Although native to Australia,
Eucalyptus
species are found throughout Europe. At present, they are located mainly in the Iberian Peninsula and
Eucalyptus globulus
is the most commonly planted ...species. Climate forecasts anticipate an expansion of
Eucalyptus
to other regions of Europe. The fast growth of
E. globulus
, together with its resprouting ability and wood properties, has promoted the use of this species in the Iberian Peninsula. The total volume of
E. globulus
harvested there was close to 14 million m
3
in 2019.
Eucalyptus
species represent the main source of raw material for the pulp and paper industries and provide an important source of income to non-industrial owners. Being exotic fast-growing trees, their expansion has also been associated with negative environmental impacts. The species therefore poses a series of challenges, while also generating opportunities. The objectives of this review paper are: (1) to summarize the importance of
Eucalyptus
plantations in Europe; (2) to analyse the opportunities and challenges of this genus in present and future plantations in Europe; (3) to assess to what extent forest management, at both stand and landscape levels, can reduce negative impacts; (4) to make policy and management recommendations that may support the use of this genus in other European regions. These aims are accomplished based on a thorough literature review, particularly focused on research developed in the Iberian Peninsula.
Hybrid eucalypt clones are grown for fiber production worldwide and to provide an ecosystem service that can store atmospheric carbon at a very fast rate. This study assessed the carbon stocks in the ...soil and various tree fractions in a 10-year-old plantation of Eucalyptus urophylla S.T. Blake × Eucalyptus globulus Labill. in Southern Brazil. Four experimental plots were established, and an inventory of Eucalyptus trees was conducted by considering five diametric classes. Three trees in each diametric class were harvested for biomass and carbon quantification. The understory biomass of native trees was quantified in five subplots and the litter was quantified in 16 subplots. Organic C was quantified in the soil (SOC) and roots (diameter ≤ 0.5 cm) to a depth of 100 cm. The C concentration in the different biomass fractions of the eucalyptus trees were 55.7% (±0.6), 50.4% (±0.4), 49.5% (±0.6) and 45.4 % (±0.9) for leaves, branches, wood and bark, respectively. The C concentrations in the understory fractions were 51.4% (±1.0) for the canopy and 50.0% (±0.9) for the stem. The carbon concentration in the fine root biomass was 45.7% (±1.4). Soil C concentrations were 1.23% (±0.32), 0.97% (±0.10), 0.45% (±0.14), and 0.24% (±0.10) for depths of 0–25, 25–50, 50–75, and 75–100 cm. C was allocated in: (a) the trees (aboveground fraction = 118.45 Mg ha−1 and belowground fraction = 30.06 Mg ha−1), (b) the understory = 1.44 Mg ha−1, (c) the litter = 8.34 Mg ha−1, and (d) the soil (without roots) = 99.7 Mg ha−1. The share of total C stock (a + b + c + d = 258.0 Mg ha−1) was similar in the aboveground (49.7%) and belowground (50.3%) fractions, thus indicating a very high rate of C sequestration in the biomass. Eucalyptus plantations in Brazil are fast growing (for this study = 36.7 m³ ha−1 year−1) and contribute to intense carbon sequestration in above and belowground biomass (14.8 Mg ha−1 year−1).
In this study, high quality radiata pine pellets were torrefied at a range of temperatures (T = 210, 240, 270 and 300 °C) and residence times (t = 20, 40 and 60 min). The effects of these treatments ...on mass yield (MY), ash content (A), volatile matter (VM) and fixed carbon (FC), high heating value on a dry basis (HHVdb) and low heating value on a wet basis (LHVwb) were investigated, and models were constructed to predict these energy properties from T and t. Untreated pellets were analysed as control samples. Threshold conditions of 240 °C 40 min yielded significant increases in HHVdb and carbon content and a significant decrease in oxygen content. This combination significantly increased A and FC and significantly decreased VM. Logistics models using T, t, t × T and T2 were able to predict A accurately, with no bias, whereas FC values tended to be underestimated. The variation in HHVdb and LHVwb was explained by linear models with t and t × T as variables. Use of the models enabled definition of torrefaction severity that ensures an A below 0.7% and a LHVwb value 30% higher than obtained with raw pine pellets. Torrefaction conditions of T = 260–270 °C and t = 50–60 min are proposed.
Developing a circular bioeconomy based on the sustainable use of biological resources, such as biomass, seems to be the best way of responding to the challenges associated with global change. Among ...the many sources, short rotation forest crops are an essential instrument for obtaining quality biomass with a predictable periodicity and yield, according to the areas of cultivation. This review aims to provide an overview of available knowledge on short rotation coppice Populus spp. plantations under Mediterranean conditions and specifically in Spain, in order to identify not only the status, but also the future prospects, for this type of biomass production. The analysis of available information was conducted by taking into consideration the following aspects: Genetic plant material; plantation design, including densities, rotation lengths and the number of rotations, and mixtures; management activities, including irrigation, fertilization, and weed control; yield prediction; biomass characterization; and finally, an evaluation of the sustainability of the plantation and ecosystem services provided. Despite advances, there is still much to be done if these plantations are to become a commercial reality in some Mediterranean areas. To achieve this aim, different aspects need to be reconsidered, such as irrigation, bearing in mind that water restrictions represent a real threat; the specific adaptation of genetic material to these conditions, in order to obtain a greater efficiency in resource use, as well as a greater resistance to pests and diseases or tolerance to abiotic stresses such as drought and salinity; rationalizing fertilization; quantifying and valuing the ecosystem services; the advance of more reliable predictive models based on ecophysiology; the specific characterization of biomass for its final use (bioenergy/bioproducts); technological improvements in management and harvesting; and finally, improving the critical aspects detected in environmental, energy, and economic analyses to achieve profitable and sustainable plantations under Mediterranean conditions.
Debarked Pinus radiata wood was blended with debarked Eucalyptus nitens wood in three different proportions: 100% pine (100P), 90% pine-10% eucalyptus (90P/10E) and 60% pine-40% eucalyptus (60P/40E). ...The pellets were torrefied in dry and non-oxidative conditions at different temperatures (210, 240, 270 and 300 °C) and residence times (40 and 60 min) to enhance the energy properties and determine the elemental composition (18 elements). For raw pellets, the concentrations of Na, K, Zn, B and Cl increased significantly with the proportion of eucalyptus wood, with Cl levels being 60% higher in the 60P/40E than in the 100P pellets. The concentrations of most elements (C, Mg, Al, P, Ca, Fe, Cu) tended to increase (+35% for C, +200–250% for the others) with torrefaction severity, independently of the mixture. Decreases in H and O concentrations were also independent of the mixture. Torrefaction decreased the Cl content by 63–77%, which compensated for the high levels in mixtures with eucalyptus. Increases in the high heating value (by as much as 37%) with torrefaction occurred in parallel with an increase in carbon content and a decrease in the atomic H:C and O:C ratios, particularly in the 260 to 300 °C transition. Torrefaction compensated for the negative effect of the inclusion of eucalyptus, with the alkali index remaining at a relatively safe maximum value of 0.10 kg GJ−1.
•Cl and K concentrations increased with the proportion of eucalyptus in the pellets.•Cl decreased by 66–77% with torrefaction severity.•The concentrations of most elements increased with torrefaction severity.•ISO 17225-8 was used to evaluate torrefied pellets.•Debarked eucalyptus can potentially substitute up to 40% of debarked pine.
This study proposes stand level models for estimating biomass yield, total energy and carbon sequestration in
Eucalyptus globulus and
Eucalyptus nitens plantations, on the basis of measurements made ...in 131 plots established at the usual range of initial forest densities for southwestern Europe. The timber volume, total aboveground biomass, logging residue biomass, crown biomass, carbon in aboveground biomass and soil organic layer, energy in aboveground biomass, energy in logging residue biomass and usable cellulose yield were represented in the form of isolines (taking mortality into account) and plotted against dominant height. These variables were calculated and compared with previously published data on two silvicultural options for short rotation forestry, one destined for bioenergy production and the other consisting of the standard silviculture regime applied to both species in southern Europe, considering the average site index for each species. Yield levels were higher in
E. nitens than in
E. globulus for all variables because of faster diameter increment at similar densities. The total yield in terms of biomass was 13.9–14.6
Mg
ha
−1
y
−1 for
E. globulus and 20.4–21.5
Mg
ha
−1
y
−1 for
E. nitens. Energy in aboveground biomass ranged between 233 and 245
GJ
ha
−1
y
−1 for
E. globulus and 345 and 364
GJ
ha
−1
y
−1 for
E. nitens, carbon accumulation rate in aboveground biomass and soil organic layer was 6.9–7.2
Mg
ha
−1
y
−1 for
E. globulus and 12.7–13.5
Mg
ha
−1
y
−1 for
E. nitens, and usable cellulose was 5.7–5.9
Mg
ha
−1
y
−1 for
E. globulus and 9.0–10.1
Mg
ha
−1
y
−1 for
E. nitens. It was found that 50% increments in the initial density result in only marginal increments in biomass and usable cellulose yields.
► We develop empirical models for bioenergy production and carbon storing in Eucalypt plantations. ► Stand density management diagram (SDMD) can provide useful insights in short rotation woody crops. ► Energy densities about 3,4–4.1
TJ
ha
−1 can be reached with SRC Eucalypt plantations in south Europe. ► Increasing stand density from 1600 to 2400 results in marginal increases in biomass yield. ►
Eucalyptus nitens grows faster in diameter than
E. globulus and reach higher energetic yield.
This study aims to quantify the potential contribution of nutrients derived from leaf litter in a short rotation coppice plantation which includes monocultures of the species Populus alba (PA) and ...Robina pseudoacacia (RP) as well as a mixture of 50PA:50RP, in the middle of the rotation. The P. alba monoculture was that which provided the most leaf litter (3.37 mg ha−1 yr−1), followed by the 50PA:50RP mixture (2.82 mg ha−1 yr−1) and finally the R. pseudoacacia monoculture (2.55 mg ha−1 yr−1). In addition to producing more litterfall, leaves were shed later in the P. alba monoculture later (December) than in the R. pseudoacacia monoculture (October) or the mix (throughout the fall). In terms of macronutrient supply per hectare, the contributions derived from leaf litter were higher for K, P and Mg in the case of P. alba and for N in R. pseudoacacia, the mix presenting the highest Ca content and intermediate concentrations for the rest of the nutrients. In addition, other factors such as C:N or N:MO ratios, as well as the specific characteristics of the soil, can have an important impact on the final contribution of these inputs. The carbon contribution derived from leaf fall was higher in the P. alba monoculture (1.5 mg ha−1 yr−1), intermediate in the mixed plot (1.3 mg ha−1 yr−1) and slightly lower for the R. pseudoacacia monoculture (1.3 mg ha−1 yr−1). Given these different strategies of monocultures with regard to the dynamism of the main nutrients, species mixing would appear to be suitable option to achieve a potential reduction in mineral fertilization in these plantations.
Climatic conditions have been shown as a major driver of the fate of Hg in forest ecosystems at a global scale, but less is known about climatic effects at shorter scales. This study assesses whether ...the concentration and pools of Hg in soils collected from seventeen Pinus pinaster stands describing a coastal-inland transect in SW Europe vary along a regional climatic gradient. In each stand, samples of the organic subhorizons (OL, OF + OH) and the mineral soil (up to 40 cm) were collected and some general physico-chemical properties and total Hg (THg) were analyzed. Total Hg was significantly higher in the OF + OH than in the OL subhorizons (98 and 38 μg kg−1, respectively), favored by a greater organic matter humification in the former. In the mineral soil, mean THg values decreased with depth, ranging from 96 μg kg−1 in the 0–5 cm layers to 54 μg kg−1 in the deepest layers (30–40 cm), respectively. The average Hg pool (PHg) was 0.30 mg m−2 in the organic horizons (92% accumulated in the OF + OH subhorizons), and 27.4 mg m−2 in the mineral soil. Changes in climatic factors, mainly precipitation, along the coast-inland transect resulted in a remarkable variation of THg in the OL subhorizons, consistent with their role as the first receiver of atmospheric Hg inputs. The high precipitation rate and the occurrence of fogs in coastal areas characterized by the oceanic influence would explain the higher THg found in the uppermost soil layers of pine stands located close to the coastline. The regional climate is key to the fate of mercury in forest ecosystems by influencing the plant growth and subsequent atmospheric Hg uptake, the atmospheric Hg transference to the soil surface (wet and dry deposition and litterfall) and the dynamics that determine net Hg accumulation in the forest floor.
•Hg levels in the uppermost soil layers increased with proximity to the coastline.•Rainfall may indirectly influence Hg levels by controlling organic matter dynamics.•The content of Hg in organic horizons was higher in the more humified layer (OF + OH).•The major Hg pool was in the mineral soil below the organic horizon.•Forestry activities should proceed with caution in Hg-enriched O horizons.
Objectives This study examines the influence of tree species in relation to biomass and soil C dynamics in plantations established on former pasture land. Data on the C sink capacity of such ...plantations will provide valuable information for designing improved management strategies for afforestation programmes aimed at mitigating CO2 emissions. Methods The study was carried in the temperate forest of southern Europe, one of the most productive timber production systems in Europe. The study, designed to control most of the variability at regional level, involved a network of 120 paired plots (former pasture land-new plantations of different ages) established to construct three well-replicated chronosequences of the most common tree species in humid temperate systems. Results The mean rates of C sequestration (biomass and soil) estimated throughout the rotation ranged between 8.7 and 14.6 Mg Cha−1 year−1 (Eucalyptus nitens>Eucalyptus globulus>Pinus radiata), and the contribution of the soil (forest floor plus mineral soil) ranged from 8 to 18% (Eucalyptus nitens>Pinus radiata>Eucalyptus globulus). The humid temperate climate and the sandy loam texture of the soils favoured large losses of SOC from the uppermost mineral soils during the 10 year after afforestation. The higher loss of SOC in the Pinus radiata soil (26% of initial SOC) than in the Eucalyptus soil (19.45% of initial SOC) was attributed to the lower transfer of organic C to the mineral soil, as a result of the lower litter decomposition rate and the lower belowground litter input from associated vegetation. The rapid development of tree biomass favoured the subsequent C sequestration in biomass and soils. Conclusion The C sink capacity of forest plantations can be maximized by elongating the rotation length and adopting suitable management strategies for each species. This is especially important in intensive forest plantations in which the high intensity of harvesting may prevent accumulation of SOC in the long term.
The worldwide increase in the demand for wood pellets has led to increased interest in the use of biomass feedstock. However, the quality of pellets depends directly on the biomass feedstocks. This ...paper brings new insights about the influence of lignin distribution, physicochemical characteristics, and microstructure on the quality of pellets. The aim of the study was to characterize the physical, chemical, mechanical and energy properties of pellets produced from Pinus radiata (PR), Eucalyptus nitens (EN), Paulownia elongata × fortune (P), and Miscanthus × giganteus (MG), as well as to use microscopic techniques to examine how lignin distribution influences the mechanical properties. The findings show that the pellets made from PR were more suitable for bioenergy production compared to those produced with EN, P, and MG. Anatomical structure proved to be important in relation to pellet quality. The clear areas on the surface of the pellets presented relationship with the percentage of biomass lignin (which ranged from 26.4 to 34.2%). The P and PR pellets were more durable and had fewer empty spaces between particles. The pellets made from EN, which was the material most difficult to compact, had abundant cracks.
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•Wood, bark and branches of Miscanthus can be used to produce pellets for energy use.•The energy ranking was Pinus radiata > Eucalyptus nitens > Paulownia > Miscanthus.•Cl content is the main factor limiting the quality of Eucalyptus nitens pellets.•High percentages of lignin distributed outside the fibers increase pellet durability.•The uncracked area of the pellets was positively correlated with the lignin content.
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