Willow Growth Research Articles

Promotion of mycorrhiza formation and growth of willows by the bacterial strain Sphingomonas sp. 23L on fly ash

Re-vegetation of fly ash, the principal by-product of coal fired power stations, is hampered by its unfavourable chemical and physical properties for plant growth. In the present study, we evaluated the use of inoculation with a mycorrhiza-associated bacterial strain (Sphingomonas sp. 23L) to promote mycorrhiza formation and plant growth of three willow clones (Salix spp.) on fly ash from an over-burdened dump in a pot experiment. The high pHH2O (8.7) and low nitrogen content (Nt = 0.1 g kg−1) in combination with hydrophobicity of the particle surfaces caused low plant growth. Inoculation of the willows with Sphingomonas sp. 23L improved the nitrogen uptake by plants, increased plant growth and stimulated formation of ectomycorrhizae with an autochthonous Geopora sp. strain on all three willow clones. The ectomycorrhiza formed by the Geopora sp. was morphologically and anatomically described. The inoculation significantly increased the shoot growth of two Salix viminalis clones and the root growth of a S. viminalis x caprea hybrid clone. We conclude that inoculation with mycorrhiza promoting bacterial strains might be a suitable approach to support mycorrhiza formation with autochtonous site-adapted ectomycorrhizal fungi in fly ash and thereby to improve re-vegetation of fly ash landfills with willows.

Growth and Metal Accumulation of Geyer and Mountain Willow Grown in Topsoil versus Amended Mine Tailings

Willows (Salix spp.) are an integral component in the restoration of wetland plant communities that have been impacted by the fluvial deposition of mine tailings. A greenhouse study was conducted to compare growth and metal uptake of Geyer (S. geyeriana) and mountain (S. monticola) willow grown in topsoil versus lime and biosolids amended mine tailings. Biomass, leader length, and tissue metal contents were measured after four months growth. Above and belowground biomass and leader length of Geyer willow were greater for plants grown in topsoil compared to amended mine tailings. However, soil type did not affect mountain willow growth. Analysis for five metals yielded complex results for the two willow species and soil types. As compared to mountain willow, Geyer had greater concentrations of Mn and Pb in aboveground tissues, and Cu in senesced leaves and bark-less leaders when grown in tailings; mountain willow leaves contained greater levels of Cd than Geyer when grown in tailings. Both willow species had foliar Cd levels which were above livestock toxicity tolerance values. Based on growth characteristics, mountain willow appeared better suited for restoration of mine tailings compared to Geyer willow. However, because of the high Cd uptake by both willow species, care should be taken in restoration efforts where wildlife and domestic livestock are likely to browse on the willows.

Symptoms of pests, rust and other disorders on leaves of willow fertilised with wastewater, urine or sewage sludge

Abstract Willow (Salix viminalis) irrigated with three different dosages of wastewater has been investigated for leaf damages in four plantations located in Sweden, Northern Ireland, France and Greece, during 3 consecutive years. Control treatments were clean water and/or no water. Additionally, the plantation in Sweden included a human urine/water mix treatment and the one in N. Ireland a sewage sludge treatment. Few effects of the treatments were found. In the Greek trial, all treatments were affected by abiotic stress causing leaf discolouration, necrosis and leaf curling, but the control treatment was least affected. Mite infestations were also less prevalent in the control plots there. In the French trial, control leaves were less galled by Dasineura marginemtorquens than leaves from the lowest dose of wastewater but not compared to the two higher doses of wastewater, during 1 of the 3 years. At the same site, but in another year, Melampsora rust infection was least developed at the highest dose of wastewater but only significantly so when compared to the intermediate dose of wastewater. Urine/water treatment resulted in more rust and leaf margin damages than the control treatments in 1 year. Also, leaf spotting by leafhoppers tended to be more prevalent on the urine treatment. However, since the urine fertilisation favours willow growth as well, a somewhat enhanced biotic damage to leaves is probably no reason for avoiding this application in full-scale plantations. Damage by chrysomelid beetles was very common in the French and the N. Irish plantations, but no significant differences between treatments were found. Neither were there any treatment effects on symptoms by aphids.

Quantification of phosphorus retention efficiency by floodplain vegetation and a management strategy for a eutrophic reservoir restoration

This paper presents an ecohydrological approach to the reduction in the phosphorus load transported by the Pilica River into a lowland reservoir in the central region of Poland. The research was carried out on a 26.6 ha section of the river floodplain where vegetation was the important component accumulating phosphorus (P) in plant tissues. Quantification of P accumulation in plant tissues and retention efficiency by plant communities in the floodplain were analyzed in order to develop a vegetation management strategy that would enhance river self-purification. A Digital Terrain Model (DTM), a location–altitude map, an inundation model of the floodplain, and a map of the distribution of plant communities were used to evaluate the capacity of the floodplain to retain P. In summer, the biological potential for phosphorus retention in the floodplain was estimated to be as high as 255 kg P. However, this potential can be increased by planting fast-growing patches of willow. Therefore, covering 24% or 48% of the entire floodplain (identified by DTM analysis) where are suitable hydrological conditions for growth and cultivation of willows may increase this accumulation to 332 or 399 kg P, respectively. In the long run, an appropriate management strategy (cutting and removing the biomass from the floodplain) should favor a decrease in nutrient transport downstream.

Impact of standing vegetation on early establishment of willow cuttings in the flooded area of the Parana River Delta (Argentina)

We assessed the growth and survival of a willow clone (Salix matsudana × Salix alba ‘A 13/44’) growing under different vegetation management in the flooded area of the Parana River Delta (Argentina) during the first 2 years after planting. Treatments consisted in a combination of practices applied in the row and in the inter-row. In the row (1-m wide) vegetation was manually cut with machete (r-M), treated with glyphosate at 3% (r-H) or maintained undisturbed (r-U); in the inter-row vegetation was crushed with a roller (I-R), treated with glyphosate at 3% (I-H) or maintained undisturbed (I-U). Height, diameter and relative growth rate of the dominant sprout were evaluated. Tree survival was high (96%) and not affected by treatments. Growth was modified by the vegetation control at early stages. Height and diameter were higher in r-H plots compared to r-U plots; both were similar in the I-U and I-H plots but greater than in I-R plots. Early differences in diameter relative growth rate among row treatments were found. Possible mechanisms associated with willow growth responses such as plastic responses under resource limited conditions and amelioration of the microenvironment by the native vegetation are discussed.

Willow water uptake and shoot extension growth in response to nutrient and moisture on a clay landfill cap soil

Extension growth of willow ( Salix viminalis L.) and changes in soil water were measured in lysimeters containing clay and sandy loam soils with different amendment and watering treatments. No water uptake was found below 0.3 m in the nutritionally poor unamended clay; amendment with organic matter to 0.4 m depth resulted in water extraction down to 0.5 m depth whereas in the sandy loam, there was greater extraction from all depths down to 0.6 m. With water stress, wilting of plants occurred when the volumetric soil water content at 0.1 m was about 31% in the clay and 22% in the sandy loam. Compared with shoots on plants in the amended clay, those in the unamended treatment showed reduced extension growth, little increase in stem basal area (SBA) and a small shoot leaf area, resulting from a reduced number of leaves shoot −1 and a small average area leaf −1. Water stress also reduced shoot extension growth, SBA gain and the leaf area on extension growth. Shoot growth rates were significantly correlated with air temperature and base temperatures between 2.0 and 7.6 °C were indicated for the different treatments. These studies have helped to explain some of the large treatment effects described previously on biomass production and plant leaf area.

Elk browsing increases aboveground growth of water-stressed willows by modifying plant architecture

In the northern elk wintering range of Yellowstone National Park, USA, wolf (Canis lupus) removal allowed elk (Cervus elaphus) to overbrowse riparian woody plants, leading to the exclusion of beaver (Castor canadensis) and a subsequent water table decline in many small stream valleys. Reduced elk browsing following wolf reintroduction may or may not facilitate willow (Salix sp.) recovery in these areas. To determine if the effect of elk browsing on willow interacts with that of beaver abandonment, we manipulated elk browsing and the water table in a factorial experiment. Under the condition of an ambient (low) water table, elk browsing increased shoot water potential (Psis), photosynthesis per unit leaf area (A), stomatal conductance per unit leaf area (gs), and aboveground current annual growth (CAG) by 50%. Elk browsing occurred entirely during dormancy and did not affect total plant leaf area (L). Improved water balance, photosynthetic rate, and annual aboveground productivity in browsed willows appeared to be due to morphological changes, such as increased shoot diameter and decreased branching, which typically increase plant hydraulic conductivity. An elevated water table increased Psis, A, gs, CAG, and L, and eliminated or lessened the positive effect of browsing on CAG for most species. Because low water tables create conditions whereby high willow productivity depends on the morphological effects of annual elk browsing, removing elk browsing in areas of water table decline is unlikely to result in vigorous willow stands. As large willow standing crops are required by beaver, a positive feedback between water-stressed willow and beaver absence may preclude the reestablishment of historical conditions. In areas with low water table, willow restoration may depend on actions to promote the re-establishment of beaver in addition to reducing elk browsing.

Application of willows ( Salix viminalis) and earthworms ( Eisenia fetida) in sewage sludge treatment

The aim of the study was to verify the suitability of willows ( Salix viminalis) and earthworms ( Eisenia fetida) for sewage sludge management. The study was conducted in Tarnów city sewage plant. In April 2004, 81 pots were filled with concentrated sludge, 27 of which acted as controls, another 54 were planted with willows. In May, 20 mature earthworms were introduced to half (27) of the pots with willows. Every month the growth of willows was measured. The density of earthworms, size of willows, and the moisture content, and their chemical properties and structure of the sewage sludge were assessed in November 2004 when: (1) the moisture content of the sludge was lower in the pots with willows (49%) and with willows + earthworms (37%) than in the control (67%); (2) the mass increase of willow was higher by 38% for shoots and 41% for roots, in pots with earthworms; and (3) the introduction of willows and earthworms changed the structure of sludge. Willows and earthworms had no effect on the pH of the sludge, nor on its concentration of nutrients, heavy metals or forms of nitrogen.

WILLOW ON YELLOWSTONE'S NORTHERN RANGE: EVIDENCE FOR A TROPHIC CASCADE?

Reintroduction of wolves (Canis lupus) to Yellowstone National Park in 1995-1996 has been argued to promote a trophic cascade by altering elk (Cervus elaphus) density, habitat-selection patterns, and behavior that, in turn, could lead to changes within the plant communities used by elk. We sampled two species of willow (Salix boothii and S. geyeriana) on the northern winter range to determine whether (1) there was quantitative evidence of increased willow growth following wolf reintroduction, (2) browsing by elk affected willow growth, and (3) any increase in growth observed was greater than that expected by climatic and hydrological factors alone, thereby indicating a trophic cascade caused by wolves. Using stem sectioning techniques to quantify historical growth patterns we found an approximately twofold increase in stem growth-ring area following wolf reintroduction for both species of willow. This increase could not be explained by climate and hydrological factors alone; the presence of wolves on the landscape was a significant predictor of stem growth above and beyond these abiotic factors. Growth-ring area was positively correlated with the previous year's ring area and negatively correlated with the percentage of twigs browsed from the stem during the winter preceding growth, indicating that elk browse impeded stem growth. Our results are consistent with the hypothesis of a behaviorally mediated trophic cascade on Yellowstone's northern winter range following wolf reintroduction. We suggest that the community-altering effects of wolf restoration are an endorsement of ecological-process management in Yellowstone National Park.

Copper and Cadmium Tolerance, Uptake and Effect on Chloroplast Ultrastructure. Studies on Salix purpurea and Phragmites australis

We have compared the effect of toxic Cu and Cd concentrations on growth, metal accumulation, and chloroplast ultrastructure of willow (Salix purpurea L.) and reed [Phragmites australis (Cav.) Trin. ex Steud.]. After a 10-day treatment, both species have tolerated to some extent the lowest concentration of both metals; however, plant growth was strongly reduced at the highest Cu and Cd concentrations. These plants could be described as Cu-tolerant at the lowest concentration tested, showing a higher tolerance index in reed than in willow; in contrast, willow exhibited higher tolerance against Cd. Both plants appeared to be moderate root accumulators of Cu and Cd. Ultrastructural studies revealed special features that can provide some protection against heavy metals stress, such as ferritin aggregates in the stroma. In addition, Cu and Cd induced distortion of thylakoids, reduction of grana stacks, as well as an increased number and size of plastoglobuli and peripheral vesicles.

The susceptibility of herbal willow to Melampsora rust and herbivores

Eight Dark-leaved willow (Salix myrsinifolia) clones and two naturally hybridised clones (S. myrsinifolia × S. phylicifolia), that are considered to be suitable for herbal production, were cultivated for 2 years in Luikonlahti and Punkaharju. Both experimental sites are located in eastern Finland and the distance between the sites is 140 km. Different cultivation methods were used, including combinations of soil tillage, plastic mulch and fertilisation, with the aim of comparing the growth and susceptibility of plants to pathogens and willow-eating herbivores amongst the clones cultivated by different methods. In both study years 2001 and 2002, Melampsora rust-infected willows occurred in Luikonlahti and in Punkaharju. The extent of rust severity varied greatly between the years and experimental areas and amongst the clones. In 2002, fertilisation increased rust severity in Luikonlahti, but the effect was the converse in Punkaharju. Mulch effect on rust severity was clone-dependent. Vole feeding was observed in 56% of the plants in Luikonlahti during the winter 2001–2002 and the frequency of damaged plants was nearly twice as much amongst the willows grown in unmulched soil as those with plastic mulch. Cultivation method had no effect on feeding by leaf beetles or the abundance of aphids. Of the cultivation methods tested here, plastic mulch seems to have the most important influence on willow cultivation, particularly by improving willow growth and also by decreasing winter-feeding by voles.

Reindeer herbivory reduces willow growth and grouse forage in a forest-tundra ecotone

Abstract Browsing mammals strongly modify the structure of vegetation of forest-tundra ecotones. We investigated the impact of reindeer browsing on growth and morphology of an arctic willow, Salix glauca, by studying plants inside and outside fenced areas in a tundra habitat at the tree line. We also studied if reindeer feeding has an effect on the forage availability for willow grouse, a herbivore sharing the same food plant. Analyses of 6-year data show that reindeer strongly reduces the growth of tundra willow and changes plant morphology to a stunted growth form. Intense reindeer browsing on willow limited the forage availability for willow grouse and grouse fed less on reindeer-browsed willow than willows protected from reindeer browsing. The results of this study imply that herbivores can counteract the increase of shrubs in forest-tundra ecotones, as has been predicted in some studies discussing the effects of climatic warming on vegetation. Furthermore, trophic interactions should be incorporated in modelling vegetation changes as a response to increased temperatures.

Effects of site, clone and age on growth and wood quality of short rotation willow

The aim of the work was to asses the effects of site, clone and age on current annual increment, fibre length and wood density of 5 willow clones (S. babylonica var sacramenta «american»; hybrids of S. babylonica x S. alba «A 250-33» y «A 131-25» y S. matsudana x S. alba «A 13-44» y «NZ 26992»). Sites chosen were: Delta Medio (DM) del Río Paraná, Entre Ríos and Continental (C) Buenos Aires, Argentina. 13 years old trees were sampled and measurements of total height, diameter, growth rings, fibre length, wood density taken at 3 positions (ages) in each sample. Basal areas of current annual increments and weighted length and density were calculated. It was found that clone × site × age interaction was significant. The annual increments were found to be dependent on the site, the clone and the age under analysis. Weighted fibre length and wood density were found to be good estimates of wood quality, so the maximum fibre and density value depends both on clone growth patterns, implantation site and age. For American willow and hybrid 26992 of DM, the production of wood quality attained a maximum at 7 years old.

Short-rotation forestry of birch, maple, poplar and willow in Flanders (Belgium) I—Biomass production after 4 years of tree growth

Abstract During the last three decades, oil crises, agricultural surpluses and global climate change enhanced the interest in short-rotation forestry (SRF). In this study, the biomass production of birch ( Betula pendula Roth), maple ( Acer pseudoplatanus L.—Tintigny), poplar ( Populus trichocarpa × deltoides —Hoogvorst) and willow ( Salix viminalis —Orm) growing under a short-rotation (SR) management system were compared after a 4 years period. The plantation was established on former agricultural land. The sandy soil had a mean pH of 4.5 and a mean carbon content of 1.0%. Survival rates after 4 years were 75.8%, 96.8%, 86.3% and 97.6% for birch, maple, poplar and willow, respectively. The mean actual annual biomass production for these four species amounted to 2.6, 1.2, 3.5 and 3.4 t DM ha −1 yr −1 , respectively. The large variation in biomass production at the different plots of the plantation could not be explained by the measured soil parameters. Biomass production results found here were in the lower range of values reported in literature. However, in contrast to most other studies, no weed control, fertilisation or irrigation was applied in this experiment. As marginal agricultural soils are suboptimal for the growth of poplar and willow, birch can be considered as a very interesting alternative for the establishment of SR plantations in Flanders.

Trichoderma harzianum Rifai 1295-22 Mediates Growth Promotion of Crack Willow (Salix fragilis) Saplings in Both Clean and Metal-Contaminated Soil

We investigated if the plant growth promoting fungus Trichoderma harzianum Rifai 1295-22 (also known as "T22") could be used to enhance the establishment and growth of crack willow (Salix fragilis) in a soil containing no organic or metal pollutants and in a metal-contaminated soil by comparing this fungus with noninoculated controls and an ectomycorrhizal formulation commercially used to enhance the establishment of tree saplings. Crack willow saplings were grown in a temperature-controlled growth room over a period of 5 weeks' in a garden center topsoil and over 12 weeks in a soil which had been used for disposal of building materials and sewage sludge containing elevated levels of heavy metals including cadmium (30 mg kg(-1)), lead (350 mg kg(-1)), manganese (210 mg kg(-1)), nickel (210 mg kg(-1)), and zinc (1,100 mg kg(-1)). After 5 weeks' growth in clean soil, saplings grown with T. harzianum T22 produced shoots and roots that were 40% longer than those of the controls and shoots that were 20% longer than those of saplings grown with ectomycorrhiza (ECM). T. harzianum T22 saplings produced more than double the dry biomass of controls and more than 50% extra biomass than the ECM-treated saplings. After 12 weeks' growth, saplings grown with T. harzianum T22 in the metal-contaminated soil produced 39% more dry weight biomass and were 16% taller than the noninoculated controls. This is the first report of tree growth stimulation by application of Trichoderma to roots, and is especially important as willow is a major source of wood fuel in the quest for renewable energy. These results also suggest willow trees inoculated with T. harzianum T22 could be used to increase the rate of revegetation and phytostabilization of metal-contaminated sites, a property of the fungus never previously demonstrated.

The effect of cultivation density on dark-leaved willow (Salix myrsinifolia) growth and phenolics

The effect of cultivation density on dark-leaved willow (Salix myrsinifolia) growth and phenolics

Controlling Phalaris arundinacea (reed canarygrass) with live willow stakes: A density-dependent response

We tested the use of live willow stakes to manage reed canarygrass ( Phalaris arundinacea L.) invasions on a wetland site. We planted willow at densities of 0.60 m (2 ft) centers, 0.91 m (3 ft) centers, 1.21 m (4 ft) centers, and control (no plantings) on a sloping wetland edge at Lake Washington, Seattle, U.S.A., where reed canarygrass dominated prior to the experiment. Soil moisture content was measured along the slope gradient, resulting in three soil moisture classes per replicate. Willow leaf area index and reed canarygrass aboveground biomass were measured after each of two consecutive growing seasons and analyzed using ANCOVA. Relative to the controls, the willows reduced total biomass of reed canarygrass by 44.9% with 0.60 m spacing in the first year and by 68.0% with 0.60 m spacing and 56.1% with 0.91 m spacing in the second year. Differences in soil moisture did not affect reed canarygrass aboveground biomass or effects of willow on reed canarygrass, but did affect willow growth, perhaps through reed canarygrass competition under lower soil moisture conditions. We recommend the 0.60 and 0.91 m spacings for wetland restoration projects attempting to manage reed canarygrass through live willow staking.

Linking wolves to willows via risk-sensitive foraging by ungulates in the northern Yellowstone ecosystem

After an absence of approximately 70 years, gray wolves ( Canis lupus) were re-introduced into Yellowstone National Park in the mid-1990s. We studied the potential influence of wolf/ungulate interactions upon willow ( Salix spp.) growth in the valleys of the Gallatin and Lamar Rivers, as well as Slough and Soda Butte Creeks, in the northern Yellowstone ecosystem. When we compared willow heights from photographs taken prior to 1998 (willows <2 m tall) with those taken in 2004, we found an increase in willow height for 22 of 42 sites within the study area. Based on comparisons of the chronosequence photos, since wolf introduction none of the 16 upland riparian sites showed an increase in willow height, while 22 of 26 of the valley-bottom riparian sites had willow height increases. In 2004, willow height exhibited a strong inverse relationship with the percentage of browsed stems ( r = −0.81, p < 0.01, n = 42). Results of regressions for valley-bottom sites indicated that view distance, impediment distance, and the number of bison ( Bison bison) flops were inversely related to willow height ( p ≤ 0.02). Increased willow heights were not significantly ( p = 0.18) related to patterns of moisture availability. Willow height increases documented in this study appear to have been at least partially due to behaviorally mediated trophic cascades involving wolves and ungulates, via a mechanism of predation risk. While willow release (i.e., increased height growth) within the study area is in a very early stage, results suggest potentially important indirect effects of a top carnivore in a terrestrial food chain that may aid in the restoration of riparian species and the preservation of biodiversity.

Use of Felled Junipers to Protect Streamside Willows From Browsing

Willow (Salix) communities are important components of riparian ecosystems. However, browsing by livestock and wildlife species can negatively impact willow size and abundance, and make restoration efforts difficult. A common solution has been fencing of affected willows to exclude ungulates, but fencing is expensive and may not complement desirable land management strategies. An alternative to fencing is the use of structures that limit access to streamside willows, without excluding ungulate access to the entire riparian zone. We examined the use of felled western juniper trees (Juniperus occidentalis Hook) placed over streamside willow shrubs. Four replicates of felled western juniper treatments (covered) and noncovered treatments were applied to a 1.2-km length of stream in southeastern Oregon. Willows (< 2 m) within treatment areas were censused, tagged, examined for evidence of browse-use, and measured for maximum height during August 2002, before treatment. Posttreatment measurements were made in August and October 2003. Results indicate that by August 2003 (posttreatment) the average growth of willows in covered treatments was 25 cm (480%) greater than in noncovered treatments. By October 2003 (posttreatment), more shrubs were browsed in noncovered (84%) than covered (39%) treatments. Our data suggest that covering small willow shrubs (< 2 m tall) with felled western juniper is an effective deterrent to browsing.

Long‐term population dynamics of a sawfly show strong bottom‐up effects

Summary 1 Population dynamics of the arroyo willow stem-galling sawfly Euura lasiolepis Smith (Hymenoptera: Tenthredinidae) on its host plant, Salix lasiolepis Bentham (Salicaceae), was studied for 22 years in the vicinity of Flagstaff, Arizona, USA. 2 Comparatively low levels of population change in drier and wetter sites ranged over two orders of magnitude. 3 Time-series analysis revealed best fit models of population change that included total winter precipitation from October to May and/or cumulative Pearson Drought Severity Index (PDSI) for the same period, plus a 1-year delay in precipitation or PDSI in some cases. 4 For populations on willow clones in drier sites, the model accounted for 73% of sawfly population change, and in wetter sites, with high mean populations, the model predicted 67% of the variation in gall density. 5 The mechanistic link between predictors of water availability to host plants and sawfly populations was better growth of willow after high winter precipitation, producing more and longer shoots. Also, willow clones with younger ramets, with more vigorous growth, were more favourable to sawflies than clones with older ramets. 6 Strong female preference for longer shoots resulted in more eggs laid, and this was coupled with higher larval survival on longer shoots. The major component of loss in a cohort was aborted ovipositions, with significant and negative influence on survival through the immature stages. Survival in one generation was correlated with gall density in the following generation. 7 Dynamics were entirely driven through resource supply. 8 Combining the evolutionary Phylogenetic Constraints Hypothesis with detailed mechanistic studies reveals an explanation of population dynamics which is more broadly applicable than purely ecological studies.