Spruce planting (Picea abies) in coastal birch forests (Betula pubescens) of northern Norway could influence ground-nesting species such as willow ptarmigan (Lagopus lagopus) and black grouse (Tetrao tetrix). Predator-specific predation rates on baited trackboards were therefore studied in 3 successional edge gradients: birch forest adjacent to (1) closed spruce plantations, (2) open spruce plantations, and (3) clearings. We also examined the influence of 2 types of landscape-level variables on predation rates: the distance from sampling location to the nearest roads and buildings and the land use composition within a 1-km radius of the sample. Predation rates were dominated by 2 generalist species: red fox (Vulpes vulpes) (19.2%) and hooded crow (Corvus corone cornix) (7.5%). Predation appears dependent on the successional stage of spruce plantations, with areas near clearings (63.5%) and open spruce plantations (59.8%) experiencing higher predation pressures than closed spruce plantations (45.3%). However, predation rates were highly variable among landscape blocks. Neither landscape nor vegetation variables could explain this block-level variation. We discuss alternative mechanisms that could explain differences between landscape blocks, but further studies are needed to understand the spatial heterogeneity of predators at larger scales.

Nomenclature: Mitchell, 1974; Svensson et al., 1999; Macdonald, 2002.

Few studies have considered the effects of ultraviolet-B (UVB) radiation during different developmental stages of plants, especially on invasive alien species. We studied growth and physiological responses of night-flowering catchfly (Silene noctiflora) to UVB radiation during 2 developmental stages. Silene noctiflora plants were grown under biologically effective UVB (UVB_BE) radiation of 0, 4, 8, and 16 kJ ·m⁻²·d⁻¹ in controlled-environment growth chambers. Growth and physiological parameters of plants were measured during vegetative and reproductive stages. In general, enhanced UVB radiation reduced stem height and diameter, leaf area, and total dry matter. It also decreased leaf weight ratio, leaf area ratio, stomatal number, net CO₂ assimilation, water use efficiency, and chlorophyll concentration but increased specific leaf weight, epidermal cell size, transpiration, UV-absorbing compounds, and epicuticular wax. Plants were taller and had higher chlorophyll, UV-absorbing compounds, and wax but lower ethylene evolution in the reproductive stage than in the vegetative stage. Overall, S. noctiflora plants were damaged by a four-fold increase of UVB radiation, as was apparent from reduced total seed yield. They acclimated under ambient UVB and a two-fold increase of UVB in their reproductive stage. These results mean that this plant may remain an invasive species under increased UVB radiation.

Nomenclature: Kartesz, 1994; Royer & Dickinson, 1999.

Conservationists have proposed that maintaining key elements of the original land-cover type in modified landscapes may mitigate the detrimental effects of land-cover change on residual species. We tested this hypothesis for aquatic insect communities in tank-forming bromeliads in forested and non-forested habitats in Costa Rica. Bromeliad tanks hold much of the standing water in this region and therefore provide an important resource for insects with aquatic larval stages. We quantified the relative importance of land-use type and the bromeliad-specific “local” environment on the insect community, and also the effect of land-use type on this local environment. Insect species responded to both land-use type and the local environment, with these variables explaining a total of 36% of species densities. The local environment independently explained 19% of insect densities, while land-use type explained 17%, mainly through its modification of the local environment. Local environmental conditions were strongly correlated to land-use type (r² = 0.64), with non-forest habitat having a higher average temperature, a greater variation in temperature, and a lower density of bromeliads. Our results indicate that the land-use type in which bromeliads occur influences the relative densities of insects by altering the local environment of bromeliads. Therefore, maintaining bromeliads under land-use conversion will not necessarily maintain the bromeliad insect community of the original forested habitat.

Nomenclature: Croat, 1978; Rzedowski, 1978.

Although almost one third of Aegean islands have an area smaller than 1 km², very few studies have concentrated on this spatial scale. We investigate biodiversity patterns of terrestrial isopods in 2 island groups (Kalymnos and Astypalaia) of the Aegean Sea, consisting mainly of small islands and characterized by different geological histories, isolation, and species source pools. We focus on the species–area relationship (SPAR), community nestedness and the investigation of the small island effect (SIE) in these island groups. The slopes of the SPARs for terrestrial isopods of the 2 groups are almost identical and place the 2 island groups within the intraprovincial category. The SIE investigated was detected in both island groups, with the Kalymnos group exhibiting a higher upper limit (the island size threshold under which an increase of species number with increase of area in small islands is not observed). Both island groups are highly nested and exhibit similar levels of nestedness. Despite the different geological histories, isolation, and source pools, the 2 island groups exhibit great similarity in all the patterns investigated. The islands studied still “behave” as parts of a continuous land mass, with high numbers of species even on the smallest islands, limited net effects of island size, and a significant contribution of the interrelationship between area and environmental heterogeneity to the total species richness.

Nomenclature: Schmalfuss, 2003.

Leaf chemistry and physiology vary with light environment and are often thought to directly affect herbivory patterns. Biotic (e.g., parasitoids and predators) and abiotic (e.g., temperature, relative humidity) factors known to influence herbivory also co-vary with light environment. Irrespective of mechanism, light-based differences in herbivore damage must be the result of variable herbivore abundance, per capita effects, or both. We examined the effect of light environment on leaf defence and leaf nutritional quality in Lindera benzoin (Lauraceae) and relate this to the abundance and impact of its lepidopteran herbivore Epimecis hortaria (Lepidoptera: Geometridae). In this system we consistently observe greater natural field herbivory in shade habitats relative to high light habitats, despite similar herbivore abundances; differences in herbivory are therefore most likely attributable to different per capita impacts of herbivores across environments. Potential herbivore behaviours responsible for the observed field pattern include increased foraging per day and longer developmental periods in shade habitats. A more complete understanding of observed herbivory patterns requires incorporating variation in herbivore behaviour as influenced by abiotic or biotic factors that co-vary with the different light environments.

Nomenclature: Gleason & Cronquist, 1991.

We analyzed the role of birds and mammals as seed dispersers of 3 fleshy-fruited tree species, hawthorn (Crataegus monogyna), holly (Ilex aquifolium), and yew (Taxus baccata), in a temperate secondary forest in northwestern Spain. Seed dispersal patterns were assessed from direct observations of the disperser birds (thrushes, Turdus spp.), from the collection of bird and mammal defecations; and from seed rain estimates in fixed plots. Some highly specific interactions emerged, especially for the pairs Turdus iliacus–Ilex and T. philomelos–Taxus, due to dispersers' fruit preferences and because some fruit species were more consumed than others. Seeds removed by mammals (mainly fox, Vulpes vulpes, and badger, Meles meles) were deposited in large faecal clumps that were mainly found in open areas, whereas those removed by birds appeared in smaller clumps, located mostly in covered microhabitats. Flocking species (T. viscivorus, T. pilaris, and T. iliacus) flew longer distances after fruit consumption, whereas T. merula and T. philomelos (less gregarious and with resident populations) tended to fly shorter distances, generating a 2-peaked frequency distribution of flight distances. The refuge provided by the tree canopy seemed to be an important cue for the first perch used by birds after leaving the feeding tree. Seed rain of Ilex mainly occurred beneath conspecifics and yews; Taxus seeds were mainly found under conspecifics; and no microhabitat was clearly dominated by Crataegus seeds. In general, this study reveals that similar bird species differed in the quantity and quality (microhabitat and distance travelled) components of their dispersal effectiveness. At the same time, mammals and flocking species emerge as important dispersal vectors implicated in long-distance dispersal.

Nomenclature: Cramp, 1988; Tutin et al., 1964–1980.

This study aims to reconstruct the variations in the vegetation zonation in the Ellero Valley (Maritime Alps, Italy) since the Late Glacial. Based on analysis of percentages of dominant pollen taxa (Pinus, Abies, Fagus, deciduous Quercus, Artemisia, Poaceae) in sediment cores from 3 peat bogs at different altitudes (Pian Marchisio, 1624 m; Rifugio Mondovì, 1760 m; and Torbiera del Biecai, 1920 m), this study offers an interpretation of pollen percentages in terms of vegetation cover The correlation of the pollen zones in the 3 diagrams is validated by correspondence analysis and supported by 12 ¹⁴C (AMS) dates. The Oldest and the Younger Dryas were characterized by steppe vegetation dominated by Artemisia. The Bølling–Allerød warming, which separates the Oldest and the Younger Dryas, is characterized by a Pinus shift. Pine and birch forests develop at 1900 m asl at the beginning of the Holocene. The fir wood colonization of the mountainous and subalpine belts is dated to 9540–9406 cal BP and follows these first phases. Fir development and the arrival of beech are dated 8767–8543 cal BP: beech is recorded about 1000–2000 y earlier than in the adjacent regions. Beech forests develop between 1100 and 1600 m asl, forming a vegetation belt between the oak-wood in the lowland and the subalpine fir-wood. Fir decreases from 2792–2459 cal BP. Since this period, a beech–fir mountainous belt has been present at 1700 m. Both the suppression of the fir forest and the lowering of the upper beech wood limit to 1500 m are due to human activity during the last millennium.

Nomenclature: Pignatti, 1982.

Severe wildfires often facilitate the spread of exotic invasive species, such as Dalmatian toadflax (Linaria dalmatica). We hypothesized that toadflax growth and reproduction would increase with increasing burn severity in a ponderosa pine (Pinus ponderosa)-dominated forest. We measured toadflax density, cover, flowering stalks, and native species richness and cover on 327 plots for 3 y after a 2001 wildfire. Toadflax stem density, cover, and flowering stalks increased in 2003, then decreased in 2004 in all burn severity classes, but remained higher than initial 2002 values. Toadflax spread to previously uncolonized areas, though stem density decreased in unburned plots. Transition matrices showed that more plots on moderately (73%) and severely (74%) burned areas classified as high toadflax density in 2002 remained high density in 2004. Deterministic matrix modeling using 2002 to 2004 transition probabilities projected that the percentage of high-density plots would stabilize on moderately and severely burned sites at 41 and 61%, respectively. In contrast, 20-y rates of change (λ) for unburned and low-severity burn sites were <1.0, and stabilizing at 2% for unburned plots and 19% for low-severity burn plots. Post-wildfire conditions in high-severity burned areas favour increased density, cover, reproduction, and spread of Dalmatian toadflax, while native species richness was reduced, suggesting that the invasive species would persist, at least in the short term, at the expense of natives.

Nomenclature: USDA NRCS, 2007.

Nitrogen enters terrestrial ecosystems through multiple pathways during primary succession. We measured accumulation of total soil nitrogen and changes in inorganic nitrogen (N) pools across a 300-y sequence of river terraces in northwest Alaska and assessed the contribution of the nitrogen-fixing shrub Shepherdia canadensis. Our work compared 5 stages of floodplain succession, progressing from a sparsely vegetated silt cap to dense shrubby vegetation, balsam poplar-dominated (Populus balsamifera) and white spruce-dominated (Picea glauca) mixed forests, and old-growth white spruce forest. Total soil N (0–30 cm depth) increased throughout the age sequence, initially by 2.4 g N·m⁻²·y⁻¹ during the first 120 y of terrace development, then by 1.6 g N·m⁻²·y⁻¹ during the subsequent 2 centuries. Labile soil N, measured by anaerobic incubation, increased most rapidly during the first 85 y of terrace formation, then remained relatively constant during further terrace development. On recently formed terraces, Shepherdia shrubs enriched soil N pools several-fold compared to soil beneath Salix spp. shrubs or intercanopy sites. Total and labile soil N accretion was proportional to Shepherdia cover during the first century of terrace development, and mineral soil δ¹⁵N content indicated that newly formed river terraces receive substantial N through N-fixation. About half the 600 g total N·m⁻² accumulated across the river terrace chronosequence occurred during the 120 y when S. canadensis was dominant. Sediment deposited by periodic flooding continued to add N to terrace soils after the decline in Shepherdia abundance and may have contributed 25% of the total N found in the floodplain terrace soils.

Nomenclature: Viereck & Little, 1986.

Agricultural development on floodplains contributes to hydrologic alteration and forest fragmentation, which may alter landscape-level processes. These changes may be related to shifts in the seed bank composition of floodplain wetlands. We examined the patterns of seed bank composition across a floodplain watershed by looking at the number of seeds germinating per m² by species in 60 farmed and intact forested wetlands along the Cache River watershed in Illinois. The seed bank composition was compared above and below a water diversion (position), which artificially subdivides the watershed. Position of these wetlands represented the most variability of Axis 1 in a Nonmetric Multidimensional Scaling (NMS) analysis of site environmental variables and their relationship to seed bank composition (coefficient of determination for Axis 1: r² = 0.376; Pearson correlation of position to Axis 1: r = 0.223). The 3 primary axes were also represented by other site environmental variables, including farming status (farmed or unfarmed), distance from the mouth of the river, latitude, and longitude. Spatial analysis based on Mantel correlograms showed that both water-dispersed and wind/water-dispersed seed assemblages had strong spatial structure in the upper Cache (above the water diversion), but the spatial structure of water-dispersed seed assemblage was diminished in the lower Cache (below the water diversion), which lost floodpulsing. Bearing analysis also suggested that water-dispersal process had a stronger influence on the overall spatial pattern of seed assemblage in the upper Cache, while wind/water-dispersal process had a stronger influence in the lower Cache. An analysis of the landscapes along the river showed that the mid–lower Cache (below the water diversion) had undergone greater land cover changes associated with agriculture than did the upper Cache watershed. Thus, the combination of forest fragmentation and hydrologic changes in the surrounding landscape may have had an influence on the seed bank composition and spatial distribution of the seed banks of the Cache River watershed. Our study suggests that the spatial pattern of seed bank composition may be influenced by landscape-level factors and processes.

Nomenclature: USDA, 2005.

Sudden versus gradual mortality of canopy trees can differentially affect relative species assemblages after disturbance, although local biotic and abiotic habitat characteristics can modify expected patterns. Woody vegetation responses to moderate-severity disturbances were characterized and compared in relation to pre- and post-disturbance stand and site characteristics within Abies balsamea–Betula spp. stands of southeastern Québec, Canada. Disturbances were caused by gradual mortality due to the spruce budworm (Choristoneura fumiferana), sudden mortality due to windthrow, or a combination of both. Redundancy Analysis with forward selection was used to rank the importance of disturbance type and local stand and site characteristic variables on species regeneration patterns. In order of decreasing importance, stand composition prior to disturbance, density of coarse woody debris, slope, distance to nearest conifer stand, density of deciduous legacy trees, spruce budworm disturbance, and soil drainage were important in determining post-disturbance species composition. No distinct regeneration patterns were associated with windthrow or interaction disturbance types. Although moderate-severity disturbances affected species distribution, local biotic and abiotic stand and site characteristics, particularly pre-disturbance stand composition and density of coarse woody debris, were more important in determining post-disturbance species distribution patterns.

Nomenclature: Gleason & Cronquist, 1991.

We examined beaver (Castor canadensis) pond dynamics and associated riparian bird communities, based on call-response surveys. Following water disappearance, abandoned beaver ponds were invaded by grassy areas and alder shrubs and supported higher bird species numbers than nearby riparian areas. We detected a total of 49 species. At abandoned beaver ponds, the mean number of species was 6.4, whereas it ranged between 2.4 and 3.1 species for active beaver ponds, rivers, and lakes. Density of deciduous shrubs and graminoid cover, higher in abandoned beaver ponds, was positively associated to the number of species of birds. However, riparian avian diversity was lower near clearcuts and large water areas. Beaver population control or geographic confinement may suppress both spatial and temporal dynamics of beaver pond creation and abandonment, and could impact riparian vegetation and birds.

Nomenclature: Gauthier & Aubry, 1996.

Natural peatlands are an important component of the global carbon cycle, representing a net long-term sink of atmospheric carbon dioxide (CO₂). The natural carbon storage function of these ecosystems can be severely impacted due to peatland drainage and peat extraction, leading to large and persistent sources of atmospheric CO₂ following peat extraction abandonment. Standard restoration techniques aim to restore the peatland to a carbon-accumulating system through various water management techniques to improve hydrological conditions and through reintroducing Sphagnum at the surface. However, restoring the hydrology of peatlands can be expensive due to the cost of implementing the various restoration techniques. This study examines the net ecosystem CO₂ exchange of a new extraction–restoration technique where the acrotelm is preserved and replaced directly on the cutover surface. Peat respiration at the experimental restored acrotelm (110.5 g C·m⁻² over the study period: May 20 – August 18) was significantly lower than at the natural peatland (144.8 and 203.7 g C·m⁻², wet and dry plots respectively). However, gross ecosystem production (GEP) at the experimental site was significantly reduced (−54.0 and −34.4 g C·m⁻²) compared to the natural site (−179.2 and −162.0 g C·m⁻²). Consequently, this was a growing season net emitter of CO₂ to the atmosphere over the season at the experimental site (78.5 and 56.5 g C·m⁻²) and a growing season sink of CO₂ at the natural site (−17.6 and −22.8 g C·m⁻²). Light response curves indicated that maximum GEP was significantly lower at the experimental site; however, it is likely that the percentage of living and dead vegetation at the plots post restoration had a large control on this lower productivity as plots with more living vegetation had higher overall productivity (GEP). Nevertheless, the experimental site did maintain limited productivity post-extraction, indicating that the carbon dynamics of the system was maintained due to this acrotelm restoration process, thereby likely returning the ecosystem toward a natural sink of atmospheric CO₂ faster than natural rehabilitation and current restoration techniques. As such, this approach to peat extraction may be an environmentally preferred approach to use.

Resource pulses are common in various ecosystems and often have large impacts on ecosystem functioning. Many animals hoard food during resource pulses, yet how this behaviour affects pulse diffusion through trophic levels is poorly known because of a lack of individual-based studies. Our objective was to examine how the hoarding behaviour of arctic foxes (Alopex lagopus) preying on a seasonal pulsed resource (goose eggs) was affected by annual and seasonal changes in resource availability. We monitored foraging behaviour of foxes in a greater snow goose (Chen caerulescens atlanticus) colony during 8 nesting seasons that covered 2 lemming cycles. The number of goose eggs taken and cached per hour by foxes declined 6-fold from laying to hatching, while the proportion of eggs cached remained constant. In contrast, the proportion of eggs cached by foxes fluctuated in response to the annual lemming cycle independently of the seasonal pulse of goose eggs. Foxes cached the majority of eggs taken (> 90%) when lemming abundance was high or moderate but only 40% during the low phase of the cycle. This likely occurred because foxes consumed a greater proportion of goose eggs to fulfill their energy requirement at low lemming abundance. Our study clearly illustrates a behavioural mechanism that extends the energetic benefits of a resource pulse. The hoarding behaviour of the main predator enhances the allochthonous nutrients input brought by migrating birds from the south into the arctic terrestrial ecosystem. This could increase average predator density and promote indirect interactions among prey.

Nomenclature: Anonymous, 2007.

Testate amoebae inhabiting Sphagnum peatlands are sensitive indicators of substrate-moisture content. However, ecological data from a range of peatland types is needed to assess their indicator-value in other peatland systems. We examined testate amoeba communities and species–environment relationships at 40 locations within a pocosin of North Carolina. Primary objectives were to provide baseline data on the ecology of testate amoebae in pocosins, compare communities with those of northern peatlands, and assess the potential of using testate amoebae as environmental indicators in these systems. Results indicated that pH, substrate-moisture content, and conductivity were important controls on community composition. Communities that were relatively similar and dissimilar to those of northern peatlands were encountered, and the ecology of species with respect to water-table depth was similar in both peatland types. Cross validation of transfer functions for pH and water-table depth suggests that pocosin testate amoebae can be used as indicators for these variables. However, water-table depth was poorly inferred from communities at several dry sites characterized by high bulk density. These sites may experience large seasonal or interannual variability in moisture conditions because of differences in peat structure, suggesting that research is needed on the influence of short-term variability in shaping community structure.

Nomenclature: Radford, Ahles & Bell, 1969; Charman, Hendon & Woodland, 2000.