Willow Plantations Research Articles

Groundwater table prediction and seasonal variation influenced by short rotation willow plantation on marginal riparian lands of the Prairie potholes in Canada

Shallow groundwater consumption via phreatophytic transpiration and resulting vegetation-linked groundwater table (GWT) fluctuation is a typical soil hydrological process in wetland riparian areas. However, upland and riparian land use alterations may further influence the shallow GWT fluctuation, temporally and spatially. In this multi-year field study, we investigated whether introducing short rotation willow (SRW) positively or negatively affects the shallow GWT, soil water availability, and soil health on marginal riparian lands of the Prairie Pothole Region (PPR). We compared the impact of SRW on these parameters to two common land uses: annual crop (AC) and pasture (PA). Depth to GWT was monitored via data loggers from 28 wells in two semi-arid PPR sites. The GWT depth varied by land use practices only in site B (p < 0.001; PA > SRW = AC) but not significantly in site A (p = 0.325), and the patterns were inconsistent between sites. In GWT depth prediction, the performance of Artificial Neural Network (ANN) was better than Autoregressive Integrated Moving Average (ARIMA) models but was inconsistent alike with field observations. The GWT depth responded to seasonal precipitation and potential evapotranspiration (ET) patterns. The monthly GWT fluctuations peaked between June and August due to increased precipitation, while they were lower during May and September with reduced precipitation; however, these variations were not significant (p > 0.05). Higher precipitation and lower potential ET throughout the wet year (i.e., in 2014) significantly (p < 0.05) raised GWT (i.e., decreased depth to GWT) under all land uses, and vice versa. Our study indicated that planting SRW in marginal riparian land of the PPR would not negatively impact shallow GWT or soil water availability. Moreover, the SRW plantation could also help manage soil salinity without severely depleting the soil's nutrient pools or diminishing soil quality and health indicator parameters measured during the first rotation.

A Monte Carlo Model for WWTP Effluent Flow Treatment through Enhanced Willow Evapotranspiration

The effectiveness of using enhanced evapotranspiration rates of willow plantation is a modern environmentally friendly practice for advanced treatment of effluent WWTP flow. The key idea is that through advanced willow evapotranspiration rates, a significant proportion of the effluent flow can be transferred into the atmosphere through the physical process of evapotranspiration. This study further discusses the concept in a real-world problem using a wide dataset consisting of a recent PET monthly remote dataset namely RASPOTION, monthly recorded rainfall gauge, and experimental willow evapotranspiration surveys across Ireland, to identify the monthly cropping pattern. A Monte Carlo water balance model has been developed for the period 2003–2016. The model was applied in an existing willow plantation at Donard WWTP co. Wicklow, Ireland to identify the exceedance probability of willow plantation runoff against estimated low flows (i.e., Q95, Q99) at the adjacent small tributary. In this case study, any failure which can lead to river quality deterioration was not assessed. The overall framework aims to provide new insights considering the multiple sources of uncertainty (i.e., monthly willow cropping pattern and WWTP effluent flow) in associated environmental engineering problems.

Flooding tolerance, biomass production, and leaf nitrogen assimilatory efficiency in 29 diverse willows (Salix spp.) genotypes during early growth

ABSTRACT Willows are frequently planted as unrooted cuttings in flood-prone areas. The occurrence of a flooding episode during the early stages of the plantation causes diverse morphological and physiological changes in willows. Thus, it is important to identify traits correlating to flooding tolerance to be used to breed genotypes with enhanced tolerance to this stress. In addition, flooding can change nitrogen absorption in plants, altering leaf nitrogen concentration. These changes could influence the photosynthetic activity, and ultimately, the growth of plantations. The aims of this work were: (i) to identify traits that increase flooding tolerance in willows during early growth and (ii) to analyze the effects of flooding on Assimilatory Nitrogen Use Efficiency (ANUE, measured as foliar biomass: foliar nitrogen concentration ratio). Two-month-old plants growing in pots of 29 willow genotypes were flooded with water covering 80% of the stem, for 43 days. At the end of this period, the flooding tolerance index (ratio between the flooded plant biomass to the non-flooded plant biomass) ranged between 39% and 103%. Flooding tolerance had a significant and positive correlation to plant height, diameter, total biomass, growth rate, leaf area, leaf number, and basic wood density. ANUE decreased in flooded plants in most genotypes, despite the increase in leaf nitrogen concentration. This implies that flooded plants were less efficient in the use of nitrogen to produce leaf biomass than the non-flooded treatment. These results are relevant for the selection of flooding tolerance in young willow plants obtained from rootless cuttings.

Constructing and Validating Estimation Models for Individual-Tree Aboveground Biomass of Salix suchowensis in China

Biomass serves as a crucial indicator of plant productivity, and the development of biomass models has become an efficient way for estimating tree biomass production rapidly and accurately. This study aimed to develop a rapid and accurate model to estimate the individual aboveground biomass of Salix suchowensis. Growth parameters, including plant height (PH), ground diameter (GD), number of first branches (NFB), number of second branches (NSB) and aboveground fresh biomass weight (FW), were measured from 892 destructive sample trees. Correlation analysis indicated that GD had higher positive correlations with FW than PH, NFB and NSB. According to the biological features and field observations of S. suchowensis, the samples were classified into three categories: single-stemmed type, first-branched type and second-branched type. Based on the field measurement data, regression models were constructed separately between FW and each growth trait (PH, GD, NFB and NSB) using linear and nonlinear regression functions (linear, exponential and power). Then, multiple power regression and multiple linear regression were conducted to estimate the fresh biomass of three types of S. suchowensis. For the single-stemmed plant type, model M1 with GD as the single parameter had the highest adj R2, outperforming the other models. Among the 16 constructed biomass-estimating equations for the first-branched plant type, model M32 FW = 0.010371 × PH1.15862 × GD1.250581 × NFB0.190707 was found to have the best fit, with the highest coefficient of determination (adj R2 = 0.6627) and lowest Akaike Information Criterion (AIC = 5997.3081). When it comes to the second-branched plant type, the best-fitting equation was proved to be the multiple power model M43 with PH, GD, NFB and NSB as parameters, which had the highest adj R2 value and best-fitting effect. The stability and reliability of the models were confirmed by the F-test, repeated k-fold cross-validation and paired-sample t-tests. The models developed in this study could provide efficient tools for accurately estimating the total aboveground biomass for S. suchowensis at individual tree levels. The results of this study could also be useful for optimizing the economic productivity of shrub willow plantations.

Nutrient extraction is related to stem diameter distribution, tissue concentration, and yield in an annually harvested Salix coppice

In plantations, nutrient extraction is likely to be higher with shorter rotations. This is because thinner stems have a higher proportion of nutrient-rich bark, and sapwood contains more nutrients than hardwood. Annual willow plantations may extract even more nutrients than long rotation forests. In short rotation forest systems, the diameter of the harvested stems may affect the amount of nutrients exported with the wood. The present study investigated the effect of stem diameter distribution on nutrient extraction and nutrient use efficiency (UE). Two Salix clones were planted at low or high densities, and irrigated or left rainfed. Stems were harvested annually, and three years after planting, N, P, K, and Ca concentrations in small, medium, and big stems were determined, as well as the proportion of each stem diameter class at harvest. N extraction was the highest, followed by Ca, K, and P extraction. Nutrient extraction and nitrogen use efficiency were influenced by the proportion of small, medium, and big stems. The clones showed differences in nutrient concentration and stem diameter distribution, and irrigation increased the proportion of large stems and nitrogen concentration. Although the NUE and PUE were not linearly related to yield, they were related to the distribution of stem diameter and nutrient concentration. Higher yield resulted in higher CaUE and KUE, but the extraction of these nutrients during harvest was fine-tuned by stem diameter distribution and tissue concentration. This highlights the significance of stem diameter distribution in assessing the nutrient costs of wood production for bioenergy.

Spatiotemporal Absorption Features of Yellow Willow Water Usage on the Southern Edge of the Semi-Arid Hunshandak Sandland in China

The improvement of water usage efficiency and productivity, as well as the development of effective water management plans, necessitates a comprehensive understanding of how water utilization patterns in different soil layers within arid and semi-arid climates impact the capacity of plant roots to absorb water. However, there is currently no knowledge regarding the water use strategies employed by artificial yellow willow. So, we conducted a study on the hydrogen and oxygen isotopic composition of rainfall in yellow willow (Salix gordejevii) from the semi-arid region located at the southern edge of the Hunshandak Sandland in China. This study utilized measured data on xylem water, groundwater, soil moisture, and rainfall. By employing a combination of the direct comparison method and the MixSIAR model, we investigated the water uptake strategies employed by yellow willow throughout its growing season. The findings revealed that the mean δ D was highest in precipitation and lowest in groundwater, whereas the mean δ18O was highest in stem water and lowest in groundwater. The δ D and δ18O fluctuated significantly in precipitation but were steady in groundwater. Because precipitation was significantly less than evaporation, the slope and intercept were lower for the local than global atmospheric precipitation line. Water availability steadily declined with increasing depth. Lower δ18O values were caused by precipitation diluting the soil water. The MixSIAR results indicated that the primary source in May, September, and October was utilized at 19%, 18%, and 18%, respectively. In contrast, the utilization rate of each source varied considerably in June, July, and August (the primary source was utilized at 19%, 18%, and 18%, respectively). Comparatively high rates of water absorption and utilization were observed in June (19% of the total water source), July (18%), and August (23%). Therefore, the vertical distribution of the root system and variations in the soil water content regulate water usage for the yellow willow. To prevent excessive water usage and promote ecosystem restoration with artificial yellow willow plantations in water-limited desert settings, policy makers should consider the patterns of plant water use and soil water availability. By selecting drought-adapted plant species and optimizing irrigation management, it is possible to reduce water wastage and ensure that water is used efficiently for revegetation and ecosystem restoration, avoiding overuse of water and maintaining the sustainability of revegetation in water-stressed desert areas.

Sustainability analysis of primary wastewater treatment by willow plantations in Québec

Wastewater treatment is a necessary step to avoid environmental impacts of water consumption and usage. Traditional approaches are expensive and are limited to developed countries. Phytofiltration using fast-growing trees and shrubs like willows potentially offer an alternative. This paper aims to determine if wastewater treatment using phytofiltration can provide complementary environmental and economic benefits for rural communities in a Nordic climate such as the province of Québec, Canada. It looks at different perspectives of the wastewater treatment solution in a local and rural context. Based on life cycle analysis (LCA) and life cycle cost analysis (LCC), we found that, for an exemplar Québec municipality, the conventional wastewater treatment scenario impacted more on climate change, ecosystem quality and human health than the two phytofiltration of wastewater scenarios studied, where impact is highly dependant on the biomass valorization. The net present cost of the phytofiltration scenarios were lower than typical conventional treatment in Québec. For a biomass producer, conventional biomass production had the highest environmental impact on ecosystem quality, while biomass production from phytofiltration had the highest environmental impact on climate change, human health, and resources. We demonstrate that the phytofiltration is a viable and multifunctional technology that could provide good incentives for a local biomass value chain. it allows to both alleviate wastewater treatment burden and provide affordable biomass for bioenergy development for rural communities. Mobilizing local stakeholders will be key to make phytofiltration an alternative solution for both environmental burden alleviation and rural economic development.

Evaluating the impacts of SRC willows on phosphorus export from a temperate grassland micro-catchment

Willows (Salix SPP.) are increasingly being grown as a source of biomass which can be harnessed for energy production at a commercial scale as one example of a Short Rotation Coppice (SRC) crop. What is less widely understood is the role of the plants in reducing nutrient loads when planted as a nature-based solution to mitigate diffuse pollution from agricultural lands. Strategically planted woodland and forest can play a major role in Nature Based Solutions (NBS) approaches. SRC willows were planted in a 22-ha grassland micro-catchment located on a research farm in Northern Ireland, which is regularly grazed by cattle and sheep. The micro-catchment comprises a small ditch with upstream and downstream monitoring points where a pair of autosamplers were used to collect water samples for nutrient analysis. It was possible to reconstruct a timeseries of hourly discharge in the ungauged micro-catchment using the SHETRAN hydrological model. Subsequently, the modelled flows were used to estimate daily phosphorus (P) loads at both upstream and downstream monitoring points from the measured P concentrations. The nearly four years (June 2018–April 2022) of monitoring data allowed P loads to be calculated for pre-planting, juvenile trees and mature trees phases. A baseline scenario was run without any changes to the model; this evaluated the changes in P loads from the catchment. A further Post-Willows scenario “P–W” modified some model parameters and evapotranspiration to represent the land use change due to the willow plantation. The results from the baseline were evaluated and showed that (i) there was a statistically significant reduction in particulate P (PP) and total P (TP) concentrations at the outlet of the micro-catchment; (ii) a statistically significant reduction in PP and TP loads, indicating that the willows were reducing PP export (losses) probably by trapping fine sediment in the ditch. Results from the P–W scenario showed a smaller than expected decrease in discharge from the model results. The overall export of TP from the micro-catchment could be further decreased by additional planting of SRC willows, but the export of soluble forms of P did not decrease by a significant amount post-planting which is a recommendation for further study in mitigation programmes. The use of SRC willows in riparian buffer strips (RBS) which are a common form of NBS, has shown promising results in terms of trapping particulate forms of P. The layout of the RBS should also be carefully designed in terms of maximising the buffer strip width, here the areas planted was optimised to make best use of unproductive farmland. If the RBS can be designed to maximise the interception of runoff flowing downhill from agricultural fields then the removal rate should be even higher.

Draft Genome of Nocardia canadensis sp. nov. Isolated from Petroleum-Hydrocarbon-Contaminated Soil.

The bacterial strain WB46 was isolated from the rhizosphere of willow plants (Salix purpurea L.) growing in soil contaminated with petroleum hydrocarbons. The strain was subjected to whole-genome shotgun sequencing using Illumina HiSeq. Its draft genome is 7.15 Mb, with a 69.55% GC content, containing 6387 protein-coding genes and 51 tRNA and 15 rRNA sequences. The quality and reliability of the genome were assessed using CheckM, attaining an estimated genome completeness of 98.75% and an estimated contamination of 1.68%. These results indicate a high-quality genome (>95%) and low contamination (<5%). Many of these genes are responsible for petroleum hydrocarbon degradation, such as alkane 1-monooxygenase (alkB) and naphthalene dioxygenase (ndo). 16S rRNA gene analysis, including in silico DNA-DNA hybridization (DDH) and average nucleotide identity (ANI), showed that strain WB46 belongs to the genus Nocardia, and the most closely related species is Nocardia asteroides. The strain WB46 showed a distance of 63.4% and sequence identity of 88.63%, respectively. These values fall below the threshold levels of 70% and 95%, respectively, suggesting that the strain WB46 is a new species. We propose the name of Nocardia canadensis sp. nov. for this new species. Interestingly, the sequence divergence of the 16S rRNA gene showed that the divergence only occurred in the V2 region. Therefore, the conventional V3-V4, V5-V7, or V8-V9 targeting metabarcoding, among others, would not be able to assess the diversity related to this new species.

Manifestation of Triploid Heterosis in the Root System after Crossing Diploid and Autotetraploid Energy Willow Plants.

Successful use of woody species in reducing climatic and environmental risks of energy shortage and spreading pollution requires deeper understanding of the physiological functions controlling biomass productivity and phytoremediation efficiency. Targets in the breeding of energy willow include the size and the functionality of the root system. For the combination of polyploidy and heterosis, we have generated triploid hybrids (THs) of energy willow by crossing autotetraploid willow plants with leading cultivars (Tordis and Inger). These novel Salix genotypes (TH3/12, TH17/17, TH21/2) have provided a unique experimental material for characterization of Mid-Parent Heterosis (MPH) in various root traits. Using a root phenotyping platform, we detected heterosis (TH3/12: MPH 43.99%; TH21/2: MPH 26.93%) in the size of the root system in soil. Triploid heterosis was also recorded in the fresh root weights, but it was less pronounced (MPH%: 9.63-19.31). In agreement with root growth characteristics in soil, the TH3/12 hybrids showed considerable heterosis (MPH: 70.08%) under in vitro conditions. Confocal microscopy-based imaging and quantitative analysis of root parenchyma cells at the division-elongation transition zone showed increased average cell diameter as a sign of cellular heterosis in plants from TH17/17 and TH21/2 triploid lines. Analysis of the hormonal background revealed that the auxin level was seven times higher than the total cytokinin contents in root tips of parental Tordis plants. In triploid hybrids, the auxin-cytokinin ratios were considerably reduced in TH3/12 and TH17/17 roots. In particular, the contents of cytokinin precursor, such as isopentenyl adenosine monophosphate, were elevated in all three triploid hybrids. Heterosis was also recorded in the amounts of active gibberellin precursor, GA19, in roots of TH3/12 plants. The presented experimental findings highlight the physiological basics of triploid heterosis in energy willow roots.

Perfluoroalkyl substances exposure alters stomatal opening and xylem hydraulics in willow plants

Climate change and pollution are increasingly important stress factors for life on Earth. Dispersal of poly- and perfluoroalkyl substances (PFAS) are causing worldwide contamination of soils and water tables. PFAS are partially hydrophobic and can easily bioaccumulate in living organisms, causing metabolic alterations. Different plant species can uptake large amounts of PFAS, but little is known about its consequences for the plant water relation and other physiological processes, especially in woody plants. In this study, we investigated the fractionation of PFAS bioaccumulation from roots to leaves and its effects on the conductive elements of willow plants. Additionally, we focused on the stomal opening and the phytohormonal content. For this purpose, willow cuttings were exposed to a mixture of 11 PFAS compounds and the uptake was evaluated by LC-MS/MS. Stomatal conductance was measured and the xylem vulnerability to air embolism was tested and further, the abscisic acid and salicylic acid contents were quantified using LC-MS/MS. PFAS accumulated from roots to leaves based on their chemical structure. PFAS-exposed plants showed reduced stomatal conductance, while no differences were observed in abscisic acid and salicylic acid contents. Interestingly, PFAS exposure caused a higher vulnerability to drought-induced xylem embolism in treated plants. Our study provides novel information about the PFAS effects on the xylem hydraulics, suggesting that the plant water balance may be affected by PFAS exposure. In this perspective, drought events may be more stressful for PFAS-exposed plants, thus reducing their potential for phytoremediation.

The effect of afforestation type on soil nitrogen dynamics in the riparian zone of the upper Yangtze River of China

Afforestation is increasingly important in nutrient cycling in riparian ecotones given that ecosystems in riparian zones are susceptible to anthropogenic activities induced by land use change. However, how land use change (e.g., afforestation) with different planting types influences nitrogen (N) dynamics in riparian zones remains unclear. Here, we examined soil N dynamics following afforestation with three types of plantations of pure willow (Salix babylonica), pure mulberry (Morus alba), and the mixed two species paired with adjacent maize croplands in the upper Yangtze River of China. Our results showed afforestation with the two pure species significantly reduced soil total N (TN) concentration. Soil NO3−-N concentration was significantly reduced by the willow and mixed-species afforestation, but soil NH4+-N concentration was significantly higher in the willow and mixed woodlands compared to the paired croplands. Soil N concentrations were tightly associated with the potential N transformation rates, which showed a roughly decreasing trend in N mineralization following afforestation. Soil properties, microbial biomass, and extracellular enzymes jointly explained a large proportion of the total variation in soil N concentrations, with soil enzymes largely contributing to N variation in the topsoil and soil properties primarily contributing to N variation in the subsoil. Overall, our results demonstrate that afforestation with different planting types had contrasting effects on soil N content in the riparian zone. These findings provide new insights into the management of afforestation types to retain soil N by mediating soil properties and microbial activities in the riparian zones under future land use change.

Reducing the time-dependent climate impact of intensive agriculture with strategically positioned short rotation coppice willow

In this study the implementation of a short rotation coppice willow system, planted as a riparian buffer in an intensive agricultural setting, to intercept and reduce nutrient losses, was investigated. The aim of the work was to assess how such a system could reduce the overall climate impact of an intensive agricultural setting. A life cycle assessment was carried out for a combined Irish dairy farm and willow buffer system considering the impact category, climate impact. The climate impact was considering using the time-dependent climate impact metric, with the results given in terms of the impact on the global surface temperature. The results were compared to an Irish dairy farm in which no willow was planted. Such a system has not previously been investigated in this way and this was the first time-dependent climate impact assessment of a willow plantation planted on pastureland. Geographic information systems software, was used to map areas particularly susceptible to agricultural run-off and suitable for willow planting, using the land bank of the Agri-Food and Biosciences Institute research farm in Hillsborough, Northern Ireland, for the case study. The harvested willow was assumed to be combusted in a combined heat and power plant. By implementing the willow system the time-dependent climate impact of an Irish dairy farm could be reduced by 8% with only 3.7% of the land used for willow cultivation over a 101-year study period. The results also found an immediate reduction in climate impact following the implementation of the willow system. Total GHG emissions were reduced by 131 Mg CO2eq ha−1 over the study timeframe. The results can be more broadly applied to other agricultural sectors, such as arable farming where the climate impact savings of the willow system could be even higher.

THE DISTRIBUTION OF CASH EXPENSES FOR THE CREATION OF BIOENERGY WILLOW PLANTATIONS IN UKRAINE

The economic cost analysis of creating energy willow plantations in Ukraine is provided in the present paper. The experience of creating bioenergy willow plantations at scientific and industrial institutions in Ukraine has been used in the paper. The purpose of this scientific work is to conduct an analysis of the structure of cash expenses for the creation of bioenergy willow plantations based on the experience of various institutions of Ukraine. The analysis is based on a technological map created during the study on drained peat lands at Panfyly Research Station. Analyzing the cost structure by category, the data obtained during the creation of bioenergy willow plantations of Salix Energy LLC and the Institute of Bioenergy Crops and Sugar Beet were also taken into account. After analyzing all the technology stages of growing bioenergy willow, it was revealed that the most expensive is the second stage associated with the preparation for planting and planting willow cuttings in the context of the pricing policy in Ukraine. In general, more than 60% of all expenses fall upon the first year of cultivation. According to the experience of Ukrainian institutions, the cost structure will have a significant shift towards planting material - 55-60%. The remaining costs are distributed during the use of equipment in the field, which constitute 26-30% and transportation costs respectively are 12-19%.

Expression of triploid heterosis in the biomass productivity of energy willow plants under salinity stress

Bioenergy production from short rotation woody species grown on saline soil provides multiple environmental advantages. Breeding of energy willow for salinity tolerance can support green energy utilization. Here, we quantify triploid heterosis in biomass traits under salt stresses. Crosses between diploid cultivars (Tora and Inger) and our autotetraploid plants (PPE-2/6 and PPE-7) resulted in TH16/24 and TH21/2 triploid hybrid genotypes. Growth characteristics of shoots and roots of triploid hybrids and their parental plants were monitored by pixel-based phenotyping under high salt stress (NaCl 2.0 g kg −1/EC: 8.71 mS cm−1) in greenhouse. Different values of Mid-Parent Heterosis (MPH %) were recorded by comparing these two crossing combinations and top or above views (for TH16/24 plants: 3.66% (side pixels) and 22.25% (above pixels) and for TH21/2 plants: 63.30% (side pixels) and 72.10% (above pixels). At the end of the growing period, considerable MPH values were detected in biomass parameters of TH16/24 and TH21/2 plants (shoot length: 18.26%/26.28%; green biomass weight: 40.28%/52.40%; stem diameter: 15.40%/13.98%) in soil with 2.0 g NaCl kg−1. The TH21/2 hybrid plants expressed higher hybrid vigor than plants from the TH16/24 genotype. The TH21/2 hybrid plants exhibited better water use efficiency than their parental plants and showed high MPH values for K+/Na+ ratio in soil containing 2.0 g NaCl kg−1. The presented data support a conclusion that heterosis depending on crossing partners can ensure improvement in salinity tolerance for triploid hybrids. Field experiment has been initiated for the characterization of these hybrids under natural saline soil.

The relationship between tree species and wood colonising fungi and fungal interactions influences wood degradation

Deadwood is one of the main terrestrial carbon (C) pools and its decomposition is fundamental in biogeochemical cycles. As fungi are the main wood degraders, a study was carried out on deadwood-colonising fungal community changes as a function of host plants and wood degradation. Deadwood fungal communities were investigated in adjacent woody plantations of hybrid poplar, willow and black locust established in the early 2000 s and abandoned for fifteen years. Lying deadwood was estimated in the three plantations and wood decay (WD) visually assessed using a 3-class scale. Fungal colonization of wood samples was assessed using culture-based methods and identified with morphological and molecular features. Wood colonising fungal communities differed in composition both between host plants and WD classes (P < 0.001). Ligninolytic white rot fungal species (Basidiomycota) prevailed in black locust and poplar, where they co-colonised all three wood decay classes in association with soft rot fungal agents. In willow, Daldinia chilidiae, a ligninolytic ascomycete, co-colonised deadwood with fungal species associated with tree dieback (Botryosphaeriaceae); whilst soft rot fungi principally colonised the highest wood degradation class. Results showed high fungal preference towards tree species that was most evident in ligninolytic fungi. Moreover, different wood decay paths were deduced from fungal changes across the three wood degrading classes and the necromass distribution in those classes. The co-habitation of white rot and soft rot fungi in all the wood decay classes of poplar and black locust indicated a continuum decay process; whilst the prevalence of soft rot fungi in the almost decomposed class in willow, suggested sequential succession of primary and secondary phases in deadwood degradation. Wood degradation is influenced by plant species and the native fungal microbiome and is mediated by multiple biotic interactions and environmental factors, which supports the use of wood colonising fungi as indicators of forest ecosystem health.

Landscape Metrics and Land-Use Patterns of Energy Crops in the Agricultural Landscape

Energy crops are a new player in the traditional agricultural landscape. The present paper analyses the land uses surrounding and the spatial characteristics of the main energy crops in Sweden (willow, poplar, hybrid aspen and reed canary grass) compared to traditional agricultural crops during the period 2006–2018. Spatial metrics (number of shape characterising points, shape index and rectangularity ratio) are calculated for each field, as well as the nearby land uses at varying distances, at radius: 500 m, 1000 m, 2000 m and 5000 m. A total of 1560 energy crop fields are studied in the 2006 dataset and 3416 fields in the 2018 dataset, which are compared to 58,246 fields with cereal crops in 2006 and 131,354 fields in the 2018 dataset. Results show that, despite being established on previous agricultural land, energy crops present a different spatial profile compared to traditional agricultural crops. Field shapes present less complexity than before, and the overall spatial features become more regular with time in both cases of energy crops and cereals, suggesting an increasing trend in cost-efficient agricultural practices and planning. Important differences concerning land use diversity at different scales are found between plantations versus grasses. In general, willow plantations are located in agriculture-dominated areas (> 70% at 500 m, > 50% at 2000 m), whereas reed canary grass is in forest-dominated landscapes (> 30% at 500 m, > 60% at 2000 m); both contribute to diversifying existing land uses although with varying effects. The results of this study are a basis to assess the impacts of energy crops at landscape level and can translate into applications in energy policy and planning.

Comparative wood anatomy, composition and saccharification yields of wastewater irrigated willow cultivars at three plantations in Canada and Northern Ireland

Conventional wastewater treatment strategies can have high financial costs which often leads to discharge of undertreated wastewater into the ecosystem. In parallel, the cultivation of willows for bioenergy can be limited due to their high water demand. Despite the potential for treatment using willow plantations, the effect of wastewater irrigation on biomass development and biofuel potential has yet to be investigated across different cultivars and sites. Here, the effect of secondary treated wastewater irrigation on wood anatomy, biomass composition and enzymatic saccharification were investigated in one poplar and thirteen willow cultivars planted at one of three sites in either Canada or Northern Ireland. There was significant anatomical and compositional variation between cultivars at all three sites, but wastewater irrigation had little impact on biomass development. Vessel and fibre cell frequencies ranged between cultivars from 129 to 178 and 4322–7058 per mm2, with average transverse areas of 838–1278 and 120–190 μm2, respectively. Glucan and lignin content varied from 42.3 to 50.7% dry matter (DM) and 27.3–32.4% DM, respectively, whereas glucose release varied from 50 to 160 mg g−1 of glucan or 30–90 mg g−1 of DM. Glucan content and fibre cell frequency had significant positive correlations with glucose release yields, whereas average fibre cell area had an inverse correlation. These findings suggest both cell wall structure and tissue morphology could be important factors when considering biomass recalcitrance to deconstruction. Maintenance of biomass quality during irrigation provides evidence that integration of dedicated bioenergy production with environmental wastewater treatment using willow phytofiltration has potential as a promising clean biotechnology.

Treatment of Landfill Leachate by Short-Rotation Willow Coppice Plantations in a Large-Scale Experiment in Eastern Canada

The treatment of leachate by vegetative filters composed of short-rotation willow coppice (SRWC) has been shown to be a cost-effective alternative to conventional and costly methods. However, few studies have considered the treatment capability of willow filters at a scale large enough to meet the industrial requirements of private landfill owners in North America. We report here on a field trial (0.5 ha) in which a willow plantation was irrigated with groundwater (D0) or aged leachate at two different loadings (D1 and D2, which was twice that of D1). Additionally, half of the D2-irrigated plots were amended with phosphorus (D2P). The system, which operated for 131 days, was highly efficient, causing the chemical oxygen demand concentration to drop significantly with the total removal of ammonia (seasonal average removal by a concentration of 99-100%). D2P efficacy was higher than that of D2, indicating that P increased the performance of the system. It also increased the willow biomass 2.5-fold compared to water irrigation. Leaf tissue analysis revealed significant differences in the concentrations of total nitrogen, boron, and zinc, according to the treatment applied, suggesting that the absorption capacity of willows was modified with leachate irrigation. These results indicate that the willow plantation can be effective for the treatment of landfill leachate in respect of environmental requirements.

Phytostabilization Potential of Salix alba as Biomonitors of Heavy Metals in Soil Pollution near the Erzeni Riverbank

The great sources of water pollution in Albania in the last decade are urban discharges which indicate in other sistems. The aim of this study was to evaluate the concentration of heavy metals in the soil and plant of Salix alba. Samples was collected from the Erzen riverbed. The objectives are based on assessment of the concentrations of physico-chemical characteristics heavy metals obtained from the sediment and willow (Salix alba) in Erzeni river. The presence of organic matter in soil - the willow plant - was also analyzed. The use of plants in the recuperation of contaminated soil is low cost, sustainable, and environmentally sound. Heavy metals concentration in soil range as follows: Ni (42.2–98.4 mg/kg); Cr (18.9- 34.5 mg/kg), and Pb (53.2-98.4 mg/kg). Some statistically significant differences were observed in the data on the amounts of metals accumulated in the soil, significantly more than in the data on the metal concentrations achieved in the tissues of the Salix alba plant. Heavy metal concentration in plants reach values Ni (0.9–3.54 mg/kg); Cr (0.57 - 0.89 mg/kg), and Pb (0.06 -0.19 mg/kg). Average concentrations in heavy metal plant samples were listed in the order Ni&gt; Cr&gt; Pb. The results of nickel, chromium, and lead clearly show higher concentrations in samples 0-25 cm across the range of extractors. The use of diversified plant materials is essential and optimal for the phytoremediation process. These species offer different opportunities through their metallic tolerance and accumulation of underground biomass metals for the permanent removal of these metals from the terrestrial substrate.