Search Results (227)

Citrus creasing is a physiological rind disorder. Satsuma mandarin (Citrus unshiu Marc.) is the most widely cultivated mandarin variety worldwide and exhibits a high susceptibility to creasing. To investigate the physiological mechanisms underlying creasing, satsuma mandarin trees were treated with different drought stress during fruit expansion, then the relationship between the soil water content and creasing incidence was analyzed, while also examining the rind morphology, oil gland distribution in the flavedo, antioxidant enzyme activities, hormone concentrations, cell wall components, mineral content of creasing fruit, and the impact of creasing on fruit quality. Results showed that severe water stress (35% SRWC) increased the creasing incidence rate by 28% compared to well-irrigated treatments (80% SRWC). The creasing fruit oil gland diameter reduced by 35.7% and the density increased by 149.7% compared to healthy fruits. Simultaneously, the content of H₂O₂ and proline elevated by 47.1% and 8.3% respectively, and the activities of SOD, POD, and CAT of the creasing rind were enhanced significantly. Additionally, the content of IAA, ZR, and MeJA decreased by 17.2%, 7.8%, and 50.2%, respectively. Cell wall components such as cellulose, hemicellulose, and protopectin content reduced by 44.6%, 31.7%, and 33.1%, while soluble pectin increased by 36.3%. Significant alterations were observed in several minerals (Al, Fe, Na, Ni, V, Ga, Zn, Ba, Sn, Hg, Sc, Y, and La). However, fruit quality remained unaffected by creasing. These results demonstrate that drought is a key factor inducing creasing. Increased oil gland density, the degradation of cell wall components, elevated oxidative stress, reductions in phytohormones, and altered mineral element content work together to contribute to rind cells’ structural instability and lead to creasing in the satsuma mandarin. Full article

Machilus thunbergii Siebold & Zucc. is recognized as an excellent tree species for landscaping and shelter forest. Excessive drought can affect the changes of physiological and biochemical substances in plants. However, little is known at present regarding the drought stress of M. thunbergii seedlings. In this paper, matrix water content, the anatomical structure of leaves, relative water content of leaves, and physiological characteristics index of leaves under droughting stress were dynamically observed. Droughting stress led to the wilting of M. thunbergii leaves, gradual closure of stomata on leaf epidermis, increases in stomatal density, gradual loosening of leaf cell structure arrangement, a thickening in leaf palisade tissue, and reductions in spongy tissue. Droughting stress caused the relative water content of the cultivation substrate to decline, the cultivation substrate reached the moderate drought level, and the seedlings began to die. Droughting stress led to the destruction of activity and balance of the leaf protective enzyme system, excessive accumulation of free radicals, the destruction of enzyme structure and function, and the production of lipid peroxidation product MDA. Droughting stress reduced the relative water content of leaves as a whole, the content of osmotic adjustment substances proline and soluble protein continued to decline, and a large number of electrolyte leakage in cells, causing serious damage to seedlings. Full article

The cumulative impact of decades of oil and gas exploration has left Alberta’s boreal forests densely fragmented by seismic lines, which are expected to naturally regenerate; however, recovery is often highly variable and generally poor in peatlands due to increased wetness and reduced microtopography. In this study, we evaluated seismic lines in lowland ecosites with some degree of successful natural regeneration to gain a better understanding of the natural recovery process in these areas. We compared stand characteristics between the seismic line (23 to 48 years post-disturbance) and the adjacent undisturbed forest. We found that soil properties were similar, but seedling (height < 1.3 m) density was significantly higher on the seismic line, with 252% more tamarack and 65% more black spruce than in the adjacent forest. Relative to the adjacent forest, there were significantly fewer trees (height > 1.3 m) on the seismic line, with an 84% and 50% reduction in black spruce and tamarack, respectively. By analyzing tree ring data from seismic lines, we found that the length of time before tree establishment was 10 years for black spruce and 8 years for tamarack. On average, it took 12 years for tree density to reach 2000 stems per hectare (sph). We modeled growth rates for black spruce and tamarack and found that they were growing faster than their adjacent forest counterparts, reaching 3 m after an average of 38 and 33 years, respectively. Stands on seismic lines were projected to a final stand age of 61 years using the Mixedwood Growth Model (MGM) to evaluate future stand characteristics. Full article

The cessation of traditional mountain grazing has emerged as a principal driver of habitat degradation and the local extinction of Parnassius apollo (Linnaeus, 1758) in Serbia. While previous studies have cited multiple contributing factors, our research provides evidence that the abandonment of extensive livestock grazing has triggered vegetation succession, the disappearance of the larval host plant (Sedum album), and a reduction in microhabitat heterogeneity—conditions essential for the persistence of this stenophagous butterfly species. Through satellite-based analysis of vegetation dynamics (2015–2024), we identified clear structural differences between habitats that currently support populations and those where the species is no longer present. Occupied sites were characterized by low levels of exposed soil, moderate grass coverage, and consistently high shrub and tree density, whereas unoccupied sites exhibited dense encroachment of grasses and woody vegetation, leading to structural instability. Furthermore, MODIS-derived indices (2010–2024) revealed a consistent decline in vegetation productivity (GPP, FPAR, LAI) in succession-affected areas, alongside significant correlations between elevated land surface temperatures (LST), thermal stress (TCI), and reduced photosynthetic capacity. A wildfire event on Mount Stol in 2024 further exacerbated habitat degradation, as confirmed by remote sensing indices (BAI, NBR, NBR2), which documented extensive burn scars and post-fire vegetation loss. Collectively, these findings indicate that the decline of P. apollo is driven not only by ecological succession and climatic stressors, but also by the abandonment of land-use practices that historically maintained suitable habitat conditions. Our results underscore the necessity of restoring traditional grazing regimes and integrating ecological, climatic, and landscape management approaches to prevent further biodiversity loss in montane environments. Full article

Urochloa brizantha (Brizantha) is cultivated under varying altitudinal and management conditions. Twelve full-sun (monoculture) plots and twelve shaded (silvopastoral) plots were established, proportionally distributed at 170, 503, 661, and 1110 masl. Evaluations were conducted 15, 30, 45, 60, and 75 days after establishment. The conservation and integration of trees in silvopastoral systems reflected a clear anthropogenic influence, evidenced by the preference for species of the Fabaceae family, likely due to their multipurpose nature. Although the altitudinal gradient did not show direct effects on soil properties, intermediate altitudes revealed a significant role of CaCO₃ in enhancing soil fertility. These edaphic conditions at mid-altitudes favored the leaf area development of Brizantha, particularly during the early growth stages, as indicated by significantly larger values (p < 0.05). However, at the harvest stage, no significant differences were observed in physiological or productive traits, nor in foliar chemical components, underscoring the species’ high hardiness and broad adaptation to both soil and altitude conditions. In Brizantha, a significant reduction (p < 0.05) in stomatal size and density was observed under shade in silvopastoral areas, where solar radiation and air temperature decreased, while relative humidity increased. Nonetheless, these microclimatic variations did not lead to significant changes in foliar chemistry, growth variables, or biomass production, suggesting a high degree of adaptive plasticity to microclimatic fluctuations. Foliar ash content exhibited an increasing trend with altitude, indicating greater efficiency of Brizantha in absorbing calcium, phosphorus, and potassium at higher altitudes, possibly linked to more favorable edaphoclimatic conditions for nutrient uptake. Finally, forage quality declined with plant age, as evidenced by reductions in protein, ash, and In Vitro Dry Matter Digestibility (IVDMD), alongside increases in fiber, Neutral Detergent Fiber (NDF), and Acid Detergent Fiber (ADF). These findings support the recommendation of cutting intervals between 30 and 45 days, during which Brizantha displays a more favorable nutritional profile, higher digestibility, and consequently, greater value for animal feeding. Full article

In the process of plant protection for fruit trees using rotary-wing UAVs, challenges such as droplet drift, insufficient canopy penetration, and low agrochemical utilization efficiency remain prominent. Among these, the uncertainty in the spatio-temporal distribution of downwash airflow is a key factor contributing to non-uniform droplet deposition and increased drift. To address this issue, we developed a wind field numerical simulation model based on an improved hierarchical leaf density model to clarify the spatio-temporal characteristics of downwash airflow, the scale of turbulence regions, and their effects on internal canopy airflow under varying flight altitudes and different rotor speeds. Field experiments were conducted in orchards to validate the accuracy of the model. Simulation results showed that the average error between the simulated and measured wind speeds inside the canopy was 8.4%, representing a 42.11% reduction compared to the non-hierarchical model and significantly improving the prediction accuracy. The coefficient of variation (CV) was 0.26 in the middle canopy layer and 0.29 in the lower layer, indicating a decreasing trend with an increasing canopy height. We systematically analyzed the variation in turbulence region scales under different flight conditions. This study provides theoretical support for optimizing UAV operation parameters to improve droplet deposition uniformity and enhance agrochemical utilization efficiency. Full article

This study investigated the production of biodiesel from canola oil, the formulation of sustainable ternary fuel blends with diesel and alcohol (ethanol or propanol), and the experimental and machine learning-based modeling of their physical properties, including density and viscosity over a temperature range of 10 °C to 40 °C. Biodiesel was synthesized via alkali-catalyzed transesterification (6:1 methanol-to-oil molar ratio, 0.5 wt % NaOH of oil) and blended with diesel and alcohols (ethanol and propanol) in varying volume ratios. The experimental results revealed that blend density decreased from 0.8622 g/cm³ at 10 °C to 0.8522 g/cm³ at 40 °C for a blend containing ethanol. Similarly, the viscosity showed a significant reduction with temperature, e.g., the blend exhibited a viscosity decline from 8.5 mPa·s at 10 °C to 7.2 mPa·s at 40 °C. Increasing the alcohol or diesel content further reduced density and viscosity due to the lower intrinsic properties of these components. The machine learning models, Gaussian process regression (GPR), support vector regression (SVR), artificial neural networks (ANN), and decision tree regression (DTR), were applied to predict the properties of these blends. GPR demonstrated the best predictive performance for both density and viscosity. These findings confirm the strong potential of GPR for the accurate and reliable prediction of fuel blend properties, supporting the formulation of alternative fuels optimized for diesel engine performance. These aspects contribute new insights into modelling strategies for sustainable fuel formulations. Full article

Light Detection and Ranging (LiDAR) provides three-dimensional information that can be used to extract tree parameter measurements such as height (H), canopy volume (CV), canopy diameter (CD), canopy area (CA), and tree stand density. LiDAR data does not directly give diameter at breast height (DBH), an important input into allometric equations to estimate biomass. The main objective of this study is to estimate tree DBH using existing allometric models. Specifically, it compares three global DBH pantropical models to calculate DBH and to estimate the aboveground biomass (AGB) of the Lake Broadwater Forest located in Southeast (SE) Queensland, Australia. LiDAR data collected in mid-2022 was used to test these models, with field validation data collected at the beginning of 2024. The three DBH estimation models—the Jucker model, Gonzalez-Benecke model 1, and Gonzalez-Benecke model 2—all used tree H, and the Jucker and Gonzalez-Benecke model 2 additionally used CD and CA, respectively. Model performance was assessed using five statistical metrics: root mean squared error (RMSE), mean absolute error (MAE), mean absolute percentage error (MAPE), percentage bias (MBias), and the coefficient of determination (R²). The Jucker model was the best-performing model, followed by Gonzalez-Benecke model 2 and Gonzalez-Benecke model 1. The Jucker model had an RMSE of 8.7 cm, an MAE of −13.54 cm, an MAPE of 7%, an MBias of 13.73 cm, and an R² of 0.9005. The Chave AGB model was used to estimate the AGB at the tree, plot, and per hectare levels using the Jucker model-calculated DBH and the field-measured DBH. AGB was used to estimate total biomass, dry weight, carbon (C), and carbon dioxide (CO₂) sequestered per hectare. The Lake Broadwater Forest was estimated to have an AGB of 161.5 Mg/ha in 2022, a Total C of 65.6 Mg/ha, and a CO₂ sequestered of 240.7 Mg/ha in 2022. These findings highlight the substantial carbon storage potential of the Lake Broadwater Forest, reinforcing the opportunity for landholders to participate in the carbon credit systems, which offer financial benefits and enable contributions to carbon mitigation programs, thereby helping to meet national and global carbon reduction targets. Full article

This study presents the development of particleboards made from olive tree pruning (OTP) residues and truck industry by-products (RCM), using PUR resin as a binder. Five formulations with different OTP/RCM ratios were designed and physical, thermal, mechanical, chemical and microstructural properties were evaluated. The results showed that increasing the RCM content improves the dimensional stability, reduces water absorption and swelling and decreases thermal conductivity, reaching 0.061 W/mK. At the mechanical level, MOR, MOE and IB values of 7.11, 630 and 0.134 MPa, respectively, were obtained. A higher OTP content allows a reduction in the density of the particleboard (752.67 kg/m³) due to the granulometry of the material. FTIR and SEM analyses confirmed the good integration of the materials with the resin, highlighting a lower porosity and higher compaction in formulations with a high RCM content. These results demonstrate that the combination of agricultural and industrial by-products is feasible to manufacture a sustainable particleboard with customizable properties, promoting the circular economy and reducing the dependence on virgin raw materials in the construction sector. Full article

Old-growth forests are rare in Europe, yet they play a critical role in biodiversity and carbon storage. This study examines the structural dynamics of the Janj old-growth forest in the Dinaric Alps using repeated field measurements from 2011 and 2021 at 39 systematically arranged 12 m radius plots. All trees (DBH ≥ 7.5 cm), regeneration (10 cm height to 7.5 cm DBH), and coarse woody debris (CWD) were assessed. Results revealed that total basal area declined by 3.5 m² ha⁻¹ over the decade, primarily driven by significant reductions in stem density for silver fir (p = 0.001) and Norway spruce (p = 0.001). In contrast, European beech maintained a stable basal area throughout the study period. Moreover, silver fir exhibited a significant increase in mean diameter (p = 0.032) and a pronounced rise in regeneration individuals (t = 3.257, p = 0.002). These findings underscore a gradual compositional shift towards European beech dominance, with conifers facing higher mortality in larger diameter classes. The substantial volume of CWD (463 m³ ha⁻¹) highlights advanced decay dynamics consistent with mature forest conditions. This study emphasizes the value of repeated measurements to capture subtle yet important successional changes in primeval forests, which is essential for conservation planning and sustainable forest management. Full article

Michelia macclurei, a valuable native broad-leaved species with good ecological and economic benefits and a key afforestation tree in South China, is facing progressive stand degradation and soil fertility decline with age. To investigate age-dependent dynamics of stand structure and soil properties, this study examined five stands (5, 10, 15, 20, and 42 a) in Yunfu City, Guangdong Province. The results revealed that (1) spatial distribution shifted from aggregated in young stands (5–10 a) to random in mature stands (42 a), with diameter and height class distributions becoming more diverse with age. Notably, topsoil (0–20 cm) in near-mature stands (15–20 a) exhibited not only significantly higher capillary porosity, non-capillary porosity, and water-holding capacity compared to young stands but also increased bulk density, indicating soil physical degradation. (2) Soil nutrient decline was observed in over-mature stands (42 a), characterized by a reduction in soil total nitrogen to 1.08 ± 0.06 g·kg⁻¹ and total phosphorus to 0.16 ± 0.02 g·kg⁻¹ in the topsoil (0–20 cm layer), suggesting age-related soil nutrient degradation. (3) Correlation analysis revealed a significant negative correlation between total potassium content and crown uniformity indices (p < 0.01), while available phosphorus was significantly positively correlated with crown and tree growth (p < 0.05). These findings provide critical insights for developing stage-specific management strategies in Michelia macclurei plantations. Full article

Case studies of climate adaptation approaches are needed to inform the broader use of these strategies across longleaf pine (Pinus palustris Mill.) ecosystems in the Southern US. To address this need, we evaluated overstory structure and tree regeneration in longleaf pine-hardwood stands, and a transition approach was implemented to intentionally facilitate change to encourage adaptive responses. Stand density reduction and species selection were prescribed to reduce tree vulnerability to drought stress. Turkey oaks (Quercus laevis W.) were also planted as a part of an assisted population migration strategy. After the treatments, Hurricane Michael impacted the study stands. The percent reduction in large overstory longleaf pines due to the hurricane was 6.3 ± 6.1% (grand mean ± standard deviation, which was derived from the stand means). At least one live planted turkey oak was present in 74 ± 26% of the planted clusters of turkey oaks that could be located six years after planting them. Our findings demonstrate the ability of transition stands to accommodate a large-scale disturbance event and maintain ecosystem functionality, the desired stand structure, and species composition. The relative success of forestry assisted migration plantings of turkey oaks may alleviate some concerns about the risk of maladaptation. Full article

While urban greenery is known to regulate microclimates and reduce air pollution, its integrated effects remain insufficiently quantified. Through field monitoring and ENVI-met 5.1 modeling of high-rise residential areas in Jinan, the results demonstrate that: (1) vegetation exhibits distinct spatial impacts in air-quality impacts, reducing roadside PM_2.5 by 26.63 μg/m³ while increasing building-adjacent levels by 17.5 μg/m³; (2) shrubs outperformed trees in PM_2.5 reduction (up to 65.34%), particularly when planted in inner rows, whereas tree crown morphology and spacing showed negligible effects; (3) densely spaced columnar trees optimize cooling, reducing T_a by 3–4.8 °C and the physiological equivalent temperature (PET*) by 8–12.8 °C, while planting trees on the outer row and shrubs on the inner row best balanced thermal and air-quality improvements; (4) each 1 m²/m³ leaf area density (LAD) increase yields thermal benefits (ΔT_a = −1.07 °C, ΔPET* = −1.93 °C) but elevates PM_2.5 by 4.32 μg/m³. These findings provide evidence-based vegetation design strategies for sustainable urban planning. Full article

Climate models have predicted changes in woody plant growth, vitality, and species distribution. Those changes are expected mainly within the boundaries of species ranges. We studied the influence of changing hydrothermal and burning-rate regimes on relict pine stands at the southern edge of the Pinus sylvestris range in Siberia. We hypothesize that (1) warming has stimulated pine growth under conditions of sufficient moisture supply, and (2) increased burning rate has threatened forest viability. We found that the increase in air temperature, combined with the decrease in soil and air drought, stimulated tree growth. Since the “warming restart” around 2000, the growth index (GI) of pines has exceeded its historical value by 1.4 times. The GI strongly correlates with the GPP and NPP of pine stands (r = 0.82). Despite the increased fire rate, the GPP/NPP and EVI index of both pine stands and surrounding bush–steppes are increasing, i.e., the pine habitat is “greening” since the warming restart. These results support the prediction (by climatic scenarios SSP4.5, SSP7.0, and SSP8.5) of improvement in tree habitat in the Siberian South. Meanwhile, warming has led to a reduction in the fire-return interval (up to 3–5 y). Although the post-fire density of seedlings on burns (ca. 10,000 per ha) is potentially sufficient for pine forest recovery, repeated surface fires have eliminated the majority of the undergrowth and afforestation. In a changing climate, the preservation of relict pine forests depends on a combination of moisture supply, burning rate, and fire suppression. Full article

Since its first detection in 2013, Xylella fastidiosa subsp. pauca (Xfp) has caused a devastating Olive Quick Decline Syndrome (OQDS) outbreak in Southern Italy. Effective disease surveillance and treatment strategies are urgently needed to mitigate its impact. This study investigates the short-term (1.5 years) effects of thymol-based treatments on infected olive trees of the susceptible cultivar Cellina di Nardò in two orchards in Salento, Apulia region. Twenty trees per trial received a 3% thymol solution either alone or encapsulated in a cellulose nanoparticle carrier. Over two years, sap flux density and canopy-transmitted solar radiation were monitored using TreeTalker sensors, and spectral greenness indices were calculated. Xfp cell concentrations in plant tissues were quantified via qPCR. Neither thymol treatment halted disease progression nor significantly reduced bacterial load, though the Xfp cell concentration reduction increased over time in the preventive trial. Symptomatic trees exhibited increased sap flux density, though the treatment mitigated this effect in the curative trial. Greenness indices remained lower in infected trees, but the response to symptom severity was delayed. These findings underscore the need for longer-term studies, investigation of synergistic effects with other phytocompounds, and integration of real-time sensor data into adaptive disease management protocols. Full article