Short Rotation Coppice Research Articles

Neighbourhood effects on herbivory damage and chemical profiles in short-rotation coppice willows and their hybrids

Short rotation coppices (SRCs) represent an important source of biomass. Since they are grown in various mixtures, SRCs represent an excellent opportunity for assessing the effects of local plant neighbourhoods on their performance. We used a common garden experiment consisting of plots that varied in genotype diversity of SRC willows to test for the effects of chemical traits of individual plants and chemical variation in the plots where they grew on insect herbivory. We also explored whether the composition of willows planted in a plot affected their chemistry. To do this, we performed untargeted metabolomics and quantified various chemical traits related to the total set of metabolites we detected, flavonoids, and salicinoids in four willow genotypes. We measured the leaf herbivory that the plants suffered. The genotypes differed in most chemical traits, yet we found only limited effects of individual traits on herbivory damage. Instead, herbivory damage was positively correlated with structural variation in salicinoids in a plot. When analysing the effects of plot chemical variation on herbivory damage separately for each genotype, we found both positive and negative correlations between the two, suggesting both associational resistance and susceptibility. Finally, we also observed a significant effect of the interaction between genotype and plot composition on structural variation in plant chemistry. Overall, our results suggest that high chemical variation in mixed willow SRCs does not necessarily lower the herbivory damage, possibly due to spillover effects of insect herbivores among genotypes. Our results also show that different genotypes respond differently to plot composition in terms of herbivory damage and chemical composition, which may affect their suitability for growing in mixed stands.

Are biomass feedstocks sustainable? A systematic review of three key sustainability metrics

AbstractBiomass feedstocks are growing in importance due to their ability to serve as a renewable alternative to fossil fuels for large scale energy generation, with bioenergy projected to be a growing part of the UK's energy mix. Combined with technologies such as carbon capture and storage, sustainable bioenergy has the potential to produce negative emissions with including counterbalancing residual emissions. This paper presents a systematic review of the sustainability impacts of wood biomass (forestry/SRC) and Miscanthus, which are grown as energy fuels, comparing the three key indicators of sustainability: soil organic carbon sequestration rates, biodiversity, and water use efficiency (WUE). Analysis has shown significant influence from primary soil composition (p < 0.001) and previous land use (p < 0.001) on soil organic carbon sequestration rates following conversion to biomass feedstock production. Conversion from arable to forestry can have positive rates of sequestration of 1.4 ± 0.3 Mg C ha−1 year−1 on mineral soils, while similar conversions on a highly organic soils can lead to losses of −25 Mg C ha−1 year−1. This indicates a strong need for careful site selection for future forestry plantations. Miscanthus showed no preference under mineral or organic soils for carbon sequestration rate. Biodiversity at different trophic scales is impacted differently by biomass feedstock production. No significant impact on invertebrates was demonstrated between feedstocks but there is a significant difference between crops (p < 0.001) for vertebrates at higher trophic levels. A limited dataset was collected for WUE from the review, but analysis showed comparable WUE rates for Miscanthus and short rotation coppice, while forestry had significantly lower (p < 0.001) WUE. With global temperatures increasing and changes to climate, water stress is likely to increase. WUE will play an important role in the considerations dfor long term biomass feedstock planning and sourcing.

A spatial analysis of the economic returns to land‐use change from agriculture to renewable energy production: Evidence from Ireland

AbstractCountries are looking to reduce their agricultural sector's carbon footprint while encouraging economic and environmental sustainability. One proposed method of making agriculture more sustainable while maintaining farm incomes is through the production of bioenergy feedstocks. We examine the spatial aspect of the production of renewable energy feedstocks in Ireland. Two feedstocks are looked at—grass silage and short‐rotation coppice (SRC) willow. Spatial microsimulation analysis is utilised to assess the spatial suitability for alternative land uses, simulating land‐use change to compare economic returns with the current agricultural use. A farm‐based carbon subsidy is modelled based on avoided agricultural emissions and carbon sequestered. We find that midlands counties, especially those in the north midlands, have the highest proportion of land where feedstocks would be more profitable than the current agricultural use. Counties on the western seaboard have the lowest proportion of land where feedstocks would give greater returns. The amount of land where feedstocks are more profitable increases as greater carbon subsidies are provided. Of the two feedstocks assessed, SRC willow cultivation is more profitable than grass silage production. The overwhelming majority of land where producing feedstocks would be more profitable has cattle farming as its current use.

Active Remote Sensing Assessment of Biomass Productivity and Canopy Structure of Short-Rotation Coppice American Sycamore (Platanus occidentalis L.)

The short-rotation coppice (SRC) culture of trees provides a sustainable form of renewable biomass energy, while simultaneously sequestering carbon and contributing to the regional carbon feedstock balance. To understand the role of SRC in carbon feedstock balances, field inventories with selective destructive tree sampling are commonly used to estimate aboveground biomass (AGB) and canopy structure dynamics. However, these methods are resource intensive and spatially limited. To address these constraints, we examined the utility of publicly available airborne Light Detection and Ranging (LiDAR) data and easily accessible imagery from Unmanned Aerial Systems (UASs) to estimate the AGB and canopy structure of an American sycamore SRC in the piedmont region of North Carolina, USA. We compared LiDAR-derived AGB estimates to field estimates from 2015, and UAS-derived AGB estimates to field estimates from 2022 across four planting densities (10,000, 5000, 2500, and 1250 trees per hectare (tph)). The results showed significant effects of planting density treatments on LIDAR- and UAS-derived canopy metrics and significant relationships between these canopy metrics and AGB. In the 10,000 tph, the field-estimated AGB in 2015 (7.00 ± 1.56 Mg ha−1) and LiDAR-derived AGB (7.19 ± 0.13 Mg ha−1) were comparable. On the other hand, the UAS-derived AGB was overestimated in the 10,000 tph planting density and underestimated in the 1250 tph compared to the 2022 field-estimated AGB. This study demonstrates that the remote sensing-derived estimates are within an acceptable level of error for biomass estimation when compared to precise field estimates, thereby showing the potential for increasing the use of accessible remote-sensing technology to estimate AGB of SRC plantations.

Salix species and varieties affect the molecular composition and diversity of soil organic matter

Abstract Background and aims Most studies of the relationships between the composition of soil organic matter and plant cover have been carried out at the plant genera level. However, they have largely overlooked the potential effects that plant varieties, belonging to the same genus, can have on soil organic matter. Methods We investigated whether plant varieties belonging to different Salix species (S. dasyclados and S. viminalis) impacted the composition of organic matter using mid-infrared spectroscopy and pyrolysis GC/MS. Top-soils were taken from an 18 year-old long-term field trial where six Salix varieties were grown as short-rotation coppice under two fertilisation regimes. Results Significant differences in the molecular composition and diversity of the soil organic matter were observed in the fertilised plots. The effects were mostly visible at the species level, i.e. the organic matter in soil under S. dasyclados varieties had higher molecular diversity and lignin content than under S. viminalis, potentially due to differences in the amount and composition of their litter inputs. Smaller differences among varieties from the same species were also observed. No significant effects of Salix varieties were observed in the unfertilised plots. The relatively high degree of spatial variability of several soil properties found in these plots may have masked plant variety and/or species effects. Conclusion This study provides evidence that the identity of Salix species or varieties can affect the molecular composition and diversity of soil organic matter. The corresponding traits should be considered in breeding programmes to enhance soil organic C accumulation and persistence.

Modelling the impact of business risk on the competitiveness of purpose-grown biomass of annual and perennial crops

Perennial energy crops compete with conventional annual crops in land-use. The production price of biomass from perennial energy crops is thus derived on the basis of the opportunity cost principle. This means that in deciding whether to grow perennial energy crops, the farmer will demand a price for biomass that will at least provide him with the same economic effect over the lifetime of the plantation in the form of the present value of net cash flows over the lifetime of the energy crop plantation. The level of discounts used to discount the cash flows associated with (annual) conventional crops and perennial energy crops plays an important role in modelling the biomass production price. The business risk associated with the two types of crops is different, with generally higher risk associated with perennial energy crops. This study focuses on developing a methodology to incorporate the risk associated with growing conventional and energy crops and to derive the discount rate for both crop groups. The methodology is demonstrated using the example of the Czech Republic and the price level in 2021. The analysis using Czech data led to a discount rate of 8.5 % for conventional crops and 11.5 % for perennial energy crops. The increase in the discount value for perennial energy crops leads to an increase in the expected biomass sales price by a producer. The sensitivity of the biomass production price level to an increase in the discount rate is lower for Miscanthus plantations compared to short rotation coppice.

Tackling climate change: Agroforestry adoption in the face of regional weather extremes

The cultivation of agroforestry systems is regarded as an effective strategy that can help synergistically mitigate and adapt to the adverse impacts of climate change and regional extreme weather events. This study addresses the question of whether, and under what conditions, farmers are likely to adopt agroforestry systems in response to regional weather extremes and presents a novel research approach to tackle this question. A discrete choice experiment was conducted to elicit farmers’ preferences for agroforestry and wood-based land use systems. The results were combined with geospatial weather information. Assuming adaptive weather expectations, land users’ dynamic responses to extreme weather were simulated in terms of adoption probabilities. Farmers in the case study region in southeastern Germany were found to have a negative preference for alley cropping systems (i.e. agroforestry) and short rotation coppice, compared to an exclusively crop-based land use system. However, the results from the simulation of a 2018-like extreme weather event showed that alley cropping has a high probability of being adopted in the long-term. This study provides novel insights into the adaptive uptake of climate-resilient agroforestry systems. This information can be used to develop more effective policies and programs to promote agroforestry as a climate-resilient land-use strategy.

Endophyte-Mediated Populus trichocarpa Water Use Efficiency Is Dependent on Time of Day and Plant Water Status

Endophytes are potential partners for improving the resource use efficiency of bioenergy feedstock systems such as short rotation coppice Populus species. Endophytes isolated from members of the Salicaceae family have broad host compatibility and can improve water use efficiency (WUE) through decreases in stomatal conductance. However, the literature is inconsistent with regard to the environmental conditions and temporal patterns of these benefits. This study investigated how endophyte-mediated changes in Populus trichocarpa ‘Nisqually-1’ stomatal conductance and WUE shift with time and scale in response to water deficit stress. Leaf gas exchange and aboveground productivity were used to evaluate the carbon and water balance of greenhouse-grown plants in response to endophyte inoculation and water deficit. Differences in stomatal conductance between control and inoculated plants were more pronounced (39.7% decrease, Welch two-sample t [14.34 adjusted degrees of freedom] = –2.358, P = 0.033) under water deficit conditions in the late morning during a period of higher light intensity. The decrease in stomatal conductance accompanied a substantial increase in intrinsic WUE (iWUE) for water deficit inoculated plants. However, increases in iWUE did not result in improvements in aboveground productivity or shoot biomass WUE for water deficit inoculated plants. This decoupling between iWUE and aboveground productivity may be an indicator of assimilate allocation to microbial metabolism as an additional carbon sink or a shift in carbon allocation toward belowground biomass. Future work should take a whole plant approach that accounts for diurnal patterns in incident irradiance to evaluate the impact of endophyte inoculation on host WUE and stress tolerance.

Beyond biomass production: Enhancing biodiversity while capturing carbon in short rotation coppice poplar plantations

Biodiversity is essential for the functioning of ecosystems and the provision of services. In recent years, the role of plantations in mitigating climate change through carbon sequestration has been highlighted. In the Mediterranean area, high-density poplar plantations in short-rotation with resprouting management (SRC) have been established for biomass purposes on mostly irrigated agricultural land, coexisting with rainfed and irrigated agricultural crops. This study aims to assess the contribution of these plantations to this type of agroforest ecosystem in terms of biodiversity. For this purpose, both flora and fauna diversity were evaluated both within and outside of the plantation. Additionally, the accumulated carbon in the biomass, as well as in the accompanying vegetation within the plantation, was assessed. Different indices were used to evaluate both the intrinsic diversity of the forest plantation and the degree of substitution and complementarity between the different communities of the landscape. Our findings reveal distinct biodiversity patterns in the land-use scenarios sampled. Specifically, we observed significantly higher flora-species richness in SRC plantations than in the adjacent agricultural land, whereas fauna richness showed a similar but slightly higher level in the forested area. A moderate level of complementarity between land uses was found for insects and mammals (around 45 %), contrasting with high complementarity for birds (87 %) and flora (90 %). This suggests substantial turnover and replacement among these ecological environments. Our results indicate that a second rotation (4 year) plantation could accumulate a total of 61.6 Mg C ha−1, and even though adventitious flora represents <2 % of the total carbon accumulated, its importance in providing ecosystem services is considerable. Hence, these findings evidence the fact that SRC poplar plantations can enhance biodiversity in Mediterranean agroforest ecosystems and actively contribute to various provisioning ecosystem services, including carbon sequestration, reflecting a multi-objective approach that extends beyond biomass production.

Production and investigation of water absorbent fibre pellets from unutilised lignocellulosic biomass pre-processed in a twin-screw extruder

Organic livestock farming requires all resource input to be organic as well. Competition for raw materials as bedding increases the demand for alternative bedding materials. The production of absorbent fibre pellets from underutilized lignocellulosic plant material is therefore a research area that needs further attention. Precise research on processing methods and absorbent quantity is essential for the development of sustainable, high-quality absorbent bedding pellets. Twin-screw extruded fibre from eight different raw materials were processed into absorbent pellets. These pellets were investigated for physical properties including absorbency, mechanical durability, particle-size distribution and bulk density in accordance with relevant standards. Due to the absence of a standardised method for assessing absorbency, a testing method was devised. This involved submerging the produced pellets in deionized water for durations of 30 s, 300 s, and 1200 s. This research analysed various raw materials for suitability in absorbent pellet production. Poplar pellets performed good in absorbency (130 %, 172 %, 194 % respectively) and mechanical durability (95 %). As a result, larger quantities of absorbent pellets could be produced from poplar if needed since poplar wood chips are of higher availability due to existing short rotation coppices. This article emphasised producing absorbent bedding pellets, prioritising, using twin-screw extruded lignocellulosic fibre, revealing significant raw material influence on absorption properties.

SDEWES 2023: Barriers and Possibilities for the Development of Short-Rotation Coppice as an Agroforestry System for Adaptation to Climate Change in Central European Conditions

This article compares different production, economic, and selected environmental aspects of agroforestry systems in a standard (alley cropping) and a newly proposed design with fast-growing trees grown in short-rotation coppice. Our models of agroforestry systems (AFSs) are as follows: (i) alley cropping AFS with cherry and walnut trees in single rows (tree strips) with 28 m-wide arable fields between them (crop strips), and (ii) coppiced tree belt AFS with poplars and willows and 25 m-wide arable fields between them (crop strips). To evaluate the production characteristics of trees, we used yield curves from experimental plantations in conditions of the Czech Republic from previous research projects. Cost data were collected from long-term experimental plantations and combined with current operation and energy prices. The article presents an economic methodology for assessing the competitiveness of biomass production in AFSs under the current identified market conditions. Our results show that AFSs with short-rotation coppice can have similar economic and production results as annual crops if grown on suitable sites and with appropriate quality of agronomy. In comparison, alley cropping AFSs with fruit trees would not be economically viable for farmers without a significant subsidy for establishment and maintenance in the first years after establishment. Concerning the latest economic and political developments, the product from SRC (energy woodchips) can be evaluated as strategic, increasing the producer’s independence from purchased energy fuels.

Economic and environmental assessment of a multifunctional poplar plantation for roundwood and wood chip production in Spain

Aim of study: To analyze the environmental and economic performance of a multifunctional poplar plantation (MPP), which was managed to produce timber for sawn wood and chips for bioenergy. Area of study: The plantation was located in Southern Spain producing roundwood and woodchips (from tops and branches). Material and methods: The life cycle assessment (LCA) methodology was chosen to perform the environmental impact assessment from a cradle-to-gate perspective. Capital goods, including machinery-manufacturing processes, were included. One oven dry tonne (odt) of forest biomass was chosen as functional unit. The economic analysis was performed using present costs and common indicators: net present value (NPV) and internal rate of return (IRR). Main results: The harvest operations are the most environmental impacting subsystem and cultivation the costliest. Chipping was the process contributing the most to the environmental burden. The use of fertilizers, within the cultivation subsystem, had a notable impact on certain midpoint categories. In terms of climate change potential, 1 odt of delivered wood chips generated 64.1 kg CO2-eq. When considering the whole system (including the roundwood fraction), this value was 45.2 kg CO2-eq odt-1. MPP was hardly profitable with land rental and irrigation being the most expensive items. NPV, including harvesting and transport subsystems, was 1,582 € ha-1, while IRR reached 6.3%. Research highlights: Our results allow to identify the costliest operations and those with the greatest impact to improve the system. Finally, these figures can be compared with other crop alternatives such us poplar short rotation coppice (SRC).

Harvesting Losses for a Cut-and-Chip Harvesting System Operating in Willow Short-Rotation Coppice

In any short-rotation coppice (SRC) operation, a certain percentage of harvestable material is unrecovered, which contributes to harvesting system losses. This material may be in the form of merchantable and non-merchantable components. These losses affect economics but also influence yield, nutrient cycling, and carbon sequestration. There are very few estimates for harvesting losses available in the literature, and they are limited by small sample sizes. The objective of this work was to provide a broad overview of harvesting losses in willow SRC over a wide range of standing biomass and harvesting conditions. The average total harvesting losses were between 3 and 4 Mg ha−1, which is between 6 and 7 percent of the standing biomass. Losses can spike to nearly 40% on less than 3% of the area. Harvesting losses are significantly, but weakly, correlated with increased standing biomass. These results highlight the complexity and variability in harvesting losses as well as which aspects of harvesting systems might be targeted to reduce or partition material losses. These results have implications for designing machinery and economic modeling of these systems.

Forest Carbon Modeling in Poplar and Black Locust Short Rotation Coppice Plantation in Hungary

Forest carbon dynamic modeling for estimating the carbon stock in short rotation coppice bioenergy plantation in Hungary will be vital for better comprehending the role of black locust (Robinia pseudoacacia) and poplar (Populus sp.) in carbon dioxide sequestration from the atmosphere. The research aims were to estimate the potential carbon stock and describe the carbon distribution of the short rotation coppice bioenergy plantation above and below ground. Various sources were used to acquire parameterization data for developing forest carbon dynamic models. CO2FIX modeling V.3.2 was utilized in the data analysis to estimate the total carbon stock in biomass, soil, harvested wood products, and bioenergy compartments. Modeling has been around for 45 years. In this research, the total carbon stock of black locust and poplar at the end of the simulation period was 64.13 and 131.08 MgC.ha-1, respectively. The average carbon allocation above and below ground for black locust and poplar was 0.76, 19.76, 1.80, and 21.67 MgC.ha-1, respectively. In conclusion, poplar outperformed black locust regarding carbon storage in the short rotation coppice bioenergy plantation. Below ground carbon allocation was much higher than above ground. Therefore, more attention should be paid on below ground allocation through environmentally friendly soil management. Keywords: bioenergy plantation, carbon dynamics, climate change mitigation, CO2FIX model, fast growing species

Pellets from mixtures of short rotation coppice with forest-derived biomass: Production costs and energy intensity

The demand for feedstock for pellet production is growing, with a consequent increase in the cost of their purchase and the cost of production. The objective of this study was to determine the cost and energy intensity of pellet production from forest biomass (Scots pine, silver birch) and short rotation coppice – SRC (black locust, poplar and willow) and their mixtures. The lowest cost (339.7 € Mg−1) and energy input (1448 kWh Mg−1) for pellet production were determined for Scots pine. The cost of pellet production from poplar and willow was higher by 5–6% compared with Scots pine pellet. The energy input for pellet production from willow, black locust and poplar was higher by 48.1%, 50.4% and 53.2%, respectively. The feedstock purchase cost (50.3–57.8%) and energy input for drying them (74.6–82.6%) accounted for the largest portion. Increasing the share of SRC biomass from 25% through 50%–75% relative to Scots pine and silver birch biomass resulted in a cost and energy intensity increase and decrease in the energy efficiency of pellet production. Three pellet types: produced from Scots pine and those with an addition of 25% of willow or poplar made up one cluster.

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

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

Design, implementation, and evaluation of a short rotation coppice system for wastewater treatment and resource recovery in India

Despite growing health concerns and increasing water scarcity, adequate wastewater treatment and reuse remains limited in India. Low-cost, decentralised, and nature-based on-site sanitation systems could play a key role in a circular water approach. This paper evaluates the performance of a Wastewater Fertigated Short Rotation Coppice (wfSRC) system based on willow, poplar, and bamboo species as a potential solution, offering low-cost, efficient water treatment, and high biomass production. Through a full-scale wfSRC pilot plant (250 m3·day−1 municipal wastewater on 6864 m2) established at Aligarh Muslim University, Uttar Pradesh, India, treatment capacities, biomass production rates, and contamination tolerance of different willow, poplar, and bamboo species were investigated. The chemical compositions of incoming wastewater, percolation water, soil, and biomass were monitored regularly. Despite the high load, all plant sections of the wfSRC system showed efficient removal of wastewater-originated pollutants. BOD5 and COD removal efficiencies were up to 99% and 95% respectively. Removal efficiencies for PO4-P reached 93% and for TN 91%. In general, total nitrogen and phosphate loads appear to be the limiting design parameters under the conditions at Aligarh to meet all discharge limits in India. Biomass production was projected to be >225 tDM·ha−1·yr−1 for bamboo, 65 tDM·ha−1·yr−1 for willow, and 206 tDM·ha−1·yr−1 for poplar. The pilot, conducted from March 2022 to June 2023, showcased how these densely planted agroforestry systems can effectively treat wastewater through natural processes such as oxidation, microbial degradation, and plant uptake. The findings demonstrate wfSRC's potential to serve as a nature-based, sustainable approach to wastewater treatment, particularly beneficial for suburban and rural areas in India and similar regions worldwide. This paper also provides recommendations for future implementation of wfSRC systems, emphasizing the need for careful planning regarding plant selection, system design, and operational strategies to maximize treatment efficiency and biomass production.

Organic Amendments to Short Rotation Coppice (SRC) Plantation Affect Species Richness and Metal Accumulation of Spontaneously Growing Herbaceous Plants

Excess potentially toxic metals (PTMs) in soils require ad hoc approaches to salvage. Hence, this study explored the shoot accumulation of cadmium (Cd), lead (Pb), and zinc (Zn) by herbaceous plants growing under previously established Salix and Populus clones Short Rotation Coppice (SRC) with compost and sewage sludge applications in an abandoned metallurgical site, Podlesí, Czech Republic; PTM decontamination of soils. Soils within the SRC experimental site and outside considered as control were analyzed for their chemical properties by multi-analytical techniques. Shoots of spontaneously growing herbaceous plants under trees in the site and without trees in control were determined for pseudo-total Cd, Pb, and Zn contents. Moderately to slightly acid soils, high cation exchange capacity, and C/N ratio supported mineralization and relative mobility of total Cd (7.7–9.76), Pb (1541–1929), and Zn (245–320 mg kg−1) in soils. Although soil amendments improved chemical properties, compost application supported higher species richness than sewage sludge. Over 95% of plants accumulated Cd and Zn above the WHO threshold and green fodder in the Czech Republic, with 36% Pb above the regional limit (40 mg kg−1). Approximately 100, 50, and 6% of herbaceous species had Cd, Pb, and Zn accumulation, respectively, higher than published average upper limits in plants (0.2 Cd, 10 Pb, and 150 Zn mg kg−1). Dicots recorded higher Cd content, Tenacetum vulgare (L.), Hypericum maculatum (Crantz), and Cirsium arvense (L.); Stachys palustris (L.), Lamium perpereum (L.), and Campanula patula (L.) for Pb; Glechoma hederaceae (L.), C. patula, and C. arvense for Zn in all treatments. Appropriate soil amelioration of SRC-supported PTM mobility and excess herbaceous species shoot accumulation, growth, and richness.

The Effects of Vegetation Structure and Timber Harvesting on Ground Beetle (Col.: Carabidae) and Arachnid Communities (Arach.: Araneae, Opiliones) in Short-Rotation Coppices

Landscape complexity is a crucial factor for insect diversity in agricultural landscapes. Short-rotation coppices (SRCs) are characterised by high habitat heterogeneity. The impact of vegetation structure on the composition and diversity of ground beetle and arachnid communities was therefore investigated in four SRCs and six reference plots. The study site was located in Hesse, Germany. The invertebrates were surveyed from 2011 to 2014 using pitfall traps, and the vegetation structure was quantified by estimating the percentage cover of 10 structural variables. The impact of the selected structural variables on community composition was analysed during grove growth as well as after a timber harvest. We found correlations between the cover percentages of structural variables and the quantitative and qualitative species composition in both animal groups (p ≤ 0.05). The share of individuals of forest species increased with rising shading and litter cover, while those of open land decreased. The opposite trends were found the year after the timber harvest. The SRCs showed a higher structural diversity compared to the reference biotopes (p ≤ 0.05). This was positively correlated (p ≤ 0.001) with species diversity and the variety of habitat preference groups in both animal groups. The high diversity within the habitat preference groups indicated a functional redundancy among species for both animal groups and, consequently, a high level of resilience within these communities. Little is known about the functional aspects of ground beetles and spiders in ecosystems, and detailed studies are urgently needed. We conclude that SRCs can contribute to the diversification of agricultural landscapes as an alternative to traditional crop cultivation.

Torrefaction of Portuguese woody biomasses and the evaluation of its properties

Torrefaction is an option for improving biomass properties for fuel application. Biomass undergoes chemical changes reflected on the upgrading of its properties as a biofuel, such as higher calorific power, lower O/C and H/C ratios, lower higroscopicity or better grindability. The objectives of this experimental study were to analyze the effects of torrefaction, under standard conditions of 265 ºC, and residence time of 15 minutes in a nitrogen atmosphere and during a total 1h45m heating period, on a set of sixteen woody biomasses coming from poplar short rotation coppice (SRC) and other Portuguese roundwoods. Average mass loss was higher than 40%. The set of poplar clones and common broom provided torrefied products with higher quality than the set of roundwood forest species. The results on other parameters for proximate and ultimate analysis corroborate this global picture. Correlation analysis showed a higher degree of interconnectedness between LHV and proximate analysis results, for poplar clones and common broom, comparatively with roundwood biomasses.