Grey Willow Research Articles

Herbarium records in Arctic dwarf shrub dendrochronology: Methodological approach and perspectives

Our work aims to investigate whether herbaria resources can be used for the extension of Arctic dwarf shrub chronologies. The current use of herbaria reaches far beyond their initially aims; among the new applications, phenology observations and conservation biology can be mentioned. However, to this date, no studies on the use of herbarium specimens for dendrochronological research have been published. Examples of perennial plants from herbarium sheets that could potentially be used for such studies are dwarf shrubs, samples of which often consist of whole specimens, including the root system, the root collar and branches. Here, we present a protocol for the selection and processing of historical material. Based on the collections from Kew and Copenhagen, which are among of the largest herbaria with Arctic plants, a database of 25 areas from the Atlantic sector of the Arctic was created. Material from the following most common species was collected: grey willow (Salix glauca L.), polar willow (Salix polaris Wahlenb.), dwarf willow (Salix herbacea L.), net-leaved willow (Salix reticulata L.), arctic willow (Salix arctica Pall.), mountain avens (Dryas octopetala L.), dwarf birch (Betula nana L.). We present the preliminary results of a case study using historical samples of Salix arctica from the Thule (Qaanaaq) area, NW Greenland. Dwarf shrubs can commonly reach the age of 80–100 years or beyond, while herbaria resources may allow the extension of such series over the last centuries. Therewith, these resources may provide an excellent proxy data source on the changing natural environment beyond the northern and upper tree limits, where well-replicated proxy time-series remain sparse.

Characterization of ashes produced from different biomass fuels used in combustion systems in a pulp and paper industry towards its recycling

In the boilers of pulp mills the fuel blends used vary because they are essentially composed of residual forest biomass. Consequently, the physical-chemical properties of the produced ash streams can exhibit high temporal variability, making their proper management and recycling difficult. This study aims to characterize the ash from the incineration of biomass samples used as fuel in order to understand its influence on the properties of the generated ash fluxes. This can anticipate suitable blending procedures that minimize the variability of the ash characteristics. For this purpose, typical biomass samples (eucalyptus bark, treetops and knots, pine treetops, silver wattle, Sydney golden wattle, white poplar, and grey willow) were incinerated (at 550 and 825 °C) and the resulting ashes were characterized. The thermal behavior of the biomass was evaluated by TG/DTA and the generated ash content was determined. The particle size distribution (laser diffraction), morphology (SEM), mineralogy (XRD), and chemical composition (XRF) were other evaluated properties. From the results obtained it is concluded that the ashes cannot be used as raw materials for clinker production. However, they can be used in concrete and mortar formulations, as a cement substitute or as filler. The maximum incorporation amount depends on the type of biomass used, ranging from 54 wt% for pine treetops to 100 wt% for eucalyptus bark. This knowledge is fundamental to understand how to optimize the biomass blends used in industrial combustion systems to obtain ashes with suitable properties to be used as secondary raw materials in building materials formulations.

Bacterial inoculant-assisted phytoremediation affects trace element uptake and metabolite content in Salix atrocinerea

Natural plant-associated microorganisms are of critical importance to plant growth and survival in field conditions under toxic concentrations of trace elements (TE) and these plant-microbial processes can be harnessed to enhance phytoremediation. The total bacterial diversity from grey willow (Salix atrocinerea) on a brownfield heavily-polluted with lead (Pb) and arsenic (As) was studied through pyrosequencing. Culturable bacteria were isolated and in vitro tested for plant growth-promotion (PGP) traits, arsenic (As) tolerance and impact on As speciation. Two of the most promising bacterial strains - the root endophyte Pantoea sp. AV62 and the rhizospheric strain Rhodococcus erythropolis AV96 - were inoculated in field to S. atrocinerea. This bioaugmentation resulted in higher As and Pb concentrations in both, roots and leaves of bacterial-inoculated plants as compared to non-inoculated plants. In consequence, bacterial bioaugmentation also affected parameters related to plant growth, oxidative stress, the levels of phytochelatins and phenylpropanoids, together with the differential expression of genes related to these tolerance mechanisms to TE in leaves. This study extends our understanding about plant-bacterial interactions and provides a solid basis for further bioaugmentation studies aiming to improve TE phytoremediation efficiency and predictability in the field.

RIPARIAN AND SWAMP FORESTS AND SCRUB OF THE PINÉ PLATEAU (TRENTINO, NORTHERN ITALY)

The riparian and swamp forests/scrub of black alder (Alnus glutinosa), white alder (Alnus incana), grey willow (Salix cinerea) and bay willow (S. pentandra) of the Piné Plateau (Trentino, central Alps) are described here in terms of their floristic composition. They are assigned to the following associations: Filipendulo vulgarisAlnetum glutinosae, Stellario nemorum-Alnetum glutinosae, Carici elongatae-Alnetum glutinosae, Carici elataeAlnetum glutinosae, Frangulo-Salicetum cinereae and Salicetum pentandro-cinereae. In addition, information regarding the distribution of the previous woody communities in the Trentino-Alto Adige Region and their corresponding vegetation series and geosigmeta are provided.

The Relative Effects of Willow Invasion, Willow Control and Hydrology on Wetland Zooplankton Assemblages

Few studies have examined zooplankton assemblages associated with grey willow (Salix cinerea) invasions in wetlands. Our aim was to quantitatively examine zooplankton composition among S. cinerea stands within the South Taupō Wetland, New Zealand, to determine whether these assemblages are affected by willow growth and willow control treatment using the herbicide metsulfuron (C14H15N5O6S). Alternatively, we examined whether wetland hydrology had an over-riding influence. Sampling was performed on three occasions (late-summer, mid-winter, and early-summer). Using Multidimensional Scaling and ANOSIM, we found no significant differences in zooplankton composition or environmental variables among native vegetation, live and dead S. cinerea sites, except for a difference in willow canopy density between late summer and winter. However, zooplankton composition differed on either side of a sand bar, suggesting areas separated by this barrier functioned independently. Overall, we found zooplankton communities to be regulated more by wetland hydrology than by willow presence. A limited willow effect was possibly due to the wetland being at an early stage of invasion, representing stand-alone individuals, with a continuous canopy not yet having formed. Alternatively, willows have lesser effects on invertebrates in wetlands than in streams. Ground control treatment of S. cinerea using metsulfuron had no apparent impact.

Trade-offs Between Wood and Leaf Production in Arctic Shrubs Along a Temperature and Moisture Gradient in West Greenland

Warming environmental conditions are often credited with increasing Arctic shrub growth and altering abundance and distribution, yet it is unclear whether tundra shrub expansion will continue into future decades. Water availability may begin to limit Arctic shrub growth if increasing air temperatures create drier soil conditions due to increased evapotranspiration and permafrost-thaw-induced soil drainage. However, few studies have effectively considered how dominant tundra shrub species respond to variations in both temperature and moisture. To better understand the key effects of temperature variation and soil moisture on two dominant circumpolar deciduous shrubs, we studied shrub growth along a natural landscape gradient in West Greenland, which is a region observed to be drying due to ongoing warming. We found that the growth forms of both grey willow (Salix glauca) and dwarf birch (Betula nana) were sensitive to warmer and drier conditions. For both species, increases in air temperature positively correlated with greater shrub volume, with the doubling of canopy volume due to increased woody biomass. Leaf biomass was best predicted by edaphic features including extractable ammonium, which was positively related to soil moisture, and bulk density. Warmer soils tended to be drier, suggesting that ongoing warming in the area could lead to significant water limitation. Our findings suggest that drier soil conditions might be limiting foliar production despite warming temperatures for two circumpolar dominant shrubs, Betula nana and Salix glauca, which could have wide-ranging, biome-level consequences about ongoing and predicted shrub growth and expansion.

Immediate and carry‐over effects of insect outbreaks on vegetation growth in West Greenland assessed from cells to satellite

AbstractAimTundra ecosystems are highly vulnerable to climate change, and climate–growth responses of Arctic shrubs are variable and altered by microsite environmental conditions and biotic factors. With warming and drought during the growing season, insect‐driven defoliation is expected to increase in frequency and severity with potential broad‐scale impacts on tundra ecosystem functioning. Here we provide the first broad‐scale reconstruction of spatio‐temporal dynamics of past insect outbreaks by assessing their effects on shrub growth along a typical Greenlandic fjord climate gradient from the inland ice to the sea.LocationNuuk Fjord (64°30′N/51°23′W) and adjacent areas, West Greenland.TaxaGreat brocade (Eurois occulta L.) and grey willow (Salix glauca L.).MethodsWe combined dendro‐anatomical and remote sensing analyses. Time series of ring width (RW) and wood‐anatomical traits were obtained from chronologies of >40 years established from 153 individuals of S. glauca collected at nine sites. We detected anomalies in satellite‐based Normalized Difference Vegetation Index (NDVI) related to defoliation and reconstructed past changes in photosynthetic activity across the region.ResultsWe identified outbreaks as distinctive years with reduced RW, cell‐wall thickness and vessel size, without being directly related to climate but matching with years of parallel reduction in NDVI. The two subsequent years after the defoliation showed a significant increase in RW. The reconstructed spatio‐temporal dynamics of these events indicate substantial regional variation in outbreak intensity linked to the climate variability across the fjord system.Main conclusionsOur results highlight the ability of S. glauca to cope with severe insect defoliation by changing carbon investment and xylem conductivity leading to high resilience and rapid recovery after the disturbance. Our multiproxy approach allows us to pinpoint biotic drivers of narrow ring formation and to provide new broad‐scale insight on the C‐budget and vegetation productivity of shrub communities in a widespread arctic ecosystem.

Proposal of new syntaxa and series of Grey Willow forests of humid dunes slacks of the North-Atlantic coasts of Europe

This article aims to point out the recent emergence of willows within the dune slacks of the Atlantic coasts following land abandonment. Firstly, a new association present in Brittany is examined: the Epipactido palustris – Salicetum atrocinereae ass. nova hoc loco with a detailed description about its physiognomic, floral, and ecological characteristics. Related dynamico-catenal trajectories that follow the expression of those forests are also described. This survey highlights an original littoral forest formation that could constitute the head of a vegetation series. Elements of reflection are proposed as for the conservation of the dune slacks woodlands and should allow the managers to refine their strategies. Secondly, the existence of a similar association along the coasts of the Channel and the North Sea is reported (Hydrocotylo vulgaris – Salicetum cinereae ass. nova). A new alliance (Carici flaccae – Salicion cinereae all. nova) is proposed in order to regroup these Northwest-European willow forests of the dune slacks and to clarify their synsystematic status.

The Characteristic Medicinal Plants of Different Vegetation Types from the Niraj Valley, Romania

Abstract In this study the medicinal plants of some representative vegetation types from a human-modified Eastern European landscapes were investigated. The studied territory is part of a Special Protection Area for bird species. The following sampling areas were included in the study: humid grasslands; mountain hay meadows; semi-natural dry grasslands; Sub-pannonic steppic grasslands; fringe communities of mesothermophilic forest edges; grey willow scrubs; thickets of willow; forests of white willow; hornbeam-beech, oak-hornbeam, and sessile oak forests; scrubs of blackthorn and hawthorn; Subcontinental peri-Pannonic scrubs. The ordering of medicinal plants on the basis of presence/absence data and the abundance data presented the grouping in the following typical communities: to the deciduous forests, to the coppices and scrubs, and to the grasslands and meadows. A total of 208 medicinal plants were found from which 37 species are included in the European Pharmacopoeia, and 13 in the Romanian Pharmacopoeia. The existing list of medicinal plants of the Niraj Valley in the scientific literature was completed with 33 taxa. The medicinal plants containing tannins (18.93%) were in higher percentage followed by those with essential oils (10.68%), flavonoids (10.68%), saponins (9.71%), alkaloids (7.77%), mucilages (6.80%), coumarins (5.34%). However rational (sustainable) exploitation of these natural resources is necessary.

Can aerial herbicide application control Grey Willow (Salix cinerea L.) and stimulate native plant recovery in New Zealand wetlands?

SummaryGrey 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.

Application of methyl jasmonate to grey willow (Salix cinerea) attracts insectivorous birds in nature

It has been suggested that insectivorous birds may be guided by herbivore-induced plant volatiles (HIPVs) to herbivore-rich trees with herbivorous damage. The HIPV production in plants is partly mediated by jasmonic acid signalling pathway. Methyl jasmonate (MeJA) was proved to be a suitable agent for induction of HIPVs similar to those induced by herbivorous insects in many plant species. We studied the effects of methyl jasmonate on volatile emission and natural enemy attraction using mature grey willow (Salix cinerea) under natural conditions in Czech Republic. We treated 12 experimental shrubs with 30 mM MeJA and completed the experiment with 12 control shrubs. We monitored attacks by natural predators with artificial plasticine caterpillars which were checked daily. Birds most often pecked the caterpillars exposed on MeJA-treated shrubs and this attractiveness differed significantly from control. Attractiveness of MeJA-treated shrubs did not differ significantly from control shrubs for arthropod predators. Spraying MeJA on grey willows resulted in significantly higher production of α-pinene, β-pinene, 3-carene, limonene and β-ocimene. There was a marginally significant positive correlation between the predation rate by birds and relative change in α-pinene emissions.

Glyphosate redirects wetland vegetation trajectory following willow invasion

AbstractAimsAerially 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.LocationWhangamarino Wetland, Waikato, New Zealand.MethodsA 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.ResultsAerial 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.ConclusionsAerial 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.

Mapping Grey Willow (Salix cinerea) stand architecture using airborne laser scanning: implications for large‐scale tree weed control

SummaryWe 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.

Aerial glyphosate application reduces grey willow (Salix cinerea) canopy cover, increases light availability, and stimulates kahikatea (Dacrycarpus dacrydioides) growth

Aerial glyphosate application reduces grey willow (Salix cinerea) canopy cover, increases light availability, and stimulates kahikatea (Dacrycarpus dacrydioides) growth

Impact of the European beaver (Castor fiber L.) population on the woody vegetation of Wigry National Park

Research on the impact of the European beaver population on the species composition of forest stands was conducted in Wigry National Park, situated in north-eastern Poland. The study was conducted in forest stands on a dystrophic lake of the ‘suchar’ type,� i.e. a dystrophic lake with high acidity and low species diversity of vegetation on its shores, on the banks of a river and a drainage ditch, and in a field environment. A ThermoPro TP8 thermal imaging camera with an uncooled microbolometer matrix of 384x288 pixels was used to confirm that the designated observation areas were inhabited by beavers. In each research area five transects four metres in width were established, where measurements were taken of five classes of trunk damage and two classes of trunk diameter. We examined the seasonal preferences of beavers in gnawing particular species of woody plants. An analysis was performed for each environment. The results indicate that after an average 15-year presence of beavers in the areas, which they inhabited rotationally, the percentage of healthy woody plants was 73.09%. Of the 17 species of woody plants, the ones most readily cut down by the beavers were grey willow (25.19%) and common hazel (32.36%). The analysis demonstrated that the rodents showed the greatest interest in plants with a trunk diameter of <10 cm (98.28%). The river and drainage ditch were the most exploited environments; here beavers cut down 40.27% and 42.70%, respectively, of the available woody plants.

Responses of invertebrates to herbicide in Salix cinerea invaded wetlands: Restoration implications

SummaryThe 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.

Selective growth inhibition of cyanobacteria species (Planktothrix agardhii) by a riparian tree leaf extract

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.

Biological characterization of aggregates clogging fishing nets on the Basque coastal waters of France

Over the past fifteen years, gillnets used by fishermen of the Basque coast of France have been seasonally covered with aggregates. By making the nets more visible, this disrupts the coastal fishing activity and sometimes causes skin allergies. In 2010, we deployed for the first time a fine mesh device which was immersed permanently and attached to the bottom off the Bay of Saint-Jean-de-Luz in order to collect samples of these aggregates throughout the summer period.The first results reported in this work deal with the origin and biology of organisms forming these aggregates, excluding biochemical and bacteriological aspects. A remarkable feature is the wide variety of both planktonic and benthic components in the collected matter. More than 111 taxonomic units have been so far identified. In addition to these elements of marine origin, these aggregates deposited on fishing nets also contain exogenous matter of continental origin, mainly Grey Willow Salix atrocinerea silk's seeds, mammals' hairs and pollen. In this work, particular attention is also given to the potentially irritating and stinging organisms present in the aggregates. Finally, hypotheses are developed about the aggregation process of these living organisms and their pelagic sedimentation induced by the presence of fishnets in the water column.

Invertebrate community turnover following control of an invasive weed

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.

Detectability of landscape effects on recolonization increases with regional population density.

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.