Dead Sea & Arava Science Center

Yotvata, Israel

Dead Sea & Arava Science Center

Yotvata, Israel
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Yizhaq H.,Dead Sea & Arava Science Center | Yizhaq H.,Ben - Gurion University of the Negev | Stavi I.,Dead Sea & Arava Science Center | Shachak M.,Ben - Gurion University of the Negev | Bel G.,Ben - Gurion University of the Negev
Ecological Complexity | Year: 2017

Interactions between biotic and abiotic factors dictate the response of ecosystems to varying conditions and disturbances. The importance of the relationship between these factors is demonstrated in the extensively studied interactions between water-limited vegetation and its ecosystem's physical components. Landscape geodiversity is often neglected in studies of vegetation dynamics and response to drought. Here, we combine field studies and mathematical modeling to elucidate the effects of geodiversity on shrub mortality following drought. In Israel's semi-arid northwestern Negev Desert, we found that homogeneous hillslopes, with little or no stoniness, experienced considerable shrub mortality following droughts, while neighboring slopes with higher stoniness showed little or no mortality. A mathematical model describing the dynamics of water-limited vegetation and accounting for landscape geodiversity predicted similar responses. The measurements and the model suggest that geodiversity increases the amount of water available for the shrubs, thereby increasing their durability. Future climate predictions of reduced precipitation and increased drought frequency in many regions make studies of ecosystem responses to water deficiency timely. Our findings suggest that future studies should account for landscape geodiversity in order to explain local differences in vegetation mortality and to better assess the possible impacts of climate fluctuations on ecosystem dynamics. In particular, geodiversity has a great effect on regime shifts and their nature. © 2017 Elsevier B.V.


Elmann A.,Israel Agricultural Research Organization | Telerman A.,Israel Agricultural Research Organization | Ofir R.,Dead Sea & Arava Science Center | Kashman Y.,Tel Aviv University
Journal of Molecular Neuroscience | Year: 2017

Glutamate toxicity is a major contributor to the pathophysiology of numerous neurodegenerative diseases including amyotrophic lateral sclerosis and Alzheimer’s disease. Therefore, protecting neuronal cells against glutamate-induced cytotoxicity might be an effective approach for the treatment of these diseases. We have previously purified from the medicinal plant Achillea fragrantissima two bioactive compounds which were not studied before: the sesquiterpene lactone achillolide A and the flavonoid 3,5,4′-trihydroxy-6,7,3′-trimethoxyflavone (TTF). We have shown that these compounds protect astrocytes from oxidative stress-induced cell death and inhibit microglial activation. The current study examined for the first time their effects on differentiated mouse neuroblastoma N2a cells and on glutamate toxicity. We have found that, although these compounds belong to different chemical families, they protect neuronal cells from glutamate toxicity. We further demonstrate that this protective effect might be, at least partially, due to inhibitory effects of these compounds on the levels of reactive oxygen species produced following treatment with glutamate. © 2017, Springer Science+Business Media New York.


Stavi I.,Dead Sea & Arava Science Center | Argaman E.,Soil Erosion Research Station
Catena | Year: 2016

Water availability is a major limiting factor for dryland afforestation. Earthworks that modify natural landforms for the formation of runoff harvesting systems are prevalent in the Israeli drylands, with the aim of establishing afforestation projects. However, serious concerns alarm that such earthworks have detrimental effects on the geo-ecosystem functioning. Therefore, the objective of this study was to examine the impact of the establishment of contour bench terrace (also called shichs/shychs/shikim) runoff harvesting systems on selected soil properties, with particular focus on soil aggregation. Thus, we assessed the effect of the establishment of contour bench terraces in a multi-aged forestry land, comprised of 2-year-old and 9-year-old afforestation areas, and compared them to ‘natural’ hillslopes as a reference treatment. The study was implemented in the Ambassadors' Forest, located in the semi-arid northern Negev of Israel, where we sampled the surface soil (at a depth of 0–5 cm) in north- and south-facing hillslopes. Considerable differences were recorded for the afforestation systems between the source (inter-terrace area) and sink (terrace-bottoms) areas. Data normalizing according to the relative cover percentage of the terraces and inter-terrace areas showed that the mean values of mean weight diameter (MWD), stable aggregate content, and particulate organic carbon in the natural hillslopes were 1.4%, 32.4%, and 20%, respectively, greater than in the 9-year-old afforestation systems, and 12.1%, 28.9%, and 31%, respectively, greater than in the 2-year-old systems. Means of clod content, aggregate slaking index, and clay dispersion index in the natural hillslopes were 62.3%, ~ twofold, and 35.0%, respectively, smaller than in the 9-year-old systems, and almost threefold, nearly twofold, and 46.2%, respectively, smaller than in the 2-year-old areas. The soil calcium carbonate content was similar in soils of the natural hillslopes and 9-year-old afforestation lands, which was ~ 17% smaller than in the 2-year-old afforestation systems. Considerable differences among the land-uses were also recorded for the soil texture. Mean coarse root biomass, despite revealing only a marginally-significant effect (p-value = 0.0765), was 40.0% greater in the natural hillslopes than in the 9-year-old systems, and more than twofold greater than in the 2-year-old systems. Hillslope aspect affected some of the measured properties, revealing only slightly better soil conditions in the (mesic) north- than in the (xeric) south-aspects. The data revealed that forestry-related earthworks degrade the soil quality and geo-ecosystem functioning in the short term. Yet, despite some discrepancies, the data also showed the occurrence of self-restoration processes of the geo-ecosystem over the long term. © 2016 Elsevier B.V.


Sohbati R.,University of Aarhus | Sohbati R.,Technical University of Denmark | Murray A.S.,University of Aarhus | Porat N.,Geological Survey of Israel | And 2 more authors.
Quaternary Geochronology | Year: 2015

The construction age of a pavement in a "Rodedian" prehistoric cult site in Negev desert, Israel, is established by determining the burial age of (i) a cobble used in the pavement, and (ii) the underlying sediment. The quartz OSL age and the K-feldspar corrected IR50 age from the sediment and the corrected IR50 and pIRIR225 ages from the cobble surface are all consistent, and give an average age of 4.22 ± 0.06 ka. Although the very similar ages indicate the reliability of the methods, these ages are ~3-4 ka younger than that expected for the Rodedian sites. The IR50 and pIRIR225 luminescence-depth profiles from the cobble indicate multiple exposure and burial events in the depositional history. The apparently young ages may thus represent a later intervention in the site during the late 3rd millennium B.C. More sites need to be dated by the use of both rocks and sediments to confirm this suggestion. Important information on the bleaching history of the rock surfaces directly obtained from these luminescence-depth profiles is not available in the underlying unconsolidated sediments. This is a significant advantage of rock surface dating over more conventional sediment dating. © 2015 Elsevier B.V.


Mejia A.Y.,University of Rome Tor Vergata | Rotini A.,University of Rome Tor Vergata | Lacasella F.,University of Wisconsin - Madison | Bookman R.,Haifa University | And 4 more authors.
Ecological Indicators | Year: 2016

Seagrasses are one of the most valuable marine ecosystems on earth, yet they are declining worldwide at alarming rates. With most of seagrass monitoring based on long term responses to environmental pressures, there is growing interest in developing alternative diagnostic tools that more effectively identify changes in seagrass ecological status at an early stage. Besides morphological indicators, functional and biochemical descriptors may provide a good understanding of plant's responses to environmental changes. Moreover, the epiphytic microbial communities of seagrasses may also shift in response to changes in environmental conditions, although these have been seldom used as a descriptor of environmental change. In this study three Halophila stipulacea (Forsk.) Aschers meadows, found in the Gulf of Aqaba (northern Red Sea), were characterized using an integrated approach to highlight possible differences in the meadows ecological status. Plant descriptors, including leaves morphometrics (leaf size, leaf number/plant, leaves with lost apex), photosynthetic pigments (Chlorophylls, Carotenoids) and total phenols contents, were investigated and coupled with the plants' epiphytic microbial community structure and composition, studied using pyrosequencing. The entire suite of descriptors highlighted differences among the meadows ecological status based on changes in plants' morphology and biochemistry, and their associated microbial communities, in response to the different environmental conditions (water column turbidity, seawater and sediment nutrients) and the geomorphological features (bottom slope, granulometry) of the stations. Leaf morphology and photosynthetic pigment content were modulated in H. stipulacea in response to light availability and hydrodynamics in the Gulf of Aqaba. The highest leaf surface area and photosynthetic pigment contents were observed at the lowest irradiance and hydrodynamics/granulometry among stations. Total phenol content showed differences among stations with increasing concentrations from north to south. The microbial communities showed differences among stations and plant compartments, with high incidence of Gammaproteobacteria and Bacteroidetes in light limiting conditions, while Cyanobacteria and Rhodobacteraceae thrived in conditions of high light availability and hydrodynamics. The mutual response of the seagrass plants and the microbial communities provided evidence of their functional relationship, which undoubtedly needs further investigation. To the best of our knowledge, this is the first time that such descriptors have been used in an integrated approach. We provide evidence of their effectiveness in discriminating seagrass ecological status, even at small spatial scales. This work constitutes a new approach to the assessment of seagrasses and a stepping stone in the application of microbial communities as a putative marker in a changing environment. © 2015 Published by Elsevier Ltd.


Stavi I.,Dead Sea & Arava Science Center | Barkai D.,Israel Agricultural Research Organization | Islam K.R.,Ohio State University | Zaady E.,Israel Agricultural Research Organization
Agronomy for Sustainable Development | Year: 2015

Stubble grazing by livestock in post-harvest wheat fields is a common practice. Current knowledge usually shows that grazing has negative effects on soil quality. Therefore, here, we studied the stubble grazing impact on soil quality and crop yields of continuous wheat croplands in the semi-arid northern Negev of Israel. These croplands have experienced the same stubble residue management, meaning, moderate grazing or entire retention, for 18 consecutive years. Cropland soils were also compared with soils of natural lands. Vegetation and 0–10 cm depth soils were sampled in 2013. Results reveal that overall soil quality was generally similar between the two wheat treatments. Moreover, results show that soil under stubble grazing treatment has greater carbon pool index and carbon management index than soil under stubble retention treatment. These findings suggest that the disturbance of soil organic carbon pool is smaller for stubble grazing, contrary to current knowledge. We propose a conceptual model to explain such findings. © 2015, INRA and Springer-Verlag France.


Stavi I.,Dead Sea & Arava Science Center | Bel G.,Ben - Gurion University of the Negev | Zaady E.,Israel Agricultural Research Organization
Agronomy for Sustainable Development | Year: 2016

Soil tillage, crop residue management, nutrient management, and pest management are among the core farming practices. Each of these practices impacts a range of soil functions and ecosystem services, including water availability for crops, weed control, insect and pathogen control, soil quality and functioning, soil erosion control, soil organic carbon pool, environmental pollution control, greenhouse gas refuse, and crop yield productivity. In this study, we reviewed relevant bibliography and then developed a simple conceptual model, in which these soil functions and ecosystem services were scored and compared between conventional, conservation, and integrated agricultural systems. Using this conceptual model revealed that the overall agro-environmental score, excluding crop yield productivity, is largest for conservation systems (71.9 %), intermediate for integrated systems (68.8 %), and the smallest for conventional systems (52.1 %). At the same time, the crop yield productivity score is largest for integrated systems (83.3 %), intermediate for conventional systems (66.7 %), and the smallest for conservation systems (58.3 %). This study shows the potential of moderate-intensity and integrated farming systems in carrying on global food security while adequately sustaining environmental quality and ecosystem services. © 2016, INRA and Springer-Verlag France.

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