Aims In this study, we quantified the carbon sequestration capacity of willow plantations established on sites with contrasting land-use histories, such as agricultural, contaminated brownfields or landfills. Methods On each plantation site, soil samples were collected in planted and unplanted plots to better determine the influence of willow plantations on various parameters such as total soil carbon stocks, organic matter content, carbon fractionation as well as soil respiration and microbial activity. Results On agricultural sites, willows were shown to have no discernible influence on different soil carbon pools, microbial activity or microbial respiration. In contrast, carbon pools on brownfield sites were usually negatively impacted by the presence of certain willow cultivars notably Salix miyabeana and S. purpurea ‘Fish Creek’, but these same cultivars had a positive influence on microbial respiration levels. On a landfill, where willows were recently established on bare technosol, we observed a positive impact on total soil carbon pool in comparison to unplanted plots. Conclusions These results show that the type of site on which willow plantations are established has a great influence on the way with which it will impact soil carbon. The results also point towards a relationship between soil microbial activity levels and carbon sequestration potential. In situations where microbial respiration is higher, soil carbon stocks tend to be much lower, as microbial communities mineralize labile carbon pools the more active, they are. Nitrogen content was also found to be closely correlated both to the different carbon pools tested and microbial indicators, regardless of site type.

Global demand for aluminium continues to rise, generating bauxite tailings that release hyperalkaline leachates enriched in metals and metalloids. These leachates accumulate in retention basins and pose environmental risks, while treatment is particularly challenging in cold climates. A passive, nature-based treatment approach for bauxite residue leachate in a humid continental climate was evaluated using locally available substrates and native plants. In an 8-week controlled microcosm experiment, sewage sludge–amended systems planted with Calamagrostis canadensis, Scirpus cyperinus, Salix nigra, or Typha latifolia were irrigated with leachate applied as undiluted (pH 11.5), diluted 1:1 (v/v) with tap water or acidified to pH 10.0. Across measured performance metrics, T. latifolia showed the strongest overall response: aerial biomass did not differ significantly among leachate treatments (38.6–49.1 g DW; − 16

Willows can alleviate soil salinisation while generating sustainable feedstock for biorefinery, yet the metabolomic adaptations underlying their tolerance remain poorly understood. Salix miyabeana was treated with two environmentally abundant salts, NaCl and Na2SO4, in a 12-week pot trial. Willows tolerated salts across all treatments (up to 9.1 dS m-1 soil ECe), maintaining biomass while selectively partitioning ions, confining Na+ to roots and accumulating Cl- and SO 4 2 - $$ {\mathrm{SO}}_4^{2-} $$ in the canopy and adapting to osmotic stress via reduced stomatal conductance. Untargeted metabolomics captured >5000 putative compounds, including 278 core willow metabolome compounds constitutively produced across organs. Across all treatments, salinity drove widespread metabolic reprogramming, altering 28% of the overall metabolome, with organ-tailored strategies. Comparing salt forms at equimolar sodium, shared differentially abundant metabolites were limited to 3% of the metabolome, representing the generalised salinity response, predominantly in roots. Anion-specific metabolomic responses were extensive. NaCl reduced carbohydrates and tricarboxylic acid cycle intermediates, suggesting potential carbon and energy resource pressure, and accumulated root structuring compounds, antioxidant flavonoids, and fatty acids. Na2SO4 salinity triggered accumulation of sulphur-containing larger peptides, suggesting excess sulphate incorporation leverages ion toxicity to produce specialised salt-tolerance-associated metabolites. This high-depth picture of the willow metabolome underscores the importance of capturing plant adaptations to salt stress at organ scale and considering ion-specific contributions to soil salinity.

As waste from engineered landfills decomposes, it produces nitrogen (N)-laden leachate that cannot be directly released into the environment. Plants such as willows have the potential to phytofilter this polluted water but must be able to tolerate large loads of contaminants and flooding conditions. To date, however, it is mainly exotic species that have been used in for the treatment of leachates in a pilot project conducted on a technical landfill. It would be useful to compare the effectiveness of native species from eastern Canada with that of the Salix miyabeana 'SX64', a willow cultivar used in the pilot project. Three willows indigenous to Canada: S. amygdaloides, S. bebbiana and S. nigra, were tested alongside S. miyabeana. A mesocosm experiment was conducted under semi-controlled conditions over six weeks to document the impact of various nitrogen overfertilization and flooding treatments on plant development, and to test the plants' tolerance to these constraints to evaluate their suitability for large-scale vegetative filters. Overall, growth and biomass production of S. nigra and S. amygdaloides were not affected by the treatments. Furthermore, S. nigra was ten times more efficient than the cultivar of S. miyabeana in terms of decontamination capacity. While still in the juvenile phase, S. nigra plants removed the equivalent of 240m3 per hectare of the N-contaminated water initially applied (60 kg of N), under both permanent and cyclic flooding. These results suggest that native species could be given greater in future projects.

Young landfill leachate, produced by the passage of water through operating sites at a municipal landfill, is highly concentrated in organic matter, ammonia and metals, and is typically treated using intensive, conventional systems. Studies have demonstrated efficient treatment of low-strength old leachate, produced by capped sites at a landfill, by nature-based systems such as treatment wetlands. Few studies have investigated the use of similar systems to treat young leachate. The objectives of this study were to 1) determine if vertical flow planted and unplanted aerated filters could efficiently treat young leachate COD, BOD5, TSS, NH4 and p-cresol; 2) determine the suitability and effect of two plant species on treatment efficiency; 3) quantify the denitrification capacity achieved in pre-anoxic filters; and 4) determine full-scale design criteria (hydraulic and organic loading rates and space requirements) for 1500 m3/d of young leachate. Five 430 L water-saturated vertical flow pilot- scale filters with forced aeration and 10 to 20 mm granite gravel media were operated in parallel in a greenhouse for 42 weeks total during fall 2020 and spring through fall 2021. Each filter was fed with an average of 16.4 L m- 2 d- 1 of anaerobically pretreated young leachate spiked with 3340 mu g/L of p-cresol for an organic loading rate of 3.5 g BOD5 m- 3 d- 1 to each filter. Two filters were planted with Salix miyabeana 'SX67', two were planted with Sporobolus michauxianus and one was left unplanted. Two planted filters (one with each plant species) had pre-anoxic filters for denitrification. Results indicated that planted and unplanted filters offered similar treatment, with average removal efficiencies of 74 % for COD, 98 % for BOD5, 96 % for TSS, 100 % for NH4 and 100 % for p-cresol. Young leachate treatment negatively impacted plant health and their chlorophyll fluorescence. Systems with pre-anoxic filters were able to achieve a higher total nitrogen removal efficiency of 70 % compared to 60 % on average for systems without pre-anoxic filters. The high removal efficiency achieved suggests that filter systems were operated below the treatment capacity of the microorganisms. Unplanted aerated filters are a promising technology for treatment of young landfill leachate and p-cresol.

Antimony (Sb) contamination threatens food security by lowering crop yields, reducing nutritional quality, and harming agroecosystems, underscoring the need for sustainable and eco-friendly strategies to alleviate heavy metal stress. Here arbuscular mycorrhizal fungi (AMF) role to mitigate Sb-induced stress in maize, was examined. AMF-inoculated and non-inoculated plants were grown under control and Sb stress conditions for 10 weeks, and growth, nutrient uptake, metabolic profiles, antioxidant capacity, and antimicrobial activity were assessed. Sb exposure markedly suppressed maize performance, reducing fresh and dry biomass by 66% and 65%, respectively, while also impairing the growth-promoting effects commonly associated with AMF. However, AMF inoculation significantly alleviated Sb toxicity, enhancing fresh biomass by 43% and dry biomass by 40%. The recovery was linked to improved nutrient uptake and the accumulation of primary metabolites, which promoted physiological adjustments. Moreover, AMF-inoculated plants under Sb stress showed enriched bioactive metabolites, leading to stronger antimicrobial activity and a 65% increase in antioxidant capacity. Collectively, these findings demonstrate that AMF enhance maize resilience to Sb stress by promoting growth, nutritional quality, and bioactive properties. This study demonstrates that AMF offer a sustainable strategy to enhance crop resilience and biofortification in contaminated environments.

Using by-products from local industries as fertilisers is an innovative way to connect urban and rural systems. However, positive results have been observed only in food production, while research on phytoremediation, particularly in peri-urban areas, is lacking. This study assessed the effectiveness of frass in improving the phytoremediation capabilities of two Salicaceae taxa in Cu-contaminated soils. The study was conducted over three months. Soils were amended to reach 1,000 mg Cu kg− 1 and fertilised with either frass or chicken manure (250 kg N Ha− 1). After the harvest, soil samples were analysed for nutrient (available N and P) and metal (e.g. Cu, Fe, Zn) concentrations. Plant yields were documented, photosynthetic activity was monitored, and nutrient utilisation rates were examined. Nitrogen use efficiency was higher in the Salix containers amended with manure (12

Phytomanagement of contaminated sites can mitigate exposure risks for surrounding populations while providing numerous ecological services. To meet these goals, trait-based models are proposed to guide plant selection. However, this relies on the assumption that plant traits can effectively predict key services and that traits of individual species can be used to predict mean, or community-level traits of a given species assemblage. To critically evaluate these assumptions, we conducted a mesocosm study where three willow species were planted in all possible combinations (1 to 3 species) in contaminated soil under a controlled environment, for 110 days. At the community-level (for every mesocosm), we measured ten functional traits and three phytoremediation services (i.e. phytoextraction, phytostabilization, and translocation factor). We evaluated the differences between observed community-level traits and expectations from traits of the corresponding species grown in monocultures. Then, we compared the predictability of phytoremediation services through species composition and community-level traits. Our results indicate that, despite the short phylogenetic gradient, willow species exhibit distinct and predictable traits within assemblages. Moreover, trait values measured here are comparable to the values retrieved on the TRY database, confirming the potential of global databases to guide trait-based efforts in phytoremediation. Phytoremediation services were not predicted by species composition (mean R2adj = 0.05), but rather well explained by community-level traits (mean R2adj = 0.52). This suggests that models incorporating functional information are better suited to predict and understand phytoremediation services. Phytoextraction was generally correlated to fast-to-intermediate aboveground growth strategies with fast-growing belowground tissues, while translocation factors were associated with slower root growth. Phytostabilization was associated with faster-growing root systems and stress-tolerant capacities from the aboveground tissues. This experiment represent a strong test for trait-based models, given the short phylogenetic and contamination gradients tested. This reinforces the potential of trait-based models in phytoremediation and phytotechnologies more broadly.

Green initiatives and phytotechnologies, such as phytoremediation, hold great potential for the sustainable management of contaminated brownfields. One impediment to these initiatives is the lack of alternatives for the produced biomass due to the potential contamination of plants by trace elements. We conducted an experiment to quantify the accumulation and the translocation patterns of trace elements in the aboveground parts of fifteen desirable plants species used for these kinds of initiatives, i.e. urban predominance, ecological relevance, edibility, commercial prospective, and phytoremediation potential. The experiment was set-up in a tunnel-type greenhouse in which plants were grown in pots filled with contaminated urban soil containing Cu, Zn, Se, Ag and spiked with Cd. Our results indicated that different species exhibited differential abilities to accumulate and translocate trace elements in their aboveground biomass and furthermore, exhibited different bioconcentration factors. A clear exclusion of Cd allocation was observed in fruits and flowers. However, Cd content in edible parts was still above the standard recommendations for human consumption. Our results suggest potential candidates for phytoremediation by revealing different accumulation patterns, also highlighting the importance of characterizing trace elements in the soil for selecting the appropriate plant species based on project's needs.

Willows can alleviate soil salinisation while generating sustainable feedstock for biorefinery, yet the metabolomic adaptations underlying their salt tolerance remain poorly understood. Testing two environmentally abundant salts, the response of Salix miyabeana was assessed after treatment with a moderate concentration of NaCl, and both moderate and high concentrations of Na2SO4 in a 12-week pot trial. Willows tolerated salts across all treatments (up to 9.1dS m-1 soil ECe), maintaining photosynthesis and biomass while selectively partitioning ions, confining Na+ to roots and accumulating Cl- and SO 2- in the canopy, and adapting to osmotic stress via reduced stomatal conductance. Untargeted LC-MS/MS captured over 5,000 putative compounds, characterising the baseline willow metabolome, including 278 core compounds constitutively produced across organs. Comparative statistical analyses revealed widespread metabolic reprogramming in response to soil salinity, altering 28% of the overall metabolome, and highlighting organ-tailored strategies. Comparing both salt forms at equimolar sodium, generalised salinity responses were limited to 3% of the metabolome, predominantly in roots. Anion-specific metabolomic responses were more extensive, with NaCl reducing carbohydrates and TCA intermediates, thereby exerting pressure on carbon and energy resources, alongside the accumulation of root structuring compounds, antioxidants flavonoids, and fatty acids. In contrast, Na2SO4 salinity triggered accumulation of sulphur-containing larger peptides, suggesting that excess sulphate incorporation leverage ion toxicity to produce specialized salt-tolerance associated metabolites. This high-depth picture of the willow metabolome underscores the importance of capturing plant adaptations to salt stress at organ-scale and considering ion-specific contributions to soil salinity. ### Competing Interest Statement The authors have declared no competing interest.

The rise in industrial activity has resulted in an escalating threat antimony (Sb) buildups and biomagnifications in both plants and humans. Arbuscular mycorrhizal fungi (AMF) have been thoroughly investigated as a soil enhancement due to their ability to decrease the accumulation of many heavy metals in plant tissues. However, a quantitative and data-based consensus has yet to be reached on the effect of AMF application on maize plants, focusing on plant growth, nutrient content, and antioxidant properties in maize grains subjected to antimony treatment. A notable decrease in AMF-related parameters, including colonization, hyphal length, and arbuscules, was noted when AMF was combined with Sb compared to AMF alone. The AMF treatment alone enhanced plant growth, as indicated by the increased fresh and dry biomass, while Sb treatment alone reduced substantially the total fresh (66%) and dray weight (65%). However, combining AMF with Sb resulted in significant variations in macro- and micronutrients in maize grains. Notably, the combined AMF and Sb treatment influenced the nutritional value of maize grains, showing increased levels of organic acids, amino acids, and fatty acids compared to control. Furthermore, antioxidant activity of maize grains was enhanced by AMF inoculation, as indicated by high levels of polyphenols (39%), flavonoids (63%), ascorbic acid (ASC) (71%), and glutathione (GSH) (28%) content as response to Sb application. Also, a 33% rise in total tocopherol was noted, reflecting comparable upward trends. These findings suggest that the co-application of AMF and Sb can positively influence maize nutritional quality and antioxidant properties of maize grains, offering benefits for sustainable agricultural practices.

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.

Despite the large popularity of Salix miyabeana for various environmental applications in different parts of the world, most propagation techniques rely mainly on cuttings. However in vitro propagation seems a more reliable solution when selection of new commercial clones and varieties is the goal of propagating willows. The current study is the first attempt to propagate S. miyabeana via in vitro propagation, focusing on two specific aspects: different surface sterilization procedures (i.e. combinations of different sodium hypochlorite concentrations and soaking times) and different types of explants (apical vs. lateral). Our findings show that 3% sodium hypochlorite for 20 min represents the most effective sterilization procedure to ensure healthy plants. Additionally, the material obtained from apical explants showed higher survival rate, budding ability and lower microbiological contamination compared to lateral explants.

Willow is considered an ideal plant species for environmental applications, including phytoremediation. Improving planting efficiency and reducing the costs of phytoremediation have become key steps for increasing its application. This paper reports the most update-to-date information on frequently used techniques for establishing willow, including plant material, planting methods, and the factors influencing the early establishment of trees in the field. The five main types of planting materials (rods, cuttings, billets, micro-cuttings and single-bud short branches), and the seven main planting techniques, especially different vertical and horizontal planting directions, were assessed. Factors affecting willow establishment were also reviewed, including the characteristics of planting materials (i.e., clones, cutting phenology, propagules size, pre-treatments), operation during planting (i.e., timing, orientation and planting depth) and post-planting management (i.e., soil conditions and weed management). New planting approaches with small-sized cuttings (of about 5 cm in length) have been recently proposed showing promising economical and effectiveness characteristics, especially for the establishment of willows in harsh soil and challenging conditions.

Background and aims Hyperaccumulator plants exhibit extreme ecophysiological characteristics, which make them suited for phytoremediation. Understanding their ecological strategies might help identify the species and functions to be favored in phytoremediation, restoration, and conservation projects for metalliferous sites. Methods Here, we identified the hyperaccumulator species in the worldwide plant trait database TRY and cross-referenced these trait syndromes associated with the ability of plants to concentrate metals. This allows us to link trace element hyperaccumulation with broader plant ecological strategies. Results Hyperaccumulator plant species tend to have smaller leaves and poorer competitive ability compared to non-hyperaccumulator plant species. Contrary to expectations, we found no indication of hyperaccumulator plants being more resource-conservative on the leaf economics spectrum. However, these data remain fragmentary as only 2.7% of hyperaccumulator plant species have their traits published in the TRY database. Conclusion The recent development of trait-based models to construct plant communities providing optimal ecosystem services (e.g. , phytoremediation, restoration) requires further research to identify predictable trait-service relationships. We thus call for an international collaborative sampling effort to measure traits in more hyperaccumulator plant species.

In the Montreal Botanical Garden's almost 100 years of existence, plant conservation has always been of concern, whether it has been via its plant collections policies, its educational programs, or its conservation and research projects. The garden's historical and current activities are well aligned with the North American Botanic Garden Strategy for Plant Conservation with contributions on many fronts, such as the following: national and international floristic studies; threat assessments of provincial floras; ex situ conservation of threatened taxa; conservation of natural sites; conservation of Indigenous Peoples' ethnobotanical knowledge; and the development of innovative phytotechnological approaches for the ecological restoration of degraded or contaminated sites. More recently, the Montreal Botanical Garden has also been involved in the recovery programs of two endangered species in the province of Québec, Carex lupuliformis and Cirsium scariosum var. scariosum. The garden is now looking toward the future and integrating ecological transition concepts in its development plan as well as developing citizen awareness programs to promote ecologically responsible sustainable practices.

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 mu m2, 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.

Fast-growing hybrid poplars have been tested for their potential to remove trace elements (TE) from polluted soil in several temperate regions. Despite their potential, they have rarely been tested in countries with a cold temperate climate. The current study screened four different Populus hybrids for phytoextraction of four TEs (i.e., As, Cu, Pb, and Zn) on an abandoned brownfield site in southern Quebec (Canada). The main results showed that under the current experimental conditions, the most important traits determining the actual phytoextraction rate are Biological Concentration Factor (BCF) and TE accumulation in the aboveground biomass, rather than biomass productivity. Although the overall performance of the chosen hybrids was rather poor, the presence of poplar stands enhanced the movement of mobile contaminants in soil, which led to an increase in their concentration in the root zone. This aspect suggests possible strategies for using these plants with high transpiration rates in future phytoremediation projects, including either possible rotation with more effective TE phytoextractor plants (e.g., hyperaccumulators) that can remove high TE amounts that have migrated from the deeper soil layers following poplar plantation, or phytostabilization.Although the use of fast-growing woody species is commonly reported as a feasible option for the phytoextraction of TEs in temperate climates, most available information pertains to only a few species, mostly willows. This is one of the few studies reporting the results of a field test carried out in a cold temperate region, in which different poplar hybrid clones were tested for their potential in TEs phytoextraction. This research determined that although the studied poplar genotypes have no potential under these experimental conditions, the increase in TE concentration observed in the rhizosphere after two years suggests possible alternative phytoremediation strategies (phytostabilization) for managing polluted sites in cold temperate climates.

Traditional treatment of wastewaters is a burden for local governments. Using short rotation coppice willow (SRCW) as vegetal filter has several environmental and economic benefits. Here, we investigated the effect of primary wastewater irrigation on wood structure and composition of the willow cultivar Salix miyabeana ‘SX67’ following two years of growth. Compared to unirrigated plants (UI), stem sections of plants irrigated with primary wastewater (WWD) showed an unexpected decrease of hydraulic conductance (KS) associated with a decrease in vessel density but not vessel diameter. The majority (86%) of vessels had diameters range groups [20-30[, [30-40[and [40-50[µm and contributed to > 75% of theoretical KS, while the group class [50-60[µm (less than 10% of vessels) still accounted for > 20% of total KS regardless irrigation treatments. WWD significantly alters the chemical composition of wood with an increase of glucan content by 9 to 16.4% and a decrease of extractives by 35.3 to 36.4% when compared to UI or to plants irrigated with potable water (PW). The fertigation did also increase the proportion of the tension wood which highly correlated with glucan content. In the context of energetic transition and mitigation of climate change, such results are of high interest since WWD effectively permit the phytofiltration of large amounts of organic contaminated effluents without impairing SRCW physiology.