A Complete Assessment of Carbon Stocks in Above and Belowground Biomass Components of a Hybrid Eucalyptus Plantation in Southern Brazil

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 ).The National Council of Technological and Scientific Development (CNPq—Brazil) awarded the first author with a research grant (Award Number 200589/2014-8) for a one-year stay at the USC in SpainS

A Density Management Diagram Including Stand Stability and Crown Fire Risk for Pseudotsuga Menziesii (Mirb.) Franco in Spain

A static stand density management diagram was constructed for Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) plantations in Spain on the basis of 3 equations that were fitted simultaneously by the full information maximum likelihood procedure to data derived from 172 plots measured across the Cantabrian and pre-Pyrenean ranges. The first equation relates quadratic mean diameter to the number of stems per hectare and dominant height. The other 2 equations relate stand volume and stand aboveground biomass to quadratic mean diameter, number of stems per hectare, and dominant height. An estimation of the average slenderness coefficient for the 250 largest trees per hectare and the canopy bulk density were included. The stand density management diagram outlined here enables rapid, straightforward comparisons among different thinning schedules for forest plantations in mountain regions, in which timber production, risk of crown fire, and the risk of damage from wind or snow are considered.Funding for this research was provided by the Spanish Ministry of Science and Technology through project 1FD97-0585-C03-03S

Nutritional prescriptions for Eucalyptus plantations: lessons learned from Spain

Eucalyptus globulus Labill is the main exotic broadleaf species planted and managed for pulp and energy production in Spain, where it covers an area of more than 0.6 million ha. The climatic and soil conditions of the planting areas range from the predominantly acidic or fertile soils developed over limestone in Atlantic areas of the north and northwest of the Iberian Peninsula to the less weathered soils developed from slates, sandy deposits or limestone in the drier southwest. The widely varying conditions explain the large differences in proposed fertilizer prescriptions. This review paper provides an analysis of the proposed practices and prescriptions by considering trial results and the need to develop site specific prescriptions for seedling standards and fertilization at planting establishment. Analysis of nutritional studies and of nutrient balances over a whole rotation is presented in order to provide basic information for defining maintenance fertilization, identified as the main bottleneck for sustainable wood production in these stands. Different fertilization practices are used by non industrial owners and Spanish pulp companies, with the last one applying a more intense management relying in more fertilization. A complete consideration of nutrition-related operation and decisions is shown to be essential for maintaining potential productivity, reduce biotic and abiotic damages and reduce mineral fertilization needsWe thank the National Council of Technological and Scientific Development (CNPq-Brazil) for a scholarship awarded to the first authorS

Nutrient Contribution of Litterfall in a Short Rotation Plantation of Pure or Mixed Plots of Populus alba L. and Robinia pseudoacacia L.

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 plantationsThis research was funded by MINECO (Spain) through the framework of the project’s RTA 2008-00025-C02-01 and RTA2017-00015-CO2 co-financed with funds from FEDERS

Validação de modelos portugueses para Pinus pinaster em parcelas situadas na Galiza, Espanha

A Pinus pinaster tem uma grande importância em termos produtivos e ecológicos na Galiza e no Norte de Portugal. Na Galiza elaboraram-se modelos de crescimento e produção de árvore individual para a espécie mas a disponibilidade de modelos está mais generalizada em Portugal. Este trabalho teve como objetivo avaliar o comportamento de modelos de crescimento e produção existentes em Portugal em povoamentos de Pinus pinaster na Galiza. Para o efeito, utilizaram-se 25 parcelas disponíveis, com idades entre 21 e 58 anos, para validação dos modelos. Nestas parcelas, o primeiro inventário dendrométrico foi realizado em 2006, tendo-se medido o diâmetro à altura do peito (d) e a altura total (h) em todas as árvores de cada parcela. O segundo inventário ocorreu em 2009 e posteriormente efetuou-se um terceiro inventário em 2012. Ao nível da parcela determinaram-se as variáveis altura dominante (hdom), área basal (G), o diâmetro médio quadrático (dg), o índice de qualidade da estação (Sl) e o volume em pé (V). Utilizou-se o simulador StandsSlM que prevê a evolução de diferentes povoamentos existentes numa região tendo em conta o impacto de fatores externos como a gestão florestal. O StandsSlM permite simular desbastes de vários tipos e baseando-se em vários critérios como o fator de Wilson, área basal residual ou % de área basal removida. As variáveis de input para simular cada parcela são: altitude, idade, área, número de árvores, idade de corte, d de todas as árvores, h das árvores dominantes, estado de cada árvore (viva ou morta), número de árvores por hectare, número de anos a projetar e fator de Wilson para as parcelas com desbaste ou alguma perturbação que implique a remoção de madeira (e.g., derrubes pelo vento). Para a previsão do crescimento em altura dominante, para além da equação embutida no StandsSlM estudaram-se 4 equações GADA (generalized algebraic difference approach). Para os dados das parcelas estudadas, a GADA 1, derivada da função Korf, sobrestimou a hdom em cerca de 0.73 m em 2009 e 1 m em 2012. Detetou-se que esta equação pode apresentar, pontualmente, estimativas de S que podem ser desajustadas por excesso para idades de referência avançadas (e.g., 50 anos), associadas a parcelas jovens com SI elevado. Este resultado foi também já observado para algumas parcelas jovens com SI elevado, em Portugal. A tendência de sobrestimação de hdom manteve-se, tendo mesmo aumentado ligeiramente quando se usou a versão da GADA1 com expansão dos parâmetros de modo a incorporar informação de variáveis climáticas da Galiza. Estudaram-se 3 novas equações GADA que revelaram um comportamento preditivo que parece adequado, próximo do comportamento da equação ADA (algebraic difference approach) que o StandsSlM utiliza e sem o problema mencionado para o SI da GADA1. Os resultados obtidos com o simulador revelaram-se, em geral, bastante satisfatórios. Observou-se uma tendência de subestimação de G (entre 0 e 4 m2/ha) e dg (entre 0 e 2 cm) na maioria das parcelas estudadas. Quanto ao volume em pé, observou-se uma tendência de sobrestimação, maioritariamente no intervalo entre 0 e 50 m3/ha. Este fato poderá estar associado a uma ligeira sobrestima da altura individual em algumas parcelas.info:eu-repo/semantics/publishedVersio

Effects of Shoot Size and Genotype on Energy Properties of Poplar Biomass in Short Rotation Crops

Eight poplar genotypes grown in a short rotation forest plantation established in an acid soil in South Europe were sampled at the age of 7 years to determine the energy properties regarding thermochemical conversion. The goal was to address the effect of selection of genotypes or shoot size at harvest on the energy quality of biomass. Between 34 and 50 biomass samples were obtained for each genotype: three disks were systematically sampled along the stem and were pooled together with a subsample of leafless branches representative of the biomass share of this component. Several energy properties were determined: higher calorific value, net calorific value, fresh moisture content, basic density, ash, volatile matter, fixed carbon content and elemental composition. Genotype had a significant effect on most of these properties, and the balsam genotypes displayed superior quality parameters and also higher biomass yield than the Euramerican genotypes. As a covariate, shoot basal diameter had a significant effect on the moisture content, basic density, ash content and on the concentrations of the elements N, K, Ca, Mg, S, Na and C. It was concluded that genotypes with low nutrient requirements planted at low density (<8000 cuttings ha−1 ) and harvested at a long enough rotation (7 years) produce good yields and high chip quality. Poplar short rotation crops can be grown to produce chips of A2 quality for non-industrial heating use (according to UNE-EN ISO 17225-4), able to be combusted in domestic thermal facilities of <1 MWth power.This work was financially supported by project RTA2014-00007-00007-C03-02, Spanish Ministry of Economy and CompetitivityS

Poplar Short Rotation Coppice Plantations under Mediterranean Conditions: The Case of Spain

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 conditionsThis research was funded by the Ministry of Science and Innovation (Spain) through the framework of the INIA projects RTA2017-00015-CO2, co-financed with funds from FEDERS

Growing Poplar in Acid Soils: Biomass Yield and Ash Behavior

Atlantic areas of southern Europe have low water restrictions but are also characterized by acid soils with low intrinsic fertility, so the selection of clones that have adapted to these characteristics is essential. In this study, biomass yield data for eight poplar clones established in two trials were evaluated after the first rotation. Both sites were representative of acid soils that had previously been used for agriculture and had low levels of alkali and alkaline earth elements. The first trial was used to determine which clones performed the best in terms of biomass and stem size, testing two Populus × euramericana (Dode) Guinier (I-214 and AF2), two P. × interamericana Van Brokehuizen × P. nigra L. (Monviso, AF6), three P. × interamericana (Unal, Beaupre and Raspalje), and one P. trichocarpa Torr & A. Gray (Trichobel) clone. The second trial explored the possibility of simultaneously growing biomass and timber, specifically considering the Raspalje and Trichobel balsam poplar clones. To complete a previous study on energy properties, nine biomass samples were obtained from each of the eight clones to evaluate the composition and behavior of the ash generated during combustion, particularly the sintering risk. Several indices of sintering risk were explored and compared with the actual sintering using the BioSlag test. The results show large differences in biomass yield between clones, with the balsam poplar derived clones (both hybrid or pure Populus trichocarpa) performing the best. Growth results for stems planted for wood and the cuttings planted in between these stems show that a mixed biomass–timber arrangement provides good results, at least during the first rotation. The relative proportion of oxides in the poplar ash followed the order CaO > K2O > MgO >> P2O5 >> SiO2 > Al2O3 > Na2O > Fe2O5 >> TiO2. Significant differences between clones were found for K2O and MgO. Risk indices showed moderate levels of sintering derived from alkali elements, with significant differences between clones. The actual slagging and the hardness of the slag particles were very low thus, denoting good ash behavior during combustion, particularly for the clones selected for biomass yield. No significant covariate effect of basal diameter was found for any of the analyzed variables. We conclude that growing site-undemanding poplar clones in acid soils can yield both reasonable levels of biomass yield and good quality chips for combustion in domestic thermal systemThis research was financially supported by project RTA2017-00015-C02-02, Spanish Ministry of Economy and CompetitivityS

Elemental composition of raw and torrefied pellets made from pine and pine-eucalyptus blends

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−1This research was partly funded by a Grant from the Competitive Reference Research Unit Program of the Galician Autonomous Government, cofunded by ERDF (ref. EDC431C 2022/28). The laboratory pelletizer was also funded by the Consellería de Cultura, Educación e Universidade (contract 2021-1716)S

Biomass and carbon content in Galicia (NW Spain) Eucalyptus globulus Labill. stands

Northwestern Spain is one of the most productive forest areas in Europe, being Eucalyptus globulus Labill. the most important species in the area. Stands (pure and mixed) of the species cover more than 400,000 ha, and almost four million cubic metres of timber were produced annually between 2008 and 2012. In this paper we present estimations of total aboveground biomass and the corresponding carbon content in Eucalyptus globulus plantations in Galicia, as useful information for further analysis on carbon sequestration balance. We developed several easy-to-use biomass equations, using data collected from cut trees across Galicia, and these were applied to data from the Third (1997) and Fourth (2011) National Forest Inventories in the region. The fitted model with diameter and height as independent variables showed the best estimates (R2 Adj = 0.9965, RMSE = 6.28). Estimations of current (2011) total aboveground biomass was 34.8 Mt and for the carbon was 15.7 MtS