Analysis of edaphic and ecophysiological parameters in relation to nutrient levels and growth of Pinus pinaster in acidic soils

The main aim of this doctoral research was to improve the understanding of the relationships between the ecophysiological and edaphic parameters that determine the growth of Pinus pinaster and its ability to adapt to different environments. The relationships between soil properties, foliar nutrients and growth were studied in plots of Pinus pinaster established in soil over different types of bedrock. Good adaptation of Pinus pinaster was observed in soils developed over biotitic schist, granitic rocks, gneiss and migmatites, in which growth of the species was highest. Foliar Ca and K, soil depth and average annual temperature explained around 52% of the variability in site index. Needle length, width and thickness were closely related to climate conditions, year of formation and also foliar concentrations of N and Mg. Foliage biomass and leaf area index were negatively correlated with needle age and positively correlated with site index and foliar nutrients. In the soil over biotitic schist, the concentrations of oxalate and pyrophosphate Al were higher than in other soils and tended to form highly stable organic–aluminium complexes. The toxicity indices considered indicated a higher risk of Al toxicity in the plots developed over slate and mica schist, but no risk of Al toxicity in the plots on biotitic schist

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

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

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

Variation of Hg concentration and accumulation in the soil of maritime pine plantations along a coast-inland transect in SW Europe

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGClimatic 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.Ministerio de Educación y Formación Profesional | Ref. FPU17/05484Ministerio de Ciencia e Innovación | Ref. PID 2021-125114OB-I00Consellería de Cultura, Educación e Universidade (Xunta de Galicia) | Ref. ED431C2021/46- GRCUniversidad de Vigo/CISU

Needle age and precipitation as drivers of Hg accumulation and deposition in coniferous forests from a southwestern European Atlantic region

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGVegetation and climate are critical in the biogeochemical cycle of Hg in forest ecosystems. The study assesses the influence of needle age and precipitation on the accumulation of Hg in needle biomass and its deposition by litterfall in thirty-one pine plantations spread throughout two biogeographical regions in SW Europe. Welldeveloped branches of Pinus pinaster were sampled and pine needles were classified according to 4 age classes (y0, y1, y2, y3). The concentration of total Hg (THg) was analyzed in the samples and Hg content in needle biomass and its deposition by litterfall were estimated. The concentration of total Hg (THg) increased with needle age ranging from 9.1 to 32.7 μg Hg kg−1 in the youngest and oldest needles, respectively. The rate of Hg uptake (HgR) three years after needle sprouting was 10.2 ± 2.3 μg Hg kg−1 yr−1, but it decreased with needle age probably due to a diminution in photosynthetic activity as needles get older. The average total Hg stored in needle biomass (HgWt) ranged from 5.6 to 87.8 mg Hg ha−1, with intermediate needle age classes (y1 and y2) accounting for 70% of the total Hg stored in the whole needle biomass. The average deposition flux of Hg through needle litterfall (HgLt) was 1.5 μg Hg m−2 yr−1, with the y2 and y3 needles contributing most to the total Hg flux. The spatial variation of THg, HgWt and HgLt decreased from coastal pine stands, characterized by an oceanic climate, to inland pine stands, a feature closely related to the dominant precipitation regime in the study area. Climatic conditions and needle age are the main factors affecting Hg accumulation in tree foliage, and should be considered for an accurate assessment of forest Hg pools at a regional scale and their potential consequences in the functioning of terrestrial ecosystems.Ministerio de Educación y Formación Profesional | Ref. FPU17/05484Xunta de Galicia | Ref. ED431C 2021/46-GRCXunta de Galicia | Ref. ED431F2018/06-EXCELENCIAXunta de Galicia | Ref. ED431C2018/0

Mercury in a birch forest in SW Europe: Deposition flux by litterfall and pools in aboveground tree biomass and soils

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGAtmospheric mercury (Hg) is largely assimilated by vegetation and subsequently transferred to the soil by litterfall, which highlights the role of forests as one of the largest global Hg sinks within terrestrial ecosystems. We assessed the pool of Hg in the aboveground biomass (leaves, wood, bark, branches and twigs), the Hg deposition flux through litterfall over two years (by sorting fallen biomass in leaves, twigs, reproductive structures and miscellaneous) and its accumulation in the soil profile in a deciduous forest dominated by Betula alba from SW Europe. The total Hg pool in the aboveground birch biomass was in the range 532–683 mg ha−1, showing the following distribution by plant tissues: well-developed leaves (171 mg ha−1) > twigs (160 mg ha−1) > bark (159 mg ha−1) > bole wood (145 mg ha−1) > fine branches (25 mg ha−1) > thick branches (24 mg ha−1) > newly sprouted leaves (20 mg ha−1). The total Hg deposition fluxes through litterfall were 15.4 and 11.7 μg m−2 yr−1 for the two years studied, with the greatest contribution coming from birch leaves (73 %). In the soil profile, the pool of Hg in the mineral soil (37.0 mg m−2) was an order of magnitude higher than in the organic horizons (1.0 mg m−2), mostly conditioned by parameters such as soil bulk density and thickness, total C andNcontents and the presence of certain Al compounds.Ministerio de Educación y Formación Profesional | Ref. FPU17/05484Xunta de Galicia | Ref. ED431C2021/46-GRCXunta de Galicia | Ref. ED431F2018/06- EXCELENCI

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 (&lt;8000 cuttings ha&minus;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 &lt;1 MWth power