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Mixed forests are usually associated with higher resource utilization compared to the corresponding monocultures; however, the tree mixing effects of carbon (C), nitrogen (N), phosphorus (P) ecological stoichiometry in coastal forest ecosystems remains largely unknown. We compared the C, N, P stoichiometry in different ecosystem components (i.e., canopy layer, herb layer, litter layer, 0–20 cm and 20–40 cm soils) among two monocultures (Casuarina equisetifolia and Eucalyptus saligna) and their mixture in Taizhou, Zhejiang province, China. We also assessed the effects of the main microhabitat factors (wind speed, soil salinity, soil moisture and pH) on C, N, P stoichiometry. Two monocultures and their mixture showed the same elemental pattern of “low C and high P” for both the canopy and herb layers, and soil, indicating evident N limitations; however, the mixture intensified the N deficiency more. The mixture showed stronger correlations among the C, N, P stoichiometry than the monocultures. Redundancy and hierarchical partitioning analysis showed the overall and independent effects of the microhabitat factors on the C, N, P stoichiometry separately, in which soil moisture presented more effects on shallow soil (20–40 cm) C, N, and P, while soil salinity mainly affected the herb and litter layers; wind speed had greater effects on canopy layer C, N, P stoichiometry. These results are expected to provide a management reference for the regeneration of degraded plantations in the southern Zhejiang province of China.

The determination of leaf nitrogen content (LNC) by indirect methods is essential for silvicultural management of forest crops. The application of photography or rapid measurement equipment, such as chlorophyll index (soil-plant analysis development-SPAD), is increasingly used due to its low-cost, ease of estimation and accuracy. Therefore, the aim of this study was to estimate foliar nitrogen content from nondestructive methods in plantations of Eucalyptus tereticornis and Eucalyptus saligna using three urea treatments (120 kg N ha-1, 240 kg N ha-1 and a control treatment without urea). For each treatment, 10 trees were selected, including four for the validation of the equations. The LNC was directly evaluated for color with the CIEL*a*b* model, photographic measurement with the RGB model, SPAD measurement and destructive estimation of nitrogen in leaves. The results showed negative relationships with the L* (luminosity) and b* (trend from yellow to green) indices, while the a* (red to green trend) index was discarded, with SPAD positive relationships were found with LNC and RGB space. In the R and B indices, the greatest negative relationships were found. It was determined that the multivariate equation Y=a+b1x1+b2x2+…+bnxn can be used for this type of study. It was also determined that the LNC=0.389+0.026SPAD model was the optimum for E. tereticornis and the LNC=3.826- 0.001R- 0.10B equation was the optimum for E. saligna. RESUMEN La determinación del contenido de nitrógeno foliar (LNC) por métodos indirectos es esencial para el manejo silvícola de cultivos forestales. La aplicación de fotografía o equipos de medición rápida, como el índice de clorofila (SPAD), se utiliza cada vez más debido a su bajo costo, facilidad de estimación y precisión. Por tanto, el objetivo de este estudio consistió en estimar el LNC a partir de métodos no destructivos en plantaciones de Eucalyptus tereticornis y Eucalyptus saligna utilizando tres tratamientos de urea (120 kg N ha-1, 240 kg N ha-1 y un tratamiento testigo sin urea). Para cada tratamiento, se seleccionaron 10 árboles, incluidos cuatro utilizados para la validación de las ecuaciones. El LNC se evaluó directamente en cuanto a color con el modelo CIEL*a*b*, medición fotográfica con el modelo RGB, medición SPAD y estimación destructiva de nitrógeno en hojas. Los resultados mostraron relaciones negativas con los índices L* (luminosidad) y b* (tendencia de amarillo a verde), mientras que se descartó el índice a* (tendencia de rojo a verde), encontrándose SPAD relaciones positivas con el espacio LNC y RGB. En los índices R y B, mostraron las mayores relaciones negativas. Se determinó que la ecuación multivariada Y=a+b1x1+b2x2+…+bnxn se puede utilizar para este tipo de estudio. También se determinó que el modelo LNC=0,389+0,026SPAD fue el óptimo para E. tereticornis y la ecuación LNC=3,826-0,001R-0,10B fue la óptima para E. saligna.

The present investigation proposes to determine the form factor of the species Eucalyptus saligna in a commercial forest plantation of the Tambillo bajo sector, of the Colta canton, Chimborazo province. For this purpose, 100 individual specimens with straight shafts and without bifurcations were taken as a sample, and each individual’s commercial and total height, diameter at breast height, and diameters along the stem were measured, to determine the real volume of the wood using the Smalian and Newton formulas, the graphical method, and with a form factor of 0.70. Based on the measured data, a comparative analysis of the calculation of real volume by the method used was performed; the results obtained showed significant differences between calculation methods. In addition, five potential volume equations that presented the highest adjusted coefficient of determination and the lowest mean square error were selected. To verify the commercial volume calculated with the estimated form factors against the volume equations, the commercial volume was recalculated based on the form factors and equations found. The calculation of the commercial volume by the Smalian formula is taken as the exact value, and the other methods are taken as approximated values. Keywords: dasometry, form factor, forest plantation, volumen equations, commercial volume. Resumen La presente investigación propone: determinar el factor de forma de la especie Eucalyptus saligna en una plantación forestal comercial; para lo cual se toma como muestra 100 individuos con fustes rectos y sin bifurcaciones, a cada individuo se midió la altura comercial y total, diámetro a la altura del pecho y diámetros a lo largo del fuste, para determinar el volumen real de madera utilizando la fórmula de Smalian, Newton, método gráfico y con un factor de forma de 0,70. En base a los datos medidos, se realiza un análisis comparativo del cálculo de volumen real por método empleado, los resultados obtenidos mostraron diferencias significativas entre métodos de cálculo empleados. Además, se seleccionó 5 ecuaciones de volumen potenciales los cuales presentaron mayor coeficiente de determinación ajustado y menor error cuadrático medio. Para la verificación del volumen comercial calculado con los factores de forma estimados frente a las ecuaciones de volumen se vuelve a calcular el volumen comercial a partir de los factores de forma y ecuaciones encontrados, se toma como valor exacto el cálculo de volumen comercial por la fórmula de Smalian y como valor de aproximación los demás métodos. Palabras clave: dasometría, ecuaciones de volumen, factor de forma, plantación forestal, volumen comercial.

Morpho-physiological characteristics in Eucalyptus species can determine N (NUE) and P (PUE) use efficiency and, consequently, the plant's responses to fertilization. The study aimed to evaluate whether morphological and physiological characteristics of seedlings from Eucalyptus species affect the N and P use efficiency. For this, in a greenhouse, Eucalyptus grandis (GPC 23) and Eucalyptus saligna (32864) clones were grown in Hoagland nutrient solution for 21 days, followed by N and P restriction in CaSO4 solution 0.1 mol L−1 during 15 days. Morphological parameters from shoot and root system, dry mass of organs, photosynthetic pigments concentration, and chlorophyll a fluorescence of Eucalyptus species were evaluated, and NUE and PUE were calculated. Eucalyptus grandis presented the highest NUE and PUE values. The highest surface area, volume, and roots length values contributed to these results, justifying the highest dry mass production from leaves, stem, roots, and plant. Eucalyptus saligna presented the lowest NUE and PUE values, which negatively influenced photosynthesis (higher F0 values and lower concentrations of photosynthetic pigments). Root morphological parameters had a strong relationship with NUE and PUE and can be used to select Eucalyptus species, and breeding programs, as they can predict the ability of development of Eucalyptus species under low N and P availability.

The Pampa biome comprises a high species richness, but has been transformed by various human activities, threatening its inherent diversity. One of the mechanisms that contributes to conservation is the Permanent Preservation Areas (PPA); however, studies related to the vegetation of these areas are scarce, especially regarding the herbaceous stratum, creating a gap in the evaluation of the conservation of the Pampa biome's grassland formations. The objective of this study was to characterize the structure of fragments of grasslands in PPA, with and without cattle grazing, inserted in a plantation of Eucalyptus saligna Sm. in the Pampa biome. The survey was conducted on 40 systematically distributed sample units in six grassland areas, three of which were occasionally exposed to grazing and three fenced off with no grazing. Cover and frequency values ​​(absolute and relative) and importance value index (IVI) were estimated for species, exposed soil and dry plant material. The difference between the areas was evaluated by the Principal Coordinate Analysis (PCoA) and ANOSIM, complemented by SIMPER. Richness, dry plant material and exposed soil were evaluated using the Kruskall-Wallis test. A total of 210 species were registered, with the Poaceae family being the most numerous, followed by Asteraceae (41), Cyperaceae (19), Fabaceae (12) and Rubiaceae (9). The areas differed in relation to richness, with grazing showing more diversity. Enclosure Area 3 did not differ from open areas 2 and 3, possibly due to the greater proximity and low cattle interference. The exposed soil did not vary according to the enclosure; however, the dry plant material was higher in the enclosed areas. The distribution of species, as well as their cover and frequency were regulated according to grazing. The presence of animals in PPA has modified the dynamics and botanical composition of the areas, in which richness was promoted.

Fuel moisture content is one of the key parameters controlling the flaming ignition of wildland fuel. However, the role of fuel moisture content in assessing the flammability of different fuel curing (dead and live fuel) is still not well understood. This paper presents the results of ignition tests of fuel beds consisting of dead and live Eucalyptus saligna leaves under a wide range of moisture contents. External heat flux and fuel moisture content are shown to significantly influence time to ignition and mass loss rate at the ignition of Eucalyptus saligna leaves, thus illustrating distinctive heating processes in the fuel bed. The thermal behaviour of the leaf bed before ignition is analysed using the analytical solution to the heat conduction equation, as the classical ignition correlations yield inconclusive results. This approach allows identification of thermally thick and thin behaviours for distinct ranges of heating, with the transition (thermally intermediate) region observed at higher external heat fluxes for higher moisture content. Additionally, a flammability assessment based on time to ignition confirms the inadequacy of the common assumption that live fuel can be considered as moist dead fuel.

The litter horizon on forests ecosystems acts on the nutrient cycling and on the soil’s microclimate conditions. However, to reforestation ecosystems the litter attributes can conduct to alterations that can diminish the seedling establishment, as well can act on the herbivory rates. In this context, this study aimed to verify the differences and relationships between woody species diversity, the herbivory index, the litter attributes, and the canopy openness among a fragment of Atlantic Forest on secondary succession and commercial plantation of Eucalyptus saligna Smith abandoned to regeneration. This study was conducted at the Klabin’s Company “Ecological Reserve”, at Telêmaco Borba – PR, Brazil. There weren’t observed differences on the species richness and abundance among the studied sites. Litter mass and thickness were higher in E. saligna environment. However, the litter attributes only presented relationship with the woody vegetation at the Atlantic Forest site, such as abundance and species richness with litter mass (r2=0.53 and r2=0.40, respectively) and abundance with litter thickness (r2=0.63). The herbivory index was greater on the forest patch. The canopy openness was superior in the E. saligna site. At this site, the herbivory index presented a positive relation with the canopy openness (r2=0.48) and a negative with abundance (r2=0.48). Abundance also presented a negative relation with the canopy openness (r2=0.58) in the E. saligna environment. The litter horizon on the E. saligna plantation doesn’t seem to offer restrictions to regeneration of the woody vegetation. However, at this site, the higher canopy openness and the herbivory pressure over the woody vegetation may lead to a lower rate of secondary succession compared to the Atlantic Forest fragment.

Ecological and hydrological impacts are expected when watersheds are under commercial eucalyptus. In this study we evaluated event-based hydrology and sedimentation in paired watersheds under commercial eucalyptus and grasslands cover. Flow, suspended sediment concentration, and sediment production were measured and simulated with the Limburg Soil Erosion Model (LISEM) in paired hydrographic watersheds located in southern Brazil; one occupied with 7-years old Eucalyptus saligna plantation (forest watershed-FW; 0.83 km2) and another Pampa biome with native and exotic grasses used for beef cattle production (grassland watershed-GW; 1.10 km2). The effect of rainfall on hydrological and sedimentological variables was more evident in GW compared with FW. The shape of the hydrograph was steepest in GW, with rapid, marked increase and decrease in flow during rainfall. The parameters changed for model calibration in FW and GW were soil saturated hydraulic conductivity, initial soil moisture, and Manning roughness coefficient, whereby the statistical performance was classified as good (NSE> 0.75). Fourteen events different from those used in the calibration process were validated for FW and GW, with NSE index classified as “good” and “very good” for hydrology. Our study shows limitations of LISEM in calibrating and validating the sediment yield for individual events due to the spatial variability of factors controlling soil erosion. The validated modeling results of this study may be applied in simulating soil and crop scenarios in watersheds cultivated with commercial forest and grassland for grazing.

Considering the increasing need for renewable products, the present work aims to evaluate the physical-chemical properties of the eucalyptus harvest residues and its constituent fractions individually (barks, leaves, and branches), through proximate, ultimate, energetic and thermal analyzes. The biomass studied was Eucalyptus saligna species, cultivated mainly for the production of pulp and paper. The proximate analysis of the residue resulted in the moisture content of 10.1%, ash content of 3.9%, volatile materials about 81.1%, and fixed carbon of 15.0%, showing similar values to the constituent fractions. The ultimate analysis of the residue resulted in 46.5% of carbon content, 5.8% of hydrogen, and 43.2% of oxygen. The high heating value (HHV) for the residue is 17.93 MJ/kg, comparable to other biomasses of importance, including eucalyptus wood, the noblest part of the forest cultivation. The thermogravimetric (TGA) and differential thermal analysis (DTA) were carried out and the resulting thermograms show three main ranges of biomass degradation. The first range, from 30 to 150 °C, corresponds to the drying of the material; in the range from 200 to 325 °C hemicelluloses degrade, with partial degradation of lignin and cellulose, and in the range from 325 to 380 °C, the majority of cellulose degradation takes place. The physical-chemical data demonstrate that the eucalyptus residue is an excellent source of biomass for thermal conversion processes. Obtaining products with higher added value from this residue contributes to the implementation of new technological practices that link economic development to environmental responsibility. Considerando a crescente necessidade de produtos renováveis, o presente trabalho tem como objetivo avaliar as propriedades físico-químicas dos resíduos da colheita do eucalipto e suas frações constituintes individualmente (cascas, folhas e galhos), por meio de análises imediata, elementar, energética e térmica. A biomassa estudada foi a espécie Eucalyptus saligna, cultivada principalmente para a produção de celulose e papel. A análise imediata do resíduo resultou em teor de umidade de 10,1%, teor de cinzas de 3,9%, materiais voláteis em torno de 81,1% e carbono fixo de 15,0%, apresentando valores semelhantes entre as frações constituintes. A análise elementar do resíduo resultou em 46,5% de teor de carbono, 5,8% de hidrogênio e 43,2% de oxigênio. O poder calorífico superior do resíduo foi determinado em 17,93 MJ/kg, comparável a outras biomassas importantes, incluindo a madeira de eucalipto, a parte mais nobre do cultivo florestal. A análise termogravimétrica (TGA) e térmica diferencial (DTA) foram realizadas e os termogramas resultantes mostram três faixas principais de degradação da biomassa. A primeira faixa, de 30 a 150 °C, corresponde à secagem do material; na faixa de 200 a 325 °C as hemiceluloses degradam, com degradação parcial da lignina e celulose, e na faixa de 325 a 380 °C, ocorre a maior parte da degradação da celulose. Os dados físico-químicos demonstram que o resíduo do eucalipto é uma excelente fonte de biomassa para processos de conversão térmica. A obtenção de produtos de maior valor agregado a partir desse resíduo contribui para a implantação de novas práticas tecnológicas que vinculam o desenvolvimento econômico à responsabilidade ambiental.

We evaluated whether phytotoxic effects of the essential oil from Eucalyptus saligna Sm. leaf litter were related to its major compounds 1,8-cineole (eucalyptol) and α-pinene. Effects of the essential oil and its major compounds, combined and alone, were tested on germination and growth of the weed Eragrostis plana Ness. Volatile organic compounds (VOCs) emitted from the essential oil were determined in the airspace of Petri dishes during the experimental period. These volatile fractions were obtained by solid-phase microextraction (SPME) followed by gas-chromatography coupled to mass spectrometry (GC-MS). Effects of the oil and its major compounds were also assessed in aqueous solution on coleoptile growth of Triticum aestivum L. The essential oil showed the strongest phytotoxic effects on E. plana, followed by eucalyptol, eucalyptol + α-pinene, and α-pinene. A similar order of phytotoxicity was observed on coleoptile growth of T. aestivum. The proportion of oxygenated monoterpenes increased along the experimental period, mainly eucalyptol, and of monoterpene hydrocarbons diminished in the volatile fractions. We conclude that phytotoxicity of E. saligna leaf litter essential oil may be mainly related to eucalyptol and additive or synergistic effects of other minor compounds. Analysing VOCs emission is relevant to elucidate compounds involved in phytotoxicity of a plant species.

Rising atmospheric [CO2 ] (Ca ) generally enhances tree growth if nutrients are not limiting. However, reduced water availability and elevated evaporative demand may offset such fertilization. Trees with access to deep soil water may be able to mitigate such stresses and respond more positively to Ca . Here, we sought to evaluate how increased vapor pressure deficit and reduced precipitation are likely to modify the impact of elevated Ca (eCa ) on tree productivity in an Australian Eucalyptus saligna Sm. plantation with access to deep soil water. We parameterized a forest growth simulation model (GOTILWA+) using data from two field experiments on E. saligna: a 2-year whole-tree chamber experiment with factorial Ca (ambient =380, elevated =620 μmol mol-1 ) and watering treatments, and a 10-year stand-scale irrigation experiment. Model evaluation showed that GOTILWA+ can capture the responses of canopy C uptake to (1) rising vapor pressure deficit (D) under both Ca treatments; (2) alterations in tree water uptake from shallow and deep soil layers during soil dry-down; and (3) the impact of irrigation on tree growth. Simulations suggest that increasing Ca up to 700 μmol mol-1 alone would result in a 33% increase in annual gross primary production (GPP) and a 62% increase in biomass over 10 years. However, a combined 48% increase in D and a 20% reduction in precipitation would halve these values. Our simulations identify high D conditions as a key limiting factor for GPP. They also suggest that rising Ca will compensate for increasing aridity limitations in E. saligna trees with access to deep soil water under non-nutrient limiting conditions, thereby reducing the negative impacts of global warming upon this eucalypt species. Simulation models not accounting for water sources available to deep-rooting trees are likely to overestimate aridity impacts on forest productivity and C stocks.

The carbon market has been attracting attention as an additional source of revenue associated with growing planted forests. In addition to the economic importance, planted forests play an essential role in mitigating climate change due to their high potential to sequester carbon from the atmosphere and store it in soil, biomass or litter. Therefore, forest cultivation and the carbon market present win-win opportunities for both the economic and ecological systems. One question that arises for those who intend to invest in planted forests projects for carbon credits trading is: which species within Pinus or Eucalyptus, performs better in Carbon Sequestration and Storage (CSS)? Based on a systematic review of the scientific literature, we ranked the cultivated species of the genus Eucalyptus and Pinus based on their CSS performance. The findings suggest that Eucalyptus performs slightly better than Pinus, given that this supremacy was reported in 60% of the studies analyzed. However, paired analysis between species show that Pinus patula , P. halepensis, and P. radiata presented better performance than Eucalyptus saligna, E. occidentalis, and E. globulus, respectively. At the same time, Eucalyptus spp., E. cloenziana, E. grandis, and E. tereticornis performed better than Pinus spp., P. armandii, P. massoniana, P. taeda, P. caribaea, and P. roxburghii, respectively. However, species' effective performance in sequestering and storing carbon depends on other issues such as technical factors, management practices, and biophysical conditions. We identified that biophysical conditions, such as the site index, soil type, soil density, stand elevation, water deficit, soil clay, aluminum content, edaphoclimatic conditions and land use change were the most important. Thus, besides the species to be cultivated, the potential for generating carbon credits by planted forests also depends on local biophysical conditions and management practices adopted.

Water availability is a limiting factor for the establishment and development of forest species. To understand the appropriate conditions for the initial post-transplanting phase, it is necessary to understand the specific morphophysiological characteristics of the species, such as the leaf water potential and the efficiency of photosystem II. We aimed to identify the influence of different water regimes on the morphophysiological aspects of young plants of two forest species (Cedrela fissilis Vellozo and Eucalyptus saligna Sm.). Two greenhouse experiments were conducted for 28 days; one for each species. The design was completely randomized, and the treatments consisted of six different water regimes. Leaf water potential (Ψw) and chlorophyll a fluorescence were evaluated every 7 days. At the end of the experiment, morphological attributes (height, collection diameter, root volume, and dry matter) were measured and histological blades were made. The water demand of E. saligna was higher than that of C. fissilis and required greater replacement within a shorter period. The rehydration from Ψw = − 2 Mpa allowed for a fast recovery of the young C. fissilis plants (Ψw = − 1.5, Fv/Fm = 0.796), which indicated good physiological plasticity of this species when submitted to water stress at a level that is not severe. The total dry matter allocation was different among species. Seedlings of E. saligna presented the best responses when submitted to a continuous water supply regime, while C. fissilis seedlings presented the best response under intermittent irrigation conditions.

Eucalyptus clones are selected according to productivity, wood quality, rooting capacity, and resistance to drought, frost and diseases. However, kinetic and morphological parameters that determine the absorption efficiency of nutrients such as nitrate (NO3−) and ammonium (NH4+) are often not considered in breeding programs. The objective of this study was to evaluate the morphological, physiological and kinetic parameters of nitrogen uptake by clones of Eucalyptus saligna (32,864) and Eucalyptus grandis (GPC 23). Morphological parameters in shoot and root systems, biomass and N concentrations in different organs, photosynthetic pigment concentrations, parameters of chlorophyll a fluorescence and photosynthetic rates were evaluated. Kinetic parameters, maximum absorption velocity (Vmax), Michaelis–Menten constant (Km), minimum concentration (Cmin) and influx (I) were calculated for NO3− and NH4+ in the two clones. E. grandis clone was more efficient in the uptake of NO3− and NH4+, and showed lower Km and Cmin values, allowing for the absorption of nitrogen at low concentrations due to the high affinity of the absorption sites of clone roots to NO3− and NH4+. Higher root lengths, area and volume helped the E. grandis clone in absorption efficiency and consequently, resulted in higher root and shoot biomass. The E. saligna clone had higher Km and Cmin for NO3− and NH4+, indicating adaptation to environments with higher N availability. The results of NO3− and NH4+ kinetic parameters indicate that they can be used in Eucalyptus clone selection and breeding programs as they can predict the ability of clones to absorb NO3− and NH4+ at different concentrations.

This study based on woody biomass was conducted under an experimental design of randomized complete blocks with two species, Eucalyptus saligna and Eucalyptus tereticornis, in three planting densities, 5000 trees ha−1, 10 000 trees ha−1, and 20 000 trees ha−1. Data were collected at 3, 12, and 24 months and growing relationships were analyzed. Adobe ground biomass, soil carbon reserve, plant issue nutrients, and woody biomass were determined. Results showed statistically significant differences between species in biomass production, obtaining values from 36.80 to 117.42 Mg ha−1 in E. tereticornis and 36.10 to 107.67 Mg ha−1 in E. saligna. Optimum planting density for both species proved to be 10 000 trees ha−1, which showed better biomass accumulation and growth performance in addition to lower mortality, and less impact on productivity. Regarding soil nutrition, it was determined that as crop density increased, the loss of nutrients (N, P, K, Ca) increased, with a loss of up to 33% in 24 months in the density of 20 000 trees ha−1. For both species, the treatment of 10 000 trees ha−1 provided the highest concentration of organic matter in the top 20 cm of soil. Finally, wood chemical aspects did not show differences in the properties with any treatment. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

The demand for environmentally safe preservatives for wood is increasing all around the world. This study is focused on the evaluation of the ability of Neem (Azadirachta indica) seed oil and copper-ethanolamine to protect Sydney blue gum (Eucalyptus saligna) and Ayous (Triplochiton scleroxylon) against termites. Wood blocks were impregnated with solutions of Neem oil in acetone and/or an aqueous solution of copper-ethanolamine. Impregnated woods with a retention rate of up to 108.3 kg/m3 were obtained. A leaching experiment was used to determine the fixation of preservatives in wood. The termicidial effect of the preservatives was studied through exposure in a termitarium. Neem oil was less efficient for Sydney blue gum but showed significant protection for Ayous at a higher retention rate. At the concentration investigated, the treatment of both wood species with copper-ethanolamine solution was not suitable. However, a combination of copper-ethanolamine and Neem oil showed an improvement in the protection of Sydney blue gum wood. Nevertheless, the impregnated woods still suffered an increased termite attack after leaching.

Eucalyptus saligna tends to develop defects during its drying process, thus limiting its use as construction or furniture material. Intermittent drying, which applies non-heating phases between heating phases, has the potential to overcome this issue. This study evaluated the effects of 3 intermittent and 1 continuous schedule on the species’ drying performance and post-drying qualities. The results showed that the boards from all intermittent schedules exhibit significantly slower drying rates (from -9.4x10-3 /hour to -1.57 x10-2 /hour) than those from the continuous schedule (from -5.12 x10-2 /hour to -1.03 x10-2 /hour). The intermittently-dried boards also developed lower collapse depth (1.162-2.032 mm) than the continuously-dried boards (5.12 mm). Nevertheless, applying higher temperature than that used in the continuous schedule, during the heating phase of the intermittent schedule, potentially increased the moisture gradient, residual drying stress, end check length, internal check percentage, and spring depth.

13 páginas.- 7 figuras.- 92 referencias, The mechanisms by which woody plants recover xylem hydraulic capacity after drought stress are not well understood, particularly with regard to the role of embolism refilling. We evaluated the recovery of xylem hydraulic capacity in young Eucalyptus saligna plants exposed to cycles of drought stress and rewatering. Plants were exposed to moderate and severe drought stress treatments, with recovery monitored at time intervals from 24 h to 6 months after rewatering. The percentage loss of xylem vessels due to embolism (PLV) was quantified at each time point using microcomputed tomography with stem water potential (Ψx) and canopy transpiration (Ec) measured before scans. Plants exposed to severe drought stress suffered high levels of embolism (47.38% ± 10.97% PLV) and almost complete canopy loss. No evidence of embolism refilling was observed at 24 h, 1 week, or 3 weeks after rewatering despite rapid recovery in Ψx. Recovery of hydraulic capacity was achieved over a 6-month period by growth of new xylem tissue, with canopy leaf area and Ec recovering over the same period. These findings indicate that E. saligna recovers slowly from severe drought stress, with potential for embolism to persist in the xylem for many months after rainfall events. © 2022 John Wiley & Sons Ltd., This study was supported by an ARC Discovery Project (DP170100761) to BC and TJB and an ARC Future Fellowship (FT130101115) to BC. BM acknowledges support from the ARC Laureate Fellowship FL190100003. CMR‐D was supported by an Individual Fellowship from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska‐Curie grant agreement no. 751918‐AgroPHYS. JMRP was supported by the ORNL, managed by UT‐Battelle, LLC, for the DOE under contract DE‐AC05‐1008 00OR22725.

O Eucalyptus saligna (E.saligna) é uma árvore nativa das regiões tropicais e subtropicais, com crescimento rápido, que atinge, para a mesma idade, comprimento e diâmetro do tronco maiores que os das espécies de Eucalyptus globulus (E. globulus), espécie comummente usada na indústria de pasta e papel nacional. Os objetivos deste trabalho foram essencialmente (i) a caraterização química da madeira E.saligna, (ii) avaliação experimental do desempenho no cozimento kraft e no branqueamento e (iii) potencial papeleiro do E. saligna proveniente do Haumbo (região do planalto central de Angola) usando como referência o E. globulus nacional. No presente trabalho foi usada madeira de E. saligna com 6 anos de idade. Para concretizar estes objetivos numa primeira fase procedeu-se ao destroçamento da madeira a fim de se obter aparas com dimensões uniformes. Após o destroçamento efetuou-se a crivagem em frações com 6 granulometria diferentes, sendo que a fração com granulometria 2 foi moída a 40-60 mesh e usada para a caraterização química da madeira. A caraterização química envolveu a determinação do teor de extratáveis em etanol: tolueno (1:2, v/v) (4,5% m/m), de lenhina Klason (28,9% m/m), de pentosanas (19,5% m/m) e celulose (47,9% m/m). Posteriormente, efetuaram-se cozimentos da madeira de E. saligna e de E. globulus ocorridos nas mesmas condições quer em relação a composição do licor branco (alcalinidade 24% e Índice de sulfureto 30%), quer em relação as condições processuais (temperatura 160ºC e tempo 197min). Os rendimentos depurados e a percentagem de incozidos obtidos foram 47,7% e 0,04% no caso do E. saligna, no caso do E. globulus foram 50,1% e 0,2 respetivamente. O rendimento em pasta do E. globulus foi mais elevado, isso deve-se essencialmente por ser a espécie com maior massa volúmica básica, maior teor de celulose e menor teor de lenhina. O valor do índice Kappa obtido para a pasta de E. saligna foi 15,6 e 11,9 para a pasta de E. globulus nas mesmas condições de cozimento, o que mostra que o E. globulus necessita de menos carga alcalina para atingir o valor de 15-16 IK, por outro lado, o E. saligna consome uma quantidade considerável de reagente (mais 6% de alcalinidade, AA) em relação ao E. globulus. Posteriormente a pasta de E. saligna foi submetida a branqueamento ECF, com uma sequência DEDED, atingindo no final uma brancura de 88% ISO e consumindo 56 kg de ClO2 como cloro ativo/tonelada de pasta. No caso do E. globulus, consome-se menos ClO2 (52 kg como cloroativo/tonelada de pasta) e obtem-se uma brancura maior 90% ISSO. No sentido de avaliar as propriedades papeleiras da pasta de E. saligna, comparativamente a pasta kraft de E. globulus, a pasta kraft branqueada de E. saligna foi sujeita a refinação no refinador PFI a 1500 revoluções e preparadas folhas laboratoriais com gramagem de 69 gseca/m2 . A pasta refinada de E. saligna apresenta maior drenabilidade (20ºSR) do que a pasta refinada de E. globulus a 1500 revoluções PFI (27ºSR), o que significa que a pasta de E. saligna é menos refinável que a do E. globulus, ou seja nas mesmas condições de refinação, gasta-se mais energia no caso da pasta de E. saligna. Em termos de propriedades papeleiras, verifica-se uma melhoria da pasta de E. saligna refinada para a não refinada, mas esta melhoria não é acentuada quando comparada a pasta refinada de E. globulus nacional, especialmente no que respeita as propriedades estruturais, de resistência e óticas da folha. Eucalyptus saligna (E.saligna) is a fast growing tree native to tropical and subtropical regions, reaching, for the same age, trunk length and diameter greater than those of Eucalyptus globulus (E. globulus), species commonly used in the national pulp and paper industry. The objectives of this work were essentially (i) the chemical characterization of E. saligna wood, (ii) experimental evaluation of performance in kraft cooking and bleaching and (iii) papermaking potential of E. saligna from Haumbo (central plateau region of Angola) using the national E. globulus as a reference. In the present work, wood from 6 years old E. saligna was used. In order to achieve these objectives, in the first phase, the wood was chipped in order to obtain chips with uniform dimensions. After the chipping, the sieving was carried out in fractions with 6 different particle sizes, and the fraction with particle size 2 was ground at 40-60 mesh and used for the chemical characterization of the wood. The chemical characterization involved the determination of the extractable content in ethanol: toluene (1:2, v/v) (4.5% m/m), Klason lignin (28.9% m/m), pentosans (19 .5% m/m) and cellulose (47.9% m/m). Subsequently, E. saligna and E. globulus wood was cooked under the same conditions both in relation to the composition of the white liquor (alkalinity of 24% and sulphidity of 30%) and in relation to the process conditions (temperature 160ºC and time 197min). The screened yields and the percentage of uncooked obtained were 47.7% and 0.04% in the case of E. saligna, in the case of E. globulus they were 50.1% and 0.2 respectively. The pulp yield of E. globulus was higher, this is essentially due to the fact that it is the species with the highest basic density, the highest cellulose content and the lowest lignin content. The Kappa index value obtained for the E. saligna pulp was 15.6 and 11.9 for the E. globulus pulp under the same cooking conditions, which shows that E. globulus needs less alkaline charge to reach the value of 15-16 IK, on the other hand, E. saligna consumes a considerable amount of reagent (plus 6% alkalinity, AA) compared to E. globulus. Subsequently, the E. saligna pulp was subjected to ECF bleaching, with a DEDED sequence, reaching in the end a whiteness of 88% ISO and consuming 56 kg of ClO2 as active chlorine/ton of pulp. In the case of E. globulus, less ClO2 is consumed (52 kg as active chlorine/ton of pulp) and a greater 90% brightness is obtained. In order to evaluate the papermaking properties of E. saligna pulp, compared to E. globulus kraft pulp, the bleached E. saligna kraft pulp was subjected to beating in the PFI refiner at 1500 revolutions and laboratory sheets were prepared with grammage of 69 g/m2. Beaten E. saligna pulp has greater drainability (20ºSR) than beaten E. globulus pulp at 1500 revolutions PFI (27ºSR), which means that E. saligna pulp is less refinable than E. globulus, that is, under the same refining conditions, more energy is used in the case of E. saligna pulp. In terms of papermaking properties, there is an improvement from refined to non-refined E. saligna pulp, but this improvement is not accentuated when compared to refined E. globulus national pulp, especially with regard to structural and strength properties and optic sheet properties. Mestrado em Engenharia Química