Search

The tree species Salix caprea shows high adaptability to different habitat conditions and is economically valuable as a woody crop for biomass production. Moreover, S. caprea is dependent on mycorrhizal fungi, which are crucial for its growth and adaptability in different environments. Hence, this study explores the ectomycorrhizal diversity of S. caprea by utilizing the taxonomy (morphotyping and a molecular approach using the ITS and LSU regions) and trait diversity (exploration types) at two test sites in Germany and Poland. In total, 19 ectomycorrhizal (EM) morphotypes of S. caprea were characterized. Seven taxa were identified at the species level (Hebeloma populinum, Cortinarius atrocoerulaeus, Inocybe hirtella, Laccaria cf. ochropurpurea, Tuber maculatum, Cenococcum geophilum, and Phialophora finlandia) and twelve at the genus level (Tomentella spp. 1–8, Hebeloma sp. 1, Inocybe sp. 1, and Tuber spp. 1–2). The EM colonization ranged from 14 to 28% of the fine root tips. At both test sites, the largest portion of the total EM colonization consisted of Thelephoraceae. The exploration types were classified as medium-distance smooth (Tomentella sp. 1–8 and L. ochropurpurea) and medium-distance fringe (C. atrocoerulaeus), while the other taxa were short-distance exploration types, highlighting their potential functional role in the adaptation and growth of S. caprea. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is an essential plant nutrient that can limit plant growth due to low availability in the soil. P-solubilizing bacteria in the roots and rhizosphere increase the P use efficiency of plants. This study addressed the impact of plant species, the level of plant association with bacteria (rhizosphere or root endophyte) and environmental factors (e.g., seasons, soil properties) on the abundance and diversity of P-solubilizing bacteria in short-rotation coppices (SRC) of willows (Salix spp.) for biomass production. Two willow species (S. dasyclados cv. Loden and S. schwerinii × S. viminalis cv. Tora) grown in mono-and mixed culture plots were examined for the abundance and diversity of bacteria in the root endosphere and rhizosphere during two seasons (fall and spring) in central Sweden and northern Germany. Soil properties, such as pH and available P and N, had a significant effect on the structure of the bacterial community. Microbiome analysis and culture-based methods revealed a higher diversity of rhizospheric bacteria than endophytic bacteria. The P-solubilizing bacterial isolates belonged mainly to Proteobacteria (85%), Actinobacteria (6%) and Firmicutes (9%). Pseudomonas was the most frequently isolated cultivable bacterial genus from both the root endosphere and the rhizosphere. The remaining cultivable bacterial isolates belonged to the phyla Actinobacteria and Firmicutes. In conclusion, site-specific soil conditions and the level of plant association with bacteria were the main factors shaping the bacterial communities in the willow SRCs. In particular, the concentration of available P along with the total nitrogen in the soil controlled the total bacterial diversity in willow SRCs. A lower number of endophytic and rhizospheric bacteria was observed in Loden willow species compared to that of Tora and the mix of the two, indicating that mixed growth of Salix species promotes P-solubilizing bacterial diversity and abundance. Therefore, a mixed plant design was presented as a management option to increase the P availability for Salix in SRCs. This design should be tested for further species mixtures. [ABSTRACT FROM AUTHOR]

Abstract: Willow (Salix spp.) short‐rotation coppice is commercially grown to produce lignocellulosic biomass to meet renewable bioenergy demands. Most commercial willow coppices are grown in stands of a single genotype, but biomass productivity may be greater in mixed communities, and the productivity in mixed communities may depend on the specific genotypes involved. We assessed the biomass production of four different Salix genotypes (“Björn,” “Jorr,” “Loden,” “Tora”) grown without additional nutrient fertilization during one cutting cycle at three locations in Europe (Uppsala in Sweden, Rostock and Freiburg in Germany) in plots of pure and mixed communities. We evaluated (i) the effect of genotype diversity on shoot biomass productivity, including the evidence for complementarity and selection effects; (ii) the influence of individual genotypes on mixed community productivity; and (iii) the productivity of individual genotypes in response to pure vs. mixed culture. Mean shoot biomass production after the first cutting cycle decreased in the order Rostock (8.7 Mg ha−1) > Freiburg (6.9 Mg ha−1) > Uppsala (5.7 Mg ha−1), with values similar to those for other nonfertilized willow stands after the first growth cycle. Consistently across all three locations, increasing genotype diversity did not significantly affect shoot biomass production. Using Bayesian statistics, the addition of the genotypes “Jorr” and “Loden” was predicted to enhance shoot biomass production, while “Tora” and “Björn” are more likely to reduce shoot biomass production in mixed communities. In addition, we found evidence for a negative selection effect due to the genotype “Tora” performing better in mixed than in pure communities in two of the sites (Freiburg, Uppsala). In conclusion, our results imply that increasing genetic richness has no negative effect on productivity and that there is a potential to design site‐specific genotype mixtures of short‐rotation coppice promoting both high genetic diversity and high biomass production. [ABSTRACT FROM AUTHOR]

The roots of Salix spp. can be colonized by two types of mycorrhizal fungi (ectomycorrhizal and arbuscular) and furthermore by dark-septate endophytes. The fungal root colonization is affected by the plant genotype, soil properties and their interactions. However, the impact of host diversity accomplished by mixing different Salix genotypes within the site on root-associated fungi and P-mobilization in the field is not known. It can be hypothesized that mixing of genotypes with strong eco-physiological differences changes the diversity and abundance of root-associated fungi and P-mobilization in the mycorrhizosphere based on different root characteristics. To test this hypothesis, we have studied the mixture of two fundamentally eco-physiologically different Salix genotypes (S. dasyclados cv. 'Loden' and S. schwerinii x S. viminalis cv. 'Tora') compared to plots with pure genotypes in a randomized block design in a field experiment in Northern Germany. We assessed the abundance of mycorrhizal colonization, fungal diversity, fine root density in the soil and activities of hydrolytic enzymes involved in P-mobilization in the mycorrhizosphere in autumn and following spring after three vegetation periods. Mycorrhizal and endophytic diversity was low under all Salix treatments with Laccaria tortilis being the dominating ectomyorrhizal fungal species, and Cadophora and Paraphaeosphaeria spp. being the most common endophytic fungi. Interspecific root competition increased richness and root colonization by endophytic fungi (four taxa in the mixture vs. one found in the pure host genotype cultures) more than by ectomycorrhizal fungi and increased the activities of hydrolytic soil enzymes involved in the P-mineralization (acid phosphatase and b-glucosidase) in mixed stands. The data suggest selective promotion of endophytic root colonization and changed competition for nutrients by mixture of Salix genotypes. [ABSTRACT FROM AUTHOR]

Copyright of Ecoscience (Ecoscience) is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Willow clones are used for the phytoextraction of heavy metals from contaminated soils and are usually mycorrhizal. The receptiveness of willow clones for mycorrhizal inoculum varies specific to genotype; however, it is unknown if this might have a significant impact on their efficiency in phytoextraction of heavy metals. Therefore, a model system with mycorrhizal and non-mycorrhizal willows of two different genotypes – one with usually stronger natural mycorrhizal colonization (Salix dasyclados), and one with lower natural mycorrhizal colonization (S. viminalis) – was investigated for its efficiency of phytoextraction of heavy metals (Cd, Pb, Cu, Zn) from contaminated soil. Inoculation with the ectomycorrhizal fungusAmanita muscariasignificantly decreased the biomass of leaves of both inoculated willow clones, and increased or had no effect on the biomass of trunks and roots ofS. dasycladosandS. viminalis, respectively. The concentrations of heavy metals in the biomass ofS. dasycladoswere in general higher than inS. viminalisirrespective of inoculation with the ectomycorrhizal fungus. Inoculation withA. muscariasignificantly decreased the concentration of Cu in the trunks of bothSalixtaxa, but did not affected the concentrations of other heavy metals in the biomass. In conclusion, stronger receptiveness of willow clones for mycorrhizal inoculum was correlated with an increased total extraction of heavy metals from contaminated soils. Therefore, this seems to be a suitable criterion for effective willow clone selection for phytoremediation. Increased biomass production with relatively constant metal concentrations seems to be a major advantage of mycorrhizal formation of willows in phytoremediation of contaminated soils. [ABSTRACT FROM PUBLISHER]

Abstract  Biotic interactions affect the impact of potential plant growth promoting microorganisms in the rhizosphere, but their magnitude and fundamentals are often hardly known. In a pot experiment, two physiologically different strains of the ectomycorrhizal fungus Paxillus involutus (GUL and FRA) were tested separately and in combination with associated bacteria (Sphingomonas paucimobilis 1 L, Ralstonia pickettii 16 B, Sphingomonas sp. 23 L) on their effects on the growth of willows (Salix viminalis). Both P. involutus strains significantly increased the growth of the willows compared with non-inoculated plants, but the magnitude of this effect was significantly affected by the fungal strain. The P. involutus strain GUL with higher synthesis of auxin-like substances, acid phosphatases, siderophores and faster utilisation of yeast extract in vitro increased the willow growth in situ more effectively than strain FRA. Additionally, dual inoculation with the P. involutus strains GUL and FRA in combination with the associated bacteria promoted the willow growth, especially the combination with S. paucimobilis 1 L. This bacterial strain used effectively C sources which are common components of plant root exudates, e.g. glucose, sucrose, maltose and mannose as well as compounds synthesized by fungi, e.g. trehalose in vitro. We conclude that the analyses of fungal metabolites and of C source use of associated bacteria can successfully contribute to accelerate the selection of capable plant growth promoting combinations. [ABSTRACT FROM AUTHOR]

Abstract: Low supply of the nutrients nitrogen (N) and phosphorus (P) limit plant growth and spreading, and increase the plant-microbial nutrient competition in subarctic and arctic regions. We investigated the mycorrhizal community structure of a polar shrub willow (Salix polaris) and the microbial turnover in its rhizosphere to explore the adaptation of a mycorrhizal plant in the subarctic tundra. The ectomycorrhizal colonisation ranged from 35 to 64% of the fine root tips and decreased with an increasing soil C/N ratio. In total, 16 ectomycorrhizal morphotypes were found under S. polaris (eight to 13 morphotypes per site, five morphotypes at all four sites). Cenococcum sp. was the most common EM fungus (32% of the ectomycorrhizal fine roots). The abundance of Cenococcum sp. increased with an increasing organic matter content and N/P ratio in the soil. Arbuscular mycorrhizal colonisation of S. polaris was absent or less than 1% of the fine root length. Microbial biomass P accounted for 21–75% of the organic soil P and 6–49% of the total soil P. Microbial biomass P, alkaline and acid phosphatase activities in the rhizosphere increased with increasing soil N concentration. We conclude that a higher N supply decreases the diversity in the mycorrhizal community on polar willows and increases the role of P turnover from the soil microbial biomass for the nutrient supply. [Copyright &y& Elsevier]

In order to enhance phytoremediation efficiency, we investigated the effects of dual inoculation with ectomycorrhizal fungi and the ectomycorrhiza associated bacteria Micrococcus luteus and Sphingomonas sp. on the growth and metal accumulation of willows (Salix viminalis x caprea) on contaminated soil. The bacterial strains were previously collected from sporocarps of ectomycorrhizal fungi. The bacteria increased plant growth and the mycorrhizal dependency of willows colonized with the ectomycorrhizal fungus Hebeloma crustuliniforme. The total cadmium (Cd) and zinc (Zn) accumulation in the shoot biomass was increased after inoculation with the fungal strain Hebeloma crustuliniforme in combination with Micrococcus luteus up to 53% and in combination with Sphingomonas sp. up to 62%, respectively. The dual inoculation in combination with Laccaria laccata did not increase the accumulation of Cd and Zn in the willows. We conclude that associated bacteria can enhance the ectomyorrhiza formation and growth of willows and, thereby, the Cd and Zn accumulation in the plant biomass. The results suggest that bacterial support of root growth promoting ectomycorrhizal fungi may be a promising approach to improve the remediation of metal-contaminated soils by using willows. [ABSTRACT FROM AUTHOR]

Short-rotation coppice (SRC) Salix plantations have the potential to provide fast-growing biomass feedstock with significant soil and climate mitigation benefits. Salix varieties exhibit significant variation in their physiological traits, growth patterns and soil ecology—but the effects of these variations have rarely been studied from a systems perspective. This study analyses the influence of variety on soil organic carbon (SOC) dynamics and climate impacts from Salix cultivation for heat production for a Swedish site with specific conditions. Soil carbon modelling was combined with a life cycle assessment (LCA) approach to quantify SOC sequestration and climate impacts over a 50-year period. The analysis used data from a Swedish field trial of six Salix varieties grown under fertilized and unfertilized treatments on Vertic Cambisols during 2001–2018. The Salix systems were compared with a reference case where heat is produced from natural gas and green fallow was the land use alternative. Climate impacts were determined using time-dependent LCA methodology—on a land-use (per hectare) and delivered energy unit (per MJheat) basis. All Salix varieties and treatments increased SOC, but the magnitude depended on the variety. Fertilization led to lower carbon sequestration than the equivalent unfertilized case. There was no clear relationship between biomass yield and SOC increase. In comparison with reference cases, all Salix varieties had significant potential for climate change mitigation. From a land-use perspective, high yield was the most important determining factor, followed by SOC sequestration, therefore high-yielding fertilized varieties such as 'Tordis', 'Tora' and 'Björn' performed best. On an energy-delivered basis, SOC sequestration potential was the determining factor for the climate change mitigation effect, with unfertilized 'Jorr' and 'Loden' outperforming the other varieties. These results show that Salix variety has a strong influence on SOC sequestration potential, biomass yield, growth pattern, response to fertilization and, ultimately, climate impact. [ABSTRACT FROM AUTHOR]

Short rotation forestry is a promising tool for biomass production. In order to determine long-term effects of short rotation forestry on chemical, biochemical and physical soil properties we have investigated two former arable sites with willow and poplar clones (Salix and Populus spp.) in northeast Germany. The organic carbon and the total nitrogen contents of the sandy topsoil increased up to 4.0 g kg-1 and 0.2 g kg-1, respectively after 12 years. The C/N ratio was higher under short rotation forestry caused by the stronger C than N accumulation. The contents and reserves of plant available phosphorus and potassium were decreased significantly from the 6th to the 12th year, but the plant supply was still sufficient without fertilization. The pH in the topsoil was significantly lower under willow clones than under poplar clones. Higher dehydrogenase activity of the soil was measured under poplar and willows than at tree-less control plots. The bulk density decreased and the porosity of the soil increased under short rotation forestry. In conclusion the major long-term effects of short rotation forestry on arable used Cambisols were the accumulation of organic matter followed by slightly improved soil physical conditions and increased soil biological activity. [ABSTRACT FROM AUTHOR]

• Significant impacts of Salix genotype and fertilization on soil functions. • One genotype (Jorr) favours soil functions in unfertilized condition. • Different genotypes (Tora and Tordis) are most beneficial in fertilized condition. • Genotype-specific effects on soil ecology should be considered in Salix cropping. Willows (Salix spp.) grown in short rotation coppice (SRC) for biomass production offer diverse soil ecological benefits, however fertilization might interfere these impacts. To specify the significance of demand-based fertilization (NPK 21:3:10) on genotype-specific soil ecological impacts, the upper topsoil (0–10 cm soil depth) under six willow genotypes was tested. Activities of dehydrogenases as indicator of soil microbial activity, the concentration of glomalin-related proteins (GRSP), as an indicator of arbuscular mycorrhizal fungal biomass, soil organic carbon (SOC) stock, content of plant-available phosphorus (P), and the soil aggregate stability were investigated in a Vertic Cambisol in central Sweden after a growth period of 17 years in 3-year cutting cycles. Significantly higher microbial activity in the soil after fertilization was restricted to two genotypes ('Tora' and 'Tordis') out of six. Generally, the abundance of arbuscular mycorrhizal fungi indicated by GRSP was increased after fertilization, however significantly only under the genotypes 'Jorr' and 'Loden'. Non-fertilized genotype 'Jorr' was most effective to increase the soil SOC stock in 0–10 cm soil depth from initially 14 Mg ha−1 in 2001 to 31 Mg ha−1 in 2018. Under the genotype 'Tora' the highest and under 'Jorr' the lowest P plant-availability was revealed in the fertilized treatment. Site-specifically the aggregate-stability of soil was generally high without any significant effects of willow genotype or fertilization. We conclude that, from a soil ecological perspective, the genotype 'Jorr' is most promising at non-fertilized sites whilst 'Tora' and 'Tordis' are most promising for fertilized sites. In that context, the genotype 'Gudrun' was the least promising, independent of fertilization. Our results indicate large genotype-specific effects that might exceed the impact of demand-based fertilization on the soil ecological value of willow genotypes grown in SRC, suggesting that a genotype-specific response on fertilization should be considered. [ABSTRACT FROM AUTHOR]

Plantations of willow (Salix spp.) are today grown as short-rotation coppice (SRC) for the sustainable production of biomass. While developing these production systems in the past, much ecological knowledge on plant–plant, plant–environment and trophic interactions has been generated. This knowledge can contribute to the further development of biodiversity–ecosystem function (BEF) theory, which frequently lacks a sound understanding of the complex mechanisms behind the observed patterns of diversity-productivity relationships. Thus, willow SRC systems are suitable models to explore BEF theory; they are simple enough to allow the study of the complex ecological mechanisms involved and they have many similarities to grassland systems in which much of recent BEF theory development has been achieved. This paper briefly reviews the current observational and mechanistic knowledge on diversity–productivity relationships in willow SRC, as well as the most important above- and below-ground trophic interactions that are likely to affect them. If the available knowledge is integrated and combined with further experimental work targeting mechanisms behind patterns, research on willow SRC as a model offers a great opportunity for filling the gaps in the understanding what presently hampers the development of predictive BEF theory. [ABSTRACT FROM AUTHOR]

Abstract: Under changing redox conditions some plants create plaques at their root surface, which may affect the mobility and uptake of As and heavy metals but it is unknown to what extent this also holds true for willows in contaminated floodplain soils. Therefore, willow roots were sampled from a phytoremediation trial in the contaminated floodplain of the river Elbe (Germany), cryofixed, freeze-dried, and cross sections were mapped for the distribution of As, Ca, Cu, Fe, K, Mn, Ni, S and Zn by synchrotron based X-ray fluorescence spectroscopy. The elements Ca, Cu, Ni, S and Zn were concentrated in the aerenchymatic tissue, and not associated with Fe and Mn. Mixed Fe–Mn plaques covered the surface of the willow roots and As was accumulated in these plaques. The observed association pattern between As and Fe was explained by the different sorption/desorption properties of As(III) and As(V). The Cu and Zn intensities were not associated with the intensity of Fe in the plaque, which seems to be a willow-specific difference compared to other wetland plants. These results suggested that willows are especially suited to stabilize low-phytoextractable elements like Cu and As in their roots and rhizosphere. Thus, short rotation coppicing of willows may be a practical approach to mitigate the adverse effects of floodplain soil contamination. [Copyright &y& Elsevier]