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Fast growing tree species such as Populus spp. in short rotation woody crop (SRWC) systems could be an environmentally friendly and cost-effective approach to ensure sustainable biomass production and mitigate the negative impacts on the environment caused by more intensive management aimed to promote additional biomass increment. Knowledge on variation of major biologically important elements’ and toxic heavy metals’ occurrence in fertilised hybrid aspen tree rings in marginal land may have important and relevant implications for the management practice and evaluation of element fluxes in SRWC ecosystems. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to determine the relative amount of major elements (K, Ca, Mg, P) and heavy metals (Cd, Hg, Pb) in stem wood plane on straight line trajectory starting from pith to bark with measurement step 0.1 mm. While inductively coupled plasma mass spectrometry (ICP-MS) was used to determine average content of the mentioned elements in mechanically separated tree rings to quantify data obtained using LA-ICP-MS method and expressed in relative units. Stem disc samples were collected from six year old hybrid aspen trees growing in marginal agricultural land in the central part of Latvia (hemi-boreal climate conditions) that were initially fertilised with biogas production residues, sewage sludge, and wood ash. We concluded that the content of analysed major elements and heavy metals in the hybrid aspen tree rings varied considerably not only within the analysed stem plane (across tree rings) of one sample tree, but also within one annual ring with significant differences between the content of major elements in earlywood and latewood. Nevertheless, the results of the content of major elements and heavy metals in hybrid aspen tree rings highlighted the significant impact of the initially used fertiliser (especially wood ash) on the average content of elements. Hybrid aspens can be considered bioindicators of both the management activities and general growing conditions even if soil pH is close to neutrality, suggesting a limited mobility of the heavy metals.

Latvia is at the northern border of the species range of S. alba L. in Europe, and there has been some debate whether the Latvian populations of S. alba are autochthonous, as this species has long been planted in Latvia as an ornamental tree in gardens, parks and roadsides. In addition, there is increasing interest in the use of several Salix species (including S. alba) as bioenergy crops. Natural S. alba stands throughout Latvia, as well as stands of possibly hybrid origin were analysed using nuclear and chloroplast markers. Our results showed that S. alba populations are probably natural, and that the rate of vegetative reproduction is low, supporting the evidence that Latvia is within the natural range of S. alba. These results provide the basis for the identification of possibly introduced or artificially regenerated stands of S.alba in Latvia. In addition, our results confirm that S. alba hybridises with S. fragilis, and that natural stands including hybrid individuals can be established. The analysis of chloroplast markers indicated that the predominant hybridisation occurs by fertilisation of S. fragilis by S. alba pollen; however, the extent of haplotype sharing between these two species should be further investigated.

Using biomass of various crops for bioenergy production is a common practice all over the world. Grasses, including reed canary grass (Phalaris arundinacea L.), as bioenergy crops have many advantages. Therefore it is important to look for the most effective technology to produce high biomass grass yields taking into consideration the quality parameters important for this purpose, and at the same time providing sustainable plant nutrient recycling schemes. The use of fermentation residue (FR) from biogas plants as fertiliser could be environmentally and economically cost-effective, as this by-product contain considerable amount of plant nutrients. However, there is little research on the efficiency of FR use for grassland. In our experiments we evaluated the effect of FR used at different rates (from N0 to N150 kg ha-1) and different treatment techniques (once/ twice/ or three times per season) on the productivity of RCG under two-cut and single-cut harvest regime. The data of three ley years (2012-2015) show that annual dry matter yields ranged from: 3.93-11.44 t ha-1 in two-cut and 5.89-13.94 t ha-1 in single-cut regime. The highest dry matter yield was obtained using FR at: 60 kg ha-1 N using the entire amount in a single application at the beginning of the season; 120 and 150 kg ha-1 N split for three applications. The chemical composition of reed canary grass biomass was mostly influenced by harvest regime: late harvest at single-cut regime ensured more appropriate sward quality for bioenergy production with a higher carbon and lower ash, nitrogen, potassium and phosphorus content. [ABSTRACT FROM AUTHOR]

Seven different tree species (coniferous and broad leaved) were selected for small scale pelletizing tests: birch (Betula sp.), aspen (Populus tremula L.), grey alder (Alnus incana L.), poplar (Populus sp.), European larch (Larix decidua Miil.), pine (Pinus sylvestris) and lodgepole pine (Pinus contorta). Tree species were mixed in different combinations and proportions. Wood mixture from one tree specie (several tree species were tested as base material during study) was used as base material with volume share in the mix at least 70% and mixtures from other tree species were used as additives. In total 49 different tree mixes were tested in pellet production where mechanical durability and water absorption was later measured for each sample. Mechanical durability where grey alder was mixed with pine was 98.8% (fulfils ENplus quality class). Poplar also showed high results and in some mixes meet the criteria for mechanical durability with best result 99% in mixes with European larch and lodgepole pine (proportions 80:10:10). From 9 different poplar mixes 7 of them showed mechanical durability higher than 97.5%. In tests where no additives was added (100% poplar), poplar pellets mechanical durability was 98.8%. Other mixes with birch, aspen and grey alder when they were taken as base material for pellet production (base material wood volume share in the mixture at least 70%, where remaining 30% consists of other tree specie mixtures) didn't meet the mechanical durability limit for ENplus quality classes and it was lower than 97.5%. Also in samples where birch and grey alder were used without adding other tree species durability was under 97.5%. European larch was the only one from coniferous trees was tested as base material and the best results in mechanical durability showed in mixes with lodgepole pine (proportion 70:30). From 9 different European larch mixes 7 of them showed mechanical durability higher than 97.5%, which is suitable for ENplus certification. Water absorption in pellets with different tree species composition does not change significantly and ranges from 0.70 to 0.73 ml g-1 when in commercially available litter material it is 0.75-0.8 ml g-1 . Water absorption tests leads to a conclusion that if pellets mechanical durability is not sufficient to sell it as combustion material in could be sold as litter material for animals. [ABSTRACT FROM AUTHOR]

Tall growing perennial grasses such as Phalaris arundinacea and Festulolium can be used as an alternative source for bioenergy production in northern latitudes as they can be grown in less cultivated areas and can be potentially used as a dual purpose crop (bioenergy and forage). The aim of studies was to investigate the effectiveness of using bioenergy waste products -- fermentation residues (digestate) and wood ash as fertilisers for perennial grasses. The field experiment was conducted in the central part of Latvia (56°42' N and 25°08' E) from 2013 to 2015. For all fertiliser treatments (wood ash, digestate once per season; digestate twice per season and mineral fertilisers) the same amount of plant nutrients (N, P, K) was applied annually: N (100), P2O5 (80), K2O (160); and the missing quantities of elements in ash and digestate were compensated by mineral fertilisers. Dry matter yield (DMY) in two harvest regimes (single cut and two cut) and chemical composition (ash content; total C and N) of grass biomass partitioning among tillers, leaves and panicles were estimated. Biomass yield in the three years of use varied considerably depending on the fertiliser, harvest regime and species, ranging up to 10.0 Mg ha-1 for RCG and 7.73 Mg ha-1 for festulolium. All fertilisers provided a significant increase of DMY, however, better results for both species were obtained using wood ash and mineral fertilisers. The harvest regime and species affected directly the quality of biomass, single cut of RCG contained significantly less ash and more carbon. There were significant differences between sward fractions -- culms in comparison with leaves contained less ash and nitrogen, and more carbon, what are desirable features for solid fuel. [ABSTRACT FROM AUTHOR]

The Nordic and Baltic countries are in the frontline of replacing fossil fuel with renewables. An important question is how forest management of the productive parts of this region can support a sustainable development of our societies in reaching low or carbon neutral conditions by 2050. This may involve a 70% increased consumption of biomass and waste to meet the goals. The present review concludes that a 50â100% increase of forest growth at the stand scale, relative to todayâs common level of forest productivity, is a realistic estimate within a stand rotation (~70Â years). Change of tree species, including the use of non-native species, tree breeding, introduction of high-productive systems with the opportunity to use nurse crops, fertilization and afforestation are powerful elements in an implementation and utilization of the potential. The productive forests of the Nordic and Baltic countries cover in total 63 million hectares, which corresponds to an average 51% land cover. The annual growth is 287 million m and the annual average harvest is 189 million m (65% of the growth). A short-term increase of wood-based bioenergy by utilizing more of the growth is estimated to be between 236 and 416 TWh depending on legislative and operational restrictions. Balanced priorities of forest functions and management aims such as nature conservation, biodiversity, recreation, game management, ground water protection etc. all need consideration. We believe that these aims may be combined at the landscape level in ways that do not conflict with the goals of reaching higher forest productivity and biomass production.33

In the context of climate change, it is necessary to establish forest management by balancing more products, using less area, and minimizing environmental impacts. The use of different industrial bio-based by-products as soil conditioners in the last few decades has gain more interest, because it leads to an extended use time of these products and supports the circular economy. The aim of this study was to determine the effect of fertiliser made from cattle and pig manure biogas fermentation digestate and wood ash from two cogeneration plants, applied in different mixture ratios, to test its suitability for fertilisation of deciduous trees, using the physiological, morphological, and chemical parameters of the leaves as an indicator. We selected two poplar clones: foreign 'OP42' (syn. Hybrid 275) and local 'AUCE' annual shoot stem cuttings as planting materials. A negative control group with acidic forest mineral soil as substrate and four fertilised groups with different applied digestate and wood ash ratio mixtures to forest soil was established (ash:digestate 0:0 (Control), 1:1, 2:1, 3:1, 4:1). Mixture application improved growing conditions because all fertilised group poplars had longer growth periods and photosynthetic rates in August than the control group. Both local and foreign clones showed a good response to fertilisation in terms of leaf parameters. Poplar is a suitable culture to fertilise with bio-waste biogenic products, because of its capacity to absorb nutrients and fast response to fertilisation.

Biorefining by enzymatic hydrolysis (EH) of lignocellulosic waste material due to low costs and affordability has received enormous interest amongst scientists as a potential strategy suitable for the production of bioactive ingredients and chemicals. In this study, a sustainable and eco-friendly approach to extracting bound ferulic acid (FA) was demonstrated using single-step EH by a mixture of lignocellulose-degrading enzymes. For comparative purposes of the efficiency of EH, an online extraction and analysis technique using supercritical fluid extraction-supercritical fluid chromatography-mass spectrometry (SFE-SFC-MS) was performed. The experimental results demonstrated up to 369.3 mg 100 g -1 FA release from rye bran after 48 h EH with Viscozyme L. The EH of wheat and oat bran with Viscoferm for 48 h resulted in 255.1 and 33.5 mg 100 g -1 of FA, respectively. The release of FA from bran matrix using supercritical fluid extraction with carbon dioxide and ethanol as a co-solvent (SFE-CO 2 -EtOH) delivered up to 464.3 mg 100 g -1 of FA, though the extractability varied depending on the parameters used. The 10-fold and 30-fold scale-up experiments confirmed the applicability of EH as a bioprocessing method valid for the industrial scale. The highest yield of FA in both scale-up experiments was obtained from rye bran after 48 h of EH with Viscozyme L. In purified extracts, the absence of xylose, arabinose, and glucose as the final degradation products of lignocellulose was proven by high-performance liquid chromatography with refractive index detection (HPLC-RID). Up to 94.0% purity of FA was achieved by solid-phase extraction (SPE) using the polymeric reversed-phase Strata X column and 50% EtOH as the eluent.

The choice of revegetating via direct seeding or planting nursery-grown seedlings influences the potential stresses suffered by seedlings such as herbivory and drought. The outcome of the balance between both revegetation methods may ultimately depend on how species identity and traits such as seed and seedling size interact with environmental conditions. To test this, we will conduct a continental-scale experiment consisting of one mini-experiment replicated by multiple participants across Europe. Each participant will establish a site with seeded and planted individuals of one or more native, locally growing oak (Quercus) species; the selection of this genus aims to favour continental-scale participation and to allow testing the response of a widely distributed genus of broad ecological and economic relevance. At each site, participants will follow the present protocol for seed collection, seeding in the field, nursery cultivation, outplanting, protection against herbivores, site maintenance, and measurement of seedling performance and environmental variables. Each measurement on each species at each site will produce one effect size; the data will be analysed through mixed-effects meta-analysis. With this approach we will assess the main effect of revegetation method, species, plant functional traits, and the potential effect of site-specific effect moderators. Overall, we will provide a continental-scale estimate on the seeding vs. planting dilemma and analyse to what extent the differences in environmental conditions across sites, seed size, functional traits, and the phylogenetic relatedness of species can account for the differences in the effect of revegetation method on seedling performance across study sites and species., Competing Interests: The authors have declared that no competing interests exist.

With the developments in DNA nanoball sequencing technologies and the emergence of new platforms, there is an increasing interest in their performance in comparison with the widely used sequencing-by-synthesis methods. Here, we test the consistency of metabarcoding results from DNBSEQ-G400RS (DNA nanoball sequencing platform by MGI-Tech) and NovaSeq 6000 (sequencing-by-synthesis platform by Illumina) platforms using technical replicates of DNA libraries that consist of COI gene amplicons from 120 soil DNA samples. By subjecting raw sequencing data from both platforms to a uniform bioinformatics processing, we found that the proportion of high-quality reads passing through the filtering steps was similar in both datasets. Per-sample operational taxonomic unit (OTU) and amplicon sequence variant (ASV) richness patterns were highly correlated, but sequencing data from DNBSEQ-G400RS harbored a higher number of OTUs. This may be related to the lower dominance of most common OTUs in DNBSEQ data set (thus revealing higher richness by detecting rare taxa) and/or to a lower effective read quality leading to generation of spurious OTUs. However, there was no statistical difference in the ASV and post-clustered ASV richness between platforms, suggesting that additional denoising step in the ASV workflow had effectively removed the 'noisy' reads. Both OTU-based and ASV-based composition were strongly correlated between the sequencing platforms, with essentially interchangeable results. Therefore, we conclude that DNBSEQ-G400RS and NovaSeq 6000 are both equally efficient high-throughput sequencing platforms to be utilized in studies aiming to apply the metabarcoding approach, but the main benefit of the former is related to lower sequencing cost., Competing Interests: The authors declare that they have no competing interests., (© 2021 Anslan et al.)

We studied long-term effects of fertilization with wood ash on biomass, vitality and mycorrhizal colonization of fine roots in three conifer forest stands growing in Vacciniosa turf. mel. (V), Myrtillosa turf. mel. (M) and Myrtillosa turf. mel./Caricoso-phragmitosa (MC) forest types on peat soils. Fertilization trials amounting 5 kg/m(2) of wood ash were established 12 years prior to this study. A total of 63 soil samples with roots were collected and analysed. Ectomycorrhizal (ECM) fungi in roots were identified by morphotyping and sequencing of the fungal internal transcribed spacer (ITS) region. In all forest types, fine root biomass was higher in fertilized plots than in control plots. In M forest type, proportion of living fine roots was greater in fertilized plots than in control plots, while in V and MC, the result was opposite. Fifty ECM species were identified, of which eight were common to both fertilized and control plots. Species richness and Shannon diversity index were generally higher in fertilized plots than in control plots. The most common species in fertilized plots were Amphinema byssoides (17.8%) and Tuber cf. anniae (12.2%), while in control plots, it was Tylospora asterophora (18.5%) and Lactarius tabidus (20.3%). Our results showed that forest fertilization with wood ash has long-lasting effect on diversity and composition of ECM fungal communities.