Search Results (138)

Forest fires are recurrent in Spain and affect tree species in different ways. Fire incidence in the main Spanish forest species, both native and alien, is estimated in this study based on actual fire occurrences. Indices of presence, burned area, fire extent, frequency, and recurrence were calculated for each species, and with them, fire incidence indices were obtained. Significant fire incidence was detected in Pinus canariensis, P. pinaster, Eucalyptus globulus, Quercus robur, Betula spp., Castanea sativa, Pinus radiata, and Quercus pyrenaica. Most of the species with the highest fire incidence are not located in the areas with the highest climatic hazard. There is limited correlation between flammability and fire extension, and this is not significant when considering fire incidence. The relationship between fire incidence and conifers is valid in absolute terms, but only partially in relative terms. Similarly, there is no general relationship between relative fire incidence and species with a natural or reforested origin. Some native hardwood species have unexpectedly high incidence, probably due to collateral damage caused by fires in nearby pine and eucalyptus stands. The fire incidence index of forest species is useful for forest management and for protecting species that are suffering severely from fire effects. Full article

Water scarcity is a key constraint for commercial Eucalyptus plantations, particularly given the increasing frequency of droughts driven by climate change. This study assessed annual transpiration (Tr) and water use efficiency (WUE) across eight genotypes subjected to contrasting irrigation regimes (WR). A split-plot design was implemented, comprising two irrigation levels: high (maintained above 75% of field capacity) and low (approximately 25% above the permanent wilting point). The genotypes included Eucalyptus globulus (EgH, EgL), E. nitens × globulus (EngH, EngL), E. nitens (En), E. camaldulensis × globulus (Ecg), E. badjensis (Eb), and E. smithii (Es). Between stand ages of 7 and 9 years (2020–2023), we measured current annual increment (CAI), leaf area index (LAI), Tr, and WUE. Under high WR, CAI ranged from 8 to 36 m³ ha⁻¹ yr⁻¹, Tr from 520 to 910 mm yr⁻¹, and WUE from 0.7 to 2.9 kg m⁻³. Low irrigation reduced CAI by 5–25% and Tr by 10–35%, while WUE responses varied across genotypes, ranging from a 12% decrease to a 48% increase. Based on their functional responses, genotypes were grouped as follows: (i) stable performers (Es, Ecg, Eb) exhibited high WUE and consistent Tr under both WR; (ii) partially plastic genotypes (EgH, EngH) combined moderate reductions in Tr with improved WUE; and (iii) water-sensitive genotypes (EgL, EngL, En) showed substantial declines in Tr alongside variable WUE gains. These findings underscore the importance of selecting genotypes with adaptive water-use traits to improve the resilience and long-term sustainability of Eucalyptus plantations in Mediterranean environments. Full article

Accurate biomass estimation is important for forest management and climate change mitigation. This study evaluates the potential of using LiDAR (Light Detection and Ranging) data, acquired through Unmanned Aerial Vehicles (UAVs), for estimating above-ground and total biomass in Eucalyptus globulus and Pinus pinaster stands in central and northern Portugal. The acquired LiDAR point clouds were processed to extract structural metrics such as canopy height, crown area, canopy density, and volume. A multistep variable selection procedure was applied to reduce collinearity and select the most informative predictors. Multiple linear regression (MLR) models were developed and validated using field inventory data. Random Forest (RF) models were also tested for E. globulus, enabling a comparative evaluation between parametric and machine learning regression models. The results show that the 25th height percentile, canopy cover density at two meters, and height variance demonstrated an accurate biomass estimation for E. globulus, with coefficients of determination (R²) varying between 0.86 for MLR and 0.90 for RF. Although RF demonstrated a similar predictive performance, MLR presented advantages in terms of interpretability and computational efficiency. For P. pinaster, only MLR was applied due to the limited number of field data, yet R² exceeded 0.80. Although absolute errors were higher for Pinus pinaster due to greater biomass variability, relative performance remained consistent across species. The results demonstrate the feasibility and efficiency of UAV LiDAR point cloud data for stand-level biomass estimation, providing simple and effective models for biomass estimation in these two species. Full article

Water use strategies reflect the ability of plants to adapt to drought caused by climate change. However, how these strategies change with stand development and seasonal drought is not fully understood. This study used stable isotope techniques (δD, δ¹⁸O, and δ¹³C) combined with the MixSIAR model to quantify the seasonal changes in water use sources and water use efficiency (WUE) of Eucalyptus urophylla S.T.Blake × E. grandis (E. urophylla × E. grandis) at four stand ages (2-, 4-, 9- and 14-year-old) and to identify their influencing factors. Our results showed that the young (2-year-old) and middle-aged (4-year-old) stands primarily relied on shallow soil water throughout the growing season due to the limitations of a shallow root system. In contrast, the mature (9-year-old) and overmature (14-year-old) stands, influenced by the synergistic effects of larger and deeper root systems and relative extractable water (REW), exhibited more flexibility in water use, mainly relying on shallow soil water in wet months, but shifting to using middle and deep soil layer water in dry months, and quickly returning to mainly using shallow soil water in the episodic wet month of the dry season. The WUE of E. urophylla × E. grandis was affected by the combined effect of air temperature (T), vapor pressure deficit (VPD), and REW. WUE was consistent across the stand ages in the wet season but decreased significantly with stand age in the dry season. This suggests that mature and overmature stands depend more on shifting their water source, while young and middle-aged stands rely more on enhanced WUE to cope with seasonal drought stress, resulting in young and middle-aged stands being more vulnerable to drought stress. These findings offer valuable insights for managing water resources in eucalyptus plantations, particularly as drought frequency and intensity continue to rise. Full article

The establishment of forest stands after harvest requires an understanding of biomass and nutrient dynamics to support management decisions and ensure system productivity and sustainability. This study evaluated biomass and nutrient accumulation in Eucalyptus urophylla aged 2 to 5 years under planting and coppicing systems. A total of 1152 trees were assessed across eight treatments, combining four ages and two management systems. Aboveground biomass was estimated using 10 trees per treatment, while root biomass was assessed in 8 trees at ages 3 and 5. Nutrient concentrations were determined using three intermediate-diameter class trees per treatment. Biomass data were analyzed using Tukey’s test (5%), and biomass expansion factors (BEF) and the root-to-shoot ratio (R) were used to estimate root carbon. Total biomass was higher in the coppicing system (153 Mg ha⁻¹) compared to the planting system (119 Mg ha⁻¹), with greater root accumulation and carbon sequestration (≈17.2 t C ha⁻¹). The biological use coefficient (BUC) increased with age, except for Mn. Planted stands showed higher BUC for N and P, while coppiced stands were more efficient in Mg use. These results reinforce the need for distinct fertilization strategies for each system, aiming at productivity, nutrient efficiency, and carbon stock enhancement. Full article

Integrating different ecosystem services (ES) to determine when to harvest a forest stand is still challenging. This is due to the difficulty of obtaining information, models, and methods to quantify those ES and achieving an adequate valuation of these services. In this study, we propose a methodology comprising two different models that could allow for different ES integration with the optimal silviculture to calculate the optimal economic rotation. We have applied both models to eucalyptus plantations in Brazil considering two ES: wood with four different assortments and carbon sequestration. For both models, we calculated a ranking with previously defined management alternatives, with decreasing trees-per-hectare compared to traditional plantations. For the first model, when the ES are measured in monetary units, the optimal rotation corresponds to fewer trees per hectare than the traditional plantations and greater associated profitability. The second model incorporates the ES in physical units through a multi-criteria decision-making model and results in a longer rotation with again fewer trees per hectare. This study suggests that optimum forest rotation analysis should consider ES other than timber production integrated with silvicultural alternatives, such as spacing. Full article

Eucalyptus plantations suffer from soil degradation and reduced productivity due to short rotation cycles and multiple generations of replanting. This study investigated the effects of different thinning intensities (CK, 30%, 45%, and 60%) on the size composition, stability, and distribution of metal nutrient elements (K, Ca, Mg, Fe, Mn, Cu, and Zn) of soil aggregates in Eucalyptus plantations by collecting 0–20 cm soil samples and using the dry-sieving method to separate soil aggregates into four sizes (>2 mm, 1–2 mm, 0.25–1 mm, and <0.25 mm). Our findings were as follows: (1) The majority of aggregates comprised larger sizes, predominantly exceeding 2 mm in diameter, which were the most abundant. (2) Compared with unthinned stands (CK) and stands that were thinned by 30%, those thinned by 45% and 60% demonstrated enhanced soil aggregate stability. (3) The stands that were thinned by 30% had the highest Mg and Fe content, whereas those that were thinned by 45% contained the highest levels of Ca, Mn, Cu, and Zn. Larger aggregates (>2 mm) harbored the greatest quantities of metal nutrients, whereas smaller aggregates (<0.25 mm) stored the least. (4) The primary determinants of the metal nutrient content were the soil’s pH and organic carbon levels. (5) The distribution of aggregate sizes played a pivotal role in influencing the nutrient reserves within the aggregates. Overall, this study demonstrated that the thinning intensity not only impacts the stability of soil aggregates in Eucalyptus plantations, but also influences the accumulation of metal nutrient elements within these aggregates, which confirms the significance of macroaggregates as a reservoir for metal nutrient elements. To preserve and enhance soil macroaggregates, it is recommended to implement measures such as reducing the amount of mechanical disturbance, increasing the amount of organic matter, optimizing the stand structure, mitigating water erosion risks, and promoting biological activity while conducting regular assessments of the aggregate stability. Full article

(1) Background: Nature-based solutions (NbS), particularly through forest biomass, are crucial in mitigating climate change. While forest plantations play a critical role in carbon capture, the absence of species-specific biomass estimation models presents a significant challenge. This research focuses on developing allometric models to accurately estimate the aboveground biomass of Eucalyptus saligna Sm in Ecuador’s Lower Montane thorny steppe. (2) Methods: Conducted at the Tunshi Experimental Station of ESPOCH in Chimborazo, Ecuador, the research involved 46 trees to formulate biomass predictive models using both destructive and non-destructive methods. Sixteen generic models were tested using the ordinary least squares method. (3) Results: The most effective allometric equation for estimating six-year-old E. saligna biomass was Ln(B) = −0.952 + 1.97∗Ln(dbh), where B = biomass in kg/tree, and dbh = diameter at breast height in cm. This model represents a valuable contribution to improve biomass and carbon estimates in mitigation projects in Ecuador. (4) Conclusions: The tested models stand out for their simplicity, requiring only dbh as input, and demonstrate high accuracy and fit to contribute to the field of climate change mitigation. Full article

The diversity of commercial tree planting sites, with their distinct environmental conditions, directly influences tree growth and consequently impacts the wood properties in various ways. However, there is limited research evaluating the impact of these variations in nondestructive testing. Therefore, this study aimed to investigate whether edaphoclimatic variations affect parameters obtained through nondestructive tests conducted on standing trees. To this end, 30 specimens were selected from 3 Eucalyptus sp. clones, aged 1, 3, and 4 years, grown in 2 regions, totaling 540 trees. Tree development was monitored quarterly over 12 months. The tests included ultrasound propagation, drilling resistance, and penetration resistance, and the trees were measured for diameter at breast height (DBH) and height. Among the edaphoclimatic factors evaluated, only temperature and soil water storage differed statistically between the two study regions. The higher temperature and lower soil water storage in region 2 promoted tree growth, with these trees showing greater drilling resistance and higher longitudinal wave velocities. In addition, the influence of climatic factors was evidenced by the variation of wave propagation velocity throughout the year. Periods of lower water availability resulted in higher velocities, while periods of greater precipitation were associated with lower velocities. The research results showed that temperature and soil water storage had significant effects on tree growth (DBH and height), as well as ultrasound wave propagation velocity and drilling resistance. Full article

Nocturnal water consumption (NWC), known as including stem refilling (SR) and nocturnal transpiration (NT), has been documented in many plant species, but we do not yet have a clear understanding of species differences and the biotic and abiotic regulation of this phenomenon, especially for subtropical and tropical plantations. In this study, we examine the magnitude, seasonality, and biotic and abiotic regulation of NWC, SR, and NT in three widely planted subtropical and tropical species, Eucalyptus spp., Hevea brasiliensis, and Castanopsis hystrix, through the measured sap and meteorological variables. Stand-level NWC and SR differ significantly among the three plantations, where the mean daily NWC and SR of Eucalyptus spp. (2022–2023), Hevea brasiliensis (2014), and Castanopsis hystrix (2022–2023) are 0.08 mm and 0.05 mm, 0.36 mm and 0.28 mm, and 0.14 mm and 0.12 mm, respectively. Their stand-level NT values are 0.03 mm, 0.08 mm, and 0.02 mm, respectively. Additionally, distinct differences in the seasonality of NWC, SR, and NT are observed among the three plantations, with higher values during spring and autumn and lower values in summer and winter. SR is identified as the predominant role in NWC for all the plantations. VPD is identified as the primary meteorological factor driving NWC, SR, and NR in Eucalyptus spp. and Hevea brasiliensis plantations, while no prominent abiotic variables show the main driver in Castanopsis hystrix. Our findings reveal important implications for the NWC of tropical plantations related to soil–plant–atmosphere equilibrium and hydrology modeling. Full article

Mechanization in timber harvesting has improved the comfort and safety of operator workstations. However, there is an imminent ergonomic risk in relation to the repetition of movements, which can cause musculoskeletal injuries. The aim of this study was to apply infrared thermography to identify musculoskeletal overload in the hand region of harvester operators. This study was conducted on wood harvesting of homogeneous Eucalyptus urophylla × Eucalyptus grandis stands using a forestry harvester tractor. Thermographic images were taken of seven operators at the beginning and end of the working day during six days of the shift. The maximum, average, and minimum temperatures were measured in 14 hand regions of interest (ROI), verifying the existence of a difference between the beginning and the end of work (p-value < 5%) by using the Mann–Whitney test. The operators presented hyperradiant temperature variation in the hand region after work, with a variation above 2.5 °C, indicating a high degree of abnormality. There was greater temperature variation in the right hand (3.7 °C) due to the greater concentration of commands on the machine’s right joystick. Infrared thermography has proven to be an important tool for functional imaging diagnosis, contributing to the reduction in risks of developing Repetitive Strain Injury/Work-Related Musculoskeletal Disorder (RSI-WMSD). Full article

Several polymeric compounds are obtained from synthetic organic solids containing petrochemical derivatives. Biochar fines are considered waste and an alternative bio-reinforcement in composite materials, potentially serving as a possible substitute for non-renewable polymers based on petrochemical derivatives. In this context, the present study focuses on analyzing the properties of biochar fines obtained from the pyrolysis of Eucalyptus sp. biomass, aiming to support the use of this waste in the fabrication of a composite using biochar as a bio-reinforcement. The biochar was produced through pyrolysis in a muffle furnace at a final temperature of 800 °C, with a heating rate of 5 °C min⁻¹ and a residence time of 60 min. The characterization of the obtained fines involved proximate analysis, Brunauer–Emmett–Teller (BET) analysis, scanning electron microscopy (SEM), Fourier-Transform Infrared Spectroscopy (FTIR), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). The results show that the material has a high fixed carbon content, high density, and good thermal resistance, making it stand out for use in composites. Full article

We studied the effects of stand age on the allocation of biomass and allometric relationships among component biomass in five stands ages (1, 3, 5, 7, and 8 years old) of two eucalypts hybrids, including Eucalyptus urophylla × E. grandis and E. urophylla × E. tereticornis, in the Leizhou Peninsula, China. The stem, bark, branch, leaf, and root biomass from 60 destructively harvested trees were quantified. Allometric models were applied to examine the relationship between the tree component biomass and predictor variable (diameter at breast height, D, and height, H). Stand age was introduced into the allometric models to explore the effect of stand age on biomass estimation. The results showed the following: (1) Stand age significantly affected the distribution of biomass in each component. The proportion of stem biomass to total tree biomass increased with stand age, the proportions of bark, branch, and leaf biomass to total tree biomass decreased with stand age, and the proportion of root biomass to total tree biomass first decreased and then increased with stand age. (2) There were close allometric relationships between biomass (i.e., the components biomass, aboveground biomass, and total biomass per tree) and diameter at breast height (D), height (H), the product of diameter at breast height and tree height (DH), and the product of the square of the diameter at breast height and tree height (D²H). The allometric relationship between biomass and measurement parameters (D, H, DH, D²H) could be applied to the biomass assessment of eucalypts plantation. (3) Allometric equations that included stand age as a complementary variable significantly improved the fit and enhanced the accuracy of biomass estimates. The optimal independent variable for the biomass prediction model varied according to each organ. These results indicate that stand age has an important influence on biomass allocation. Allometric equations considering stand age could improve the accuracy of carbon sequestration estimates in plantations. Full article

The suitability of different agroecosystems (native forest, soybean, artificial forest with Eucalyptus sp., mixed horticulture and fruticulture, and dairy prairies) for settling and managing hives for honey production were appraised via holistic surveys of the spatial and seasonal occurrence of floral resources. Metadata were obtained from a project developed by our group, which took place between 2014 and 2017. Species richness, abundance, growth habit (tree, shrub, stand, scrub or stem, accompanying species), and the flowering period for each melliferous plant across the different seasons in 120 samples were measured. Using the Shannon–Wiener diversity index and the floral characteristics of the different species in each environment, an Agroecosystem Apibotanical Index was developed. It revealed that the best agroecosystems for honey production were the most biodiverse native forest as well as mixed horticulture and fruit culture. Knowledge of the floral characteristics and species arrangement enabled the categorization of agroecosystems, aiming for rational management to enhance honey production. Full article

Many eucalypt trees shed their bark annually. This bark becomes a component of the litter layer, which acts as fuel, especially during surface fires. The amount and quality of shed bark vary greatly among species, which might have important effects on forest surface fire behavior. In this study, we aimed to compare the bark fuel bed flammability of eight eucalypt tree species and tried to link their bark litter traits via the surface fuel bed structure to bark flammability. In controlled laboratory burns, three flammability parameters, the fire spread rate, total burning time, and maximum temperature, were measured. The bark litter traits included length, curliness, thickness, dry matter content, tissue density, carbon content, nitrogen content, and terpene content, while the litter bed packing ratio and packing density were also measured. We found significant differences in bark traits and flammability among species. Thicker bark fragments of the eucalypt tree species had higher packing densities in fuel beds, a slower fire spread, and a longer burning time. This relationship was strongly driven by the thick bark fragments of Eucalyptus punctata DC. Still, also within the other seven species, bark thickness was the strongest predictor of bark fuel bed flammability, with some additional explanatory power for bark length. For the first time, our study demonstrates that bark traits, particularly litter fragment thickness and length, drive bark litter flammability of eucalypt tree species through their effects on bark fuel bed structure. These findings contribute to our understanding and predictive power of wildfire behavior in forest stands dominated by different eucalypt species. Full article