Short Rotation Coppice Willow Research Articles

Utilization of Fish Farm Effluent for Irrigation Short Rotation Willow (Salix alba L.) under Lysimeter Conditions

Efficient utilization, treatment, and disposal of agricultural wastewater and sewage sludge are important environmental risks. In our research, effluent water from intensive aquaculture was evaluated for the irrigation of short rotation energy willow in a lysimeter experiment. Two different water types and their combinations were applied with weekly doses of 15, 30, and 60 mm, respectively. Our results revealed that implementing effluent water instead of fresh water could potentially increase the yield of the willow due to its higher nitrogen content (29 N mg/L). The biomass of irrigated short rotation coppice (SRC) willow plants were between 493–864 g/plant, 226–482 g/plant, and 268–553 g/plant dry weight during experiment period (2015–2017), respectively. However, due to the chemical properties (Na concentration, SAR value) of effluent water, the increase of the soil exchangeable sodium percentage (ESP) was significant and it can lead to soil degradation in the long term. The current study also investigated the relationship between chemical composition of the plant tissue and the irrigation water. In the case of K-levels of willow clones, an increasing trend was observed year-by-year. In terms of N and Na content was localized in leaf parts, especially in samples irrigated with effluent. Less N and Na values were detected in the stem and in the samples irrigated with surface water. In SRC willow plants, phosphorus was mostly localized in the stem, to a lower extent in the leaf part. The difference is mostly observed in the case of the amount of irrigation water, where the P content of the examined plant parts decreased with the increase of the amount of irrigation water. In the case of phenological observations, higher values of plant height were measured during diluted and effluent irrigation. Moreover, the SPAD of the plants irrigated with effluent water exceeded the irrigated ones with surface water.

Quantitative analysis of feedstock structural properties can help to produce willow biochar with homogenous pore system

Novel bioeconomic approaches call for increasingly faster production of lignocellulosic biomass and its better-tailored use for higher added value. The high-yield capacity and structural properties of willows (Salix spp.) suggest their excellent potential for the production of designed biochar for use in agronomic, electronic and technical applications. All these applications rely on the internal pore structure of biochar. However, we lack an in-depth quantitative understanding of the interlinkages between the feedstock properties and the physical quality of the biochar produced. We studied quantitatively how the clonal and within-plant properties of five different willow clones (hybrids of Salix schwerinii E.L. Wolf) affected the micrometre-scale pore properties of the produced biochars (pyrolyzed at + 462 °C). The porosity and pore size distribution were analysed before and after slow pyrolysis by X-ray microtomography and image analysis. We also studied the potential of conventional low-cost fibre analysis techniques to be used to predict biochar pore properties directly from fresh feedstock. The total porosity (0.55–0.62) and the pore size distribution of willow wood and derived biochars varied between clones. Approximately two-thirds of the biochar total porosity was associated with pores formed by wood fibres. Pyrolysis levelled off the structural variation detected between and within the clones. Pyrolysis-induced shrinkage reduced the pore sizes and narrowed the pore size distribution. The results suggest that conventional fibre analysis techniques could be utilized to predict biochar homogeneity. Short rotation coppice willows are suitable feedstock to produce homogenous biochar precursor for production of bio-based carbon materials to be used in high value-added technical applications. The structural homogeneity of the feedstock and produced biochar can be enhanced by selecting proper harvesting strategy and clones used in plantations. From the industrial perspective, comprehensive understanding of feedstock properties helps to control quality of the produced biochar.

Torrefaction of Short Rotation Coppice Willow. Characterization, hydrophobicity assessment and kinetics of the process

Short Rotation Coppice Willow (SRCW) is one of the newest sources of renewable energy. Torrefaction enhances the initial poorest characteristics of SRCW, such as hygroscopicity or low heating value compared to traditional fuels, to use it as a fuel. Non-oxidative and oxidative torrefaction of SRCW were compared. Torrefaction were conducted within the range 200–240 °C and torrefied SRCW and released gases were characterized (proximate, ultimate, compositional and heating value analysis as well as hydrophobicity assessment, Py-GC/MS and chemical-kinetics parameters). At optimal torrefaction temperature, mass and energy yields were around 88% and 93%, respectively, moisture was reduced up to 1.22–1.28% and H/C and O/C atomic ratios up to 1.4 and 0.6, respectively. Biomass turns hydrophobic since contact angle increase and the amount of water absorb decrease in contact angle and liquid penetration studies, respectively. The global reaction order was 2 and kinetic constant values were in the range 4.6 10−5 s−1–3.6 10−5 s−1.

Use of ensiled green willow biomass in biogas fermentation.

The biggest challenges of our era include climate change and the global fossil energy problem. Extensive utilization of renewable energy sources should be a part of the solution for both these problems. Biogas is a versatile renewable energy carrier that has the potential to substitute fossil fuels. The most frequently utilized substrates for the anaerobic digestion (AD) process include maize silage today, but there is an increasing demand for second-generation biomass sources, which are cheaper and do not interfere with the cultivation of food production. Green biomass from short rotation coppice willow (GWB) may be a promising alternative. However, to ensure feedstock quantity and quality all year round, a preservation method has to be developed. We attempted to ensilage the biomass and subsequently utilized the resulting willow-silage in batch fermenters. Various mixtures of lactic acid bacteria were employed to facilitate ensiling by inoculation of the substrate in anaerobic jars for 60days. During the ensiling analytical investigations, (HPLC, pH, oTS/TS%) were carried out in order to follow the build-up of fermentation products. AD fermentations were assembled from the ensilaged biomass and the methane production was measured for 56days. The total methane yields of the ensilaged biomass were 8-15% higher than that of the fresh biomass and methane production rates were also improved. Our findings suggest that ensiling is not only an excellent preservation method for willow biomass, but also stimulates its AD.

Earthworm community development in soils of a reclaimed steelworks

Long-term studies are essential to learn earthworm community development and soil formation post reclamation. Investigations were undertaken at a former steelworks site at Hallside, near Glasgow, UK, reclaimed in the 1990s using a mixture of colliery spoil and sewage sludge. The site was largely planted for production of short rotation coppice willow (Salix spp.). Earthworm inoculation formed a part of the restoration process. Minimal monitoring occurred in the interim, but some records of earthworm sampling existed in 2000 and 2005. This study focused on monitoring earthworms and soil properties across the site, drawing comparisons with adjacent unspoiled soil. Results showed that after 22 years, a species-rich community of earthworms (n = 16) colonized the site, with endogeic Aporrectodea caliginosa being dominant by number and anecic A. longa by mass. Across the site, earthworm community density and biomass were 208 individuals m-2 and 71 g m-2, respectively. The Shannon diversity index for earthworms was 1.89, with an evenness of 0.68. The sewage sludge increased the soil organic matter, but the stone content of the colliery spoil prevented digging in some locations. Soil chemistry had no negative effect on earthworms, but the compacted substrate did hinder water infiltration. Earthworms colonized the reclaimed site from adjacent areas, and community structure and density below well-drained, scrub-free willow, birch, and grassland were not significantly different (P > 0.05) from those of the adjacent unspoiled areas. The results show that the historical earthworm inoculation was unnecessary and badly timed. Future reclamations of similar sites can learn from this investigation.

Ground Beetles (Carabidae) in the Short-Rotation Coppice Willow and Poplar Plants—Synergistic Benefits System

In a short period, we have observed the rapid expansion of bioenergy, resulting in growth in the area of energy crops. In Europe, willow and poplar growing in short-rotation coppices (SRC) are popular bioenergy crops. Their potential impact on biodiversity has not yet been fully investigated. Therefore, there are many uncertainties regarding whether commercial production can cause environmental degradation and biodiversity impoverishment. One of the aspects examined is the impact of these crops on entomofauna and ecosystem services. The best-studied insect group is ground beetles from the Carabidae family. This work gathers data on biodiversity and the functions of carabids in willow and poplar energy plants. The results of these investigations show that energy SRC plants and Carabidae communities can create a synergistic system of mutual benefits. Willow and poplar plants can be a valuable habitat due to the increased biodiversity of entomofauna. Additionally, SRC creates a transitional environment that allows insect migration between isolated populations. On the other hand, ground beetles are suppliers of ecosystem services and make a significant contribution to the building of sustainable agriculture by pest control, thereby ameliorating damage to field crops.

Willow coppice in intensive agricultural applications to reduce strain on the food-energy-water nexus

The focus of this study is to show that by understanding the food-energy-water nexus, potential unforeseen negative outcomes can be avoided in the pursuit of sustainable development. To do this, this paper uses a novel approach to compare a combined farm and short rotation coppice willow system, in which the willow was planted as a riparian buffer, with a food-only and an energy only system. The impact of each system was investigated through the lens of the food-energy-water nexus using life cycle assessment techniques. Data from previous research was adapted in order to quantify the impacts for a typical Irish dairy farm, which is indicative of intensive agriculture across Europe. On a typical Irish dairy farm, the implementation of a short rotation coppice willow riparian buffer strip could reduce total nitrogen and phosphorus leachate by 14% and 9% respectively. Total CO2eq emissions could be reduced by 16.5% if energy from the willow displaces fossil fuels, while the impact on milk production and profit is minimal. Thus, the use of short rotation coppice willow as a riparian buffer strip has the potential to reduce strain on the entire food-energy-water nexus. By considering the food-energy-water nexus, the negative impacts of the food-only and energy-only systems were also highlighted.The paper also shows how a better understanding of the food-energy-water nexus supports the United Nations Sustainable Development Goals and could help ameliorate the impact of climate change on the food-energy-water ecosystem.

Sprout Regeneration of Shrub Willows after Cutting.

Shrub willow (Salix L. spp.) is a promising bioenergy resource crop due to its high growth rates and superb regenerative ability. Sprouting capacity is influenced by many factors, such as parent tree species and size, which are important limiting factors for stump survival or sprout growth. In this study, we aimed to quantify the survival and regeneration performance of sprouts (including sprout height, sprout diameter, sprout number, leaf morphological traits, leaf chlorophyll content, and ground part dry biomass) from the stumps of two Salix species from three diameter classes (10–15, 16–19, and 20–30 mm). An attempt was made to explore why the stump size affects the regeneration of willows by analyzing the carbon and nitrogen proportion of stumps. Stump survival did not differ between the two Salix species. However, the sprout regeneration of S. triandra was much better than that of S. suchowensis. An increase in stump diameter caused increases in the number of sprouts produced per stump, the mean height and basal diameter of sprouts per stump, the leaf chlorophyll content, and the biomass of sprouts per stump. By contrast, stump diameter did not significantly affect stump survival. The results indicate that the larger stumps store more carbon and nitrogen than small-sized stumps, which may be one of the reasons why the larger willow stumps have a stronger resprouting ability. This study provides essential information regarding the sprout regeneration of short-rotation coppice willow plantations after harvest.

The effects of weather, harvest frequency, and rotation number on yield of short rotation coppice willow over 10 years in northern Japan

Under global warming, expectations for woody biomass as a renewable energy are increasing. Short rotation coppice willow is the most widely planted energy wood crop. In this study, we examined the effect of harvest frequency on willow yield across multiple harvest rotations, something which is poorly understood. We planted 18 clones of Salix pet-susu and S. sachalinensis at a density of 25,000 or 16,667 cuttings ha−1 in Hokkaido, northern Japan, and harvested either annually or biennially for 10 years (2009–2018). Annual variation in willow yield per stool was analyzed using five linear mixed-effect models incorporating the number of rotations, harvest interval, and weather parameters during the growing season with clones and plant density as random factors. Number of rotations had a significant negative effect on annual yield in all five models. We estimated that yield could be halved over 10 consecutive years of harvesting. In three out of the five models, biennial harvesting had a significant positive effect on yield in comparison with annual harvesting. In addition, we found that weather conditions, such as hours of sunshine during growing season, air temperature in May (when leaf flushing occurs), and precipitation in July (when vigorous height growth occurs) have significant positive effects on willow yield. These results suggest that, to maintain willow vigor for longer time periods biennial, or more than two-year-harvest, cycle is recommended rather than annual harvest.

Optimization of the wastewater treatment capacity of a short rotation willow coppice vegetation filter

The objective of this study was to determine the conditions to optimize the wastewater treatment efficiency of a short rotation willow coppice (SRWC) plantation (Salix miyabeana ‘SX67’) used as a vegetation filter to treat small municipal primary effluents (with less than 800 population equivalent). With the aim of maximizing the annual amount of wastewater treated, the effect of adjusting the hydraulic loading rate (HLR) according to the estimated evapotranspiration was tested at demonstration scale under humid continental climate conditions. We proposed a new method to calculate the evapotranspiration rate from plant physiological data, introducing an α factor based on direct transpiration measurements. This method increased the accuracy of the water balance, with a prediction of the crop coefficient (kc) based on either an seasonal approach (R2 of 0.88) or a monthly approach (R2 of 0.94). This led to a more precise estimation of the pollutant loading reaching the groundwater and could be used after plantation establishment as a fine-tuning tool. Adjusting the HLR to that of evapotranspiration between May and October led to an annual increase of 2 mm/d (around 0.35 m3/m2 per growing season) in HLR, while maintaining a pollutant loading removal efficiency of at least 96% for organic matter, 99% for total phosphorus and 93% for total nitrogen. A high HLR at the end of the season caused nitrogen leaching into groundwater, indicating that the HLR should be decreased in October, when willow growth is greatly reduced.

Phytomanagement Reduces Metal Availability and Microbial Metal Resistance in a Metal Contaminated Soil.

Short rotation coppice (SRC) with metal tolerant plants may attenuate the pollution of excessive elements with potential toxicity in soils, while preserving soil resources and functionality. Here, we investigated effects of 6 years phytomanagement with willow SRC on properties including heavy metal levels, toxicity tested by BioTox, microbial biomass, enzyme activities, and functional gene abundances measured by GeoChip of soils contaminated by As, Cd, Pb and Zn, as compared to the same soils under non-managed mixed grassland representing no intervention treatment (Unt). Though metal total concentrations did not differ by SRC and Unt, SRC soils had lower metal availability and toxicity, higher organic carbon, microbial biomass, phosphatase, urease and protease activities, as compared to Unt soils. Significantly reduced abundances of genes encoding resistances to various metals and antibiotics were observed in SRC, likely attributed to reduced metal selective pressure based on less heavy metal availability and soil toxicity. SRC also significantly reduced abundances of genes involved in nitrogen, phosphorus, and sulfur cycles, possibly due to the willow induced selection. Overall, while the SRC phytomanagement did not reduce the total heavy metal concentrations in soils, it decreased the heavy metal availability and soil toxicity, which in turn led to less metal selective pressure on microbial communities. The SRC phytomanagement also reduced the abundances of nutrient cycling genes from microbial communities, possibly due to intense plant nutrient uptake that depleted soil nitrogen and phosphorus availability, and thus site-specific practices should be considered to improve the soil nutrient supply for phytomanagement plants.

Potential of Virginia Mallow as an Energy Feedstock

This study aims to compare the potential of Virginia mallow to other high yielding perennial grasses and hardwoods by characterising and comparing fast pyrolysis product yields. Feedstocks selected for this study include miscanthus (Miscanthus x giganteus), Virginia mallow (Sida hermaphrodita), willow short rotation coppice (SRC) (Salix viminalis) and oak (Quercus robur). The experimental work was split into two sections: analytical (Py–GC–MS) and laboratory-scale processing using a 300 g h−1 continuous bubbling fluidised bed reactor. Pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) has been used to quantify pyrolysis products from these feedstocks by simulating fast pyrolysis heating rates using a CDS 5200 pyrolyser closed coupled to a PerkinElmer Clarus 680 GC–MS. High bio-oil yields were achieved for Virginia mallow, willow SRC and oak (65.36, 62.55 and 66.43 wt% respectively), but miscanthus only produced a yield of 53.46 wt% due to increased feedstock ash content. The water content in the bio-oil is highest from miscanthus (17.64 wt%) and relatively low in the Virginia mallow and hardwoods willow SRC and oak (12.49, 13.88 and 14.53 wt%). Similar high yields of bio-oil and low yields of char and non-condensable gas compared to willow SRC make Virginia mallow an attractive feedstock for fast pyrolysis processing.Graphic

Effects of cutting size on the growth and wood property traits of short-rotation coppice willows

Short-rotation coppice willows, which are commonly propagated with cuttings, are promising bioenergy resource crops. In this study, a field trial with a completely randomized block design was carried out with 787 clones from three full-sib pedigrees involving two shrub willow species. A total of 7083 cuttings were planted in the field, and the mass of each cutting was recorded correspondingly. The mortality rate, growth traits, and wood property traits of each cutting-propagated plant were measured throughout a complete growing season. The obtained data showed that heavier cuttings produced shoots with lower mortality rate, higher height, thicker ground diameter, and larger biomass production than lighter cuttings. The cutting mass significantly improved plant performance, especially at the early developmental stages. However, the cutting mass had no effect on the basic density and the main chemical composition (i.e., cellulose, hemicellulose, and lignin) of willow wood. This study provided essential information for improving the establishment of short-rotation coppice willow plantations.

Estimation of Yield Loss Due to Deer Browsing in a Short Rotation Coppice Willow Plantation in Northern Japan

Deer browsing is a major factor causing significant declines in yield in short rotation coppice (SRC) willow, but the resultant yield loss is difficult to estimate because it requires extensive investigation, especially when the standard yield is unknown. We investigated a simple method for estimating yield loss due to deer browsing. We enclosed an experimental SRC willow plantation in Hokkaido, northern Japan, planted with 12 clones, with an electric fence; deer browsing did, however, occur in the first summer of the second harvest cycle. We counted the number of sprouting stems and deer-browsed stems per plant and, after three years, the yield of each clone was analyzed using a generalized linear model with the above two parameters for the numbers of stems as explanatory variables. The model explained the yield of 11 out of the 12 clones, and estimated that browsing of a single stem per plant could reduce yield to 80%. Losses due to deer browsing were estimated to be as much as 6.0 oven dry ton ha−1 yr−1. The potential yield in the absence of deer browsing ranged from 2.2 to 7.5 oven dry ton ha−1 yr−1 among clones, and was significantly positively correlated with the estimated yield loss due to deer browsing. Our results suggest that a generalized linear model can be used to estimate the yield loss due to deer browsing from a simple survey, and deer browsing could significantly reduce willow biomass yield from the clones we studied, and thus countermeasures to control deer browsing are therefore necessary if sufficient willow biomass yield is to be produced.

Soil carbon stock impacts following reversion of Miscanthus × giganteus and short rotation coppice willow commercial plantations into arable cropping

AbstractThere are posited links between the establishment of perennial bioenergy, such as short rotation coppice (SRC) willow and Miscanthus × giganteus, on low carbon soils and enhanced soil C sequestration. Sequestration provides additional climate mitigation, however, few studies have explored impacts on soil C stocks of bioenergy crop removal; thus, the permanence of any sequestered C is unclear. This uncertainty has led some authors to question the handling of soil C stocks with carbon accounting, for example, through life cycle assessments. Here, we provide additional data for this debate, reporting on the soil C impacts of the reversion (removal and return) to arable cropping of commercial SRC willow and Miscanthus across four sites in the UK, two for each bioenergy crop, with eight reversions nested within these sites. Using a paired‐site approach, soil C stocks (0–1 m) were compared between 3 and 7 years after bioenergy crop removal. Impacts on soil C stocks varied, ranging from an increase of 70.16 ± 10.81 Mg C/ha 7 years after reversion of SRC willow to a decrease of 33.38 ± 5.33 Mg C/ha 3 years after reversion of Miscanthus compared to paired arable land. The implications for carbon accounting will depend on the method used to allocate this stock change between current and past land use. However, with published life cycle assessment values for the lifetime C reduction provided by these crops ranging from 29.50 to 138.55 Mg C/ha, the magnitude of these changes in stock are significant. We discuss the potential underlying mechanisms driving variability in soil C stock change, including the age of bioenergy crop at removal, removal methods, and differences in the recalcitrant of the crop residues, and highlight the need to design management methods to limit negative outcomes.

Productivity in partly mechanized planting operations of willow short rotation coppice

Biomass for energetic use can be procured from various sources including willow short rotation crops (WSRC). The feasibility of willow crops, however, is dependent on the costs incurred by operations such as the plantation, maintenance, harvesting and transport. In small scale applications, cost balancing often results in the use of equipment designed for general agricultural purposes to carry on the operational management of WSRC. This study evaluated the productive performance in planting operations of WSRC for a planting equipment consisting of regular farming tractors used to propel machines designed to support planting on single twin rows. Planting equipment consisting of 4 different types of farming tractors fitted with willow planting equipment was tested in 14 filed plots to be able to compute the main performance indicators such as the net and gross productivity rates. An evident variability in terms of time consumption on categories was observed at plot-level, and the planting time was related to a great extent to the operated area. The size of areas subjected to planting operations was the most important factor that affected productive performance. Variation of net productivity rate was explained largely by the ratio of the length of headland returning maneuvers to total length covered in a given plot. The model developed for the total study time shows that, in the observed conditions, it may take more than 7 h to plant one hectare. The equipment taken into study stands for a flexible option for small-scale farmers which could increase the utilization rates of their farming tractors by using them in other agricultural operations when needed. In addition, the studied equipment fits well to very narrow and small-sized plots, as such situation is typical to Romania and other European countries.

High Biomass Productivity of Short-Rotation Willow Plantation in Boreal Hokkaido Achieved by Mulching and Cutback

Weed control, which is commonly achieved by herbicides, is important in successfully establishing short-rotation coppice (SRC) of willow. In this study, we examined agricultural mulch film as a means of effective weed control and the influence of cutback practice (coppicing the first year’s shoot growth in the winter following planting) on biomass production in boreal Hokkaido, Japan. One-year-old cuttings from two clones each of Salix pet-susu and S. sachalinensis were planted in double-rows at a density of 20,000 plants ha−1. All plants were harvested three growing seasons after cutback. Average oven-dried biomass yield was 5.67 t ha−1 yr−1 with mulching, whereas it was 0.46 t ha−1 yr−1 in the unmulched control with a weed biomass of 4.13 t ha−1 yr−1, indicating that mulching was an effective weed control. However, weeds grew vigorously on the ground between mulch sheets and their dry biomass amounted to 0.87 t ha−1 yr−1. Further weeding between the mulch sheets enhanced the willow biomass yield to 10.70 t ha−1 yr−1 in the treatment with cutback. In contrast, cutback even reduced the willow yield when there were weeds between the mulch sheets. This negative effect of cutback on the willow yield resulted from nutrient competition with weeds; there was similar leaf nitrogen content and dry biomass per unit land area for the weeds and willows combined in the control and mulching treatments. These results suggest that growing SRC willow is feasible in boreal Hokkaido if combined with complete weed control and cutback, and is facilitated by using mulch film.

Carbon sequestration at land use conversion – Early changes in total carbon stocks for six tree species grown on former agricultural land

Changing land use from agriculture to forestry affects global carbon (C) balances. In addition to reduce using fossil fuels, climatic benefits may be reached by increasing forested areas where appropriate. At present, there is limited data concerning whether differences in C sequestration rates occur among tree species. In this study we evaluated the effects of various species on C sequestration at an early stage of afforestation. Total C stocks, i.e. C in biomass, litter and soil, were compiled for hybrid aspen, poplar, silver birch, Norway spruce, larch and willow. The species were planted in random blocks on five sites at different latitudes. Soil, litter and plant biomass were sampled repeatedly, except for root biomass which was calculated from functions found in the literature. There were no differences between species in total C stocks after 8–9 years growth, except for short rotation coppice (SRC) willows that reached a high production early due to a higher stand density compared to the species managed with short rotation forestry (SRF). Total C sequestration rates for sites varied from zero to 2.3–4.9 Mg C ha−1 year−1. There were no effects of species on soil organic carbon (SOC), but significant decreases were noted for sites with high initial amounts, while SOC was unchanged or increased on sites with lower initial amounts. Mean SOC sequestration rates for sites ranged between −3.0 to 0.78 Mg C ha−1 year−1. Thus, former land use and time since abandonment rather than species seemed to influence the SOC pools at this early stage of afforestation. There were few differences between species in litter C in these young stands. We conclude that increased tree productivity had a positive effect on total C sequestration. It is crucial to include C in both biomass and soil when discussing C capture at land use change. The time factor is important and experiments like this should be followed for an extended time.

Edible wild plants growing in adjacent spontaneous vegetation of energy plantations in southwest Slovakia

This paper evaluates the potential and perspectives of wild plant species and macrofungi from short rotation coppice. The research was conducted during the years 2014 - 2018 in stands of short rotation coppice willow and miscanthus grass in southwest of Slovakia. Evaluated wild plant species and macrofungi were divided into four groups (green vegetables, fruits and seeds, flowers and nectar, subterranean parts). The results showed that ground flora of short rotation coppice consisted of 74 edible species from 34 botanical families. Asteraceae, Rosaceae, Poaceae, Polygonaceae and Cichoriaceae families were represented the most. From the evaluated categories the most species belonged to the category with consumable aerial parts like leaves and shoots (59 species). The similar representation of species was found in the category of wild fruits and seeds consumed in the raw or preserved state and in category of edible subterranean parts (27 species and 22 species respectively). Principal component analysis showed that the edible parts with the strongest effect on the functional group differentiation were the fruits, seeds and subterranean parts.

Early growth of different tree species on agricultural land along a latitudinal transect in Sweden

Abstract Fast-growing tree species will be an important tool in the future production of renewables and in substituting non-renewable fossil energy sources. Sweden, like other countries around the Baltic Sea, has large areas of abandoned farmland usable for biomass production, but knowledge of growth performance of tree species candidates is insufficient. An experiment was initiated where six potentially high-producing tree species were compared. The best available plant material for each species was used on five sites over latitudes 56–64°N in Sweden. Results from the first 8–9 years are reported. Short rotation coppice willow (Salix schwerinii Wolf × S. viminalis L., clone ‘Tora’) had the fastest initial growth and production in southern Sweden. Hybrid aspen (Populus tremula L. × P. tremuloides Michx.) and poplar (Populus spp., section Tacamahaca), grown as short rotation forest, grew well over all sites and showed the highest productivity at the two northern sites. Hybrid larch (Larix ×eurolepis Henry) displayed a high potential at the two most southerly sites, whilst silver birch (Betula pendula Roth) was a medium-producing species at all sites. Norway spruce (Picea abies (L.) Karst.) started slowly, and Siberian larch (L. sukaczewii Dylis) produced poorly at the two northern sites in the initial stage. All tree species followed existing height development curves for the respective species on a high site quality level. Currently, well-growing clones of Populus spp. indicated that a wider selection of tree species can be used at high latitudes under climate change. The study showed a high growth potential for most species on former agricultural lands. However, measures to reduce climate and biological damage must be included in future efforts.