up and top-down ecosystem processes.

Balancing between predation risk and food by boreal breeding ducks.

Wetlands belong to the globally most threatened habitats, and organisms depending on them are of conservation concern. Wetland destruction and quality loss may affect negatively also boreal breeding ducks in which habitat selection often needs balancing between important determinants of habitat suitability. In Finland duck population trajectories are habitat-specific, while the reasons behind are poorly understood.

The economic costs, management and regulation of biological invasions in the Nordic countries.

A collective understanding of economic impacts and in particular of monetary costs of biological invasions is lacking for the Nordic region. This paper synthesizes findings from the literature on costs of invasions in the Nordic countries together with expert elicitation. The analysis of cost data has been made possible through the InvaCost database, a globally open repository of monetary costs that allows for the use of temporal, spatial, and taxonomic descriptors facilitating a better understanding of how costs are distributed.

Ecology and extent of freshwater browning - What we know and what should be studied next in the context of global change.

Water browning or brownification refers to increasing water color, often related to increasing dissolved organic matter (DOM) and carbon (DOC) content in freshwaters. Browning has been recognized as a significant physicochemical phenomenon altering boreal lakes, but our understanding of its ecological consequences in different freshwater habitats and regions is limited. Here, we review the consequences of browning on different freshwater habitats, food webs and aquatic-terrestrial habitat coupling.

Large herbivores facilitate an insect herbivore by modifying plant community composition in a temperate grassland.

Large herbivores often co-occur and share plant resources with herbivorous insects in grassland ecosystems; yet, how they interact with each other remains poorly understood. We conducted a series of field experiments to investigate whether and how large domestic herbivores (sheep; ) may affect the abundance of a common herbivorous insect (aphid; ) in a temperate grassland of northeast China. Our exclosure experiment showed that 3 years (2010-2012) of sheep grazing had led to 86% higher aphid abundance compared with ungrazed sites.

Can reed harvest be used as a management strategy for improving invertebrate biomass and diversity?

The succession-driven reed bed habitat hosts a unique flora and fauna including several endangered invertebrate species. Reed beds can be managed through commercial winter harvest, with implications for reed bed conservation. However, the effects of winter harvest on the invertebrate community are not well understood and vary across studies and taxonomic levels.

Effects of grazing on C:N:P stoichiometry attenuate from soils to plants and insect herbivores in a semi-arid grassland.

Understanding the processing of limiting nutrients among organisms is an important goal of community ecology. Less known is how human disturbances may alter the stoichiometric patterns among organisms from different trophic levels within communities. Here, we investigated how livestock grazing affects the C:N:P ecological stoichiometry of soils, plants (Leymus chinensis), and grasshoppers (Euchorthippus spp.

Invertebrates are declining in boreal aquatic habitat: The effect of brownification?

Surface water browning affects boreal lakes in the Northern Hemisphere. This process is expected to increase with global warming. Boreal lakes are the most numerous lakes on Earth.

Changes in species richness and composition of boreal waterbird communities: a comparison between two time periods 25 years apart.

Global measures of biodiversity indicate consistent decline, but trends reported for local communities are more varied. Therefore, we need better understanding of mechanisms that drive changes in diversity of local communities and of differences in temporal trends between components of local diversity, such as species richness and species turnover rate. Freshwater ecosystems are vulnerable to multiple stressors, and severe impacts on their biodiversity have been documented.

Reciprocal facilitation between large herbivores and ants in a semi-arid grassland.

While positive interactions have been well documented in plant and sessile benthic marine communities, their role in structuring mobile animal communities and underlying mechanisms has been less explored. Using field removal experiments, we demonstrated that a large vertebrate herbivore (cattle; ) and a much smaller invertebrate (ants; spp.), the two dominant animal taxa in a semi-arid grassland in Northeast China, facilitate each other.

Mechanisms of density dependence in ducks: importance of space and per capita food.

The growth rate of populations usually varies over time, often in a density-dependent manner. Despite the large amount of literature on density dependence, relatively little is known of the mechanisms underlying the density-dependent processes affecting populations, especially per capita natality. We performed a 20-year study on the density dependence of brood production in two duck species differing in the stability of habitat use.

Dry paths effectively reduce road mortality of small and medium-sized terrestrial vertebrates.

Wildlife passages are widely used mitigation measures designed to reduce the adverse impacts of roads on animals. We investigated whether road kills of small and medium-sized terrestrial vertebrates can be reduced by constructing dry paths adjacent to streams that pass under road bridges. The study was carried out in southern Finland during the summer of 2008.

Experimental evidence for density-dependent survival in mallard (Anas platyrhynchos) ducklings.

It is unresolved to what extent waterfowl populations are regulated by density-dependent processes. By doing a 2-year crossover perturbation experiment on ten oligotrophic boreal lakes we addressed the hypothesis that breeding output is density dependent. Wing-clipped mallard (Anas platyrhynchos) hens were introduced with their own brood and then monitored for 24 days.

Habitat selection rules in breeding mallards (Anas platyrhynchos): a test of two competing hypotheses.

Ideal preemption and conspecific attraction are alternative hypotheses of the habitat selection rules used by individuals. According to the former an occupied site is assumed to be preempted and therefore not available for later arriving individuals, whereas according to the latter individuals are assumed to be attracted by conspecifics to occupied sites, rather than avoiding them. We studied these competing hypotheses in breeding mallards (Anas platyrhynchos) by a cross-over experiment in 2 years, introducing birds onto lakes before migratory wild mallards arrived.

Interspecific interactions and co-existence in dabbling ducks: observations and an experiment.

We studied the possible role of resource limitation and interspecific competition in assemblages of dabbling ducks on breeding lakes in Finland and Sweden with observational and experimental data. After initial vegetation mapping and yearly censuses of ducks in 1985-1990, we collected observational data in 1991-1994 from 28 lakes with natural populations of mallard Anas platyrhynchos and teal A. crecca.