Search Results (153)

The momentum transport and scale-dependent motion characteristics within vegetation canopies play a crucial role in shaping near-surface turbulent structures and exchange processes, yet the interactions among different turbulent scales and their statistical representations remain insufficiently understood. Based on a series of controlled wind tunnel experiments, this study identifies coherent turbulent structures using a phase-space algorithm constructed from streamwise velocity fluctuation u′, acceleration a, and jerk j, and compares transport efficiency (exuberance η). This study uses scale-wise (cut-off frequency) momentum flux contribution analysis, natural visibility graph (NVG), and large–small-scale amplitude modulation to examine transport and multiscale behaviors across different canopy densities, array layouts, and inflow conditions. Results show that canopy density (different C_d drag coefficient) is a primary factor governing transport efficiency. Under low-wind staggered configurations, increasing canopy density strengthens the contribution of low-frequency large-scale motions to total momentum flux. In contrast, high-wind aligned configurations intensify canopy-top shear, enhancing small-scale motions and thereby reducing the relative contribution of large-scale motions. NVG analysis further reveals that in high-density canopies, large-scale acceleration and deceleration events tend toward equilibrium, whereas deceleration events dominate consistently in low- and medium-density cases. Amplitude modulation results indicate that high-density cases exhibit highly consistent modulation behavior, followed by low-density cases, while medium-density cases display a pronounced height-dependent variation, characterized by a distinct modulation critical point. This study proposes a unified analytical framework integrating coherent structure detection, graph-theoretic analysis, multiscale transport characterization, and large–small-scale modulation, providing a comprehensive description of momentum transport and scale motions within canopy flows, and it offers new insight into the mechanisms governing complex vegetation canopy turbulence. Full article

Aquaculture-derived bio-based fertilizers (BBFs) represent a promising alternative to inorganic P in Andisols for sustainable alfalfa (Medicago sativa L.) cultivation. However, their agronomic performance and physiological impacts on alfalfa remain poorly understood. This study evaluated three BBFs, consisting of composted fish sludge (CFS), dried fish sludge (DFS), and fish bone meal (FBM), in comparison with inorganic P (InoP) and a zero-P control (NoP). Forage yield (FY), P use efficiency (PUE), spectral canopy indices, and leaf gas-exchange parameters were assessed across five harvests in a Mediterranean environment. Results showed significant differences among fertilizer types driven by their distinct P release dynamics. DFS consistently maintained stable leaf P concentrations, enhanced PUE and P uptake, and lead to higher FY, improved photosynthesis, and water use efficiency (WUE). It performs statistically similarly to the inorganic P. In contrast, CFS released P too slowly, which in turn lowered leaf P concentration, P uptake, and PUE, resulting in the lowest photosynthesis and WUE. FBM produced intermediate responses but maintained WUE comparable to inorganic fertilizer. Gas-exchange measurements demonstrated that photosynthesis ranged from 9.01 to 16.7 μmol m⁻² s⁻¹, with no significant difference between DFS and inorganic P. Transpiration remained stable across BBF treatments (mean 3.2 mmol m⁻² s⁻¹). The canopy reflectance indices such as RARS, Gite2, and PSSR proved to be strong predictors of both P concentration and PUE in alfalfa. In conclusion, DFS emerged as the most efficient BBF that matched inorganic fertilizer to enhance P nutrition, plant physiology, and FY. These findings highlight the potential of aquaculture-derived BBFs, particularly DFS as sustainable P sources for improving alfalfa productivity while reducing reliance on synthetic fertilizers. Full article

Rootstocks play a central role in modulating grapevine responses to water scarcity, yet their morpho-functional strategies remain highly genotype-dependent. This study compared three functionally contrasting rootstocks, 1103 Paulsen, 420 A, and M2, grafted with Vitis vinifera cv. Merlot, which differ in root system architecture, hydraulic efficiency, canopy development, and stomatal regulation, with the aim of elucidating their hydraulic, morphological, and physiological responses under controlled conditions. Plants were grown in containers and assessed for root system architecture, hydraulic conductance, gas exchange including transpiration rate, chlorophyll fluorescence, and biomass allocation. The results revealed three distinct adaptive strategies: 1103 P exhibited the highest structural root biomass and rootstock hydraulic conductivity, supporting elevated axial water transport, higher transpiration rates, and a larger canopy, consistent with an “active tolerance” strategy; 420 A showed balanced structural and absorptive root development, moderate hydraulic performance, and the highest transpiration rates, reflecting a flexible, opportunistic response to water availability. In contrast, M2 displayed markedly reduced structural root biomass but a high proportion of absorptive roots and the greatest scion hydraulic conductance combined with low stomatal conductance, reduced transpiration, and high intrinsic water use efficiency, which is indicative of a conservative, resource-efficient strategy. These findings demonstrate that the three rootstocks express fundamentally different drought response syndromes driven by coordinated variation in root morphology, hydraulic traits, canopy development, and stomatal behavior. The integration of hydraulic and morphological traits provides a robust framework for selecting rootstocks tailored to specific pedoclimatic and management contexts in water-limited environments. Full article

Canopy ammonia (NH₃) exchange is a major contributor to agricultural NH₃ emissions and is closely linked to nitrogen-use efficiency. Glutamine synthetase (GS) mediates plant NH₃ assimilation, yet the specific roles of different GS isoenzymes in regulating wheat canopy NH₃ exchange remain unclear. This study aimed to clarify the functional differences of wheat TaGS isoenzymes in modulating canopy–atmosphere NH₃ exchange dynamics using two wheat cultivars (Yumai 49-198 and Xinong 509) under two nitrogen application levels (120 and 225 kg N ha⁻¹). Field experiments combined with FTIR-based NH₃ flux measurement, biochemical assays, and molecular analyses were conducted at anthesis and 16, 24, and 30 days after anthesis (DAA). Results showed that the leaf NH₃ compensation point, determined by apoplastic NH₄⁺ concentration, is a key factor influencing canopy NH₃ exchange. Leaf NH₃ sources exhibited distinct temporal specificity: photorespiration and nitrate reduction dominated at anthesis to 16 DAA, whereas nitrogenous compound degradation prevailed at 24–30 DAA. This temporal partitioning was highly coordinated with TaGS isoenzyme expression: TaGS2 was highest in early grain filling, potentially supporting assimilate NH₃ from photorespiration/nitrate reduction, while TaGS1;1 expression increased progressively, aligning with the scavenging of NH₃ from organic nitrogen degradation. These coordinated patterns suggest that the TaGS isoenzymes play differentiated roles in influencing wheat canopy NH₃ exchange. This study thus provides correlative insights that point to potential molecular targets for breeding nitrogen-efficient wheat cultivars and mitigating agricultural NH₃ emissions sustainably. Full article

This study is Part II of a five-year (2018–2022) field trial in western Portugal evaluating the effects of three microbial biofertilizers—Mycoshell^® (Glomus spp. + humic/fulvic acids), Kiplant iNmass^® (Azospirillum brasilense, Bacillus megaterium, Saccharomyces cerevisiae), and Kiplant All-Grip^® (Bacillus megaterium, Pseudomonas spp.)—applied at different dosages alongside two mineral fertilizer regimes, T100 (full dose) and T70 (70% of T100, alone or combined with biofertilizers), on the physiological performance of ‘Gala Redlum’ apple trees. Part I had shown that Myc4 (Mycoshell^®, 4 tablets/tree), iNM6, and iNM12 (Kiplant iNmass^®, 6 and L ha⁻¹, respectively) consistently enhanced fruit growth, yield, and selected quality traits. While Part I showed clear agronomic gains, Part II demonstrates that these improvements occurred without significant alterations in seasonal photosynthetic performance, canopy reflectance, or chlorophyll fluorescence parameters over five years, highlighting the contrast between observed yield improvements and physiological stability. Seasonal monitoring of physiological traits—including specific leaf area (SLA), chlorophyll content index (CCI), gas exchange (A_n, g_s, E, C_i), spectral indices (NDVI, OSAVI, SIPI, GM2), and chlorophyll fluorescence (OJIP). It is clear that physiological values remained largely stable across biofertilizer treatments and years. Importantly, this stability was maintained even under a 30% reduction in mineral fertilizer (T70), indicating that specific microbial biofertilizers can sustain physiological resilience under reduced nutrient inputs, thereby providing a physiological basis for the yield-enhancing effects observed and supporting their integration into fertilizer reduction strategies in Mediterranean orchards. Full article

The Leaf Area Index (LAI) is a fundamental biophysical parameter quantifying forest canopy structure and regulating water–energy exchange. While Abies Mill. forests constitute a vital component of China’s alpine ecosystems, the spatial heterogeneity of their LAI and its sensitivity to environmental filtering remain underexplored. This study employed Random Forest (RF) and Structural Equation Modeling (SEM) to disentangle the direct and interactive effects of climate, soil, topography, and human footprint (HFP) on LAI across 17 distinct Abies forest types. The results revealed that temperature was the dominant positive driver for the overall Abies forests (Total effect = 2.197), whereas Elevation (DEM) exerted the strongest negative regulation (Total effect = −0.335). However, driver dominance varied substantially among forest types: climatic water availability was the primary constraint for Abies georgei var. smithii (Viguié & Gaussen) W.C.Cheng & L.K.Fu forest (Type 55), while DEM determined LAI in Abies fargesii Franch. forest (Type 49). Notably, we found that HFP could exert positive effects on LAI in specific communities (e.g., Abies densa Griff. forest, Type 58), likely due to understory compensation under moderate disturbance. These findings highlight the necessity of type-specific management strategies and provide a theoretical basis for predicting alpine forest dynamics under changing environments. Full article

Understanding yield improvement in horticultural systems depends on elucidating how multiple plant traits operate in concert to sustain productivity. Mulberry (Morus alba L.) provides a suitable model for examining such whole-plant integration. Under cold-region field conditions, a modern high-yield cultivar (‘Nongsang 14’) was compared with a traditional cultivar (‘Lusang 1’). Measurements encompassed canopy architecture, biomass allocation between roots and shoots, leaf economic traits, and gas-exchange parameters, allowing trait coordination to be evaluated across structural and physiological dimensions. Multivariate profiling—Principal Component Analysis (PCA) and correlation networks—was used to characterise phenotypic integration. The modern cultivar’s superior productivity emerged as a coordinated “acquisitive” trait syndrome. This strategy couples a larger canopy (higher LAI) and nitrogen-rich foliage (higher LNC) with greater stomatal conductance (G_s), operating together with reduced root-to-shoot allocation. These features form a tightly connected network where structural investment and physiological upregulation are synchronised to maximise carbon gain. These findings provide a whole-plant framework for interpreting high productivity, offering guidance for breeding programmes that target trait integration rather than single-trait optimisation. Full article

Training system selection critically influences peach orchard productivity through its effects on canopy light environment, physiological responses, and fruit quality. This study evaluated two contrasting training systems: a 2D planar fruiting wall system (Four-Axis, 1020 trees ha⁻¹) versus a 3D Quad-V system (590 trees ha⁻¹) using two peach cultivars, fresh table ‘Platibelle’ and clingstone ‘Mirel’ in Central Macedonia, Greece. Comprehensive physiological measurements including leaf gas exchange, chlorophyll fluorescence, and fruit quality parameters were assessed across two canopy zones (lower 0–1.2 m vs. upper 1.8–3.3 m) during the 2023 and 2024 growing seasons. Results demonstrated that the 2D system achieved superior leaf area index (LAI), but lower light interception, leading to enhanced photosynthetic performance with 15–20% higher net photosynthetic rates and improved water-use efficiency compared to the 3D system. Notably, the photosynthetic apparatus of fruiting wall trees maintained significantly greater efficiency (6.26 μmol CO₂ m⁻² s⁻¹) in the lower canopy zone than in Quad-V trees (3.6 μmol CO₂ m⁻² s⁻¹), indicating a more uniform and functional light environment. The 2D system produced fruits with improved flesh firmness and color development in ‘Mirel’, while higher dry matter in ‘Platibelle’. Correlation analysis revealed that Four-Axis trees enhanced the interdependence among thermal, gas exchange, and compositional traits, reflecting a shift from morphology-driven to metabolically integrated canopy function. In terms of yield, fruiting walls achieved higher efficiency and total production (Mt ha⁻¹) in ‘Mirel’, supporting their adoption to enhance productivity and peach fruit quality in Mediterranean conditions. Full article

Urban heat islands intensify heat stress and degrade air quality in densely built areas, yet the physical processes governing near-surface thermal variability remain poorly quantified. This study applies the coupled MOLOCH and PALM model system 6.0 (PALM-4U) over Bologna (Italy) during a summer 2023 heatwave to resolve meter-scale atmospheric dynamics within the Urban Canopy Layer and Roughness Sublayer at 2 m horizontal resolution. The coupled configuration was validated against in situ meteorological observations and Landsat-8 LST data, showing improved agreement in air temperature and wind speed compared to standalone mesoscale simulations. Results reveal pronounced diurnal and vertical variability of wind speed, turbulent kinetic energy, and friction velocity, with maxima between two/three times the median building height (h_c). Distinct surface-dependent contrasts emerge: asphalt and roofs act as strong daytime heat sources (Bowen ratio β_asphalt ≈ 4.8) and nocturnal heat reservoirs at pedestrian level (z ≈ 0.07 h_c), while vegetation sustains daytime latent heat fluxes (β_vegetation ≈ 0.6÷0.8) and cooler surface and near-surface air (Temperature anomaly of surface ΔT_s ≈ −9 °C and air ΔT_air ≈ −0.3 °C). Thermal anomalies decay with height, vanishing above z ≈ 2.5 h_c due to turbulent mixing. These findings provide insight into fine-scale energy exchanges driving intra-urban thermal heterogeneity and support climate-resilient urban design. Full article

The parameterization of vegetation indices (VIs) is crucial for sustainable irrigation and horticulture management, specifically for urban green infrastructure (GI) management. However, the constraints of roadside traffic, motor and industrially related pollution, and potential public vandalism compromise the efficacy of conventional in situ monitoring systems. The shortcomings of prevalent satellites, UAVs, and manual/automated sensor measurements and monitoring systems have already been reviewed. This research proposes a novel urban GI monitoring system based on an integration of gas exchange and various VIs obtained from computer vision algorithms applied to data acquired from three novel sources: (1) Integrated gas sensor data using nine different volatile organic compounds using an electronic nose (E-nose), designed on a PCB for stable performance under variable environmental conditions; (2) Plant growth parameters including effective leaf area index (LAIe), infrared index (Ig), canopy temperature depression (CTD) and tree water stress index (TWSI); (3) Meteorological data for all measurement campaigns based on wind velocity, air temperature, rainfall, air pressure, and air humidity conditions. To account for spatial and temporal data acquisition variability, the integrated cameras and the E-nose were mounted on a vehicle roof to acquire information from 172 Elm trees planted across the Royal Parade, Melbourne. Results showed strong correlations among air contaminants, ambient conditions, and plant growth status, which can be modelled and optimized for better smart irrigation and environmental monitoring based on real-time data. Full article

Thisreview provides a comprehensive synthesis of recent theoretical and experimental advances on turbulent plane jets interacting with surface waves or rigid vegetation. In wave-affected conditions, a unified mathematical framework based on velocity decomposition and the integral balances of momentum and energy reveals the fundamental scaling laws governing jet spreading and momentum exchange. The analysis demonstrates that wave-induced shear alters classical entrainment mechanisms, leading to modified power-law relationships for jet width and centerline velocity, consistent with laboratory and numerical evidence. In obstructed environments, such as canopies of rigid or flexible vegetation, distributed drag induces a transition from entrainment to detrainment. The resulting momentum loss is captured analytically by incorporating drag-induced dissipation into the Reynolds-averaged momentum equations, yielding exponential decay of jet momentum and reduced mixing efficiency. Together, these models elucidate how environmental forcing—dynamic (waves) and structural (vegetation)—controls the evolution of turbulent jets in natural and engineered aquatic systems. The review highlights key scaling relationships, theoretical developments, and experimental findings, offering a coherent basis for future studies on mixing, dispersion, and transport in complex coastal and vegetated flows. Full article

Although accurate quantification of forest soil CO₂ emissions is critical for improving global carbon cycle models, traditional chamber and gradient methods often underestimate fluxes under windy conditions. Based on long-term field observations in a subtropical maple forest, we quantified the interaction between canopy-level winds and soil pore air pressure fluctuations in regulating vertical CO₂ profiles. The results demonstrate that canopy winds, rather than subcanopy airflow, dominate deep soil CO₂ dynamics, with stronger explanatory power for concentration variability. The observed “wind-pumping effect” operates through soil pressure fluctuations rather than direct wind speed, thereby enhancing advective CO₂ transport. Soil pore air pressure accounted for 33%–48% of CO₂ variation, far exceeding the influence of near-surface winds. These findings highlight that, even in dense forests with negligible understory airflow, canopy turbulence significantly alters soil–atmosphere carbon exchange. We conclude that integrating soil pore air pressure into flux calculation models is essential for reducing underestimation bias and improving the accuracy of forest carbon cycle assessments. Full article

Water scarcity in arid regions has prompted the exploration of alternative irrigation sources, including treated wastewater, to support sustainable rangeland management. This study evaluated the effects of treated wastewater irrigation on the growth performance of native pastoral plants and soil chemical properties in the Al-Tamriat area, Al-Jouf, Saudi Arabia. Four native species—Traganum nudatum (Aldamran), Atriplex leucoclada (Alrughal), Salsola villosa (Al-Rutha), and Ziziphus nummularia (Sidir)—were cultivated under two irrigation regimes: normal water and treated wastewater. In a 12-month period, plant morphological traits (plant height, stem diameter, and canopy width) were monitored monthly, alongside soil chemical properties (pH, electrical conductivity, total organic carbon, organic matter, available phosphorus, exchangeable potassium, and available nitrogen) assessed at two soil depths (0–20 cm and 20–40 cm). Results showed species-specific responses to irrigation water quality where Atriplex leucoclada and Ziziphus nummularia exhibited superior growth performance (average heights of 54.78 cm and 53.09 cm, respectively), compared to the Traganum nudatum and Salsola villosa. Overall, normal water irrigation promoted greater plant growth (mean height: 36.61 cm) compared to treated wastewater (29.60 cm), likely due to salinity stress. In contrast, soil fertility improved under both treatments, with total organic carbon increasing from 0.08 to 0.43% in the top layer (0–20 cm) and from 0.05 to 0.40% in the bottom layer (20–40 cm) after 12 months of experimentation. Statistical analysis (ANOVA, p < 0.05) revealed significant interactive effects between water type, species, and time on plant and soil variables. These findings illustrate the potential of using TW for rangeland irrigation, while also illustrating its potential to limit growth in sensitive species. The results emphasize the importance of choosing the right species and managing water quality when developing TW irrigation plans for arid rangelands. Full article

Urban riparian areas serve as vital blue-green infrastructure for climate adaptation, yet mechanisms governing energy exchange remain underexplored. This study aims to quantify the spatiotemporal patterns of sensible heat flux (H) and latent heat flux (LE) across riparian plant communities on daily and annual scales, and to disentangle the interactive effects of vegetation structure and water bodies on these fluxes. Using year-long field monitoring (September 2020–August 2021) across seven riparian plant communities along the Danshui River in Shanghai, environmental parameters were collected at multiple distances from the river. Interpretable machine learning models (Random Forest with SHAP analysis) were employed to identify key drivers. Results reveal significant diurnal and seasonal dynamics: LE amplitude exceeded H in summer but reversed in winter, with spatial gradients in H and LE strongly influenced by proximity to water bodies in grasslands and broadleaf forests but weakened in conifers. Meteorological factors such as photosynthetically active radiation and sunshine duration dominated daily-scale fluxes, while vegetation structures such as canopy height and leaf area index (LAI) contributed >50% to annual-scale variability. These findings underscore vegetation’s role in modulating energy partitioning, providing a theoretical basis for optimizing riparian plant configurations to enhance microclimate regulation in urban riparian. Full article

Spring droughts, increasingly coinciding with canopy shade, interactively stress the growth of urban tree species and are poorly understood in Beijing. Three-year-old saplings of Pinus tabuliformis and Robinia pseudoacacia were subjected to comparative analysis under four drought–shade sequences, with a full-light, well-watered treatment serving as the control. During two periods encompassing the drought to wilting point and subsequent rewatering, we assessed leaf morphology, water status, photosynthetic gas exchange, and chlorophyll fluorescence. Both species exhibited losses in leaf water and carbon assimilation under drought, yet their adaptive strategies substantially differed. P. tabuliformis conserved water through the stable leaf anatomy and conservative stomatal control. In particular, P. tabuliformis under full-light and drought conditions decreased their specific leaf area (SLA) by 23%, as well as showing reductions in stomatal conductance (G_s) and transpiration rate (T_r) along with the drought duration (p < 0.01). As the duration of post-drought rewatering increased, the reductions in the net photosynthetic rates (P_n) of P. tabulaeformis showed that the shade condition intensified its photosynthetic limitation and slowed recovery after drought. Under low-light drought, R. pseudoacacia exhibited a 52% increase in SLA and a 77% decline in G_s; the latter was markedly smaller than the reduction observed under full-light drought. After rewatering, G_s displayed an overcompensation response. The rise in specific leaf area and the greater flexibility of stomatal regulation partly offset the adverse effects of drought. Nevertheless, post-drought P_n recovered to only 40%, significantly lower than the 61% recovery under full-light drought. Moreover, the negative correlation between SLA and P_n became significantly stronger, indicating that the “after-effects” of shade–drought hindered photosynthetic recovery once the stress was relieved. Drought duration eroded the phenotypic performance in both species, while the light environment during drought and subsequent rehydration determined the time trajectory and completeness of recovery. These results validate a trade-off between shade mitigation and drought legacy, and guide species selection: plant shade-tolerant R. pseudoacacia in light-limited urban pockets and reserve sun-dependent P. tabuliformis for open, high-light sites to enhance drought resilience of Beijing’s urban forests. Full article