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Willow
Terms modified by Willow Selected AbstractsSeeing without being seen: a removal experiment with mixed flocks of Willow and Crested Tits Parus montanus and cristatusIBIS, Issue 4 2001INDRIK IS KRAMS This paper tests the hypothesis that foraging site selection reflects a trade-off between the various needs for concealment from predators, to find food, and for the individual to maintain some view of its surroundings. After removal of Crested Tits Parus cristatus (the dominant species in mixed flocks), Willow Tits P. montanus did not decrease their foraging heights as expected but remained in the most exposed parts of young pines. In contrast, after removal of Willow Tits, Crested Tits increased their foraging height from the sheltered lower canopy to sites previously occupied by Willow Tits. When flock size was reduced, the birds maintained the same high levels of vigilance without concealing themselves in dense vegetation. I suggest that flock members may benefit from foraging in sites that afford good anti-predator vigilance. [source] Water relations and gas exchange in poplar and willow under water stress and elevated atmospheric CO2PHYSIOLOGIA PLANTARUM, Issue 1 2002Jon D. Johnson Predictions of shifts in rainfall patterns as atmospheric [CO2] increases could impact the growth of fast growing trees such as Populus spp. and Salix spp. and the interaction between elevated CO2 and water stress in these species is unknown. The objectives of this study were to characterize the responses to elevated CO2 and water stress in these two species, and to determine if elevated CO2 mitigated drought stress effects. Gas exchange, water potential components, whole plant transpiration and growth response to soil drying and recovery were assessed in hybrid poplar (clone 53,246) and willow (Salix sagitta) rooted cuttings growing in either ambient (350 µmol mol,1) or elevated (700 µmol mol,1) atmospheric CO2 concentration ([CO2]). Predawn water potential decreased with increasing water stress while midday water potentials remained unchanged (isohydric response). Turgor potentials at both predawn and midday increased in elevated [CO2], indicative of osmotic adjustment. Gas exchange was reduced by water stress while elevated [CO2] increased photosynthetic rates, reduced leaf conductance and nearly doubled instantaneous transpiration efficiency in both species. Dark respiration decreased in elevated [CO2] and water stress reduced Rd in the trees growing in ambient [CO2]. Willow had 56% lower whole plant hydraulic conductivity than poplar, and showed a 14% increase in elevated [CO2] while poplar was unresponsive. The physiological responses exhibited by poplar and willow to elevated [CO2] and water stress, singly, suggest that these species respond like other tree species. The interaction of [CO2] and water stress suggests that elevated [CO2] did mitigate the effects of water stress in willow, but not in poplar. [source] Responses of Nondormant Black Willow (Salix nigra) Cuttings to Preplanting Soaking and Soil MoistureRESTORATION ECOLOGY, Issue 1 2005S. R. Pezeshki Abstract The use of willow cuttings for streambank stabilization is a common practice in riparian ecosystems throughout the United States. Many environmental factors govern the outcome of such planting. However, other factors such as preplanting treatments, planting methods, and physiological status of cuttings (dormant vs. actively growing) may also be crucial in determining the survival of willow cuttings. Actively growing (nondormant) Black willow (Salix nigra) cuttings, 30 cm in length and 1 cm in diameter at the base, were subjected to three soaking treatments (0, 7, and 15 days) prior to planting. Following the initial treatment, cuttings were grown in a greenhouse in pots under three soil moisture regimes (well-watered but not flooded, permanently flooded, and intermittently flooded). Plant gas exchange, growth, biomass, and survival were measured. Results demonstrated that soaking for 7 days was beneficial to early development of cuttings in the well-watered (control) soil moisture regime, enhancing percent bud flush and survival significantly. However, 15 days of soaking proved to be detrimental to survival of cuttings irrespective of soil moisture regimes. Results also demonstrated that the beneficial effects of 7-day soaking were limited to the well-watered soil moisture regime but not to the flooded or intermittently flooded regimes. Soaking nondormant cuttings may be worthwhile if the planting site is likely to present ample soil moisture but nonflooded conditions to the transplanted cuttings. [source] Willow (Salix spp.) and aspen (Populus tremula) regrowth after felling by the Eurasian beaver (Castor fiber): implications for riparian woodland conservation in ScotlandAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2009Kevin Jones Abstract 1.A proposed trial reintroduction of the Eurasian beaver (Castor fiber L.) to Scotland has recently been approved (May 2008). A previous proposal was turned down by the licensing authority, partly over the perceived risks to woodland within a Special Area of Conservation. 2.This paper presents data on two years of willow (Salix spp.) and aspen (Populus tremula L.) regrowth following tree felling by captive beavers within two large semi-natural enclosures in eastern Scotland. Both willow and aspen are highly preferred by beavers. 3.Regrowth of willow stems was quantified from cut stumps, felled logs and partially severed (,incompletely felled') trees, and compared with growth of stems in the canopies of untouched willows. 4.Maximum annual regrowth was observed in incompletely felled trees, followed by cut stumps and then unfelled control trees. Mean regrowth rates were ca 18 m regrowth per metre of measured tree section per year in incompletely felled trees. This was approximately 12 times more annual regrowth than that observed in unfelled trees, despite apparently selective browsing of the regrowth of incompletely felled trees by roe deer. 5.Although incompletely felled willows represent a relatively small component of felling activity (9% of all felled willow), they contribute disproportionately to the biomass of beaver-engineered riparian woodlands, creating a more multi-layered habitat structure. 6.Willow regrowth in inundated areas was avoided by deer, and harvesting of regrowth by beavers was rare. 7.Significant regrowth from 11 stumps of aspen in 2 years post-felling occurred by suckering, with 85 suckers of mean height 2.1 m being recorded, all of which were subsequently avoided by browsing deer and beavers. 8.These data suggest that rapid regeneration of willow and aspen will occur in riparian woodlands in the event of major felling activity by Eurasian beaver, even in the presence of low to moderate levels of roe deer browsing, and that the conservation status of both these trees or the wider habitats that they form would not be threatened by a well planned and managed reintroduction of beavers to Scotland. Copyright © 2008 John Wiley & Sons, Ltd. [source] Leaf beetle grazing does not induce willow trichome defence in the coppicing willow Salix viminalisAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 2 2004Peter Dalin Abstract 1,Willows are frequently attacked and defoliated by adult leaf beetles (Phratora vulgatissima L.) early in the season and the plants are then attacked again when new larvae emerge. The native willow Salix cinerea has previously been shown to respond to adult grazing by producing new leaves with an increased trichome density. Subsequent larval feeding was reduced on new leaves. This type of induced plant response may reduce insect damage and could potentially be utilized for plant protection in agricultural systems. 2,Here, we investigated if the willow species most commonly used for biomass production in short rotation coppice, Salix viminalis, also responds to adult beetle grazing by increasing trichome density. Larval performance and feeding behaviour on plants previously exposed to adult beetles was compared with that on undefoliated control plants in a greenhouse. 3,We found an overall decrease in trichome density within all the plants (i.e. trichome density was lower on new leaves compared to that for older basal leaves on S. viminalis). However, leaves of beetle defoliated plants had a higher trichome density compared to control plants. Larval growth and feeding was not affected by this difference between treatments. Larvae appeared to remove trichomes when feeding on S. viminalis, a behaviour that might explain the lack of difference between treatments. [source] Herbivores and pathogens on willow: do they affect each other?AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2003Matthias Simon Abstract 1,Willows often need to cope with attack by both rust fungi and herbivores. We studied whether rust infection on willow affects the herbivore, and vice versa, whether herbivore feeding affects the fungal infection. The system investigated by laboratory bioassays and greenhouse experiments consisted of the willow hybrid Salix × cuspidata, the rust Melampsora allii-fragilis and the willow leaf beetle Plagiodera versicolora. Effects were studied both on a local scale (rust infection and feeding on the same leaf) and systemically (rust infection and feeding on different, but adjacent leaves). 2,Rust infection was not affected by herbivore feeding on a local scale. Systemically, however, the willow's susceptibility towards rust infection was increased by herbivore feeding, as indicated by a higher number of rust sori on leaves adjacent to feeding-damaged leaves. The herbivore's performance was detrimentally affected by rust infection: increase of mortality (systemically), decrease of larval weight (locally and systemically) and prolonging of developmental time (locally and systemically). 3,Previous rust infection enhanced systemically the willow's susceptibility towards subsequent fungal infection. Previous herbivore feeding on the willow had no effects on the herbivore's developmental time and mortality. However, feeding upon previously feeding-damaged willow leaves significantly reduced larval weight. [source] Maple Trees and Weeping Willows: The Role of Time, Uncertainty, and Affinity in Intergenerational DecisionsNEGOTIATION AND CONFLICT MANAGEMENT RESEARCH, Issue 3 2008Kimberly A. Wade-Benzoni Abstract Some of the most important issues in business and society today involve a conflict of interest between present and future generations. In this article, I explore how resources are allocated across generations, articulate the role of psychological distance in intergenerational decisions, and develop the construct of intergenerational discounting. Intergenerational discounting is defined as the preference for smaller, highly probable benefits for oneself in the present to relatively larger but less certain benefits for others in the future. In three studies, I explore the role of three variables in intergenerational decisions, including time delay between decisions and their consequences, uncertainty about the future, and affinity with future generations. [source] Dendrogeomorphic reconstruction of past debris-flow activity using injured broad-leaved treesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2010Estelle Arbellay Abstract Tree-ring records from conifers have been regularly used over the last few decades to date debris-flow events. The reconstruction of past debris-flow activity was, in contrast, only very rarely based on growth anomalies in broad-leaved trees. Consequently, this study aimed at dating the occurrence of former debris flows from growth series of broad-leaved trees and at determining their suitability for dendrogeomorphic research. Results were obtained from gray alder (Alnus incana (L.) Moench), silver birch and pubescent birch (Betula pendula Roth and Betula pubescens Ehrh.), aspen (Populus tremula L.), white poplar, black poplar and gray poplar (Populus alba L., Populus nigra L. and Populus x canescens (Ait.) Sm.), goat willow (Salix caprea L.) and black elder (Sambucus nigra L.) injured by debris-flow activity at Illgraben (Valais, Swiss Alps). Tree-ring analysis of 104 increment cores, 118 wedges and 93 cross-sections from 154 injured broad-leaved trees allowed the reconstruction of 14 debris-flow events between AD 1965 and 2007. These events were compared with archival records on debris-flow activity at Illgraben. It appears that debris flows are very common at Illgraben, but only very rarely left the channel over the period AD 1965,2007. Furthermore, analysis of the spatial distribution of disturbed trees contributed to the identification of six patterns of debris-flow routing and led to the determination of preferential breakout locations of events. The results of this study demonstrate the high potential of broad-leaved trees for dendrogeomorphic research and for the assessment of the travel distance and lateral spread of debris-flow surges. Copyright © 2010 John Wiley & Sons, Ltd. [source] Dating floodplain sediments using tree-ring response to burial,EARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2005Jonathan M. Friedman Abstract Floodplain sediments can be dated precisely based on the change in anatomy of tree rings upon burial. When a stem of tamarisk (Tamarix ramosissima) or sandbar willow (Salix exigua) is buried, subsequent annual rings in the buried section resemble the rings of roots: rings become narrower, vessels within the rings become larger, and transitions between rings become less distinct. We combined observations of these changes with tree-ring counts to determine the year of deposition of sedimentary beds exposed in a 150-m-long trench across the floodplain of the Rio Puerco, a rapidly filling arroyo in New Mexico. This method reliably dated most beds thicker than about 30 cm to within a year of deposition. Floodplain aggradation rates varied dramatically through time and space. Sediment deposition was mostly limited to brief overbank flows occurring every few years. The most rapid deposition occurred on channel-margin levees, which migrated laterally during channel narrowing. At the decadal timescale, the cross-section-average sediment deposition rate was steady, but there was a shift in the spatial pattern of deposition in the 1980s. From 1936 to 1986, sediment deposition occurred by channel narrowing, with little change in elevation of the thalweg. After 1986 sediment deposition occurred by vertical aggradation. From 1936 to 2000 about 27 per cent of the arroyo cross-section filled with sediment. The rate of filling from 1962 to 2000 was 0·8 vertical m/decade or 85 m2/decade. Published in 2005 by John Wiley & Sons, Ltd. [source] Resistance and tolerance to herbivory in Salix cordata are affected by different environmental factorsECOLOGICAL ENTOMOLOGY, Issue 5 2005Kevin P. Macdonald Abstract., 1.,Effects of sand burial and nutrients on the ability of sand-dune willow (Salix cordata) to tolerate or resist herbivory by the beetle Altica subplicata were evaluated in field experiments. 2.,To assess tolerance, all combinations of sand burial (none, 50%), nutrients (presence, absence), and beetles (presence, absence) were applied to caged plants and growth responses to herbivory were measured. Sand burial increased plant growth rate, but decreased S. cordata's tolerance to herbivory. Although nutrients increased growth, tolerance to herbivory was unaffected. 3.,To assess resistance, plants were exposed to all combinations of sand burial and nutrients, and then to natural beetle colonisation. The presence of nutrients, but not sand burial, significantly increased the percentage of plants with beetles, for both adults and larvae. This decreased resistance to beetles of plants grown with added nutrients occurred only in the absence of sand burial. 4.,The performance and preference of beetles were examined in laboratory experiments. Larvae developed faster and had increased pupation success on plants with nutrients added. Beetles also showed a marginally significant feeding preference for leaves grown with added nutrients. Thus, S. cordata tolerance to herbivory was affected by sand burial, whereas resistance, preference, and performance were affected by nutrient level. [source] Structure of two macrolepidopteran assemblages on Salix nigra (Marsh) and Acer negundo L.: abundance, diversity, richness, and persistence of scarce speciesECOLOGICAL ENTOMOLOGY, Issue 4 2000Pedro Barbosa Summary 1. Most insect species occur at low abundance but a greater research effort has been devoted to so-called outbreak species and little research is available on scarce (low abundance) species that are typical of most insect species. 2. Larval free-feeding macrolepidoptera of two riparian trees Salix nigra (Marsh) (black willow) and Acer negundo L. (box elder) were sampled and sorted by species and abundance. 3. Data collected established that the majority of species in the assemblages in each tree species occurred at low abundance in each of the 5 years when larvae were sampled. 4. Species in the Noctuidae and Geometridae dominated both assemblages. 5. On both trees, assemblages were dominated numerically by relatively few species, a pattern that has been observed for insect assemblages on plants in managed and unmanaged habitats. [source] Species-specific differences in oak foliage affect preference and performance of gypsy moth caterpillarsENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2003L. K. Foss Abstract The gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), is an introduced defoliator that preferentially feeds on oaks, Quercus spp. (Fagaceae) in the north-eastern USA. As the gypsy moth expands its geographic range, the extensive oak component in forests and urban environments of the USA assure its successful establishment. Given their economic and ecological importance, and the gypsy moth's potential to cause mortality, we evaluated caterpillar preference and performance on various oaks prevalent in the central hardwoods region. Most of the physical and chemical characteristics we measured, from budbreak phenology to foliar chemistry, varied significantly among the oak species tested. Similarly, insect preference and performance varied significantly, though not always in predictable ways. Caterpillar preference was compared for black, Q. velutina Lamarck, burr, Q. macrocarpa Michaux, cherrybark, Q. pagoda Rafinesque, northern red, Q. rubra L., pin, Q. palustris Muenchhausen, swamp white, Q. bicolor Willdenow, white, Q. alba L., and willow, Q. phellos L., oaks. Gypsy moth preference was greatest for black and burr, and least for northern red, pin, and willow oaks. We assessed foliar characteristics and caterpillar performance on foliage from burr, cherrybark, northern red, pin, and willow oaks. Caterpillar preference did not always correlate with performance. Gypsy moth consumption and growth were highest, and development most rapid, on pin oak, which had high nitrogen and tannin levels, and was among the least preferred. Northern red and willow oaks were also among the least preferred and were the least suitable tested, producing caterpillars with moderate to low consumption and growth rates, as well as the longest development. Northern red oak contained the lowest foliar tannins; willow oak foliage was lowest in carbohydrates and nitrogen. Our results suggest that a combination of foliar characteristics may be responsible for gypsy moth preference and performance, and that an optimal combination of foliar components serves to maximize host suitability. These data will provide information useful for planning and managing urban forests in the presence of expanding gypsy moth populations. [source] Aryl hydrocarbon bioaccessibility to small mammals from arctic plants using in vitro techniquesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2007Sarah A. Armstrong Abstract Through their diet, herbivores inhabiting contaminated sites may be chronically exposed to a variety of aryl hydrocarbons (e.g., dioxins and polycyclic aromatic hydrocarbons [PAHs]). However, little is known about how differences in morphology and physiology among plant species alter the environmental accumulation of aryl hydrocarbons or their release and subsequent activity in the gastrointestinal tract of herbivores after ingestion. In the present study, the activity of aryl hydrocarbons during digestion was examined using six Arctic plant species growing in impacted and reference sites near Inuvik, Northwest Territories, Canada. The plant species studied were black spruce (Picea mariana), labrador tea (Ledum groenlandicum), bog birch (Betula glandulosa), green alder (Alnus crispa), water sedge (Carex aquatilis), and little-tree willow (Salix arbusculoides). Plants were digested using a simulator of the upper digestive tract, and aryl hydrocarbon release was evaluated using an aryl hydrocarbon-receptor assay. Bioaccessible aryl hydrocarbon activity varied among the plant species tested. The species with the greatest activity was green alder, and the species with the least activity was black spruce. Further investigation revealed that digested plant extracts may antagonize the aryl hydrocarbon receptor and prevent bioactivation of the aryl compound benzo[a]pyrene. Thus, PAH risk from the ingestion of vegetation varies among plant species and may depend on antagonists present in the vegetation. [source] Assessing impacts of large herbivores on shrubs: tests of scaling factors for utilization rates from shoot-level measurementsJOURNAL OF APPLIED ECOLOGY, Issue 1 2007DANIELLE M. BILYEU Summary 1Accurate methods for estimating the intensity of browsing by herbivores are fundamental to understanding the ecology of shrub communities. Quantifying browse utilization on shrubs at large scales is difficult because shrubs have complex, spatially variable growth forms. Most existing methods estimate browsing rate at the scale of linear current-year shoots or twigs. How such fine-scale estimates relate to the proportion of current-year growth consumed from whole plants or plots is often unknown. The relationship is likely to be complex because herbivores selectively browse more productive plants and plant parts. 2Using a clipping experiment designed to mimic elk Cervus elaphus browsing, we quantified how utilization estimates at the scale of individual current-year shoots of two willow species, Salix bebbiana and Salix geyeriana, relate to actual mass removed at the scale of rooted stems. Three approaches to scaling were examined: (i) taking an average, (ii) multiplying by the proportion of shoots clipped and (iii) multiplying by a novel scaling factor that weights utilization by productivity. To address how to scale-up from stems to plots, we applied the most accurate stem-level method to elk-browsed willow and compared plot-level estimates by two scaling approaches. 3In scaling from shoots to stems, the novel scaling factor was most successful and resulted in accurate estimates for up to c. 45% of current annual growth clipped. In scaling from the stem to the plot, elk preference for more productive stems caused a simple average of stem-level utilization to differ from a productivity-weighted average by 15%. 4Synthesis and applications. In order to reflect accurately the proportion of biomass consumed at a whole-plant level, fine-scale estimates of utilization should be weighted by an estimate of pre-browse productivity, as this is mathematically equivalent to summing pre-browse and post-browse mass before calculating the proportion consumed. In developing methods to estimate utilization at plot scales, an important consideration is the choice of sampling unit, which should be both amenable to unbiased sampling and tractable in terms of measuring productivity. [source] Interactive controls of herbivory and fluvial dynamics on landscape vegetation patterns on the Tanana River floodplain, interior AlaskaJOURNAL OF BIOGEOGRAPHY, Issue 9 2007Lem G. Butler Abstract Aim, We examined the interactive effects of mammalian herbivory and fluvial dynamics on vegetation dynamics and composition along the Tanana River in interior Alaska. Location, Model parameters were obtained from field studies along the Tanana River, Alaska between Fairbanks (64°50.50, N, 147°43.30, W) and Manley Hot Springs (65°0.0, N, 150°36.0, W). Methods, We used a spatially explicit model of landscape dynamics (ALFRESCO) to simulate vegetation changes on a 1-year time-step. The model was run for 250 years and was replicated 100 times. Results, Increases in herbivory decreased the proportion of early successional vegetation and increased the proportion of late successional vegetation on the simulated landscape. Erosion and accretion worked as antagonists to herbivory, increasing the amount of early successional vegetation and decreasing the amount of late successional vegetation. However, the interactive effects of herbivory and erosion/accretion were especially important in determining system response, particularly in early seral vegetation types. High erosion rates, when coupled with low herbivory, greatly increased the proportion of willow on the landscape. When coupled with high herbivory, however, they greatly increased the proportion of alder on the landscape. At low levels of herbivory, alder abundance peaked at intermediate levels of erosion/accretion. Main conclusions, Neither erosion/accretion nor herbivory produced consistent landscape patterns that could be predicted independently of the other. These findings underscore the importance of the interactive effects of biotic and abiotic disturbances in shaping large-scale landscape vegetation patterns in boreal floodplain ecosystems , systems traditionally thought to be driven primarily by abiotic disturbance alone. [source] Herbivores and pathogens on willow: do they affect each other?AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2003Matthias Simon Abstract 1,Willows often need to cope with attack by both rust fungi and herbivores. We studied whether rust infection on willow affects the herbivore, and vice versa, whether herbivore feeding affects the fungal infection. The system investigated by laboratory bioassays and greenhouse experiments consisted of the willow hybrid Salix × cuspidata, the rust Melampsora allii-fragilis and the willow leaf beetle Plagiodera versicolora. Effects were studied both on a local scale (rust infection and feeding on the same leaf) and systemically (rust infection and feeding on different, but adjacent leaves). 2,Rust infection was not affected by herbivore feeding on a local scale. Systemically, however, the willow's susceptibility towards rust infection was increased by herbivore feeding, as indicated by a higher number of rust sori on leaves adjacent to feeding-damaged leaves. The herbivore's performance was detrimentally affected by rust infection: increase of mortality (systemically), decrease of larval weight (locally and systemically) and prolonging of developmental time (locally and systemically). 3,Previous rust infection enhanced systemically the willow's susceptibility towards subsequent fungal infection. Previous herbivore feeding on the willow had no effects on the herbivore's developmental time and mortality. However, feeding upon previously feeding-damaged willow leaves significantly reduced larval weight. [source] Green Energy or Organic Food?: A Life-Cycle Assessment Comparing Two Uses of Set-Aside LandJOURNAL OF INDUSTRIAL ECOLOGY, Issue 3 2001Richard van den Broek Summary Bioenergy has a large worldwide potential in future climate change abatement, although its application may become limited by demands for land for other functions. The aim of this study was to make an environmental assessment of the use of energy crops in the Netherlands in a context that incorporates scarcity of land. A base case system was defined, consisting of conventional winter wheat production, set-aside land (1 hectare, together), and the production of coal-based electricity. Using life-cycle assessment, we compared this system with (1) a green energy system in which willow is cultivated on the set-aside land to replace the coal-based electricity and (2) an organic agriculture system in which the full hectare produces wheat under the Dutch EKO organic agriculture standard. In this way, the functional unit and the amount of land used is the same in each system. The final system comparison was based on normalized scores per environmental theme. The green energy system scored the best with respect to acidification, climate change, and energy carrier depletion. The organic food system scored best on terrestrial eco-toxicity and slightly better on the mutually related themes of seawater and seawater sediment eco-toxicity. The base case system performed slightly better with regard to eutrophication. Preferences, from an environmental point of view, for one of the systems should be determined by environmental policy priorities and the severity of local environmental problems. The case studied here shows that when climate change, energy carrier depletion, and acidification are the main drivers behind environmental policy, one should focus not on the extensification of agriculture, but rather dedicate more land to energy crops. Extensification of agriculture would be the preferred system when toxicity from pesticides is considered the main problem. [source] Complete dissolution and hydrolysis of wood in hot waterAICHE JOURNAL, Issue 10 2008Zhen Fang Abstract When willow and water were heated rapidly (7,16°C/s) to high temperatures and high pressures, most of willow (90 vol %) dissolved in water at 341°C in 2.5 s without complete dissolution. Adding 0.8 wt % Na2CO3, complete dissolution of willow (concentration up to 35 vol %) was observed at 329,367°C and water densities of 322,787 kg/m3 (14,106 MPa) in 1.5 s. By cooling the solublized willow immediately, micron particles were obtained via precipitation. If heated further to 400°C, willow was completely hydrolyzed to sugars/sugar oligomers in 14.6 s at homogeneous conditions. A flow reactor was proposed to completely solubilize willow for the production of micron particles, sugars, bio-fuels and chemicals continuously. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] Cadmium and zinc accumulation in willow and poplar species grown on polluted soils,JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 2 2007Maria N. Dos Santos Utmazian Abstract Woody plant species that produce high biomass have been proposed for use in phytoremediation technology. We investigated the accumulation of cadmium (Cd) and zinc (Zn) in Salix babylonica, S. caprea, S. dasyclados, S. matsudana × alba, S. purpurea, S. smithiana, Populus tremula, and P. nigra clones grown in a pot experiment on a Calcaric and a Eutric Cambisol (pH 7.2 and 6.4) of different levels of contamination (total metal concentrations in mg,kg,1 in soil A: 32.7 Cd, 1760 Zn; soil B: 4.34 Cd, 220 Zn). Generally, the tested clones tolerated large metal concentrations in soils and had larger Cd and Zn concentrations in leaves compared to the roots. The largest Cd concentrations in leaves were found in two clones of S. smithiana (440 mg,kg,1 on soil A; 70 mg,kg,1 on soil B). One of the S. smithiana clones had also the largest Zn concentrations (870 mg,kg,1) on soil B but accumulated slightly less Zn than a S. matsudana × alba clone (2430 mg,kg,1) on soil A. The Cd concentrations in leaves of both S. smithiana clones on soil A are the largest ever reported for soil-grown willows. The bioconcentration factors of the best performing clone reached 15.9 for Cd and 3.93 for Zn on the less contaminated soil B. Also based on the metal contents in leaves, this clone was identified as the most promising for phytoextraction. The metal concentrations in leaves observed in the pot experiment do not reflect those found in a previous hydroponic study and the leaf-to-root ratios are clearly underestimated in hydroponic conditions. This demonstrates the need for testing candidates for phytoextraction crops on soils rather than in hydroponics. Our data also show that the phytoextraction potential should be tested on different soils to avoid misleading conclusions. [source] Compositional differentiation, vegetation-environment relationships and classification of willow-characterised vegetation in the western Eurasian ArcticJOURNAL OF VEGETATION SCIENCE, Issue 1 2010A.M. Pajunen Abstract Question: How does willow-characterised tundra vegetation of western Eurasia vary, and what are the main vegetation types? What are the ecological gradients and climatic regimes underlying vegetation differentiation? Location: The dataset was collected across a wide spectrum of tundra habitats at 12 sites in subarctic and arctic areas spanning from NW Fennoscandia to West Siberia. Methods: The dataset, including 758 vegetation sample plots (relevés), was analysed using a TWINSPAN classification and NMDS ordination that also included analyses of vegetation-environment correlations. Results: Based on the TWINSPAN classification, eight vegetation types characterised by willow (cover of upright willows >10%) were discerned: (1) Salix glauca - Carex aquatilis type, (2) Aulacomnium - Tomentypnum type, (3) Salix - Betula - Hylocomium type, (4) Salix lanata - Brachythecium mildeanum type, (5) Salix - Pachypleurum type, (6) S. lanata - Myosotis nemorosa type, (7) Salix-Trollius-Geranium type and (8) Salix - Comarum palustre - Filipendula ulmaria type. Willow-characterised vegetation types were compositionally differentiated from other tundra vegetation and were confined to relatively moist valley and sloping tundra sites, from mire to mineral soils. These vegetation types were encountered across a broad latitudinal zone in which July mean temperature ranged from 6 to 10°C. Conclusions: Willow-characterised tundra vegetation forms a broad category of ecologically and geographically differentiated vegetation types that are linked to dwarf shrub tundra, shrub tundra or mire. Because of complex ecological gradients underlying compositional differentiation, predicting the responses of willow-characterised tundra vegetation to a warming climate may be complicated. [source] Evaluation of extractable elements in artificial substratum made from sewage sludge: Approach to remediation of degraded land in the ArcticLAND DEGRADATION AND DEVELOPMENT, Issue 2 2009T. T. Gorbacheva Abstract The Arctic (or subarctic) is characterized by a harsh climate and nutrient-poor soil; what makes it even harsher in Monchegorsk (67°51,N and 32°48,E) is that metal pollution originating from the Ni,Cu smelting industry has severely damaged the soil and ground vegetation, resulting in formation of an industrial desert (barren ground). A pilot-scale (4,ha) field test was carried out under such conditions to study how to apply municipal sewage sludge for rehabilitation of degraded land. After sewage sludge had been composted, an artificial substratum made from the compost was introduced to the remediation test field, and then willow, birch and grasses were planted on the substratum. The transformation of the artificial substratum was observed in the test field during 3 years. The portion of Cu in residual form was greater than that in other forms, it is hence considered that Cu has low bioavailability in the artificial substratum. Furthermore, the metal distributions statistically increased in fractions of humic acid (insoluble in water under acidic conditions), so the mobile amounts of Ni and Cu became small. The conclusion drawn from the field survey and analysis of extractable metals indicates that the lost vegetation is being restored even while pollution continues to be discharged from the smelter operation. Copyright © 2008 John Wiley & Sons, Ltd. [source] Winter browsing on Alaska feltleaf willow twigs improves leaf nutritional value for snowshoe hares in summerOIKOS, Issue 1 2003John P. Bryant In boreal forests, browsing by mammals on winter-dormant twigs increases leaf nitrogen, leaf greenness, and leaf size. This suggests browsing reduces competition among meristems for mineral nutrients, and in particular, competition for nitrogen. Winter browsing also reduces the shoot carbohydrate reserves used by leaves to produce condensed tannin. These effects of winter browsing are predicted to improve the nutritional value of leaves for mammals because they increase the mass of digestible nitrogen in leaves. This hypothesis was tested using Alaska feltleaf willow and the snowshoe hare as the experimental system. Six in vivo indicators of leaf nutritional quality were used to compare leaves from winter-browsed plants with leaves from unbrowsed plants. The indicators used were dry matter intake, nitrogen intake, condensed tannin intake, dry matter digestibility, apparent digestibility of nitrogen and nitrogen retention. The results obtained were in agreement with the above hypothesis. In early summer, at the time snowshoe hares and other northern herbivores reproduce, hares fed leaves from browsed plants consumed more nitrogen, digested more of the nitrogen they consumed, and retained more of the nitrogen they digested than did hares fed leaves from unbrowsed plants. The high nitrogen content and low tannin content of leaves from browsed plants may explain this browsing caused increase in leaf nutritional value. How these positive effects of winter browsing on snowshoe hare nutrition at the time of reproduction might affect hare population dynamics are briefly discussed. [source] Effects of permafrost degradation on woody vegetation at arctic treeline on the Seward Peninsula, AlaskaPERMAFROST AND PERIGLACIAL PROCESSES, Issue 2 2003Andrea H. Lloyd Abstract Permafrost degradation leads to substantial changes in soil thermal and hydrologic characteristics. We investigated the effects of changes in active layer thickness and soil drainage on vegetation distribution near the arctic treeline on the Seward Peninsula, Alaska. We measured active layer thickness, soil moisture, density of tall shrub species, cover of low shrub species, and reconstructed white spruce establishment history along transects across the banks of a network of thaw ponds. We found that active layer thickness did not vary along our transects, but soils on thaw pond banks were significantly drier than those on level tundra or in thaw-pond channels. Thaw-pond banks were the only sites in which trees successfully established, and shrub communities on thaw-pond banks were taller and more dominated by tall shrub species like willow and shrub birch. The data suggest that the establishment of tree and tall shrub species at the arctic treeline can be limited by the availability of well-drained microsites, and the response of these species to regional climatic changes will be constrained by the availability of such microsites and thus contingent upon further degradation of the permafrost. Copyright © 2003 John Wiley & Sons, Ltd. [source] Water relations and gas exchange in poplar and willow under water stress and elevated atmospheric CO2PHYSIOLOGIA PLANTARUM, Issue 1 2002Jon D. Johnson Predictions of shifts in rainfall patterns as atmospheric [CO2] increases could impact the growth of fast growing trees such as Populus spp. and Salix spp. and the interaction between elevated CO2 and water stress in these species is unknown. The objectives of this study were to characterize the responses to elevated CO2 and water stress in these two species, and to determine if elevated CO2 mitigated drought stress effects. Gas exchange, water potential components, whole plant transpiration and growth response to soil drying and recovery were assessed in hybrid poplar (clone 53,246) and willow (Salix sagitta) rooted cuttings growing in either ambient (350 µmol mol,1) or elevated (700 µmol mol,1) atmospheric CO2 concentration ([CO2]). Predawn water potential decreased with increasing water stress while midday water potentials remained unchanged (isohydric response). Turgor potentials at both predawn and midday increased in elevated [CO2], indicative of osmotic adjustment. Gas exchange was reduced by water stress while elevated [CO2] increased photosynthetic rates, reduced leaf conductance and nearly doubled instantaneous transpiration efficiency in both species. Dark respiration decreased in elevated [CO2] and water stress reduced Rd in the trees growing in ambient [CO2]. Willow had 56% lower whole plant hydraulic conductivity than poplar, and showed a 14% increase in elevated [CO2] while poplar was unresponsive. The physiological responses exhibited by poplar and willow to elevated [CO2] and water stress, singly, suggest that these species respond like other tree species. The interaction of [CO2] and water stress suggests that elevated [CO2] did mitigate the effects of water stress in willow, but not in poplar. [source] Responses of Nondormant Black Willow (Salix nigra) Cuttings to Preplanting Soaking and Soil MoistureRESTORATION ECOLOGY, Issue 1 2005S. R. Pezeshki Abstract The use of willow cuttings for streambank stabilization is a common practice in riparian ecosystems throughout the United States. Many environmental factors govern the outcome of such planting. However, other factors such as preplanting treatments, planting methods, and physiological status of cuttings (dormant vs. actively growing) may also be crucial in determining the survival of willow cuttings. Actively growing (nondormant) Black willow (Salix nigra) cuttings, 30 cm in length and 1 cm in diameter at the base, were subjected to three soaking treatments (0, 7, and 15 days) prior to planting. Following the initial treatment, cuttings were grown in a greenhouse in pots under three soil moisture regimes (well-watered but not flooded, permanently flooded, and intermittently flooded). Plant gas exchange, growth, biomass, and survival were measured. Results demonstrated that soaking for 7 days was beneficial to early development of cuttings in the well-watered (control) soil moisture regime, enhancing percent bud flush and survival significantly. However, 15 days of soaking proved to be detrimental to survival of cuttings irrespective of soil moisture regimes. Results also demonstrated that the beneficial effects of 7-day soaking were limited to the well-watered soil moisture regime but not to the flooded or intermittently flooded regimes. Soaking nondormant cuttings may be worthwhile if the planting site is likely to present ample soil moisture but nonflooded conditions to the transplanted cuttings. [source] Phenological stages of willow (Salix)ANNALS OF APPLIED BIOLOGY, Issue 3 2010Margaret M. Saska The practice of uniform recording of biological plant growth stages or events has long been practiced in agricultural production. In this study the BBCH (Biologishe Bundesanstalt, Bundessortenamt and CHemical Industry) code has been applied to four precocious species of willows to define growth stages important to this group. The studied taxa represent varieties of potential importance in the Floral Industry. A new BBCH code is proposed where the annual cycle of willows is divided into clearly recognisable and easily distinguishable developmental phases which include eight principal stages, 30 secondary stages and six mesostages. Photographs illustrate the physical appearance of select stages. This proposed BBCH code shows a unified approach which may be applied to a large number of Salix species. [source] The impact of the aphids Tuberolachnus salignus and Pterocomma salicis on willow treesANNALS OF APPLIED BIOLOGY, Issue 2 2001C MATILDA COLLINS Summary The effect of two species of stem-feeding aphid on the yield, phenology and water-use of soil-grown and hydroponic-cultured willow were investigated. The effects of Pterocomma salicis were less marked than those of Tuberolachnus salignus. The latter reduced not only the above and below-ground growth of trees made during and subsequent to infestation, but also altered the mass of previously developed woody tissue. The negative effects of T. salignus on the shoots and roots of established and establishing trees were drastic and were both quantitative and qualitative. They were also observed to reduce the survival of infested trees. P. salicis had negative effects on the growth of roots and shoots during infestation, but the influence of this species did not persist nor did it influence previous growth. [source] Willow (Salix spp.) and aspen (Populus tremula) regrowth after felling by the Eurasian beaver (Castor fiber): implications for riparian woodland conservation in ScotlandAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2009Kevin Jones Abstract 1.A proposed trial reintroduction of the Eurasian beaver (Castor fiber L.) to Scotland has recently been approved (May 2008). A previous proposal was turned down by the licensing authority, partly over the perceived risks to woodland within a Special Area of Conservation. 2.This paper presents data on two years of willow (Salix spp.) and aspen (Populus tremula L.) regrowth following tree felling by captive beavers within two large semi-natural enclosures in eastern Scotland. Both willow and aspen are highly preferred by beavers. 3.Regrowth of willow stems was quantified from cut stumps, felled logs and partially severed (,incompletely felled') trees, and compared with growth of stems in the canopies of untouched willows. 4.Maximum annual regrowth was observed in incompletely felled trees, followed by cut stumps and then unfelled control trees. Mean regrowth rates were ca 18 m regrowth per metre of measured tree section per year in incompletely felled trees. This was approximately 12 times more annual regrowth than that observed in unfelled trees, despite apparently selective browsing of the regrowth of incompletely felled trees by roe deer. 5.Although incompletely felled willows represent a relatively small component of felling activity (9% of all felled willow), they contribute disproportionately to the biomass of beaver-engineered riparian woodlands, creating a more multi-layered habitat structure. 6.Willow regrowth in inundated areas was avoided by deer, and harvesting of regrowth by beavers was rare. 7.Significant regrowth from 11 stumps of aspen in 2 years post-felling occurred by suckering, with 85 suckers of mean height 2.1 m being recorded, all of which were subsequently avoided by browsing deer and beavers. 8.These data suggest that rapid regeneration of willow and aspen will occur in riparian woodlands in the event of major felling activity by Eurasian beaver, even in the presence of low to moderate levels of roe deer browsing, and that the conservation status of both these trees or the wider habitats that they form would not be threatened by a well planned and managed reintroduction of beavers to Scotland. Copyright © 2008 John Wiley & Sons, Ltd. [source] Patterns of interspecific associations of stem gallers on willowsDIVERSITY AND DISTRIBUTIONS, Issue 6 2003Jens-Peter Kopelke Abstract., The pattern of interspecific associations of three stem-galling sawfly species (Euura atra, E. elaeagnos, E. purpureae) and three stem-galling gallmidge species (Rabdophaga sp. 3,5) was investigated on five willow taxa (Salix alba, S. fragilis, S. × rubens, S. elaeagnos, S. purpurea) at five natural sites in Central Europe. The willow species harboured specific species associations of two stem gallers, each pair consisting of one Euura and one Rabdophaga species. The stem gallers were patchily distributed and their densities varied significantly among willow host plant species, host plant individuals, and host plant sexes. Four of the six species showed a significant increase in galling rate with shoot length. The other two species were the sawfly and cecidomyiid pair that induce galls on S. purpurea. The preference of stem gallers to longer shoots was generally not related to higher larval performance in terms of survival. Only one species, Rabdophaga sp. 5, was found to be more abundant on male plants. The correlation of densities of the species pairs of stem gallers was independent of willow sexes. Species pairs of stem gallers co-occurring on the same willow species tended to attack different shoots within the same host plant individual. When species pairs co-occurred on shoots they were usually found in similar densities as when occurring alone on shoots. The stem-galling sawflies usually formed galls at the basal part of a shoot, whereas the gallmidge R. sp. 5 (R. sp. 3 and R. sp. 4 showed no clear tendency) preferred the middle or distal part of a shoot. This is interpreted with differences of their phenology and oviposition period. [source] Wide-area estimates of saltcedar (Tamarix spp.) evapotranspiration on the lower Colorado River measured by heat balance and remote sensing methods,,ECOHYDROLOGY, Issue 1 2009Pamela L. Nagler Abstract In many places along the lower Colorado River, saltcedar (Tamarix spp) has replaced the native shrubs and trees, including arrowweed, mesquite, cottonwood and willows. Some have advocated that by removing saltcedar, we could save water and create environments more favourable to these native species. To test these assumptions we compared sap flux measurements of water used by native species in contrast to saltcedar, and compared soil salinity, ground water depth and soil moisture across a gradient of 200,1500 m from the river's edge on a floodplain terrace at Cibola National Wildlife Refuge (CNWR). We found that the fraction of land covered (fc) with vegetation in 2005,2007 was similar to that occupied by native vegetation in 1938 using satellite-derived estimates and reprocessed aerial photographs scaled to comparable spatial resolutions (3,4 m). We converted fc to estimates of leaf area index (LAI) through point sampling and destructive analyses (r2 = 0·82). Saltcedar LAI averaged 2·54 with an fc of 0·80, and reached a maximum of 3·7 with an fc of 0·95. The ranges in fc and LAI are similar to those reported for native vegetation elsewhere and from the 1938 photographs over the study site. On-site measurements of water use and soil and aquifer properties confirmed that although saltcedar grows in areas where salinity has increased much better than native shrubs and trees, rates of transpiration are similar. Annual water use over CNWR was about 1·15 m year,1. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||