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Xue, B. ; Helman, D. ; Wang, G. ; Xu, C. - Y. ; Xiao, J. ; Liu, T. ; Wang, L. ; Li, X. ; Duan, L. ; Lei, H. The low hydrologic resilience of Asian Water Tower basins to adverse climatic changes. 2021, 155, 103996. Publisher's VersionAbstract
Climate change has a significant impact on the runoff of basins in cold, dry areas. The quantification of regional ecohydrological responses to climate change such as warming and drought is essential for establishing proper water resource management schemes. We propose a simple and novel method based on the Budyko framework to evaluate the hydrologic resilience of 16 basins that conform the Asian Water Tower in the Tibetan Plateau (TP). Our method defines two metrics within the Budyko domain – tolerance (ψ) and plasticity (φ) – that characterize the hydrologic resilience of a basin. Based on an ecohydrological point of view, a basin is considered hydrologically resilient if ψ and φ are both greater than 1 or its φ is negative and ψ is greater than 1. Our results show that ψ varies between 0.27 and 0.74, with an average value of 0.45 and φ varies between 2 and 16.33, with an average value of 6.90, for 14 out of the 16 basins. Only two basins – Taohe and Datonghe – had negative φ (-11.67 and -8.11, respectively) and ψ greater than 1 (2.26 and 19.58, respectively), suggesting that these two are the only basins with a hydrologic resilience to climatic warming/drying in the TP. Within the non-resilient basins, we found vegetation to play a key role in the level of tolerance and plasticity indicating that basins with a larger vegetation cover display a lower capability to adapt to adverse climatic changes. Following these results, we call for afforestation efforts to be carefully considered in cold, dry areas. The proposed method and conclusions drawn by this study may help predict the hydrologic responses to future adverse climatic conditions.
Saadon, T. ; Lazarovitch, N. ; Jerszurki, D. ; Tas, E. Predicting net radiation in naturally ventilated greenhouses based on outside global solar radiation for reference evapotranspiration estimation. Agricultural Water Management 2021, 257, 107102. Publisher's VersionAbstract
A reliable prediction of net radiation (Rn) inside naturally ventilated greenhouses is critical for accurate evapotranspiration evaluation and thus for water saving, considering that previous studies have indicated that evapotranspiration in such relatively decoupled greenhouses is predominantly controlled by greenhouse Rn (Rn-GH). We hypothesized here that Rn-GH in naturally ventilated greenhouses can be accurately predicted using global solar radiation in the vicinity of the greenhouse (Rs-out) as the only measured parameter, together with the calculated position of the sun, defined by the solar elevation angle and solar azimuth. To test this hypothesis, we performed experiments in two adjacent greenhouses in the Southern Negev, Israel (30.96° N, 34.69° E) under arid climate. In one of the greenhouses, tomato was grown during winter 2017–2018, while in the other, melon was grown during winter and spring 2018–2019. Our analyses demonstrated that Rn-GH can be accurately predicted (r2 = 0.982) using Rs-out as the only measured parameter, while the global solar radiation inside the greenhouse (Rs-GH), and the ratio between Rn-GH and Rs-GH are predominantly dependent on solar elevation angle and solar azimuth, as well as the greenhouse structure and cloud cover. This paper shows that the impact of these properties on the association between Rs-out and Rn-GH can be accurately resolved using multivariate regression by the k-nearest neighbors approach. This suggests that computerized modeling of the greenhouse structure and light transmission can potentially enable precise evaluation of Rn-GH and therefore also reference evapotranspiration in naturally ventilated greenhouses, using Rs-out as the only measured parameter. A calculation-based factor for the cloud effect on Rs-out transmittance into the greenhouse significantly improved the Rn-GH prediction under cloudy conditions.
Jerszurki, D. ; Saadon, T. ; Zhen, J. ; Agam, N. ; Tas, E. ; Rachmilevitch, S. ; Lazarovitch, N. Vertical microclimate heterogeneity and dew formation in semi-closed and naturally ventilated tomato greenhouses. Scientia Horticulturae 2021, 288, 110271. Publisher's VersionAbstract
The extent of the vertical microclimate heterogeneity inside a greenhouse is mostly unknown, and it can strongly affect plant production and yield quality. Tomato crop was grown in a semi-closed greenhouse equipped with horizontal ventilation and sidewall curtains, which were only opened depending on microclimate conditions; and a naturally ventilated greenhouse equipped with sidewalls curtains that were kept open. Both greenhouses had a 1,000-m2 area and a net size of 50-mesh, and were located in an arid climate zone in Israel. Vertical profiles of CO2 concentration, actual vapor pressure, air, leaf and soil temperature, net CO2 assimilation rates, stomatal conductance, and total fruit yield, fresh mass, and quality were monitored in both greenhouses for 13 days, in January 2018; CO2 concentration, actual vapor pressure, and air and soil temperature were additionally monitored in the semi-closed greenhouse for seven days in December 2016, when the ventilation was inoperative, and in December 2017, with ventilation. The vertical air temperature gradient, along with the colder microclimate inside the naturally ventilated greenhouse, led to a lack of plant uniformity and yield loss. Closing the side curtains in the fanned semi-closed greenhouse had a beneficial effect on yield, however, with mixed results for quality, due to the higher air temperature and lower carbon dioxide levels at the upper canopy. Horizontal air circulation in the semi-closed greenhouse increased transpiration and assimilation, and increased dew occurrence at night, but did not reduce the vertical heterogeneity. Significant vertical gradients affect plant physiology, and closing the curtains in winter cultivation in semi-arid/arid climates has the potential to improve fruit yield and quality. However, it must be coupled with proper air circulation and, preferably, with CO2 enrichment, or careful management of natural ventilation through side curtains, in order to maximize CO2 replenishment while minimizing heat losses.
Klausner, Z. ; Ben-Efraim, M. ; Arav, Y. ; Tas, E. ; Fattal, E. The Micrometeorology of the Haifa Bay Area and Mount Carmel during the Summer. Atmosphere 2021, 12. Publisher's VersionAbstract
The Haifa bay area (HBA), which includes Mount Carmel and the Zevulun valley is the third largest metropolitan area in Israel. It is also a centre of heavy industry and an important transportation hub which serve as sources of local anthropogenic pollution. Such sources are associated with adverse health effects. In order to estimate the possible exposure of the inhabitants in such heterogeneous orographic area, a detailed atmospheric transport and dispersion modelling study is required, which in turn must take into account the local micrometeorology. The aim of this study is to conduct a spatio-temporal analysis of the flow field in the HBA in order to identify the common patterns of the average wind and characterize the statistical parameters of turbulence in this area, essential for detailed pollutants dispersion modelling. This study analyses data collected during four months of summer in a network of 16 weather stations which extend across Mount Carmel and the Zevulun valley. It was found that, during the evening and night time on Mount Carmel, different flow patterns may develop on each side, separated by the watershed line. When such conditions do not develop, as well as during the daytime, the wind field, both on Mount Carmel and the Zevulun valley is approximately homogenous. The analysis of the Monin–Obukhov similarity theory functions for the velocity standard deviations show a distinct difference between Mount Carmel and the Zevulun valley, as well as between strong and weak winds. This difference can be clearly seen also in the diurnal hourly distribution of atmospheric stabilities which exhibit higher proportions of unstable conditions in the Zevulun valley during day time and higher proportion of stable stratifications at the Mount Carmel during night-time.
Hendel, E. ; Bacher, H. ; Oksenberg, A. ; Walia, H. ; Schwartz, N. ; Peleg, Z. Deciphering the genetic basis of wheat seminal root anatomy uncovers ancestral axial conductance alleles. Plant, Cell & EnvironmentPlant, Cell & EnvironmentPlant Cell Environ 2021, n/a. Publisher's VersionAbstract
ABSTRACT Root axial conductance which describes the ability of water to move through the xylem, contributes to the rate of water uptake from the soil throughout the whole plant lifecycle. Under the rainfed wheat agro-system, grain-filling is typically occurring during declining water availability (i.e. terminal drought). Therefore, preserving soil water moisture during grain filling could serve as a key adaptive trait. We hypothesized that lower wheat root axial conductance can promote higher yields under terminal drought. A segregating population derived from a cross between durum wheat and its direct progenitor wild emmer wheat was used to underpin the genetic basis of seminal root architectural and functional traits. We detected 75 QTL associated with seminal roots morphological, anatomical, and physiological traits, with several hotspots harboring co-localized QTL. We further validated the axial conductance and central metaxylem QTL using wild introgression lines. Field-based characterization of genotypes with contrasting axial conductance suggested the contribution of low axial conductance as a mechanism for water conservation during grain filling and consequent increase in grain size and yield. Our findings underscore the potential of harnessing wild alleles to reshape the wheat root system architecture and associated hydraulic properties for greater adaptability under changing climate. This article is protected by copyright. All rights reserved.
Shiff, S. ; Helman, D. ; Lensky, I. M. Worldwide continuous gap-filled MODIS land surface temperature dataset. Scientific Data 2021, 8 74 - 74. Publisher's VersionAbstract
Satellite land surface temperature (LST) is vital for climatological and environmental studies. However, LST datasets are not continuous in time and space mainly due to cloud cover. Here we combine LST with Climate Forecast System Version 2 (CFSv2) modeled temperatures to derive a continuous gap filled global LST dataset at a spatial resolution of 1 km. Temporal Fourier analysis is used to derive the seasonality (climatology) on a pixel-by-pixel basis, for LST and CFSv2 temperatures. Gaps are filled by adding the CFSv2 temperature anomaly to climatological LST. The accuracy is evaluated in nine regions across the globe using cloud-free LST (mean values: R2 = 0.93, Root Mean Square Error (RMSE) = 2.7 °C, Mean Absolute Error (MAE) = 2.1 °C). The provided dataset contains day, night, and daily mean LST for the Eastern Mediterranean. We provide a Google Earth Engine code and a web app that generates gap filled LST in any part of the world, alongside a pixel-based evaluation of the data in terms of MAE, RMSE and Pearson’s r.
Michael, Y. ; Helman, D. ; Glickman, O. ; Gabay, D. ; Brenner, S. ; Lensky, I. M. Forecasting fire risk with machine learning and dynamic information derived from satellite vegetation index time-series. 2021, 764, 142844. Publisher's VersionAbstract
Fire risk mapping – mapping the probability of fire occurrence and spread – is essential for pre-fire management as well as for efficient firefighting efforts. Most fire risk maps are generated using static information on variables such as topography, vegetation density, and fuel instantaneous wetness. Satellites are often used to provide such information. However, long-term vegetation dynamics and the cumulative dryness status of the woody vegetation, which may affect fire occurrence and spread, are rarely considered in fire risk mapping. Here, we investigate the impact of two satellite-derived metrics that represent long-term vegetation status and dynamics on fire risk mapping – the long-term mean normalized difference vegetation index (NDVI) of the woody vegetation (NDVIW) and its trend (NDVIT). NDVIW represents the mean woody density at the grid cell, while NDVIT is the 5-year trend of the woody NDVI representing the long-term dryness status of the vegetation. To produce these metrics, we decompose time-series of satellite-derived NDVI following a method adjusted for Mediterranean woodlands and forests. We tested whether these metrics improve fire risk mapping using three machine learning (ML) algorithms (Logistic Regression, Random Forest, and XGBoost). We chose the 2007 wildfires in Greece for the analysis. Our results indicate that XGBoost, which accounts for variable interactions and non-linear effects, was the ML model that produced the best results. NDVIW improved the model performance, while NDVIT was significant only when NDVIW was high. This NDVIW–NDVIT interaction means that the long-term dryness effect is meaningful only in places of dense woody vegetation. The proposed method can produce more accurate fire risk maps than conventional methods and can supply important dynamic information that may be used in fire behavior models.
Weksler, S. ; Rozenstein, O. ; Haish, N. ; Moshelion, M. ; Wallach, R. ; Ben-Dor, E. Detection of Potassium Deficiency and Momentary Transpiration Rate Estimation at Early Growth Stages Using Proximal Hyperspectral Imaging and Extreme Gradient Boosting. Sensors 2021, 21. Publisher's VersionAbstract
Potassium is a macro element in plants that is typically supplied to crops in excess throughout the season to avoid a deficit leading to reduced crop yield. Transpiration rate is a momentary physiological attribute that is indicative of soil water content, the plant’s water requirements, and abiotic stress factors. In this study, two systems were combined to create a hyperspectral–physiological plant database for classification of potassium treatments (low, medium, and high) and estimation of momentary transpiration rate from hyperspectral images. PlantArray 3.0 was used to control fertigation, log ambient conditions, and calculate transpiration rates. In addition, a semi-automated platform carrying a hyperspectral camera was triggered every hour to capture images of a large array of pepper plants. The combined attributes and spectral information on an hourly basis were used to classify plants into their given potassium treatments (average accuracy = 80%) and to estimate transpiration rate  
Zaarur, S. ; Stein, M. ; Adam, O. ; Mingram, J. ; Liu, J. ; Wu, J. ; Raveh-Rubin, S. ; Erel, Y. Synoptic stability and anomalies in NE China inferred from dust provenance of Sihailongwan maar sediments during the past ∼80 kyr. 2020, 239, 106279. Publisher's VersionAbstract
The paleo-synoptic conditions that prevailed during the past ∼80 kyr in northeastern China are inferred from the elemental and Sr–Nd isotopic compositions of Lake Sihailongwan Maar sediments. The detrital fraction in the lake sediments is dominated by aeolian input of felsic-rock origin, with little contribution of local volcanic material. Based on the isotopic Sr–Nd composition of the lake core-sediments, we postulate that the deserts of northern China are the main source of allochthonous particles to the lake throughout the past ∼80 kyr. Northwesterly winds associated with the East Asian winter monsoon and high latitude westerlies are the main carriers of dust from these deserts to the lake. The deserts of central China are an additional minor dust source. The episodic dust input from these deserts results from anomalous dry southwesterly winds. These could be related to either El Niño conditions, or to delays in the onset of the East Asian summer monsoon rains.
Xue, B. ; Wang, G. ; Xiao, J. ; Helman, D. ; Sun, W. ; Wang, J. ; Liu, T. Global convergence but regional disparity in the hydrological resilience of ecosystems and watersheds to drought. 2020, 591, 125589. Publisher's VersionAbstract
Drought is a major climate disturbance that can lower vegetation productivity and induce widespread vegetation die-off, which in turn can have a profound effect on the water cycle. Therefore, quantification of vegetation-specific responses to drought is essential to predict the impacts of climate change on ecosystem services. We used two previously-suggested quantitative metrics – dynamic deviation (d) and elasticity (e) based on the Budyko framework –to evaluate site- and watershed-level hydrological resilience of different plant functional types (PFTs) to drought. By using data from 41 FLUXNET sites and 2275 watersheds, we found a global convergence in hydrological resilience to drought across a variety of PFTs. Hydrological resilience of vegetation was related to drought intensity and water use efficiency. A greater hydrological resilience was found in PTFs in drier areas than in wetter areas, while this greater hydrological resilience was related to the coefficient of variation in precipitation. We also found that PFTs with a larger water use efficiency had higher hydrological resilience, particularly in drier regions, indicating adaptation strategies to changes in local climate conditions. Our findings can shed light on how ecosystems and watersheds dominated by different PFTs will respond to future climatic change and inform water resources management.
Helman, D. ; Zaitchik, B. F. ; Funk, C. Climate has contrasting direct and indirect effects on armed conflicts. Environmental Research Letters 2020, 15, 104017. Publisher's VersionAbstract
There is an active debate regarding the influence that climate has on the risk of armed conflict, which stems from challenges in assembling unbiased datasets, competing hypotheses on the mechanisms of climate influence, and the difficulty of disentangling direct and indirect climate effects. We use gridded historical non-state conflict records, satellite data, and land surface models in a structural equation modeling approach to uncover the direct and indirect effects of climate on violent conflicts in Africa and the Middle East (ME). We show that climate–conflict linkages in these regions are more complex than previously suggested, with multiple mechanisms at work. Warm temperatures and low rainfall direct effects on conflict risk were stronger than indirect effects through food and water supplies. Warming increases the risk of violence in Africa but unexpectedly decreases this risk in the ME. Furthermore, at the country level, warming decreases the risk of violence in most West African countries. Overall, we find a non-linear response of conflict to warming across countries that depends on the local temperature conditions. We further show that magnitude and sign of the effects largely depend on the scale of analysis and geographical context. These results imply that extreme caution should be exerted when attempting to explain or project local climate–conflict relationships based on a single, generalized theory.
Gabay, M. ; Raveh-Rubin, S. ; Peleg, M. ; Fredj, E. ; Tas, E. Is oxidation of atmospheric mercury controlled by different mechanisms in the polluted continental boundary layer vs. remote marine boundary layer?. Environmental Research Letters 2020, 15, 064026. Publisher's VersionAbstract
Deposition of atmospheric mercury is of global concern, primarily due to health effects associated with efficient bioaccumulation of mercury in marine food webs. Although oxidation of gaseous elementary mercury (GEM), the major fraction of atmospheric mercury, is a critical stage in regulating atmospheric mercury deposition efficiency, this oxidation is currently not well-characterized, limiting modeling-based assessments of mercury in the environment. Based on a previous study, we hypothesized that the oxidation of GEM is predominantly controlled by multistep bromine- and chlorine-induced oxidation (MBCO) in the remote marine boundary layer (RMBL), and by photochemical smog oxidants, primarily ozone (O3) and hydroxyl radical (OH), in the polluted continental boundary layer (PCBL). To test this hypothesis, we used the following analyses: (i) application of a newly developed criterion to evaluate the gaseous oxidized mercury (GOM)–O3 association based on previous studies in the RMBL and PCBL; (ii) measurement-based box simulations of GEM oxidation in the RMBL and at a PCBL site; and (iii) measurement-based analysis of photochemical oxidation vs. other processes which potentially influence GOM. Our model simulations indicated that the MBCO mechanism can reproduce GOM levels in the RMBL, but not in the PCBL. Our data analysis suggested the important role of photochemical smog oxidants in GEM oxidation in the PCBL, potentially masked by the effect of relative humidity and entrainment of free tropospheric air.
Dayan, C. ; Fredj, E. ; Misztal, P. K. ; Gabay, M. ; Guenther, A. B. ; Tas, E. Emission of biogenic volatile organic compounds from warm and oligotrophic seawater in the Eastern Mediterranean. Atmospheric Chemistry and Physics 2020, 20, 12741–12759. Publisher's Version
Dalal, A. ; Shenhar, I. ; Bourstein, R. ; Mayo, A. ; Grunwald, Y. ; Averbuch, N. ; Attia, Z. ; Wallach, R. ; Moshelion, M. A Telemetric, Gravimetric Platform for Real-Time Physiological Phenotyping of Plant–Environment Interactions. 2020, e61280. Publisher's VersionAbstract
Food security for the growing global population is a major concern. The data provided by genomic tools far exceeds the supply of phenotypic data, creating a knowledge gap. To meet the challenge of improving crops to feed the growing global population, this gap must be bridged.Physiological traits are considered key functional traits in the context of responsiveness or sensitivity to environmental conditions. Many recently introduced high-throughput (HTP) phenotyping techniques are based on remote sensing or imaging and are capable of directly measuring morphological traits, but measure physiological parameters mainly indirectly. This paper describes a method for direct physiological phenotyping that has several advantages for the functional phenotyping of plant–environment interactions. It helps users overcome the many challenges encountered in the use of load-cell gravimetric systems and pot experiments. The suggested techniques will enable users to distinguish between soil weight, plant weight and soil water content, providing a method for the continuous and simultaneous measurement of dynamic soil, plant and atmosphere conditions, alongside the measurement of key physiological traits. This method allows researchers to closely mimic field stress scenarios while taking into consideration the environment’s effects on the plants’ physiology. This method also minimizes pot effects, which are one of the major problems in pre-field phenotyping. It includes a feed-back fertigation system that enables a truly randomized experimental design at a field-like plant density. This system detects the soil-water-content limiting threshold (θ) and allows for the translation of data into knowledge through the use of a real-time analytic tool and an online statistical resource. This method for the rapid and direct measurement of the physiological responses of multiple plants to a dynamic environment has great potential for use in screening for beneficial traits associated with responses to abiotic stress, in the context of pre-field breeding and crop improvement.
Topaz, T. ; Boxall, A. ; Suari, Y. ; Egozi, R. ; Sade, T. ; Chefetz, B. Ecological Risk Dynamics of Pharmaceuticals in Micro-Estuary Environments. Environmental Science & TechnologyEnvironmental Science & Technology 2020. Publisher's VersionAbstract
Micro-estuarine ecosystems have a surface area <1 km2 and are abundant in Mediterranean regions. As a result of their small size, these systems are particularly vulnerable to the effects of chemical pollution. Due to the fluctuating flow conditions of base flow dominated by treated wastewater effluents and flood events transporting rural and urban non-point-source pollution, micro-estuaries are under a dynamic risk regime, consequently struggling to provide ecological services. This 2 year study explored the occurrence and risks of pharmaceutical contamination in the Alexander micro-estuary in Israel. Pharmaceuticals were detected in all samples (n = 280) at as high as 18 μg L–1 in flood events and 14 μg L–1 in base flow. The pharmaceutical mixture composition was affected by flow conditions with carbamazepine dominating the base flow and caffeine dominating flood events. The median annual risk quotients for fish, crustaceans, and algae were 19.6, 5.2, and 4.5, respectively, indicating that pharmaceuticals pose a high risk to the ecosystem. Ibuprofen, carbamazepine, and caffeine contributed most to the risk quotients. The current work highlights that micro-estuary ecosystems, like the Alexander estuary, are continuously exposed to pharmaceuticals and most likely to other pollutants, placing these ecologically important systems under an elevated risk in comparison to the more frequently studied large estuarine systems.Micro-estuarine ecosystems have a surface area <1 km2 and are abundant in Mediterranean regions. As a result of their small size, these systems are particularly vulnerable to the effects of chemical pollution. Due to the fluctuating flow conditions of base flow dominated by treated wastewater effluents and flood events transporting rural and urban non-point-source pollution, micro-estuaries are under a dynamic risk regime, consequently struggling to provide ecological services. This 2 year study explored the occurrence and risks of pharmaceutical contamination in the Alexander micro-estuary in Israel. Pharmaceuticals were detected in all samples (n = 280) at as high as 18 μg L–1 in flood events and 14 μg L–1 in base flow. The pharmaceutical mixture composition was affected by flow conditions with carbamazepine dominating the base flow and caffeine dominating flood events. The median annual risk quotients for fish, crustaceans, and algae were 19.6, 5.2, and 4.5, respectively, indicating that pharmaceuticals pose a high risk to the ecosystem. Ibuprofen, carbamazepine, and caffeine contributed most to the risk quotients. The current work highlights that micro-estuary ecosystems, like the Alexander estuary, are continuously exposed to pharmaceuticals and most likely to other pollutants, placing these ecologically important systems under an elevated risk in comparison to the more frequently studied large estuarine systems.
Helman, D. ; Zaitchik, B. F. Temperature anomalies affect violent conflicts in African and Middle Eastern warm regions. 2020, 63, 102118. Publisher's VersionAbstract
Several studies have linked high temperatures to increases in violent conflicts. The findings are controversial, however, as there has been no systematic cross-sectional analysis performed to demonstrate the generality of the proposed relationship. Moreover, the timescale of temperature/violence relationships have not been fully investigated; it is unclear how short versus long-term, or seasonal and inter-annual temperature variability contribute to the likelihood or frequency of violent events. We here perform systematic regional and grid-based longitudinal analyses in Africa and the Middle East for the period 1990–2017, using geolocated information on armed conflicts and a recently released satellite-based gridded temperature data set. We find seasonal synchrony between temperature and number of armed conflicts at the regional scale (climatic region), as well as a positive relationship in temperature and conflict anomalies on inter-annual timescales at the grid cell level (for the entire African and ME region). After controlling for ‘location effects’, we do not find that long-term warming has affected armed conflicts for the last three decades. However, the effects of temperature anomalies are stronger in warmer places (~5% increase per 10 °C, P < 0.05), suggesting that populations living in warmer places are more sensitive to temperature deviations. Taken together, these findings imply that projected warming and increasing temperature variability may enhance violence in these regions, though the mechanisms of the relationships still need to be exposed.
Helman, D. ; Mussery, A. Using Landsat satellites to assess the impact of check dams built across erosive gullies on vegetation rehabilitation. 2020, 730, 138873. Publisher's VersionAbstract
Gully erosion, a process of soil removal due to water accumulation and runoff, is a worldwide problem affecting agricultural lands. Building check dams perpendicular to the flow direction is one of the suggested control practices to stabilize this process. Though there are many studies on the effect of erosive controls on land stabilization, few examine its effect on the rehabilitation of vegetation. Here we use information from the satellites Landsat-7 (1999–2018) and Landsat-8 (2013–2018) to assess the effect of soil check dams built during 2012 across three gullies with distinct structures in a dryland area on vegetative cover and water status. We use a time series analysis technique to decompose Landsat-derived soil adjusted vegetation index (SAVI) into woody (SAVIW) and herbaceous (iSAVIH) contributions. The integral over the seasonal signal of the normalized difference water index (iNDWI) was used to assess changes in water status in the gully. We used herbaceous biomass collected in the field in 2014–2017 to validate iSAVIH as a proxy of herbaceous biomass. Our results show that following the construction of the check dams, the change in woody vegetation cover is best described by a sigmoid model with an increase of ~57% (95% CI: 39%–76%; p < 0.0001), while the herbaceous vegetation increases linearly at a rate of ~71% per year (95% CI: 48%–93% y−1; p < 0.0001). The correlation between iSAVIH and herbaceous biomass (R2 = 0.56; n = 16; p < 0.001) corroborates this increase. We found higher herbaceous productivity in the deeper gully compared to the shallower gullies but not statistically different increase rates. An increase in iNDWI of ~68% (95% CI: 43%–95%; p < 0.0001) likely implies an improved water infiltration rate that favored the vegetation expansion. Our satellite-based approach can be used to assess the impact of erosive control practices on vegetation rehabilitation in heterogeneous gullies.
Mor-Mussery, A. ; Helman, D. ; Agmon, Y. ; Ben-Shabat, I. ; El-Frejat, S. ; Golan, D. G. The indigenous Bedouin farmers as land rehabilitators—Setup of an action research programme in the Negev. Land Degradation & DevelopmentLand Degradation & DevelopmentLand Degrad Dev 2020, n/a. Publisher's VersionAbstract
Abstract The Negev suffers from enhanced land degradation, mostly due to lack of awareness about its state, and hostility between the region's indigenous Bedouin farmers and the authorities. In order to examine a potential solution to this 'Lose?Lose' situation, a unique project is underway, with the collaboration of the Yeroham Municipality and the adjacent Rahma Bedouin farmers' village. The concept of this ongoing Programme is based on bidirectional knowledge transfer of farming data between the farmers and land scientists, aimed to adapt Bedouin traditional cultivation methods and transform them into methods that restore the environment and are also profitable. In order to reach this goal, a highly knowledgeable Bedouin liaison person was appointed to carry out the project together with the Coordinating Team. A comprehensive study and tour were carried out in order to analyze the different landforms and Bedouin cultivation preferences. An initial survey was carried out and data from literature collected in order to determine the ecological and archaeological characteristics of the ecosystem. The area was then prepared for agricultural utilization by removing widespread garbage and dealing with wadis that have been filled with construction waste. This project, which integrates soil enhancement, agriculture utilization, and traditional Bedouin farming, aims for rehabilitation of the northern Negev gullied areas. However, the implementation of the study concept in the field is accompanied by many challenges related to Bedouin interclan communication and the diverse types of degraded lands.
Gorovits, R. ; Sobol, I. ; Akama, K. ; Chefetz, B. ; Czosnek, H. Pharmaceuticals in treated wastewater induce a stress response in tomato plants. Sci Rep 2020, 10, 1856.Abstract
Pharmaceuticals remain in treated wastewater used to irrigate agricultural crops. Their effect on terrestrial plants is practically unknown. Here we tested whether these compounds can be considered as plant stress inducers. Several features characterize the general stress response in plants: production of reactive oxygen species acting as stress-response signals, MAPKs signaling cascade inducing expression of defense genes, heat shock proteins preventing protein denaturation and degradation, and amino acids playing signaling roles and involved in osmoregulation. Tomato seedlings bathing in a cocktail of pharmaceuticals (Carbamazepine, Valporic acid, Phenytoin, Diazepam, Lamotrigine) or in Carbamazepine alone, at different concentrations and during different time-periods, were used to study the patterns of stress-related markers. The accumulation of the stress-related biomarkers in leaf and root tissues pointed to a cumulative stress response, mobilizing the cell protection machinery to avoid metabolic modifications and to restore homeostasis. The described approach is suitable for the investigation of stress response of different crop plants to various contaminants present in treated wastewater.
Grodek, T. ; Morin, E. ; Helman, D. ; Lensky, I. ; Dahan, O. ; Seely, M. ; Benito, G. ; Enzel, Y. Eco-hydrology and geomorphology of the largest floods along the hyperarid Kuiseb River, Namibia. Journal of Hydrology 2020, 582, 124450. Publisher's VersionAbstract
Flood-fed aquifers along the sandy lower reach of the Kuiseb River sustain a 130-km-long green belt of lush oases across the hyperarid Namib desert. This oasis is a year-round source for water creating dense-tall woodland along the narrow corridor of the ephemeral river valley, which, in turn, supports human activity and fauna including during the long dry austral winters and multi-year droughts. Occasional floods, originating at the river’s wetter headwaters, travel ∼280 km downstream, before recharging these aquifers. We analyzed the flood-aquifer-vegetation dynamics at-a-site and along the river, determining the relative impact of floods with diverse magnitude and frequency on downstream reaches. We find that flood discharge that feeds the alluvial aquifers also affects vegetation dynamics along the river. The downstream aquifers are fed only by the largest floods that allow the infrequent germination of plants; mean annual recharge volume is too low to support the aquifers level. These short-term vegetation cycles of green-up and then fast senescence in-between floods are easily detected by satellite-derived vegetation index. This index identifies historical floods and their magnitudes in arid and hyperarid regions; specifically, it determines occurrences of large floods in headwater-fed, ephemeral Namib streams as well as in other hyperarid regions. Our study reveals the importance of flood properties on the oasis life cycle, emphasizing the impact of drought and wet years on the Namib’s riparian vegetation.