RSS 1.0Environmental Science and Engineering Program
For more information visit: https://bese.kaust.edu.sa/study/Pages/EnSE.aspx
Recent Submissions
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Quantifying Within-Flight Variation in Land Surface Temperature from a UAV-Based Thermal Infrared Camera(Drones, MDPI AG, 2023-10-02) [Article]Land Surface Temperature (LST) is a key variable used across various applications, including irrigation monitoring, vegetation health assessment and urban heat island studies. While satellites offer moderate-resolution LST data, unmanned aerial vehicles (UAVs) provide high-resolution thermal infrared measurements. However, the continuous and rapid variation in LST makes the production of orthomosaics from UAV-based image collections challenging. Understanding the environmental and meteorological factors that amplify this variation is necessary to select the most suitable conditions for collecting UAV-based thermal data. Here, we capture variations in LST while hovering for 15–20 min over diverse surfaces, covering sand, water, grass, and an olive tree orchard. The impact of different flying heights and times of the day was examined, with all collected thermal data evaluated against calibrated field-based Apogee SI-111 sensors. The evaluation showed a significant error in UAV-based data associated with wind speed, which increased the bias from −1.02 to 3.86 °C for 0.8 to 8.5 m/s winds, respectively. Different surfaces, albeit under varying ambient conditions, showed temperature variations ranging from 1.4 to 6 °C during the flights. The temperature variations observed while hovering were linked to solar radiation, specifically radiation fluctuations occurring after sunrise and before sunset. Irrigation and atmospheric conditions (i.e., thin clouds) also contributed to observed temperature variations. This research offers valuable insights into LST variations during standard 15–20 min UAV flights under diverse environmental conditions. Understanding these factors is essential for developing correction procedures and considering data inconsistencies when processing and interpreting UAV-based thermal infrared data and derived orthomosaics.
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Boosting all-weather atmospheric water vapor harvesting with a solar-driven membrane system(Research Square Platform LLC, 2023-09-26) [Preprint]Atmospheric water vapor harvesting (AVH) is vital to supply fresh water in arid regions. Sorbent-based harvesting stands out because it can adapt to weather conditions and utilize lowgrade energy. Current harvesting research focuses on sorbent material preparation (especially solid sorbents, such as MOFs) without integrating them into advanced water production systems. Moreover, solid sorbents show poor adaptability to changing relative humidities and temperatures in real-world applications. Here, we propose a novel AVH membrane system (AVH-MS) driven by solar energy to address these challenges. Liquid hygroscopic solutions were utilized as the working fluid in the AVH-MS to avoid the solid sorbents’ limitations. The advanced design of the AVH-MS helped boost water production and adapt to all weather conditions simultaneously. The feasibility of the system was demonstrated both theoretically and experimentally. The system could produce 6.27, 2.41, and 0.82 kg freshwater/m2/day at relative humidities of 69%, 35%, and 19% at 25 °C, respectively, using solar energy. The production improved by almost 700% compared with the reported study under the same weather condition. Our system's converted water production capacity (kg/J) is also the highest under various relative humidities compared with the reported studies.
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Emerging MXenes: Revolutionizing oily wastewater treatment - a comprehensive and critical review(Separation and Purification Technology, Elsevier BV, 2023-09-26) [Article]The detrimental impacts of oily wastewater on the environment and living organisms necessitate effective wastewater treatment methods. MXenes, with their exceptional properties, have garnered significant attention in various fields since their discovery. This review offers a critical summary of the MXene materials to be successfully employed for the efficient separation of various oily emulsions. The unique characteristics of MXenes, including high specific surface areas, active sites, hydrophilicity, environmental-friendly nature, large inter-layer spacing, high chemical stability, and superior sorption/reduction capabilities, position them as ideal candidates for oil/water (O/W) separation applications. This paper critically evaluates the O/W separation mechanisms employed by MXene-based materials, thoroughly explores the regeneration, stability, and durability performance of these materials, and highlights current challenges and research gaps. Furthermore, we present future prospects to overcome these hurdles and advance the field of MXene-based O/W separation technology.
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Mesophotic and Bathyal Palaemonid Shrimp Diversity of the Red Sea, with the Establishment of Two New Genera and Two New Species(Diversity, MDPI AG, 2023-09-22) [Article]The diversity and evolution of the Red Sea invertebrates in mesophotic and deep-water benthic ecosystems remain largely unexplored. The Palaemonidae is a diversified family of caridean shrimps with numerous taxa in need of taxonomic revisions based on recent molecular analyses. The Red Sea mesophotic and bathyal palaemonid shrimps are largely unstudied. During recent expeditions off the Red Sea coast of Saudi Arabia, several palaemonid specimens were collected at a depth range of 88–494 m, spanning the mesophotic and bathyal zones. This material was examined morphologically and genetically to infer phylogenetic relationships among the Red Sea taxa and several other palaemonid genera. The concordant morphological and genetic data led to the description of two new genera and two new species. Moreover, one species was recorded in the Red Sea for the first time, with a new host record, whereas three further deep-water species, which do not occur in the Red Sea, were formally transferred to a different genus. As more exploration efforts are deployed, research on the diversity and evolutionary relationships among marine invertebrates from the Red Sea will further underline the uniqueness of its mesophotic and bathyal fauna.
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Observation and mitigation of perimeter artefacts in bench scale membrane characterization(Desalination, Elsevier BV, 2023-09-22) [Article]Perimeter artefacts, such as test cell induced membrane damage and unrepresentative hydrodynamics, can significantly affect bench scale performance evaluation using membrane coupons. By comparing separately collected center and perimeter permeate, the effect of perimeter artefacts can be identified. The additional salt passage in the perimeter area (i.e., along the edges of the membrane coupon) depends non-linearly on pressure, and is implicitly affected by flux, temperature and salinity (osmotic pressure), leading to a potential increase of the measured salt passage by a factor two. We observed a very slow dynamic response (τ ≈ 12 h) to changes in operational conditions, suggesting that in our case the perimeter artefact was diffusive in nature. Due to this slow response, the perimeter salt passage trails previously evaluated operational conditions, possibly resulting in a false trend, hysteresis or high variance, depending on the sequential ordering and duration of test condition intervals. The effect of perimeter artefacts can be largely mitigated by measuring salt rejection from only the central area of the coupon.
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Regulation of multiple signaling pathways promotes the consistent expansion of human pancreatic progenitors in defined conditions(eLife Sciences Publications, Ltd, 2023-09-19) [Preprint]The unlimited expansion of human progenitor cells in vitro could unlock many prospects for regenerative medicine but it remains an important challenge as it requires the decoupling of the mechanisms supporting progenitor self-renewal and expansion from feed-forward mechanisms promoting their differentiation. The expansion of human pluripotent stem (hPS) cell derived pancreatic progenitors (PP) will accelerate the development of novel therapies for diabetes. We obtained mechanistic insights into the expansion requirements of PP cells and leveraged them to conduct a hypothesis-driven iterative search to identify conditions for the robust and unlimited expansion of hPS cell derived PP cells under GMP-compliant conditions. We show that the combined stimulation of specific mitogenic pathways, suppression of retinoic acid signaling and inhibition of selected branches of the TGFβ and Wnt signaling pathways are necessary for the effective decoupling of PP proliferation from differentiation. This enabled the selection of PDX1+/SOX9+/NKX6.1+ PP cells and their consistent, 2000-fold, expansion over ten passages and 40-45 days. Transcriptome analyses confirmed the stabilisation of PP identity and the effective suppression of differentiation. Using these conditions, PDX1+/SOX9+/NKX6.1+ PP cells, derived from different, both XY and XX, hPS cells lines, were enriched to nearly 90% homogeneity and expanded with very similar kinetics and efficiency. Furthermore, non-expanded and expanded PP cells, from different hPS cell lines, were differentiated in micropatterned wells into homogeneous islet-like clusters (SC-islets) with very similar efficiency. These clusters contained abundant β-cells of comparable functionality as assessed by glucose-stimulated insulin secretion assays. These findings established the signaling requirements to decouple PP proliferation from differentiation and allowed the consistent expansion of hPS cell derived PP cells. They will enable the establishment of large banks of PP cells derived under GMP conditions from diverse hPS cell lines. This will also streamline the generation of SC-islet clusters for further development of the differentiation process, diabetes research, personalized medicine and cell therapies.
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Relative Insignificance of Polyamide Layer Selectivity for Seawater Electrolysis Applications(Environmental Science & Technology, American Chemical Society (ACS), 2023-09-18) [Article]Low-cost polyamide thin-film composite (TFC) membranes are being explored as alternatives to cation exchange membranes for seawater electrolysis. An optimal membrane should have a low electrical resistance to minimize applied potentials needed for water electrolysis and be able to block chloride ions present in a seawater catholyte from reaching the anode. The largest energy loss associated with a TFC membrane was the Nernstian overpotential of 0.74 V (equivalent to 37 Ω cm<sup>2</sup> at 20 mA cm<sup>-2</sup>), derived from the pH difference between the anolyte and catholyte and not the membrane ohmic overpotential. Based on analysis using electrochemical impedance spectroscopy, the pristine TFC membrane contributed only 5.00 Ω cm<sup>2</sup> to the ohmic resistance. Removing the polyester support layer reduced the resistance by 79% to only 1.04 Ω cm<sup>2</sup>, without altering the salt ion transport between the electrolytes. Enlarging the pore size (∼5 times) in the polyamide active layer minimally impacted counterion transport across the membrane during electrolysis, but it increased the total concentration of chloride transported by 60%. Overall, this study suggests that TFC membranes with thinner but mechanically strong supporting layers and size-selective active layers should reduce energy consumption and the potential for chlorine generation for seawater electrolyzers.
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Global estimates of daily evapotranspiration using SMAP surface and root-zone soil moisture(Remote Sensing of Environment, Elsevier BV, 2023-09-17) [Article]The interplay between soil moisture and evapotranspiration modulates the water available to sustain soil evaporation and influences canopy stomatal conductance controls on vegetation transpiration. Modeling this behavior remains challenging. Indeed, satellite remote sensing based Penman-Monteith (PM) ET models tend not to directly consider soil moisture constraints on evaporation and transpiration due to a lack of consistent soil moisture data. To address this issue, we modified a PM model to include satellite enhanced surface and root zone soil moisture from the National Aeronautics and Space Administration (NASA) Soil Moisture Active Passive (SMAP) mission. The resulting model was used to produce global 9-km daily ET estimates, including contributing fluxes from soil evaporation, transpiration and evaporation of canopy-intercepted precipitation. The global PM ET estimates were assessed using in situ sap flow and AmeriFlux measurements, upscaled FLUXCOM latent heat flux, as well as against other independent global ET data products (GLEAM, GLDAS, SSEBop, and LandFlux-EVAL). The modelled transpiration showed similar seasonal variation and positive correlation to in situ sap flow measurements available from several forest sites (R2 = 0.85; p < 0.01). When compared against AmeriFlux data, the PM ET estimates showed favorable agreement with annual ET measurements extracted from 34 diverse sites (R2 = 0.58; p < 0.01; RMSE = 227 mm yr−1). The PM 8-day ET results also reflected a similar hemispheric seasonality as the global FLUXCOM record (R2 = 0.94–0.98; p < 0.01), while comparisons against other global ET products showed moderate mean differences of between 49 and 107 mm yr−1 (11–25%) over the global domain. Our PM ET estimates varied up to 52% in response to SMAP surface soil moisture dynamics, displaying stronger surface (0–5 cm depth) than root zone (0–100 cm) soil moisture sensitivity. While PM ET sensitivity to soil moisture was greater in arid climate regions, it was also significant in humid climate zones, with analysis indicating that the inclusion of soil moisture predominantly acts as a sustaining influence on ET, especially in moisture limited drylands. PM ET sensitivity to temperature was stronger in humid forest regions relative to other climate and land cover regimes. Overall, the model results clarify the influence of soil moisture heterogeneity on the global ET pattern as informed by satellite-based estimates of surface and root zone soil moisture. Potential enhancements to the spatial and vertical resolution of soil moisture inputs are expected to enable further ET improvements through more realistic model representation of soil and plant available water.
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Solution-processable poly(ether-ether-ketone) membranes for organic solvent nanofiltration: from dye separation to pharmaceutical purification(Separation and Purification Technology, Elsevier BV, 2023-09-15) [Article]Through polymer engineering, the membrane properties can be considerably changed and its performance can be improved. Organic solvent nanofiltration (OSN) membranes require polymers with good solution processability to facilitate membrane preparation. However, the resultant membranes should have excellent solvent resistance. Poly(ether-ether-ketone) (PEEK) is a potential polymer for OSN applications because of its high thermal stability and excellent solvent resistance. However, commercial PEEK has limited solution processability, and its fabrication requires a harsh acidic environment. Herein, two customized PEEKs were synthesized by incorporating methyl (–CH3) and sulfonyl (SO2) groups into the polymer backbone. The membranes were prepared by phase inversion using N-methyl-2-pyrrolidone (NMP) and TamiSolve as a green alternative. The effects of the polymer structure, green solvent, and crosslinking on the membrane morphology, chemical and mechanical stability, as well as separation performance have been examined. The molecular interaction between organic solvents and PEEKs were investigated through molecular dynamic simulations and density functional theory. The molecular weight cutoff (MWCO) values of the membranes were 540–768 g mol−1, with a high corresponding permeance of 8.2–20 L m−2 h−1 bar−1 in acetone. The long-term stability of membranes was successfully demonstrated over two weeks through a continuous crossflow filtration using acetone under a pressure of 30 bar. The membranes demonstrated excellent active pharmaceutical ingredient purification through the removal a 2-methoxyethoxymethyl chloride (125 g mol−1) carcinogenic impurity from roxithromycin (837 g mol−1).
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Evaluation of Potential Peptide-Based Inhibitors Against SARS-CoV-2 and Variants of Concern(Accepted by BioMed Research International, 2023-09-11) [Article]The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has greatly affected all aspect of life. Although several vaccines and pharmaceuticals have been developed against SARS-CoV-2, the emergence of mutated variants has raised several concerns. The angiotensin-converting enzyme (ACE2) receptor cell entry mechanism of this virus has not changed despite the vast mutation in emerging variants. Inhibiting the spike protein by which the virus identifies the host ACE2 receptor is a promising therapeutic countermeasure to keep pace with rapidly emerging variants. Here, we synthesized two ACE2-derived peptides, P1 and P25, to target and potentially inhibit SARS-CoV-2 cell entry. These peptides were evaluated in vitro using pseudoviruses that contained the SARS-CoV-2 original spike protein, the Delta mutated spike protein, or the Omicron spike protein. An in silico investigation was also done for these peptides to evaluate the interaction of the synthesized peptides and the SARS-CoV-2 variants. The P25 peptide showed a promising inhibition potency against the tested pseudoviruses and an even higher inhibition against the Omicron variant. The IC50 of the Omicron variant was 60.8 µM, while the IC50s of the SARS-CoV-2 original strain and the Delta variant were 455.2 µM and 546.4 µM, respectively. The in silico experiments also showed that the amino acid composition design and structure of P25 boosted the interaction with the spike protein. These findings suggest that ACE2- derived peptides, such as P25, have the potential to inhibit SARS-CoV-2 cell entry in vitro. However, further in vivo studies are needed to confirm their therapeutic efficacy against emerging variants.
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An increasing trend in daily monsoon precipitation extreme indices over Pakistan and its relationship with atmospheric circulations(Frontiers in Environmental Science, Frontiers Media SA, 2023-09-08) [Article]This study assessed spatiotemporal trends in daily monsoon precipitation extremes at seasonal and sub-seasonal scales (June, July, August, and September) and their links with atmospheric circulations over Pakistan. The study used observed precipitation data from fifty in-situ stations and reanalysis products from the European Centre for Medium-Range Weather Forecasts (ECMWF) and National Centers for Environmental Prediction/the National Center for Atmospheric Research (NCEP/NCAR) during 1981–2018. A suite of seven extreme precipitation indices and non-parametric statistical techniques were used to infer trends in the frequency and intensity of extreme precipitation indices. An increase in frequency and intensity of overall extreme indices was evident, with a maximum tendency in the country’s northwestern (z-score=>2.5), central, and eastern (z-score > 4) monsoon-dominant parts. The northern and southwestern parts of the country exhibited a slight decrease (z-score <–2) in frequency and intensity. The Sen’s Slope estimator (SSE) shows an increase in western parts (0.20 days) indicating a shift in the maxima of the monsoon precipitation. The regional precipitation shows an increase in wet days (R1 mm) with higher values of mMK (3.71) and SSE (0.3) in region 2 Similar results of moderate regional increase are evident for extreme indices except regions 1 and 3. The extreme 1-day maximum precipitation increased in region 3 (mMK: 1.39, SSE: 2.32). The extremely wet days (R99p TOT) precipitation has a moderate increase in all regions with a decrease in region 1. The temporal mutations showed dynamic changes, clearly reflecting the country’s historical extreme events. The frequency and intensity of precipitation extremes negatively correlated with the altitude (R = −0.00039). The probability density function (PDF) showed a significant increase in the density during June and September with a probabilistic positive shift during July and August. The intensified mid-latitude westerlies and subtropical zonal easterlies teleconnections, strengthening of the monsoon trough, and land-ocean thermal contrast are the potential drivers of the increasing trend in precipitation extremes. The current study could serve as a benchmark for future researchers and policymakers to devise effective mitigation strategies for sustainable development.
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Boosting all-weather atmospheric vapor harvesting with membrane distillation system powered by solar energy(Research Square Platform LLC, 2023-09-06) [Preprint]Atmospheric vapor harvesting represents an important freshwater supply. Sorbent-based atmospheric vapor harvesting stands out because it can adapt to various weather conditions and can utilize low-grade energy. Current sorbent-based atmospheric vapor harvesting research focuses on the preparation of sorbent materials (especially solid sorbents, e.g., MOFs) without integrating them into an advanced water production system. Moreover, solid sorbents are faced with poor adaptivity to changing relative humidity in real applications. To address the issues, we proposed a novel atmospheric vapor harvesting membrane distillation system (AVH-MD) that can boost water production and adapt to all-weather conditions simultaneously. The feasibility of the system was demonstrated by both theoretical and experimental tools. The system could produce 6.27, 2.41, and 0.82 kg freshwater/m2/day at relative humidities of 69%, 35%, and 19% at 25 OC, respectively. The production improved by almost 700% compared with the reported studies under the same condition. The converted water production capacity (kg/J) in our system is also the highest under various relative humidities compared with the reported studies.
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Hydrocarbon-based membranes cost-effectively manage species transport and increase performance in thermally regenerative batteries(Electrochimica Acta, Elsevier BV, 2023-09-05) [Article]Low-temperature heat (T<130°C) can be utilized by thermally regenerative batteries (TRBs) for power production, allowing the thermal energy to be converted to storable chemical potential energy. However, TRBs suffer from high ohmic losses and ammonia crossover, which has slowed their development. In this study, we examined how the use of six different membranes influenced TRB performance, determined the most influential membrane parameters, and identified promising membrane candidates that cost-effectively increase TRB performance. Of the six membranes examined, an inexpensive, hydrocarbon CEM (Selemion CMVN) had low ammonia crossover without compromising resistance, resulting in good performance across all metrics studied. A thin anion exchange membrane (Sustainion, 50 microns) showed a high peak power density of 82 mW cm−2 due to low resistance, but the average power density and energy density were low due to high ammonia flux. Full discharge curves using Selemion CMVN provided an average power density of 26 ± 7 mW cm−2 with an energy density of 2.9 Wh L−1, which were large improvements on previous TRBs. A techno-economic analysis showed that Selemion CMVN had the lowest levelized cost of storage ($410 per MWh) at an applied current density of 50 mA cm−2.
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Selected physical and chemical cleanings remove biofilm in seawater membrane distillation without causing pore wetting(npj Clean Water, Springer Science and Business Media LLC, 2023-09-05) [Article]Membrane distillation (MD) is an emerging process with a proven ability to recover freshwater from streams with a wide range of salinities. However, MD is susceptible to biofouling. This study explores the efficiency of different cleaning strategies in biofilm removal during seawater MD. Hydraulic cleaning and chemical cleanings with 0.3%w w−1 ethylenediaminetetraacetic acid (EDTA), 0.3%w w−1 NaOCl, and 3%w w−1 citric acid were tested. The results showed that permeate flux recovery increased in the order of hydraulic cleaning <3%w w−1 citric acid <0.3%w w−1 NaOCl ≈0.3%w w−1 EDTA. Membrane cleanings substantially reduced the thickness of the residual biofilm layer and decreased its bacterial concentration and resistance to vapor pressure. The post-cleaning permeate conductivities were low suggesting that employed cleaning protocols did not cause pore wetting of hydrophobic polytetrafluoroethylene microporous (0.22 μm) membrane, and membrane rejection properties remained stable.
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Photo-Chemical Stimulation of Neurons with Organic Semiconductors(Advanced Science, Wiley, 2023-09-03) [Article]Recent advances in light-responsive materials enabled the development of devices that can wirelessly activate tissue with light. Here it is shown that solution-processed organic heterojunctions can stimulate the activity of primary neurons at low intensities of light via photochemical reactions. The p-type semiconducting polymer PDCBT and the n-type semiconducting small molecule ITIC (a non-fullerene acceptor) are coated on glass supports, forming a p–n junction with high photosensitivity. Patch clamp measurements show that low-intensity white light is converted into a cue that triggers action potentials in primary cortical neurons. The study shows that neat organic semiconducting p–n bilayers can exchange photogenerated charges with oxygen and other chemical compounds in cell culture conditions. Through several controlled experimental conditions, photo-capacitive, photo-thermal, and direct hydrogen peroxide effects on neural function are excluded, with photochemical delivery being the possible mechanism. The profound advantages of low-intensity photo-chemical intervention with neuron electrophysiology pave the way for developing wireless light-based therapy based on emerging organic semiconductors.
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Ptychographic X-ray computed tomography of porous membranes with nanoscale resolution(Communications Materials, Springer Science and Business Media LLC, 2023-09-02) [Article]New visualization methods can be utilized to resolve structures at resolutions that were previously unachievable. 3D images of porous materials with high resolution have been so far obtained using transmission electron tomography or focused ion beam coupled with scanning electron microscopy. For these methods, ultra-vacuum is required, and only a small volume of the sample is visualized. Here, we demonstrate the application of ptychographic X-ray computed tomography for the visualization of soft matter with a resolution of 26 nm over large fields of view. Thanks to the high-penetration depth of the X-ray beam, we visualize the 3D complex porous structure of polyetherimide hollow fibers in a non-destructive manner and obtain quantitative information about pore size distribution and pore network interconnectivity across the whole membrane wall. The non-destructive nature of this method, coupled with its ability to image samples without requiring modification or a high vacuum environment, makes it valuable in the fields of porous- and nano-material sciences enabling imaging under different environmental conditions.
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Controlling the degree of acetylation in cellulose-based nanofiltration membranes for enhanced solvent resistance(Journal of Membrane Science, Elsevier BV, 2023-09-01) [Article]Increasing concerns associated with the environment and global warming have triggered the exploration of the preparation of greener membranes. The abundance of renewable cellulosic biomass offers an excellent source material for membrane fabrication. In particular, cellulose acetate (CA) has been widely used as a membrane material. In this study, we explore the effect of the degree of acetylation (DoA) on membrane performance in organic solvents for the first time. We prepared CA membranes using nonsolvent-induced phase separation with Cyrene as a green solvent. Deacetylation was directly performed on the CA membranes to obtain a final DoA in the range of 1.2%–39.3%. The solvent resistance of the membranes increased as the DoA decreased. The membranes exhibited constant permeance at a pressure of 30 bar, which suggested the absence of compaction. Increasing the DoA increased the permeance of the polar aprotic solvents, whereas the permeance of the polar protic solvents showed the opposite trend. The hydrophilicity of the membranes increased with a decrease in the DoA, whereas the glass transition temperature remained quasi-constant and excellent thermal stability was maintained. The separation performance was fine-tuned with a molecular weight cut-off that ranged from 325 to 950 g mol−1 as a function of the DoA. Our results offer new avenues for tailoring solvent-resistant membrane materials from renewable polymers and solvents for application in harsh organic media.
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Synaptic and transcriptomic features of cortical and amygdala pyramidal neurons predict inefficient fear extinction.(Cell reports, Elsevier BV, 2023-08-31) [Article]Fear-related disorders arise from inefficient fear extinction and have immeasurable social and economic costs. Here, we characterize mouse phenotypes that spontaneously show fear-independent behavioral traits predicting adaptive or maladaptive fear extinction. We find that, already before fear conditioning, specific morphological, electrophysiological, and transcriptomic patterns of cortical and amygdala pyramidal neurons predispose to fear-related disorders. Finally, by using an optogenetic approach, we show the possibility to rescue inefficient fear extinction by activating infralimbic pyramidal neurons and to impair fear extinction by activating prelimbic pyramidal neurons.
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Using High Spatial Resolution Satellite Imagery for Improved Agricultural Management of Mediterranean Orchards(Elsevier BV, 2023-08-29) [Preprint]Most orchards within the Mediterranean basin tend to be irrigated. Accurate knowledge of their water requirements is essential due to both increasing droughts and water restrictions. However, determining the water needs of fruit crops can be challenging, as they depend on factors like soil, climate, and temporal variations in leaf development. Remote sensing at high spatial and temporal resolution offers the possibility to provide the information required for crop monitoring. This study proposes several methods for detecting agricultural patterns and variables affecting water requirements in orchards, such as tree age, inter-row grassiness, tree density. Three methods to assess water volumes applied to orchards were compared, with one method using variables derived from remote sensing. Various high-resolution remote sensing images were used: -Sentinel 2 data (2016-2023), 1 Pleiades image (2022) and the extraction of Google-satellite-hybrid images (GSH,2017). The methods were evaluated from a large dataset of ground observations including the boundaries of plots and land-use (1430 orchards, among them we collected accurate information on 366 fields). Surveys on the agricultural practices were carried out among 22 farmers on 749 fields. Using these farm-specific surveys, it was observed that the studied orchards were irrigated for durations varying between 3-300 hours/year, with farmers basing their irrigation decisions on tree density and plot age. Thresholding on the NDVI Sentinel 2 in the summer period allowed the identification of young orchards with an accuracy of 98%. With Pleiades and GSH, the blue band was used and two thresholds were defined to separate pixels with trees, grass or bare-soil. Supervised classification was then employed to separate grassed and non-grassed plots using three spectral bands of Sentinel 2. Classifications performed from GSH images gave more accurate results (81% well classified) compared with Sentinel 2 (79%) and Pleiades (57%) when identifying grassed plots, although results can vary with acquisition date. A pattern detection algorithm based on a Marked Point Process was applied to the GSH and Pleaides images that allowed the number of trees to be determined, yielding an r²=0.9 against ground-based accounting. Derived variables improved accuracy in computing water requirements for surveyed orchards at the watershed scale.
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Response of Ecosystem Productivity to High Vapor Pressure Deficit and Low Soil Moisture: Lessons Learned From the Global Eddy-Covariance Observations(Earth's Future, American Geophysical Union (AGU), 2023-08-25) [Article]Although there is mounting concern about how high vapor pressure deficit (VPD) and low soil moisture (SM) affect ecosystem productivity, their relative importance is still under debate. Here, we comprehensively quantified the relative impacts of these two factors on ecosystem gross primary production (GPP) using observations from a global network of eddy-covariance towers and two approaches (sensitivity analysis and linear regression model). Both approaches agree that a higher percentage of sites experience GPP reduction from high VPD than from low SM over the growing season. However, the constraint of high VPD and low SM on GPP reduction is tightly linked with climates and plant functional types. Humid and mesic ecosystems including forests and grasslands are dominated by VPD, while the semi-arid and arid ecosystems including shrublands and savannas are dominated by SM. The varying dominant role of these two factors on GPP is closely related to plant stomatal behavior, as predicted by a stomatal conductance model. Additionally, we highlight the non-linear impact of SM on GPP during droughts and the possible underestimation of the SM effects for deep-rooted plants when only using surface-layer SM. Our results shed light on a better understanding of the impacts of VPD and SM on vegetation productivity, with important implications for modeling the response and feedback of ecosystem dynamics to current and future climates.
