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The structural and functional organization of the crowns of boreal species of trees and shrubs, including willows, has not yet been sufficiently studied. The article analyzes the structure of the modular elements of the crown of S. cinerea. Materials and methods. The classification of shoots and crown shoot systems is based on three features: 1) the length of the internodes that make up the shoot, 2) the age of the shoot, 3) the presence of branching. The following classification of modular elements is used in the work: metamer, uniaxial shoot, three-year shoot system, branch from the trunk, crown as a whole. At the same time, the three-year shoot system is considered as an architectural module. The study of three-year-old shoot systems was carried out separately in female and male individuals, which revealed gender differences in the structural organization of their crowns. Results and conclusions. S. cinerea in its adult state can form life forms: a geoxyl shrub in two modifications – epigeogenic-geoxyl and hypogeogenic- geoxyl shrubs, as well as a life form of a semi-aquatic long-silorizome plantain. All life forms are confined to different environmental conditions. The life forms of the geoxyl shrub have 8 main variants of vegetative shoots of three types: short, medium-length and long. In individuals of S. cinerea of the life form of the semi-aquatic longsilorizome plantain, long shoots are not found in the crown, only 6 main variants of shoots belonging to two types have been identified: short and medium length. Medium-length shoots play the greatest role in the organization of the crowns of various life forms. Along with vegetative shoots in the crown of S. cinerea, vegetative generative shoots of regular renewal are isolated, the lower part of which remains in the crown until autumn and silleptic generative shoots from the vegetative.

More than a thousand iNaturalist NZ observations were compiled and analysed to determine common vascular epiphyte-host relationships in Hamilton, North Island, New Zealand. Dicksonia squarrosa supported the most epiphytes, followed by Salix cinerea, Melicytus ramiflorus and Cyathea medullaris. Epiphytes displaying stronger host specificity, such as Tmesipteris elongata and Phlegmariurus varius, were often on D. squarrosa. In comparison, generalist epiphytes, including Pyrrosia eleagnifolia and Lecanopteris pustulata, were mainly on M. ramiflorus and S. cinerea. A detailed study of 60 D. squarrosa in a single gully investigated factors supporting the host quality of D. squarrosa. Dicksonia squarrosa diameter at breast height (DBH), height, caudex surface area, and distance to the stream and vegetation patch edge were measured. Dicksonia squarrosa that hosted epiphytes were significantly taller, further from the patch edge and had a larger surface area. Epiphyte species richness was higher on D. squarrosa further from the patch edge. The epiphyte communities examined are likely characteristic of highly modified urban ecosystems. Future research investigating the impact of host traits and microclimate on epiphyte-host networks is required to fully elucidate these relationships in urban environments. [ABSTRACT FROM AUTHOR]

Summary: Grey Willow (Salix cinerea L.) poses a significant threat to wetland ecosystems in New Zealand. To manage the ecological impacts and to control further spread, cost‐effective large‐scale control methods are needed. We investigated the response of Grey Willow and dominant wetland plant groups to the aerial boom‐spray application of glyphosate at 9 L/ha and triclopyr (amine) at 18 L/ha at three New Zealand wetlands. We found glyphosate substantially reduced the dominance of tall (>2 m) Grey Willow with commensurate increases in the dominance of most native plant groups. Triclopyr (amine) application resulted in poor Grey Willow control, was not associated with increased native plant group dominance, and some native plant groups declined where triclopyr (amine) was applied. We conclude that the aerial application of glyphosate is an effective large‐scale Grey Willow control tool and could be used to initiate the restoration of native plant communities in wetlands dominated by Grey Willow. But, evidence of Grey Willow recovery after control suggests that increases in native plant dominance will be reversed as Grey Willow re‐establish. Further research is needed to determine how to maintain and enhance native plant dominance after control, and to determine how to manage Grey Willow in fen areas where the Grey Willow canopy is discontinuous and nontarget herbicide impacts can occur. The aerial boom‐spray application of triclopyr (amine) for large‐scale Grey Willow control should be discontinued as it does not provide effective control and results in negative ecological outcomes. [ABSTRACT FROM AUTHOR]

Aims Aerially applied glyphosate is an economic tool to deal with large areas of invasive plants. However, there are few studies investigating non-target effects or rates of reinvasion, particularly over multi-year time frames. The aims were to evaluate the effectiveness of aerial application of glyphosate for control of dense stands of the invasive grey willow Salix cinerea, and determine the vegetation trajectory over the subsequent 2 yr. Location Whangamarino Wetland, Waikato, New Zealand. Methods A before-after control-impact ( BACI) experiment was conducted in a Ramsar-listed wetland in New Zealand. Effects on S. cinerea cover, canopy light interception and non-target damage were monitored over a 7.1 ha experimental area prior to, and for 2 yr following, aerial application of glyphosate. Vegetation classification, ordination and species richness analyses were undertaken to describe community-level effects. Results Aerial application of glyphosate to an established willow canopy was effective in reducing cover to <5% on average for up to 2 yr post-spray when assessed using 100 m2 vegetation survey plots. Smaller 1 m2 plots were more sensitive for detecting willow reinvasion, which was noted from 1 yr post-spray. Collateral damage to non-target sub-canopy species was generally minimal, except for the native tree fern Dicksonia squarrosa, which showed marked reductions in cover and no recovery over the study period. Species richness was higher in sprayed plots post-spray and a shift towards a native Carex-dominated sedgeland community was detected. Conclusions Aerial application of glyphosate to a dense canopy of mature willow was effective in reducing the cover and dominance of this invasive wetland tree species. Minimal collateral damage occurred, facilitating recovery and expansion of a native sedgeland community. The risk of secondary invasion did not eventuate, although exotic species richness spiked in the year following spraying. Sedgelands are susceptible to willow reinvasion via seed, so longer-term trajectories will diverge depending on management intensity. Using currently available tools, the management options are either repeated cycles of herbicide application to redirect the trajectory from reinvasion to short-statured sedgelands, or intensive initial management to establish an alternative, more resilient trajectory to native wetland forest. [ABSTRACT FROM AUTHOR]

Grey willow (Salix cinerea) is widely established in New Zealand's remaining swamps and fens, and in many areas has replaced endemic kahikatea (Dacrycarpus dacrydioides) forest. Conservation managers need to know how to restore willow-invaded wetlands to a resilient natural state, but knowledge on how to achieve this goal is limited. We planted kahikatea seedlings into an intact stand of grey willow and into areas where the herbicides glyphosate or triclopyr had been aerially applied to control willow ~1.5 years earlier. We measured canopy cover, light availability and the growth of planted kahikatea. In areas treated with glyphosate, grey willow canopy cover was reduced to 44% ± 3.7% (95% confidence interval), light availability increased to 64% ± 15% of full sunlight, and kahikatea grew an average of 44 cm ± 11.7 cm in 14 months. In contrast, there was little or no kahikatea growth under the intact willow canopy or in the triclopyr treatment area where grey willow canopy cover remained high and mean light availability was low (25% ± 4% of full sunlight). We conclude that the removal of the grey willow canopy through aerial glyphosate application created favourable conditions for the growth of planted kahikatea and may enable the restoration of kahikatea forest in wetlands dominated by grey willow. [ABSTRACT FROM AUTHOR]

We investigated the potential of airborne laser scanning ( ALS) for mapping the stand architecture of Grey Willow ( Salix cinerea), an invasive wetland weed in New Zealand. In particular, we focused on two metrics, tree height and canopy density, both of which influence the efficacy and nontarget impacts of herbicides aerially broadcast by helicopter to control tree weeds. We compared ground-based measures of Grey Willow height and canopy density with ALS-derived data, and the relationship between canopy density as estimated by each method and aerial herbicide deposition at three wetland sites in New Zealand. Analysis revealed strong linear relationships between ground-based and ALS metrics, indicating that ALS data could be used to generate accurate, high-resolution digital maps of Grey Willow height and canopy density. These maps coupled with computer-guided variable flow rate technologies, which enable optimal placement of herbicide, could maximise Grey Willow mortality while reducing the mortality of nontarget indigenous plants. We recommend the application of ALS-derived maps and computer-guided variable flow rate technology is investigated for more targeted large-scale tree weed control. [ABSTRACT FROM AUTHOR]

Natural leaf litter inputs is one factor that may help to minimize the likelihood of excessive algal growth. We tested the allelopathic effect of the grey willow ( Salix atronicerea ) on two phytoplankton species: Planktothrix agardhii (toxic and non-toxic cyanobacterial strains) and Scenedesmus communis (a chlorophyte). Effect was evaluated by combining leaf extracts and pulse amplitude modulation (PAM) chlorophyll fluorescence yield to measure photosynthetic activity responses. Phototrophic growth of the cyanobacterial species was suppressed even at very low concentrations of the extract while growth of the chlorophyte species was not affected. In the two cyanobacteria strains, inhibition of the chlorophyll fluorescence yields was significantly higher in the microcystin-free strain. Polyphenols are suspected to cause oxidative damage to cyanobacteria and thereby induce selective growth inhibition, similarly to hydrogen peroxide treatments against harmful cyanobacteria. Our results evidence willow extract or exudate as a promising agent selectively affecting cyanobacterial growth, but further studies are needed to determine the environmental impact and the inhibiting process. [ABSTRACT FROM AUTHOR]

The use of herbicides to control weeds, particularly large invasions, has now become an essential management tool in many ecological restoration projects. The herbicide glyphosate is routinely used to control the invasive weed, Grey Willow ( Salix cinerea), within New Zealand wetlands. However, little is known about the effects of glyphosate on invertebrates. We determine the short-term effects of glyphosate on the abundance and composition of the nontarget canopy invertebrate community in wetlands invaded by Grey Willow in New Zealand. Initially, the application of glyphosate and a surfactant showed no detectable effect on the canopy invertebrates examined in this study. However, 27 days after herbicide application, significant Grey Willow canopy loss caused dramatic decreases in the abundance of invertebrates in the glyphosate-treated plots compared with the unsprayed plots. Invertebrates appeared to be sensitive to changes in vegetation structure, such as canopy loss. These results agree with previous studies that have shown that the negative impacts of glyphosate on invertebrate communities are related to indirect effects via habitat modification as the herbicide-treated vegetation dies. From a terrestrial invertebrate perspective, this study suggests that the use of glyphosate herbicide is suitable for the control of invasive weeds within wetland restoration projects as it appears to have negligible impact on the canopy invertebrate assemblage. [ABSTRACT FROM AUTHOR]

Non-native invasive plants are a significant threat to native biodiversity as they change community structure and ecosystem processes and it is becoming imperative that these invasive plants are controlled. We investigated the response of wetland invertebrates to glyphosate chemical control of an introduced tree, grey willow ( Salix cinerea), in a before-after-control-impact (BACI) experiment within a New Zealand wetland. Our findings suggest that control of grey willow resulted in significant increases in the abundance of invertebrates within 2 years after herbicide application. Analysis of beetle communities revealed that the abundance and species richness of herbivorous and predacious beetles, the abundance of introduced species, and the species richness of native and introduced species were all significantly higher in the herbicide-treated plots than in the unsprayed plots. The composition of the beetle community separated into two clear groups-plots before spray/no spray and plots 1 and 2 years after herbicide application. We suggest that the beetle compositional changes were driven by complex changes in vegetation associated with the canopy collapse of grey willow trees and the initial influx of introduced plant species, predominantly weedy annuals and perennials, after willow control. Restoration via invasive plant control can promote the reestablishment of invertebrate communities typical of native wetlands, but their long-term sustainability is contingent on prevention of grey willow reinvasion and reestablishment of the native plant habitat. [ABSTRACT FROM AUTHOR]

Variation in population size over time can influence our ability to identify landscape-moderated differences in community assembly. To date, however, most studies at the landscape scale only cover snapshots in time, thereby overlooking the temporal dynamics of populations and communities. In this paper, we present data that illustrate how temporal variation in population density at a regional scale can influence landscape-moderated variation in recolonization and population buildup in disturbed habitat patches. Four common insect species, two omnivores and two herbivores, were monitored over 8 years in 10 willow short-rotation coppice bio-energy stands with a four-year disturbance regime (coppice cycle). The population densities in these regularly disturbed stands were compared to densities in 17 undisturbed natural Salix cinerea (grey willow) stands in the same region. A time series approach was used, utilizing the natural variation between years to statistically model recolonization as a function of landscape composition under two different levels of regional density. Landscape composition, i.e. relative amount of forest vs. open agricultural habitats, largely determined the density of re-colonizing populations following willow coppicing in three of the four species. However, the impact of landscape composition was not detectable in years with low regional density. Our results illustrate that landscape-moderated recolonization can change over time and that considering the temporal dynamics of populations may be crucial when designing and evaluating studies at landscape level. [ABSTRACT FROM AUTHOR]

Abstract: Tidal wetlands experience salt intrusion due to the effects of climate change. This study clarifies that the European flood plain willows species Salix alba and Salix viminalis tolerate oligohaline conditions. Salix alba L. and Salix viminalis L. are distributed on flood plains up to transitional waters of the oligohaline to the mesohaline estuarine stretch in temperate climates. They experience spatial and temporal variations in flooding and salinity. In the past, willows dominated the vegetation above the mean high water line, attenuated waves and contributed to sedimentation. In recent centuries, human utilization reduced willow stands. Today, the Elbe estuary – a model system for an estuary in temperate zones – exhibits increasing flooding and salinity due to man-induced effects and climatic changes. Willows were described as having no salinity tolerance. In contrast, our soil water salinity measurements at willows in tidal wetlands prove that mature Salix individuals tolerate oligohaline conditions. To assess immature plant salinity tolerance, we conducted a hydroponic greenhouse experiment. Vegetative propagules originating from a freshwater and an oligohaline site were treated in four salinities. Related to growth rates and biomass production, we found interspecific similarities and a salinity tolerance up to salinity 2. Vitality and chlorophyll fluorescence indicated an acclimation of Salix viminalis to oligohaline conditions. We conclude, that the survival of S. alba and S. viminalis and the restoration of willow stands in estuarine flood plains – with regard to wave attenuation and sedimentation – might be possible, despite increasing salinity in times of climate change. [Copyright &y& Elsevier]

Structured decision making and value-of-information analyses can be used to identify robust management strategies even when uncertainty about the response of the system to management is high. We used these methods in a case study of management of the non-native invasive species gray sallow willow (Salix cinerea ) in alpine Australia. Establishment of this species is facilitated by wildfire. Managers are charged with developing a management strategy despite extensive uncertainty regarding the frequency of fires, the willow's demography, and the effectiveness of management actions. We worked with managers in Victoria to conduct a formal decision analysis. We used a dynamic model to identify the best management strategy for a range of budgets. We evaluated the robustness of the strategies to uncertainty with value-of-information analyses. Results of the value-of-information analysis indicated that reducing uncertainty would not change which management strategy was identified as the best unless budgets increased substantially. This outcome suggests there would be little value in implementing adaptive management for the problem we analyzed. The value-of-information analyses also highlighted that the main driver of gray sallow willow invasion (i.e., fire frequency) is not necessarily the same factor that is most important for decision making (i.e., willow seed dispersal distance). Value of-information analyses enables managers to better target monitoring and research efforts toward factors critical to making the decision and to assess the need for adaptive management. [ABSTRACT FROM AUTHOR]

We investigated the effects of invasion by introduced grey willow (Salix cinerea) on beetle communities within four wetland vegetation types: native vegetation, native vegetation following grey willow removal, native vegetation undergoing grey willow invasion and dense grey willow-dominated vegetation. In total, 1505 beetles from 90 species were collected using modified Malaise traps. Native wetland vegetation had significantly lower beetle species richness than willow-dominated vegetation and was dominated by herbivores, whereas detritivores characterised willow-dominated vegetation. Beetle abundance was highest in the willow-dominated vegetation and mostly comprised detritivores. In contrast, beetle abundance was lowest in native wetland vegetation, but had even proportions of herbivores and detritivores. Native wetland vegetation had a high proportion of native beetles present. As grey willows invaded, introduced beetles became more common. The beetle community composition differed significantly between grey willow-dominated vegetation and native wetland vegetation. These compositional differences were mainly due to the increasing complexity of vegetation structure following grey willow invasion. The beetle communities within restored native wetland vegetation were most similar to those within the native wetland vegetation. From a conservation perspective, these results are encouraging and suggest that, although grey willows dramatically alter the composition of beetle communities present, these communities can be restored to a beetle fauna that is similar to those found within native wetland through the removal of the willows. [ABSTRACT FROM AUTHOR]

To investigate the effect of water temperature on gamete maturation and gamete quality, European grayling ( Thymalus thymallus) were held under different temperature regimes prior to spawning. Maturation of males and females and their gamete quality depended strongly on temperature regime. The highest percentages of maturing fish and highest gamete quality were obtained under a creek water temperature regime with natural seasonal fluctuations. In warmed creek water (3-4°C), at a constant temperature of 8-9°C, and under an abruptly increasing temperature, regime maturation rates and gamete quality were reduced. The effect was more pronounced in females than in males. The spawning dates of different wild Austrian grayling populations were also correlated with water temperature data collected during the last 10-15 years. The mean spawning date expressed as the number of days from 21 December until spawning ranged from 98 to 111 days for lower elevation populations, while it was considerably delayed for an alpine population. All populations spawned at water temperatures of 5.5-7.2°C. Regression analysis indicated that spawning date correlated with (1) the overall mean water temperature from 21 December until spawning, (2) the mean water temperature during both the last 10 days and 15 days before spawning, and (3) the difference between mean January temperature and that of the last 15 days before spawning. The regression functions indicate that an increase in water temperature from 21 December to spawning of 1°C advances spawning by 5½ days, and an increase of 1°C in the last 10-15 days advances spawning by 3½ days. [ABSTRACT FROM AUTHOR]

Background: The structure and diversity of grayling (Thymallus thymallus) populations have been well studied in most of its native habitat; however the southernmost populations of the Balkan Peninsula remain largely unexplored. The purpose of this study was to assess the genetic diversity of Serbian grayling populations, detect the impact of stocking and provide guidelines for conservation and management. Methods: Eighty grayling individuals were collected from four rivers (Ibar, Lim, Drina and Rzav). The mitochondrial DNA control region (CR; 595 bp of the 3'end and 74 bp of flanking tRNA) and the ATP6 gene (630 bp fragment) were sequenced for 20 individuals (five from each locality). In addition, all individuals were genotyped with 12 microsatellite loci. The diversity and structure of the populations as well as the recent and ancient population declines were studied using specialized software. Results: We detected three new haplotypes in the mtDNA CR and four haplotypes in the ATP6 gene of which three had not been described before. Previously, one CR haplotype and two ATP6 gene haplotypes had been identified as allochthonous, originating from Slovenia. Reconstruction of phylogenetic relations placed the remaining two CR haplotypes from the River Danube drainage of Serbia into a new clade, which is related to the previously described sister Slovenian clade. These two clades form a new Balkan clade. Microsatellite marker analysis showed that all four populations are genetically distinct from each other without any sign of intrapopulation structure, although stocking of the most diverse population (Drina River) was confirmed by mtDNA analysis. Recent and historical population declines of Serbian grayling do not differ from those of other European populations. Conclusions: Our study shows that (1) the Ibar, Lim and Drina Rivers grayling populations are genetically distinct from populations outside of Serbia and thus should be managed as native populations in spite of some introgression in the Drina River population and (2) the Rzav River population is not appropriate for further stocking activities since it originates from stocked Slovenian grayling. However, the Rzav River population does not represent an immediate danger to other populations because it is physically isolated from these. [ABSTRACT FROM AUTHOR]

Soil amendments previously shown to be effective in reducing metal bioavailability and/or mobility in calcareous metal-polluted soils were tested on a calcareous dredged sediment-derived soil with 26 mg Cd/kg dry soil, 2200 mg Cr/kg dry soil, 220 mg Pb/kg dry soil, and 3000 mg Zn/kg dry soil. The amendments were 5% modified aluminosilicate (AS), 10% w/w lignin, 1% w/w diammonium phosphate (DAP, (NH4)2HPO4), 1% w/w MnO, and 5% w/w CaSO4. In an additional treatment, the contaminated soil was submerged. Endpoints were metal uptake in Salix cinerea and Lumbricus terrestris, and effect on oxidation–reduction potential (ORP) in submerged soils. Results illustrated that the selected soil amendments were not effective in reducing ecological risk to vegetation or soil inhabiting invertebrates, as metal uptake in willows and earthworms did not significantly decrease following their application. Flooding the polluted soil resulted in metal uptake in S. cinerea comparable with concentrations for an uncontaminated soil. [Copyright &y& Elsevier]

1. The possible effect of juvenile imprinting or ‘chemical legacy’ on the subsequent oviposition – often called the ‘Hopkins’ host selection principle’– has been a controversial but recurrent theme in the literature on host-plant preference. While it appears possible in principle, experimental support for the hypothesis is equivocal. The present study points out that it is also important to consider its theoretical implications, and asks under what circumstances, if any, it should be favoured by natural selection. 2. Following this reasoning, it is predicted that host preference in the polyphagous butterfly Polygonia c-album L. (Lepidoptera, Nymphalidae) should not be influenced by larval environment. This was tested by rearing larvae on three natural host plants: the high-ranked Urtica dioica and the medium-ranked Salix cinerea and Ribes uva-crispa, and exposing the naive females to oviposition choices involving the same set of plants. 3. It was found that larval host plant had no effect on oviposition decisions of the adult female. Hence, the Hopkins’ host selection principle does not seem to be applicable in this species. 4. Based on recent insights on how accuracy of environmental versus genetic information should affect the control of developmental switches, the conditions that could favour the use of juvenile cues in oviposition decisions are discussed. Although the Hopkins’ host selection hypothesis cannot be completely ruled out, we argue that the circumstances required for it to be adaptive are so specific that it should not be invoked as a general hypothesis for host selection in plant-feeding insects. [ABSTRACT FROM AUTHOR]

Climatic warming is associated with organisms breeding earlier in the season than is typical for their species. In some species, however, response to warming is more complex than a simple advance in the timing of all life history events preceding reproduction. Disparities in the extent to which different components of the reproductive phenology of organisms vary with climatic warming indicate that not all life history events are equally responsive to environmental variation. Here, we propose that our understanding of phenological response to climate change can be improved by considering entire sequences of events comprising the aggregate life histories of organisms, preceding reproduction. We present results of a two-year warming experiment conducted on 33 individuals of three plant species inhabiting a low-arctic site. Analysis of phenological sequences of three key events for each species revealed how the aggregate life histories preceding reproduction responded to warming, and which individual events exerted the greatest influence on aggregate life history variation. For alpine chickweed (Cerastium alpinum), warming elicited a shortening of the duration of the emergence stage by 2.5 days on average, but the aggregate life history did not differ between warmed and ambient plots. For gray willow (Salix glauca), however, all phenological events monitored occurred earlier on warmed than on ambient plots, and warming reduced the aggregate life history of this species by 22 days on average. Similarly, in dwarf birch (Betula nana), warming advanced flower bud set, blooming, and fruit set and reduced the aggregate life history by 27 days on average. Our approach provides important insight into life history responses of many organisms to climate change and other forms of environmental variation. Such insight may be compromised by considering changes in individual phenological events in isolation. [ABSTRACT FROM AUTHOR]

Metal concentration of plants growing on contaminated soils among other factors may depend on changes in the hydrological regime of the soil. Foliar and stem metal concentrations in Salix cinerea (grey sallow) were measured in 2 consecutive growing seasons on a submerged sediment-derived soil that underwent gradual terrestrialisation. Foliar and stem cutting concentrations for Cd, Zn and Mn increased on plots that were submerged during the first year, but emerged in the second year of monitoring. The litter layer was sampled under the shrubs of a plot with a recent abrupt change in hydrological regime and on the reference plot. It was separated in three size fractions through sieving. Analysis of the litter fractions suggested that Cd and Zn concentrations remained constant during fragmentation. However, Cr, Cu, Ni and Pb concentrations increased, which was attributed to adhesion of mineral soil particles on the fine fraction. After correction for the metal content in the mineral fraction, an increase in Cd, Mn and Cu concentration during fragmentation of the organic part of the litter layer was observed for the polluted plot. Net litter layer decomposition rate was low, which may indicate low colonisation by the decomposing community. Terrestrialisation resulted in higher Cd, Mn and Zn uptake by willows. The deviant litter layer metal concentrations for Cd, Zn and Mn and low decomposition rate must be further monitored. Feasibility of measures aiming at re-establishing wetland conditions for the dredged sediment landfill must be considered. [Copyright &y& Elsevier]

The Holocene environmental history of the eastern slope of the Polar Ural Mountains has been reconstructed using pollen, spores, algae and other microfossils from the Chernaya Gorka palsa section (67°05′N, 65°21′E, 170 m a.s.l.). An initial oligotrophic lake was formed at the study site c. 9800–9500 14C yr BP. Although tundra communities dominated the vegetation in the area, birch and larch trees might have grown at lower elevations. Dry and disturbed soil habitats also occurred around the lake. Algae (mostly Pediastrum and Botryococcus) started to expand in the lake as climate gradually improved after c. 9500 14C yr BP. However, the role of mosses (mostly Calliergon and Drepanocladus) was most important for the infilling of the lake basin. Increased temperatures and subsequent improvement of hydrological conditions resulted in vegetation changes: stands of willows developed rapidly and the role of tree birch in the local vegetation increased. The lake was completely filled at c. 8600 14C yr BP. Peat accumulation started with Bryales mosses and, later, Sphagnum became dominant. Stands of Larix, Picea and Betula became well developed during the Boreal climate optimum. Tree birch began to spread into the tundra. Different Bryales mosses formed peat c. 8000–6500 14C yr BP. Cyperaceae later became the main peat-forming element. Dense spruce canopies with Larix sibirica and Betula pubescens surrounded the study site during the Atlantic period, pointing to the warmest climate during the Holocene. Summer temperatures might have been up to 3–4°C higher than today. However, a decline of spruce and an increase of birch around 6700–6300 14C yr BP may reflect some climate deterioration. There are no dated deposits younger than 6000 14C yr BP. It is assumed that Subboreal climate deterioration resulted in the development of permafrost and formation of the palsa at the site. The deposits, now protruding above the surrounding terrain, were eroded by wind, water and cryogenic processes. [ABSTRACT FROM AUTHOR]

Willows ( Salix spp.) are Weeds of National Significance in Australia where a large number of taxa are naturalised in temperate regions and can cause serious environmental degradation of riparian and wetland habitats. Several species are of economic or ornamental value and conflicts of interest could arise with planning their suppression. Biological control of six willow species ( S. alba L., S. cinerea L ., S. fragilis L., S. nigra Marshall, S. viminalis L., S. x rubens Schrank) is under consideration in Australia using three approaches based on targeting different morphological structures. A rich phytophagous biota associated with Salix in their regions of origin indicate a range of organisms are available for development as biological control agents. Implementation strategies will depend on the host species targeted for biological control, their reproductive strategies, the level of control required to reduce environmental impacts and the level of conflict of interest associated with a biological control program. [ABSTRACT FROM AUTHOR]

Plant characteristics, such as leaf structure or hairiness, are important for the movement and attachment of insects. It has been suggested that increased trichome density on newSalix cinerea L.(Salicaceae) leaves, produced after grazing by the willow leaf beetlePhratora vulgatissima L.(Coleoptera: Chrysomelidae), function as an inducible defence against the beetle and especially its larvae. Here we studied whether and how two of the main natural enemies ofP. vulgatissima, viz.,Anthocoris nemorum L.(Heteroptera: Anthocoridae) andOrtothylus marginalis L.(Heteroptera: Miridae), were influenced by trichome density onS. cinerealeaves. The effect of trichome density on these two predators was studied on plants with different trichome densities, comparing natural enemy efficiency, measured as number ofP. vulgatissimaeggs consumed or larvae missing and/or killed. To obtain different trichome densities, cuttings of several different clones ofS. cinereawere used. In the experiment using eggs as prey, an increase in trichome density was, in addition, induced through leaf beetle defoliation on half of the plants of each willow clone. Furthermore, a field study was performed to investigate whether trichome density was correlated with natural enemy abundance. The results indicate that neither the efficiency of these two natural enemies in the greenhouse, nor their abundance in the field was influenced by trichome density. A well-known behavioural difference between the two predator species could probably account for the higher disappearance of larvae after exposure to the more active predator. These findings are relevant for the development of pest management programs, not least because the enemies are polyphagous predators. It is concluded that an induced increase in leaf hairiness in willows in response to leaf beetle grazing could be a plant resistance trait worthy of further study in this system, because no negative effects on the main natural enemies were observed. [ABSTRACT FROM AUTHOR]

Abstract: Several authors suggest that a hydrological regime aiming at wetland creation is a potential management option that favours reducing bioavailability for metal-contaminated sites. The hydrological conditions on a site constitute one of the many factors that may affect the availability of potentially toxic trace metals for uptake by plants. Bioavailability of Cd, Mn and Zn on a contaminated dredged sediment landfill (DSL) with variable duration of submersion was evaluated by measuring metal concentrations in the wetland plant species Salix cinerea in field conditions. Longer submersion periods in the field caused lower Cd and Zn concentrations in the leaves in the first weeks of the growing season. Foliar Cd and Zn concentrations at the end of the growing season were highest on the initially flooded plot that emerged early in the growing season. Foliar Zn concentrations were also high at a sandy-textured oxic plot with low soil metal concentrations. Zn uptake in the leaves was markedly slower than Cd uptake for trees growing on soils with prolonged waterlogging during the growing season, pointing at a different availability. Zn availability was lowest when soil was submerged, but metal transfer from stems and twigs to leaves may mask the lower availability of Cd in submerged soils. Especially for Cd, a transfer effect from one growing season to the next season was observed: oxic conditions at the end of the previous growing season seem to determine at least partly the foliar concentrations for S. cinerea through this metal transfer mechanism. Duration of the submersion period is a key factor for bioavailability inasmuch as initially submerged soils emerging only in the second half of the growing season resulted in elevated Cd and Zn foliar concentrations at that time. [Copyright &y& Elsevier]

Woodland colonization on wetlands is considered to have a detrimental effect on their ecological value, even though detailed analysis of this process is lacking. This paper provides an evaluation of the ecological changes resulting from succession of poor fen (base-poor mire) to willow wet woodland on Goss Moor NNR in Cornwall, UK. Different ages of willow carr were associated with eight understorey communities. During willow colonization, in the ground flora, there was a progressive decrease in poor fen species and an associated increase in woodland species, which appeared to be related to an increase in canopy cover and therefore shade. The most diverse community was found to be the most recent willow and was dominated by poor fen species. The oldest willow was the second most diverse and was associated with a reduction in poor fen species and an increase in woodland species. Architectural features were used successfully to assess the general condition and structure of willow. Tree height and DBH were identified as useful parameters to accurately assess willow age in the field. The implications of active intervention to remove willow in order to conserve the full range of communities within the hydrosere are discussed. [ABSTRACT FROM AUTHOR]

Induced increases in trichome density to grazing by herbivores have been suggested to increase plant resistance to future herbivore attack. In this paper we present results which show that plants of Salix cinerea L. respond to adult leaf beetle (Phratora vulgatissima L.) grazing by developing new leaves with an increased trichome density. The same plants are usually attacked again later in the season when the next generation of larvae hatches on the plants. The effect of the induced response was studied by comparing larval growth and feeding on newly developed leaves of plants exposed to different defoliation treatments. Larvae on plants previously exposed to adult grazing consumed less total leaf area and showed more dispersed feeding than larvae on plants protected from previous grazing. Larvae on plants exposed to mechanical defoliation responded intermediately. These results corresponded to the increased trichome density of defoliated plants. However, we found this larval response only in whole plant tests – when reared on single, excised leaves in petri dishes, larvae in all treatments behaved similarly. This discrepancy between the on-plant experiment and that in petri dishes highlights how experimental design may alter the conclusion of a study. We suggest that the induced response to adult grazing may act as a defence against subsequent larval feeding. [ABSTRACT FROM AUTHOR]

The attack by the bud-galling sawfly, Euura mucronata, on its willow host was simulated by removing every other living bud from previous year's shoots in a natural stand of Salix cinerea. The impact of simulated attack on the growth of the willow and the subsequent attack by E. mucronata was estimated after one growing season. Experimental bud-killing resulted in a growth reaction in S. cinerea characterized by significant increase in the length of new shoots produced by the remaining buds Also the number of buds and E. mucronata galls per shoot were significantly higher on bud-removal branches as compared with control branches. The overall survival of E. mucronata larvae was better on long shoots than on short shoots. The result shows that sawfly attack increases the amount of high quality resources for the subsequent generation of the same sawfly as predicted by "resource regulation hypothesis". We conclude that these highly specialized insect herbivores have adapted to utilize and lo maintain the willow's juvenile traits. Rapid regrowth of willows after damage may have originally arisen as an adaptation in response lo other, less specific pressures such as mammal browsing or snow and ice damage. [ABSTRACT FROM AUTHOR]

The impact of different concentrations of ambient CO2 on the stomatal density and index of Salix cinerea are investigated. Fossil leaves (AMS dated 9190 BP) and present-day material from the same site in south west Ireland are compared with nineteenth-century herbarium material from Ireland. Techniques for obtaining reliable counts of stomata and epidermal cells from hairy leaves with sunken stomata are reported. Stomatal density and index were both found to be inversely related to CO2 concentration. The data also demonstrate the higher intra-specific variability of stomatal density over stomatal index. Analysis of the data indicates that similar investigations should be confined to single sites. [ABSTRACT FROM PUBLISHER]

The bud-galling sawfly, Euura mucronata, attacked longer shoot length classes on its host, Salix cinerea, more frequently than shorter shoots. Shoot length accounted for 76 to 93 percent of the variance in number of galls per 100 shoots in three habitats: forest, watermeadow, and lakeside. The reasons for this pattern were addressed with studies on shoot length in relation to: 1. Number of resources (buds) per shoot; 2. Success in establishment of larvae in galls; 3. Gall size and resources per gall; and 4. Survival of larvae after establishment as influenced by plant resistance and natural enemy attack. The most important factors proved to be success in establishment of larvae, with percent of variance accounted for ranging from 57 to 77 percent in three of four sites where relationships were significant, and survival after establishment of larvae, with variance accounted for ranging from 40 to 54 percent in the same three sites. The pattern of survival was dictated by plant resistance and not by natural enemies. These two additive factors resulted in a general relationship across all sites of increasing emergence of fully developed larvae per cohort as shoot length increased, accounting for 78 percent of the variance. These adaptive advantages to attacking longer shoots are sufficient to account for the pattern of increased probability of shoots being attacked as they increase in length. [ABSTRACT FROM AUTHOR]

As ramets of the willow, Salix cinerea L. (Salicaceae) aged shoot length decreased in the six populations studied in S.E. Finland. Many traits correlated positively with shoot length: basal diameter, number of internodes, internode length, leaf size, and length of growing period. The bud-galling sawfly, Euura mucronata (Hartig) Man. (Churchill) (Hymenoptera: Tenthredinidae), responded positively to shoot length or correlated traits, and negatively to ramet age in three forest populations. This herbivore attacked the most vigorous plants in a population, and numbers of attacks declined as ramets aged and senesced. The generality of this kind of herbivore response to plant quality is emphasized. [ABSTRACT FROM AUTHOR]