department of SOlar energy and environmental physics 1

Clockwise from upper left: The effect of aeolian dust This 25m diameter, The Forest Sede-Boqer is one of 20 deposition from dust sun-tracking, parabolic Goldman-Sonnenfeldt stations around the storms such as this one, is dish was recently Building is the new world selected for being investigated by wind installed at the home of the Solar long-term monitoring tunnel simulations. Ben-Gurion National Energy and of solar radiation. Solar Energy Center. Environmental Physics Department. Department of SOlar Energy and Environmental Physics Prof. Isaak Rubinstein, Chairperson

The Department of Solar Energy and Environmental Physics integrates disciplines of natural sciences and engineering in the study of the physical environment. Its scientists come from the fields of geography, meteorology, mechanical engineering, applied mathematics, physics and chemistry. Main topics of investigation include: solar energy utilization; applied optics; the desert climate; remote sensing detection and modeling of desertification; nonlinear dynamics and thermodynamics as related to the environment; mechanics of granular materials; membrane electrochemistry and desalination. The department provides consultation services to government agencies and to municipalities on the optimal use of solar energy in specific projects, and to industrial concerns on the development of novel solar devices. There are four research groups in the department: Desert Meteorology; Remote Sensing; Environmental Physics (Theory Group); and the Ben-Gurion National Solar Energy Center. Phone: 972-8-659-6803 • Fax: 972-8-659-6921 • E-mail: [email protected] ACADEMIC STAFF Berkofsky, Louis (Professor Emeritus) Biryukov, Sergey Burde, Georgy Charach, Chaim1 (deceased, April 1999) Faiman, David1 Feuermann, Daniel Gitelson, Anatoly2 Gordon, Jeffrey M.3 Gutman, Lev (Professor Emeritus) Karnieli, Arnon2 Katz, Evgeny Meron, Ehud1 Offer, Zvi Y.4 Time evolution of spatio-temporal Orlovsky, Leah chaos in a model of a chemical Prigozhin, Leonid5 reaction. The dark and light Rubinstein, Isaak5 shades represent chemical states 5 with different chemical Zaltzman, Boris concentrations. [Courtesy of Ehud Zangvil, Abraham4 Meron] Zarmi, Yair1 Zemel, Amos6 ASSOCIATE STAFF Berman, David Ibbetson, Peter

1 Joint appt. with BGU’s Dept. of Physics 2 Joint appt. with BGU’s Dept. of Geology 3 Joint appt. with BGU’s Dept. of Mechanical Engineering 4 Joint appt. with BGU’s Dept. of Geography and Environmental Development 5 Joint appt. with BGU’s Dept. of Mathematics and Computer Science 6 Joint appt. with BGU’s Dept. of Industrial Engineering and Management

energy physics 2 Research Activities

Desert Meteorology

The desert meteorology group investigates desert climates in general and the Negev desert in particular. Studies focus on the structure and dynamics of atmospheric circulation systems and their variations in time and space – more specifically, the structure, motion and trajectories of Mediterranean disturbances and the importance of the large-scale moisture field in these processes; atmospheric fronts and their effect on rainfall in the region; water vapor recycling and its effect on climate; climate change and El Niño and their effect on the weather and climate in Israel. Researchers investigate how air circulation feeds cyclones with the moisture necessary for rain formation, with emphasis on understanding the basic mechanisms and their influence on the hydrological cycle and climate change. This work is part of the Global Energy and Water Cycle Experiment (GEWEX), a component of the World Climate Research Program. Special mechanisms of rain formation are studied experimentally and by mathematical modeling. Another area of research is the interaction of atmospheric dust with ecological systems and The effect of aeolian dust study of the erosion, transport and deposition of atmospheric dust both by theoretical deposition from dust storms such modeling and wind tunnel simulations (investigations which have practical applications in as this one, is being investigated agriculture, solar systems efficiency, road transport and environmental preservation). by wind tunnel simulations. Research topics also include dew formation, the variations of solar radiation and theoretical modeling of the atmosphere’s effect on heat stress in humans. Theoretical studies concern different types of atmospheric instability and new explicit solutions to the Naviar-Stokes equations related to the atmospheric boundary layer and methods for the solution of partial differential equations. At six major dust collection stations (Sede-Boqer, Shivta, Avdat, Mashash, Sayeret-Shaked and Beer-Sheva) in the Negev desert, members of the group conduct both routine and special meteorological and dust measurements at ground level and several meters above ground. In collaboration with the Israel Meteorological Service the group is part of the global Baseline Surface Radiation Network (BSRN). Sede-Boqer is one of 20 stations around the world selected for long-term monitoring of solar radiation.

Atmospheric fronts and We constructed hydrodynamic models of atmospheric fronts and, on the basis of frontogenesis closed-form solutions of the problems of mature meteorological fronts, developed a new Burde, Zangvil, Gutman classification of mature fronts in terms of only two dimensionless parameters. The model has been evaluated qualitatively by comparing some characteristics of the model with those observed for actual fronts. The comparison shows that the model provides a rational basis for interpreting observations and classification of fronts. With: E. Morozovsky, Ben-Gurion University

Frontogenesis in the We generalized the semigeostrophic, two-dimensional, uniform potential vorticity presence of thermal Eady-wave model developed by Hoskins and Bretherton to embed the Newtonian (radiative) forcing cooling. The observation that with this modification the potential vorticity varies in a known Burde manner following fluid particles has provided the retention of the analytical representation of the solution. Our investigation indicates that the effects of thermal forcing may critically change the dynamics of semigeostrophic frontogenesis even though the damping timescale significantly exceeds the flow timescale. In particular, the formation of a frontal discontinuity from short-wave initial disturbances, with the wavenumbers beyond the short-wave cutoff of the adiabatic theory, becomes possible.

physicenergys 3 A comparative analysis: Because of the impact of cyclones and cyclone tracks on local climate and the general disturbance tracks over circulation of the atmosphere, analysis of cyclone tracks has been a topic of continuing active the Mediterranean Region research in meteorology. The most widely used method in cyclone track analysis used Zangvil centers of minimum pressure on surface synoptic charts. Sometimes centers of maximum relative vorticity, or satellite cloud pictures have been used for that purpose. The problem with these methods is that there is no clear distinction between stationary and transient disturbances. For example, if track analysis is performed in the usual manner in the summer over the eastern Mediterranean region, only stationary low pressure systems appear in certain locations such as Cyprus or Iraq. We developed a method by which the stationary disturbances are filtered out of the synoptic data and transient disturbances can be discerned. We also study the connection of these disturbances with local weather. Very large data sets of meteorological variables at several elevations extending in time for two decades over Europe and the Mediterranean were used in this comprehensive study. With: S. Karas, Ben-Gurion University

water vapor budget This investigation is part of an ongoing joint effort with the Cooperative Institute for components over Mesoscale Meteorological Studies of the University of Oklahoma. The atmospheric moisture Central North America budget of a given continental region is a complex function of the meteorological and and in Israel in relation hydrological processes within the region and surrounding areas, and of the soil to precipitation characteristics and type of land use. We are studying the relationship between the different Zangvil moisture budget components and precipitation. The main dynamical processes reflected in the moisture budget are water vapor storage and the horizontal and vertical advection of moisture within the region. All these interact in several ways with the inflow and outflow of water vapor at the region’s vertical and horizontal (the earth’s surface) boundaries. In this study we are performing calculations of the moisture budget components using measured meteorological data from a region of about one million km2 over the central USA and comparing it with Israel and vicinity, in an effort to understand the above-mentioned interactions. With: D.H. Portis, P.J. Lamb, University of Oklahoma

Observational and Generally, precipitation over a given region derives from both moisture advected into the theoretical studies of region by winds, and by moisture evaporating at the surface within the region. The water vapor and contribution of local evaporation to local precipitation, called "recycling,” may provide a precipitation recycling feedback mechanism between land surface processes and precipitation, which may be Burde, Zangvil reflected in the moisture budget of the region. In this context, the contribution of local evaporation in a given continental region is studied by two different approaches – observationally, by extending the conventional moisture budget calculations, and theoretically, by extending Budyko’s one-dimensional equation to two dimensions and by other theoretical considerations. We developed a fluid dynamics approach to the quantification of the precipitation recycling process, which allows for the role of atmospheric flow structure. The new approach improves the ability to estimate precipitation recycling, and also makes it possible to incorporate the atmospheric flow structure in the feedback mechanisms in hydrological and climatological processes. With: P.J. Lamb, University of Oklahoma

The global Baseline The BSRN, a project that was initiated over 10 years ago, is an international network of Surface Radiation about 20 meteorological stations that monitor the temporal variation of solar radiation Network (BSRN) reaching the surface of the earth at locations representing different global climates. The Zangvil international BSRN panel decided to locate one of its stations (which is run in collaboration with the Israel Meteorological Service) at Sede-Boqer because: 1) Sede-Boqer is ideal for solar radiation measurements in a remote desert location. 2) The meteorology group has been collecting solar radiation and other meteorological data on a routine basis since 1981. These data are available on site. With: A. Manes, Israel Meteorological Service and the World Meteorological Organization

energy physics 4 Characterization of sky A method has been proposed to characterize the sky and cloud conditions (SCC) by using conditions by the use of ground-based global and diffuse radiation data. The term SCC is defined for the purpose of solar radiation data this study as the bulk effect of clouds and other atmospheric constituents on the values of Zangvil the diffuse fraction of solar radiation (D/G) and the ratio between the global to extra- terrestrial radiation (KT). However, there is difficulty in using the measured values of these two parameters since they are influenced by the solar zenith angle as well as by meteorological factors. We overcame this problem by developing a semiempirical scheme which removes zenith angle-dependent, seasonal and latitudinal variations of the above parameters, leaving only variations due to meteorological factors. The method is demonstrated on monthly mean D/G-KT relations calculated from three years of global and diffuse irradiance measured at Sede-Boqer. We found very good correspondence between measured sky and cloud conditions at Sede-Boqer and the D/G-KT relations as corrected by our method. With: P.J. Lamb, University of Oklahoma comparative analysis of This is a continuation and extension of the above-mentioned investigation of the behavior of disturbance tracks over disturbances and disturbance tracks over the northern Red Sea Region (Red Sea Troughs) the northern Red Sea and their influence on the weather in Israel. Zangvil With: Y. Zvieli, Ben-Gurion University.

Dew measurements We analyzed dew measurements taken at Sede-Boqer for nearly 6 years and described in the Negev several parameters of dew formation. The total monthly amount of dew and the distribution Zangvil of the number of dew nights shows two distinct maxima (in September and December-January) and two minima (in April and November). The average dew deposit per dew night behaves differently: the most striking feature is the appearance of distinct winter and summer regimes, with the winter having more dew per dew night. The average duration of dew per dew night appears to follow very closely the length of the night: there is a clear maximum of dew duration in December (7.9 hrs) and a minimum in July (5.5 hrs). The rate of dew accumulation is found to have distinct dry season, and rainy season (winter) regimes.

Aeolian dust deposition Dust is an important component in the desert climate as well as in shaping the morphology in the desert of the land surface. To study its effects, research was conducted by means of field Offer experiments and wind-tunnel simulations. In a 24-month experiment, aeolian accumulation of natural atmospheric dust in a desert environment was investigated. Dust accumulation by day was systematically higher than at night. Dust that accumulated at night was coarser than dust accumulated during daytime. The average monthly concentration and accumulation are considerably influenced by high-magnitude dust events, either dust storms or dust hazes. The velocity of accumulation, defined as the ratio between accumulation and concentration, varied between 1.18 m/s and 4.53 m/s. A study of aeolian erosion of natural dust was conducted on two types of hills, located in a rocky desert, by means of field measurements and wind-tunnel simulations. Erosion was measured along three transects: one across the elongated hill and two across the conical hill. In the field, erosion was measured on erosion plots during two wind storms. In the wind tunnel, erosion was measured on topographic scale models. The wind tunnel experiments and field experiments showed good agreement: Dust erosion was most pronounced on the windward hill slopes, and more particularly on their upper part, close to the top. The highest erosion occurred at or immediately before the top. Downwind of the top, on the lee slope, erosion drops considerably. The areas that are most sensitive to wind erosion are accurately Dust collection devices are predicted in wind tunnel simulations. mounted at different levels at the Sede-Boqer meteorological In addition, the spatial pattern of short-term aeolian dust deposition on and around observation station. cone-shaped hills was investigated by a wind-tunnel simulation of dust storms over a topographic scale model of a conical hill in the Negev desert. Conical hills create an elongated area of low deposition (“dust shadow”) in their lee. Downwind from the shadow zone, a local area of more-than-normal (compared to the undisturbed surroundings) deposition occurs. On the lateral flanks of the hill, and also on the small convex windward physicenergys 5 slope just upstream of the top (and at the top itself), dust deposition remains low to very low. It is the lowermost, concave windward slope that receives the largest amount of dust. With: D. Goossens, Leuven University, Belgium

Airborne particle Results of wind-tunnel simulations and field experiments indicate that airborne dust particles dynamics: toward a settle on the windward side of hills whereas sand particle deposition is mainly observed on theoretical approach the leeward side. That and other aspects, such as the existence of several deposition regimes Offer relating to wind intensity, call for theoretical explanations. We presented some preliminary considerations leading to such a theoretical framework and also established the first steps toward a general model of morphological changes of the relief under dust dynamics. With: L. Brenig, Brussels University, Belgium

Aeolian particle input to In arid and semiarid regions, aeolian particle input is one of the major sources of soil the soil surface at the nutrients. The particle input also improves the soil depth and strongly influences the northern border water-holding capacity of the soil. The measurements of the components of the aeolian of the Negev desert deposition and accumulation were carried out for 3 years (1992-1995). The average soil Offer accumulation for this period was 0.22 g/m2/d (80.64 g/m2/year). Significant differences were obtained during the whole study period regarding the slope direction of the watershed. Almost all the granulometric analyses conducted on monthly collected samples showed significant amounts of clay-size and silt-size particles. Chemical composition of the airborne particles showed that two major constituents, Si and Ca, dominate all the samples. With: E. Zaady, M. Shachak, BIDR

exact solutions of fluid By applying a new approach for finding similarity solutions, we obtained a number of new dynamics equations explicit solutions of the Navier-Stokes equations and the boundary layer equations. Many of Burde the solutions are of interest from theoretical and engineering points of view.

Extensions to Extensions to the classical and nonclassical Lie group methods have been developed. The Lie group methods extensions produce symmetry reductions and solutions which are not obtainable by either Burde classical or nonclassical group methods.

Convective and A dynamic model of a spontaneous dust fallout intended to give a dynamic explanation of a baroclinic instability special kind of dust storm has been developed. The model links this phenomenon with the problems nonlinear stage of the instability of the dust-laden stream. We also investigated the effects of Burde Newtonian cooling in baroclin stability on the basis of the Eady model and found new types of dynamic behavior.

Remote Sensing

Remote sensing is a cost-effective method of gathering an enormous amount of information on vast expanses of unsettled lands. Of particular importance is the study of environmental problems related to drylands, such as desertification and climatic change. Conventional survey methods require considerable investments in manpower and are not always practical in such areas. The remote sensing laboratory is an interdisciplinary research group. Its researchers develop scientific theories, methodologies and applications in remote sensing, image processing and Geographic Information System (GIS) management of the earth’s resources. Working with Ground truth spectral other BIDR researchers, members of the group apply satellite, aerial imagery and ground measurements and multiband photography used in field project data to environmental problems, with special emphasis on drylands. with NASA to assess desertification. The laboratory has two long-term collaboration agreements with NASA headquarters: 1) routine monitoring of aerosol properties and surface spectral properties, and conducting short field experiments that will relate these measurements to space observations; 2) exploitation in research of ocean color data from the SeaWiFS program. This latter agreement enables the remote sensing laboratory to receive, store and analyze digital data from the SeaWiFS satellite. energy physics 6 Remote sensing There are several difficulties in detecting and monitoring temporal changes in vegetation techniques specific to using multispectral imagery from airborne or spaceborne sensors. These difficulties are due vegetation detection in to: 1) temporal change in the vegetation state; 2) temporal change in the soil/rock signature; arid regions and 3) difficulty in discriminating vegetation from soil or rock background. Karnieli There are three ground features to be considered: i) the phenological cycle of perennial plants is related to their adaptation to the scarcity of water; ii) annuals, which are green only for a relatively short period during the wet season and turn into dry organic matter during the summer; iii) microphytic communities (lower plants) of the biogenic crusts which are rapidly affected by moisture and turn green within minutes after the first rain. In arid environments, where the higher plants are sparse, the biogenic crusts have considerable importance in the overall production of the greenness signal. In remote sensing, crust-covered areas are visually similar to bare soil throughout the dry period. Our findings show that the temporal analysis of natural vegetation in semiarid regions should take into account the three ground features – annuals, perennials, and biogenic crusts – in a way that is not commonly considered either in agricultural areas or in humid regions. In arid areas, the three phenological cycles should be studied separately. (From the remote sensing point of view, the biogenic crusts of microphytic communities can be considered as soil during the dry season and as vegetation during the wet season.) We are calibrating and validating spectral models and remote sensing equations for maximum discrimination of sparse arid and semiarid vegetation and ground features.

Remote sensing of Spectral methods and image processing techniques are practical for assessing and monitoring desertification processes desertification processes, including vegetation and soil degradation, dune movements, Karnieli, Orlovsky salinization and dust loading over wide-ranging areas in different parts of the world. Research is conducted in the Middle East as well as in Africa (Senegal and Burkina Faso) and Central Asia (Turkmenistan, Uzbekistan, and Kazakhstan). Our studies examine current remote sensing methods to interpret how vegetation cover is affected by biogenic crusts of microphytic communities in arid and semiarid regions.

DAVID/MSRS We are developing new technology in an Israeli-German commercial small satellite for an Karnieli innovative application of remote sensing, namely, ‘precision agriculture’. Still in its infancy, precision agriculture is a holistic approach for micromanaging agricultural landscapes based on the information received through this new technology. The payload, called DAVID (developed by OHB-Systems, Germany), will carry the Multi-Spectral High Resolution Remote Sensing System, (MSRS, developed by El-Op, Israel). The system’s main characteristics are 12 narrow spectral bands in the visible and near infrared regions, high spatial resolution, and high revisit time of three days. Our feasibility studies show that these features are ideal for developing precision agriculture and determining water quality of coastal and inland water bodies. We are developing and testing the components of the system prior to launching the satellite, which is scheduled for the year 2002.

Detection of dust Dust is a dominant feature in satellite images, and is suspected to extract large radiative over deserts forcing of climate. While remote sensing of dust over the dark oceans is feasible, adequate Karnieli techniques for remote sensing over the land still have to be developed. Here, similar to remote sensing of aerosol over vegetated regions, we use a combination of visible and mid-IR solar channels to detect dust over the desert. Analysis of Landsat TM images over Senegal taken in 1987 shows that the surface reflectance at 0.64 æm is between 0.54ñ0.05 of the reflectance at 2.1 æm, and reflectance at 0.47 æm is 0.26ñ0.03 of that at 2.1 æm, surprisingly similar to relationships in nondesert sites. We also found that dust has only a small effect on the surface + atmosphere reflectance at 2.1 æm over the desert. Therefore, in the presence of dust, we use the Landsat TM data at 2.1 æm channel to predict the surface reflectance at 0.64 and 0.47 æm. The difference between the satellite-measured reflectances of surface + atmosphere and the predicted surface reflectances are used to derive the dust optical thickness, t, at 0.64 and 0.47 æm. Results show that t can be derived within Dt=ñ0.5 for the range of 0

Optical properties of In several related studies we developed models for analyzing the pigment content of plant higher plant leaves leaves on reflectance and transmittance spectra. These are noninvasive techniques which Gitelson enable scientists to conduct wide-scale analyses of vegetation characteristics. By measuring reflectance and absorption spectra in visible and near infrared ranges, we were able to estimate the chlorophyll content of several different nonrelated species from different climatic regions. We also developed a model for simultaneous retrieval of pigment content (chlorophyll, caretenoids and antothyans) from the reflectance spectra of the leaves. These algorithms are simple ratios between percent reflectance at spectral regions that are highly sensitive (540 to 630 nm and around 700 nm) to insensitive (near infrared) to variations in chlorophyll content. The developed models predicting leaf chemistry from the leaf optics were validated for nine plant species in the range of chlorophyll content from 0.27 to 62.9 (mg/cm2). An error of less than 4.2 (mg/cm2) in chlorophyll prediction was achieved. The use of green and red channels increases the sensitivity of Normalized Difference Vegetation Index (NDVI) to chlorophyll content by about five-fold. With: C. Buschmann and H. K. Lichtenthaler, University of Karlsruhe, Germany; M. Merzlyak, Moscow State University

Using AVHRR data for A Vegetation Condition Index (VCI) is a measure of weather impact on vegetation. We quantitative estimation developed a VCI which measures weather impact on vegetation, and compares vegetation of vegetation conditions density, biomass and reflectance. For the first time it was shown that the VCI-derived Gitelson vegetation condition data can be effectively used for quantitative assessments of both vegetation state and productivity (density and biomass) over large areas. Test fields were located in Kazakhstan, in several ecological zones with different climatic conditions, where elevations range from 200 to 700 m and annual precipitation from 150-700 mm. The NDVI variation ranged from 0.05 to 0.47. A determination coefficient between AVHRR (advanced very high resolution radiometer) derived vegetation state and actually measured vegetation density of more than 0.76 was achieved. With: F. Kogan, NOAA/NESDIS, USA; E. Zakarin and L. Spivak, Academy of Sciences, Kazakhstan

Remote sensing of We developed comprehensive remote technology to monitor vegetation status in terms of biomass and vegetation photosynthetic pigment concentration and vegetation fraction water content from satellites. status The system gives us a considerable amount of information on plant physiology, including the Gitelson ability to detect the early stages of stress in vegetation. Most animals (including humans) use a green spectral range to sense the presence and vitality of vegetation. However, most satellite sensors use a combination of red and near infrared channels for that purpose. These sensors are not sensitive to the chlorophyll concentration in yellow-green to green leaves. We found (not surprisingly) the maximum sensitivity to chlorophyll concentration is around the green band (from 520 to 630 nm and also near 700 nm). We developed the Green Atmospherically Resistant Vegetation Index (GARI) which is sensitive to chlorophyll content, measures the rate of photosynthesis and monitors plant stress. Using the GARI, we investigated the reason for the repeatedly reported increase of fluorescence ratio during the stress or damage-induced breakdown of chlorophyll in plants. The results demonstrate that at least more than 92% of the ratio variation in leaves during development or at damage and stress events is determined by the variation in Chl content and corresponding changes of the optical properties of leaves. We also developed a technique for estimating pasture and crop productivity in semiarid zones using AVHRR data. With: Y. Kaufman, NASA Goddard Space Flight Center, Maryland; M. Merzlyak, Moscow State University; Optical properties of D. C. Rundquist, University of Nebraska-Lincoln energy physics 8 phytoplankton and Most of the information pertaining to remote sensing of phytoplankton was developed for remote sensing of oligotrophic waters, where detritus and inorganic particles are scarce or their phytoplankton density concentrations correlate with phytoplankton density. In our study we concentrated on in productive waters inland and productive coastal waters, with the initial work done in Lake Kinneret, Israel. The Gitelson primary objectives were: 1) to study the reflectance of different water bodies during different seasons of the year in order to find spectral features that are closely related to phytoplankton density; and 2) to devise and validate algorithms for chlorophyll estimation using reflectance data as the measured variables. We devised optical models of turbid waters and found that the information gained from several spectral bands in the red and near infrared ranges of the spectrum allowed us to construct algorithms to estimate phytoplankton density. These algorithms were validated in Lake Kinneret and, with slight modifications, in other environments: the polluted water of Haifa Bay (Mediterranean Sea), fish ponds and wastewater reservoirs in Israel, lakes with diverse trophic status in northwestern Iowa, and lakes in Germany, Hungary and eastern Nebraska (USA). Within the context of information essential for estimating chlorophyll concentration by remotely operated instruments, we suggest that satellite sensors would be expedient tools for monitoring water quality and pigment content (chlorophyll, caretenoids and phycocyanin) in productive aquatic ecosystems. With: Y.Z. Yacobi, the Yigal Allon Kinneret Limnological Laboratory, Israel; J.F. Schalles, Creighton University, Omaha, NE; D.C. Rundquist, University of Nebraska, Lincoln

Environmental Physics (Theory Group)

Many processes and phenomena in science, technology and the environment, although seemingly different and unrelated, have common features when looked upon from the mathematical-physical point of view. For example, the formation of sand dunes, river networks and the magnetic field in a superconductor have a common mathematical description that uses some very sophisticated mathematical tools. In a totally different arena, concentrators for solar radiation, special luminaires, certain aspects of the vision mechanism of living things, and the use of solar radiation for solar surgery (instead of expensive lasers) are all applications of a special branch of optics called “nonimaging optics”. Another example is the common mathematical-physical basis of water desalination and the physiology of living cells. The power of the mathematical-physical approach as a tool for describing and analyzing environmental processes is the raison d’être of the environmental physics group. Members of the group are involved in topics related to environmental research including modeling of climatic phenomena in the desert, the interaction of dust particles with the environment and their effect on the climate, applied optics in relation to solar energy utilization, the analysis of nonlinear dynamic systems, modeling of desertification, water desalination, phase change processes, applied thermodynamics and resource economics under uncertainty. To accommodate the interdisciplinary nature of environmental research, the group is composed of scientists with varied backgrounds in the mathematical and physical sciences. optimal management of The methods of dynamic optimization are employed to derive optimal policies for managing natural resources various environmental problems arising from the depletion of natural resources. These Zemel problems include groundwater exploitation, energy policies, pollution control and the conservation of endangered species. The solutions include time profiles and steady states of the optimal processes. Comparing the solutions derived with and without environmental uncertainty allows us to elucidate the effect of uncertainty on the optimal policies. We characterized this effect in terms of the nature of the uncertainty (endogenous vs. exogenous), and of the environmental impact (reversible vs. irreversible). Our recent studies consider optimal R&D investments in alternative technologies (solar energy, desalination) to replace conventional resources that are nearing depletion. At the present time solar energy and desalination technologies are expensive and used as alternatives mostly in certain small-scale situations, where fossil energy and fresh water are prohibitively expensive. We recommend immediate, maximum investment in developing clean and efficient alternative physicenergys 9 technologies, so that these will be in place when the depletion of natural resources becomes a wide-spread, critical issue. With: Y. Tsur, Hebrew University of Jerusalem

Characterization of the Optimality conditions associated with dynamic optimization problems are typically described in equilibrium structure of terms of a system of coupled differential equations that admit analytical solutions only under the dynamic optimization simplest specifications. The prevailing approach to analyse steady state behavior borrows heavily problems from differential equation theory to explore the long-run behavior of the optimal pro-cesses. In Zemel this work we develop an alternative approach which does away with the dynamic equations altogether. Using a variational approach, we reduce the identification of the optimal equilibria to the simple algebraic problem of solving the roots of a given function of the state variable. The application of the method is illustrated by considering several resource exploitation methods. With: Y. Tsur, Hebrew University of Jerusalem

Simultaneous vs. We consider development projects in which the activities can be classified in two types: sequential engineering uncertainty resolving R&D efforts which accumulate in the form of knowledge to eventually activities in risky R&D give rise to a discovery, and routine technical investments which aim at improving the projects profitability of the project once the discovery has been made. The advantage of initiating Zemel routine preparatory activities prior to the achievement of a technological breakthrough in such projects, sometimes termed "concurrent engineering," is analyzed within a suitable dynamic optimization framework. The optimal double expenditure policy is compared with the conservative delayed investment policy, under which all the routine engineering activities are delayed until the risky R&D efforts culminate in a breakthrough. A criterion for the optimality of the latter policy is developed on the basis of the probability distribution of the discovery date. The application of the criterion is illustrated for a variety of specifications regarding the uncertainty associated with the R&D process. We find that simultaneous investment is the optimal policy for a large class of probability distributions. However, if the conditional probability of immediate discovery is always below some critical value, it is optimal to delay the preparatory activities until the discovery event. With: I. David and A. Mehrez, Ben-Gurion University

Regulating When private provision of a public good (such as the eradication of some source of intertemporal public pollution) is a temporal process, regulation should provide the right incentives with regard projects to the timing of the project's activities and its duration. This task becomes involved for Zemel projects that are indivisible or when monitoring the project's activities is costly. We characterize optimal incentive schemes to regulate such projects, based on the project duration (T) only. The mechanism consists of an auction to select the performing firm and a T-dependent payment schedule that induces the selected firm to carry out the project according to the socially desirable plan. A dominant strategy implementation is offered. With: Y. Tsur, Hebrew University of Jerusalem

Optical design and Many important optical systems are concerned with power transfer and brightness rather radiative transfer than with image fidelity. These applications include fiber optic coupling, radiant heating, at the thermo- projection, solar energy, illumination and detection. Nonimaging optics is a new design dynamic limit approach that departs from the methods of traditional optical design to develop new Gordon, Feuermann techniques for maximizing the collecting power of concentrator and illuminator systems. Nonimaging devices substantially outperform conventional lenses and mirrors in these applications. In fact, the performance of nonimaging devices may approach the theoretical (thermodynamic) limit. Practical nonimaging optical systems are now finding applications in many of these areas. Their use promises higher efficiency, relaxed physical tolerances, heightened optical uniformity, and reduced manufacturing costs. Our research in this area and our development projects with Israeli high-tech industries have generated new designs of both fundamental and commercial value, with special applications to remote lighting, infrared irradiation in the semiconductor industry, infrared detection and solar energy. With: H. Ries, Optics and Energy Consulting, Germany energy physics 10 Biomedical optics Many minimally-invasive medical procedures involve the delivery of laser power inside the Gordon, Feuermann human body via optical fibers. There is considerable room for improvement in current devices, in the efficient coupling of laser light out of fibers and its uniform wide-angle distribution into human tissues. By foregoing conventional imaging optical systems and inventing nonimaging mirrors and aspheric lenses that are tailored to the specific needs of laser fiber-optic surgery, we can now offer superior designs for a range of medical treatments. An especially novel advance is solar surgery, in which we recognized that in many important laser operations the expensive surgical laser can be replaced by an inexpensive novel solar concentrator no more than 20 centimeters in diameter. Whereas no conventional light sources can even approach the enormous power densities required for many surgical procedures and produced by lasers, the power density at the surface of the sun is adequate. Neither the coherence nor the monochromaticity of the laser is crucial in many operations: only the extremely high flux density. Our advanced optical design should be able to concentrate sunlight to levels even higher than those at the surface of the sun and to channel the power to the surgical target.

Predictive, diagnostic Using basic irreversible thermodynamics, we have developed analytical models for the and optimization tools performance of a wide range of cooling systems (chillers). These models for air-conditioning for cooling devices and refrigeration devices allow the user to extract powerful diagnostic and predictive from irreversible information from a small number of noninvasive measurements that can readily be thermodynamics performed in the laboratory or at the actual chiller installation. In the process, the behavior Gordon of seemingly different types of cooling systems can be understood in a single universal thermodynamic framework. All modeling work has been supported and validated with extensive experimental data from commercial chillers. We have documented diagnostic case studies for installed cooling plants, as well as manufacturer-driven optimizations of chiller configurations and operating conditions. Toward the end of 1999 Cambridge International Science Publishing commissioned a new text, "Cool Thermodynamics", by J.M.Gordon and K.C. Ng, that presents the major progress in this area. With: K.C. Ng, National University of Singapore

Solar energy We have proposed a paradigm shift in the way sunlight can be collected, concentrated and concentration delivered to remote receiving and conversion units: solar fiber-optic mini-dish systems. They Gordon, Feuermann offer substantial advantages in efficiency, compactness, reduced mechanical loads, and ease of fabrication and installation relative to conventional solar designs. The system’s building block is a miniature solar dish (around 0.2 m in diameter) which concentrates sunlight into a single optical fiber. The fiber transports power to a remote receiver. Nonimaging second-stage concentrators can boost flux levels to those approaching the thermodynamic limit. Considerable flexibility is gained in receiver design whereby one can now tailor solar optics to receiver constraints rather than vice versa. Systems are modular and can be employed in central or localized power generation from the kilowatt to the megawatt level. At the end of 1999, the Israel Ministry of National Infrastructures awarded us a special grant for the experimental realization of this new concept. With: H. Ries, Paul Scherrer Institute, Germany

Consultation for Israeli We have worked with several Israeli high-tech companies in the development of assorted high-tech industries advanced optical systems. The applications span: (a) medical diagnostic systems in radiology Gordon, Feuermann laboratories and for the detection of peptic disorders; (b) the detection of micro-faults in visual displays; (c) the development of stationary solar energy concentrators for steam production and solar-driven absorption air conditioners; and (d) the design of special drying systems in the digital printing industry.

physicenergys 11 Closed system For better control of the climate in greenhouses, we are investigating a new type of greenhouses greenhouse. To increase crop yield plants are fertilised with carbon dioxide. Quadrupling the Feuermann carbon dioxide concentration in the greenhouse atmosphere (compared to ambient air) can increase crop yield by 30 to 150%. This is only possible if the greenhouse is closed, a requirement that is difficult to achieve due to overheating of the greenhouse. Shading alone is insufficient and reduces the level of light necessary for plant growth. The new greenhouse cladding removes a large part of the near infrared solar radiation (which the plants do not need for photosynthesis) by means of a liquid radiation filter. This filter flows in the double layered roof of the greenhouse and acts as a solar collector for the near infrared radiation. New temperature-dependent material introduced into the filter produces a dynamic shading device which can improve the greenhouse functioning. With: J. Gale, R. Kopel, and S. Levi, BIDR

Perturbative analysis of The method of normal forms has been employed in the perturbative analysis of nonlinear nonlinear systems systems. Emphasis was given to the use of freedom of choice of the zero, as well as the Zarmi higher-order terms inherent in the expansion, for improving or simplifying the perturbative approximation. The approach was applied to the differential equation in the operator representation of the anharmonic oscillator. In addition, It has been shown that the freedom in the expansion is lost to a great extent in the method of Multiple Time Scales. The freedom in the expansion is applied to the analysis of the perturbed Burgers equation. With: Peter B. Kahn, State University of New York, Stony Brook

Quantitative aspects In reactors for mass cultivation of unicellular algae, the cells are forced to move back and forth of mass cultivation between the illuminated and dark zones. This is achieved by means of air bubbles that are passed of algae through the culture. The motion is random. We employed methods of stochastic processes for Zarmi analyzing the motion of the cells, as the distribution of the times they spend in both zones affects the biomass productivity of the reactor. Simple arguments have been developed for explaining the observed increase of productivity, as well as the value of the optimal culture density. With: Amos Richmond, BIDR

Desalination: This long-term research project concerns a theoretical and experimental study of ionic Electroconvection in transport in electrolyte solutions in relation to membrane electrochemistry, in particular to electrodialysis desalination by electrodialysis. This includes the analysis of fluid dynamic instabilities arising Rubinstein, Zaltzman in these systems and the resulting nonlinear flows – specifically, electroconvection in strong electrolytes. Our study focuses on the electroconvectional stability of a conduction state in an electrolyte layer adjacent to cation-permselective electrodialysis membranes. The asymptotic analysis of the nonequilibrium double layer, developing at the membrane surface under the passage of the ‘overlimiting’ electric current, was carried out and the relevant electro-osmotic slip condition was derived. Thus far, this condition yields the only model for which it has been shown definitively that nonlinear electro-osmotically driven electroconvection may provide an efficient mechanism of overlimiting conductance through the electrodialysis membranes. In the experimental part of this research we distinguished between the bulk electroconvection and electro-osmotic mechanisms of overlimiting conduction by studying concentration polarization at the cation exchange membranes coated by thin aqueous uncharged polymeric layers of variable thickness. This study showed that the overlimiting conduction disappears at a coated membrane, suggesting that the respective convection in the diffusion layer is surface- rather than bulk-driven.

Diffusional mechanism This research concerns the coarsening of particles of the condensed phase, at the late stage of strong selection in of the first order phase transition. This phenomenon, known as Ostwald ripening, is modeled Ostwald ripening by the classical Lifshitz-Slyozov-Wagner mean-field model. We showed through a systematic Rubinstein, Zaltzman asymptotic analysis, that fluctuations (accounted for as a diffusional perturbation in the aforementioned model) provide a mechanism for the so-called ‘strong’ selection. This latter picks a single limiting solution out of a one-parameter family of similarity solutions with a finite support, as the sole attractor of time evolution in the system. energy physics 12 Thermodynamically The principal applications of this study are to the solidification of pure materials and binary consistent schemes for alloys. Thermodynamically consistent derivations of equations governing non-isothermal phase field equations melting/solidification processes were addressed. We allowed the gradient terms to be Charach present not only in the free energy density and entropy but also in internal energy for both nonconserved and conserved order parameter fields. Due to the gradient terms in internal energy there exists a one-parameter family of alternative theories.

Solidification in binary This research focuses on the development of kinetic phase diagrams for binary alloys. At very alloys: Capillarity and low velocities the solidification processes are defined by the equilibrium phase diagrams. solute trapping effects However as the growth rate increases both the liquid and the solid phases change. Such Charach diagrams are of great interest in materials science and have various technological applications. In addition, the phase diagrams are affected by capillarity undercooling at curved interfaces. In the frame of the present research we developed phase field models which predict the capillarity and trapping of impurities in the process of crystal growth. We considered that model accounting for gradient terms in the free energy and entropy account for nonlocal contributions of both the phase field and the concentration fields. The later contributions are correlated with the growth of partition coefficient at sufficiently large velocities.

Multiphase patterns in A conspicuous property of systems driven far from thermal equilibrium is the possible periodically forced appearance of persistent oscillations. Biological rhythms, like the heartbeat, provide good oscillatory systems examples. The oscillatory systems encountered in nature are usually not isolated and quite meron often the interaction with the environment takes the form of a periodic forcing in time, as in Circadian rhythms entrained by the 24-hour day-night periodicity. Pattern formation phenomena in such systems arise due to multiplicity of phase states in various entrainment resonances. These phenomena can best be studied using simpler case models, like oscillating chemical reactions in controlled laboratory experiments. In 1997 Petrov, Ouyang and Swinney reported in Nature their observations of standing and traveling wave patterns in a periodically forced oscillatory chemical reaction. Motivated by these observations we studied oscillatory systems close to the onset of oscillations (or to the Hopf bifurcation). We discovered a new front instability in even resonances, 2n:1 (n>1) (forcing frequency is about 2n times natural frequency). A stationary front, shifting the oscillation phase by π loses stability as the forcing strength is decreased past a critical value and decomposes into n traveling π/n-fronts each shifting the oscillation phase by π/n. The instability within the 2n:1 resonance designates a transition from standing two-phase patterns at high forcing strength to traveling 2n-phase patterns at low forcing strength. An experiment to test these predictions is being carried out by Swinney’s group in Austin. The current theory is based on an amplitude equation approach which is strictly valid only in the vicinity of the Hopf bifurcation. The experiments on the oscillating chemical reaction, however, are not close to the Hopf bifurcation. We are currently investigating the effects of the distance to the Hopf bifurcation on front solutions and instabilities within various resonances (3:2, 2:1, 3:1,4:1). We also plan to investigate the effects of shifting the system from the oscillatory to the excitability regime. With: A. Hagberg, Los Alamos National Laboratory; H.L. Swinney, University of Texas, Austin; A. Yochelis, Ben-Gurion University

Vegetation patterns in The low precipitation in semiarid and arid lands does not allow for complete coverage of arid lands land by vegetation. As a result vegetation patterns appear. On hill slopes, patterns consisting Meron of vegetation bands aligned perpendicular to the slope tend to form. On flat areas spot patterns are more common. Band and spot patterns have been observed in Nigeria, Somalia and many other places. We have constructed a model that reproduces these patterns. The model is being used to classify levels of aridity and to interpret desertification phenomena using concepts of dynamical system theory. With: J. von Hardenberg, M. Shachak, and Y. Zarmi, Ben-Gurion University

physicenergys 13 Pattern dynamics Catalytic surface reactions, involving adsorption and desorption of molecular species on in anisotropic crystal surfaces, provide a special class of pattern-forming systems where processes bistable systems occurring on microscopic (nanometer) and macroscopic (micrometer to millimeter) scales meron are coupled together: intrinsic crystal anisotropy affects diffusion on a micrometer scale, while adsorption of molecular species, controlled by macroscopic nonequilibrium conditions, may change or induce surface anisotropy. A common spatial structure appearing in surface reactions is a front separating domains with different adsorbate coverages. The direction of front propagation may not be unique. Coexistence of fronts propagating in opposite directions has been observed in the catalytic CO oxidation on a platinum surface. This phenomenon has been attributed to a front bifurcation that takes a single stable front into a pair of counter-propagating stable fronts. Similar bifurcations have also been found in bulk chemical reactions and in liquid crystals, and are known as nonequilibrium Ising-Bloch (or NIB) bifurcations.We studied the effect of anisotropy on pattern formation in bistable systems undergoing nonequilibrium Ising-Bloch (NIB) front bifurcations. We found that anisotropy may induce front transitions leading to blob formation and to a state we term ‘stratified chaos’, characterized by strong correlations along one of the principal axes. The mechanism of stratified chaos is elucidated using equations that describe the dependence of front motion on the direction of propagation. This study will be extended along the following lines: 1) understanding additional mechanisms of pattern formation resulting from anisotropy of diffusion; 2) applying theoretical results to experiments on catalytic surface reactions; and 3) linking processes at a macroscopic scale (micrometer and above) to underlying processes at a microscopic scale (nanometer). With: M. Baer, MPI, Dresden; R. Imbhil, University of Hanover; M. Eiswirth, Fritz Haber Institute, Berlin; L. Pismen, Technion, Haifa

bacterial crust growth The microflora in arid lands often include thin crusts of microorganisms covering the soil in arid lands surface. One type of these crusts, consisting primarily of cyanobacteria, covers extended Meron parts of the Negev’s sandy soil. The crust stabilizes the soil against erosion, affects the water regime and dryland ecosystems, and slows down sand-dune motion. We are in the course of developing a continuum model for the growth of bacterial crusts. The model consists of nonlinear partial differential equations for the bacterial density, the surface wetness and the bacterial growth rate. The model will allow studying possible modes of crust growth (uniform, finger-like, etc.) and the effects of environmental factors such as precipitation. With: M. Baer, MPI, Dresden; A. Provenzale, Torino; J.von Hardenberg, Ben-Gurion University

Modeling the phenomena Segregation phenomena in urban systems attract enormous attention by social geographers. of population One recent approach to studying urban segregation involves computer simulations of discrete segregation in urban mathematical models. Implicit in this approach is the assumption of a hidden mathematical environments structure underlying the phenomena. The discrete models are too complicated to unravel this meron structure. In this study we propose a continuum modeling approach which is more amenable to analysis.We developed a specific model to address the dynamics of two distinct populations in an urban environment where migration is dominated by socio-economic status considerations. In addition to the two population densities, we introduced a third dynamic variable representing the local socio-economic status. The model is suitable for studying segregation of new immigrants or foreign workers in veteran neighborhoods. The model suggests two forms of segregation. Weak segregation arising from a finite wave-number instability of a uniform mixed population state, and strong segregation involving interfaces separating pure population states. It gives a mathematical interpretation of the tipping point phenomenon and suggests two modes of population invasion, smooth and finger-like. The preliminary model discussed above assumes migration to nearby neighborhoods (e.g. because of community service conveniences). It is being extended to include nonlocal migration within the city (i.e. to distant neighborhoods). Further extensions will include stochastic elements and additional variables like cultural affinity. We also plan comparisons of theoretical results with simulations on discrete models and possibly with real data. With: Y. Yizhaq, Ben-Gurion University energy physics 14 Nonlinear dynamics of Aeolian sand ripples form regular patterns on coastal beaches and desert floors, indicating aeolian sand ripples instability of the flat sand surface as winds transport and rearrange the loosely packed sand. prigozhin Despite the significant progress in understanding the nature of sand ripples, major questions about the most interesting part of ripple formation remain open; these involve the nonlinear interactions that follow the initial instability. We studied the salient features of sand ripple formation by means of a mathematical model that accounts for saltation and reptation [types of movement] of sand grains. The linear stability analysis of this model confirms that ripples t −−> grow because of the geometrical effect of greater impact and ejection flux on upwind-oriented slopes than on downwind-oriented slopes. The rolling of dislodged particles down the surface slopes and scattering of ejected reptating grain trajectories by an uneven sand surface have a smoothing effect and tend to hinder the ripple growth. Taking all x Simulation of typical ripple these effects into account we were able to simulate not only the development of a typical interaction, (region bounded by the asymmetric ripple shape but also the evolution of sand ripple patterns characterized by the diagonal, thin lines). Wind direction is ripple wave-length growth. We suggest that the coarsening of ripple array occurs not via a bottom to top. To show details, ripples are stretched in horizontal direction. simple merger of ripples, as is usually assumed, but via soliton-like interactions with partial material exchange between interacting ripples.

Physics of surface This area of research has recently attracted much interest among physicists, partly because granular flow it was realized that the rich and complicated behavior exhibited by the granular state of Prigozhin matter is still not well understood, partly due to the crucial role the granular materials play in various industries. We proposed a full-dimensional generalization of a popular BCRE model for the surface granular flow and dynamics of pile surface. It has been shown that in the long scale limit this model tends to the variational model proposed and studied in my previous works. This result explains why different models should be employed for, say, simulating formation of small Aeolian ripples and large dunes; it makes clear that the issue of scaling becomes most important in this context and narrows the gap between current approaches to modeling surface granular flows. The model for surface granular flows has been extended to flows of polydisperse materials accompanied by segregation of differing species. Free-surface segregation in size has been studied theoretically and experimentally. The model predictions agree with the experimental results. With: B. Zaltzman, BIDR; H. Kalman, Ben-Gurion University

The Ben-Gurion National Solar Energy Center Prof. David Faiman, Director

The Ben-Gurion National Solar Energy Center houses five laboratories, each of which studies one or more aspects of solar energy conversion. The Photon Energy Transformer and Astrophysics Laboratory (PETAL) is centered around the recently-built 400 sq.m parabolic dish multi-purpose research facility. At this laboratory studies are currently in progress towards the possibility of conducting concentrator photovoltaics research during the day, and gamma ray astronomy at night. The Photovoltaic Advanced Materials Laboratory (PAMAL) performs research into novel materials with potential solar energy applications. Our current research efforts in this laboratory focus on various methods to produce high-efficiency solar cells from fullerene, a Air glow from the intensely recently-discovered form of carbon. The Parabolic Trough Laboratory (PATROL) contains a concentrated sunlight in the focal 960 sq.m oil-heating loop of old Luz LS-2 collectors (currently being refurbished), and 2760 region of sun-tracking, parabolic sq.m of LS-3 collectors, with tilted axes, originally designed by Luz for direct steam dish (with receiver removed). generation. Current work at this laboratory aims at using the LS-2 loop to test some receiver tubes, newly-developed by Solel Corp., and the LS-3 loop to investigate some system aspects associated with the use of these tubes. The outdoor Photovoltaic Test Laboratory (PVTEL) studies the aging of solar panels and associated system components under conditons of desert usage. In addition, the special climatic conditions at Sede-Boqer enable this outdoor facility to be used for the performance of solar cell characterizations of unique precision. physicenergys 15 The Meteorological Data Laboratory (MEDAL) monitors solar radiation in a variety of spectral bands and geometrical configurations, together with a number of additional meteorological parameters. The laboratory is the base station for the ongoing Negev Radiation Survey, which aims at identifying optimal locations for future solar power plants and establishing a data base of climatic parameters for their design. The Center’s current research program includes solar radiation studies, the use of novel materials for photovoltaic devices, photovoltaic module characterization, photovoltaic system design and testing, various aspects of solar-thermal research and dust prevention studies. A number of research collaborations involve colleagues in Ben-Gurion University’s Department of Physics and other laboratories in Israel and overseas. The Center organizes and hosts a periodic series of Sede-Boqer Symposia on Solar Electricity Production. The 10th Symposium took place October 30 - November 1, 2000. The Center also runs a public outreach program in the form of audio-visual presentations and a guided tour of the systems.

Phone: 972-8-659-6934 • Fax: 972-8-659-6736 • E-mail: [email protected]

Photovoltaic research This is an ongoing effort to fabricate solar cells from C60, the newly-discovered ‘fullerene’

with C60 crystals and form of carbon. One aspect of this work involves the use of high-quality thin films of C60, thin films which are grown in the physics department at Beer-Sheva (Prof. Shaul Goren’s group), using Faiman, Katz a newly-developed technique of ours (Patent granted). The electronic properties of these films are studied in Sede-Boqer, Beer-Sheva and at Tel Aviv University (Prof. Yoram Shapira’s group), and the films are used to make inorganic photovoltaic devices. Another aspect of this work, performed in collaboration with universities in Austria, Italy, the Netherlands, Spain and Sweden, involves the creation of "plastic" solar cells employing fullerenes embedded in conjugated polymers. (Funding: Ministry of National Infrastructures and The European Community).

Dry-cleaning for solar This project is part of an ongoing study to develop an alternative to the use of water for collector surfaces cleaning the dust from the mirrors of solar power stations. We solved the problem of dry Biryukov deposition by means of an electric field, which protects surfaces from airborne dust and cleans them (Patent granted). The method uses very little energy and is capable of cleaning large collector areas. The present part of the study addresses the problem of keeping wet surfaces free of dust. (Funding: Ministry of National Infrastructures). With: S. Levy, BIDR

Direct observation Current approaches to protecting solar power plants from the deleterious effects of sudden of clouds sun-shading caused by passing clouds are ineffective. This is because the signals, indicating Biryukov that action is necessary, appear as feedback only at the actual moment of shading. For the effective smoothing of transitional effects, the correcting signal should monitor and anticipate cloud formation and movement. We solved the technical problem of how to view cloud motion in the vicinity of the sun using a computerized video-camera. Then, using algorithms for image sequence analysis, we can precalculate, automatically, the moment of shading. We are creating a computerized data base of cloud types and their manner of evolution, together with an expert-system that will provide control instructions for the optimal and safe operation of large solar power plants under cloudy conditions. A computer, armed with such a data base and expert-system, would periodically study video images of the sky from cameras situated in the vicinity of solar power plants, in order to provide real-time optimal control strategies for the plant operators. (Funding: Ministry of National Infrastructures).

energy physics 16 High-flux parabolic dish The overall goal is to use solar energy as a source of low-cost electric power. Our first solar concentrator approach will be to collect solar energy with "PETAL", our large (25m diameter), Faiman, Biryukov sun-tracking, parabolic dish concentrator, which is essentially a mosaic of relatively low-cost glass mirrors, and to concentrate the energy onto a small photovoltaic power conversion unit, located at the focus. In order to do this, the light rays, reflected from the dish at concentrations of the equivalent of several thousands of suns, must be deconcentrated and distributed over the cell panel with uniform intensity, thereby achieving maximum efficiency from the solar cells. This requires an unconventional optical technique unique design, the so-called kaleidoscope\de-concentrator, a concept which was developed for this project by Prof. J.M. Gordon. Construction of PETAL commenced in early 1998. The working dish was first turned on the sun in July 1999 and some optical characterization tests, using the moon and the planet Jupiter, were carried out at the end of the year [See Figure]. During the performance of these checkout tests a number of design deficiencies were identified - particularly in the dish’s hydraulic system - which will need urgent attention. Investigation has started (together with Prof. David Eichler of BGU’s Physics Dept.) into possibilities for using Rear-view of PETAL focused on this parabolic concentrator as a major component of an atmospheric Cherenkov detector the moon. which will record parameters for very energetic gamma-ray astronomy. (Funding: Rashi Foundation; Ministry of National Infrastructures).

Solar-Thermal Research Work began during 1999, in collaboration with Solel Solar Systems Ltd, to refurbish the LS-2 with Parabolic Trough loop at Sede-Boqer and to rebuild the long-neglected Luz "DSG" system. The former will be Collectors used to test a number of newly-developed advanced components, whose system properties Faiman will then be studied in the DSG array. (Funding: Belfer Foundation and Rashi Foundation; Ministry of National Infrastructures).

Photovoltaic Module Our studies involve PV modules which feed a variety of electrical loads (specifically, the Stability electricity grid or zenar diodes). Several times a year, the modules are disconnected from Faiman, berman their loads, cleaned, and characterized by a uniquely accurate method that owes its existence to the natural AM1.5 spectrum (a climatic rarity) that exists at Sede-Boqer on clear days for a few hours around solar noon. This natural phenomenon allows us to measure cell efficiencies to an accuracy of ± 1%. In this manner, the time-dependence of module degradation due to such phenomena as the so-called "EVA-browning" can be quantified. During 1999 aging and stability tests began on several examples of new-technology PV modules. These include multijunction amorphous Si, CdTe and CIS thin film cells. (Funding: Ministry of National Infrastructures).

Monitoring and analysis This ongoing study involves (in addition to the routine monitoring of various parts of the of solar radiation solar spectrum and maintenance of instruments), the development of calibration methods in Israel and various instrument studies. It includes, specifically, the development of a calibration Faiman, Berman, Ibbetson technique for ultraviolet light sensors which permits hourly and seasonal corrections to be made to instrument readings. (Funding: Ministry of National Infrastructures).

Data Processing for This is an ongoing study which aims to establish a data base of solar radiation components Negev Radiation Survey and other relevant meteorological parameters in order to permit the optimal design of solar Faiman, Feuermann, power plants of the future. Data are provided by the Meteorological Service, from 8 stations Ibbetson, Zemel in the Negev (Arad, Beer-Sheva, Besor Farm, Eilat, Hatzeva, Sede-Boqer, Sedom and Yotvata), and processed into user-friendly form at Sede-Boqer. The survey’s purpose is to establish a data base that will enable designers of future solar power stations to identify optimal sites for building the stations, and to predict their economic viability. A CD-ROM (published March 1999) contains a set of typical meteorological year files, based on up to 8 years of data, for each site. In addition, the CD-ROM contains all of the raw data from each of the sites through 1996, for those who wish to use this information for other scientific purposes. (Funding: Ministry of National Infrastructures). With: A. Israeli, V. Liubansky and I. Seter, Israel Meteorological Service

physicenergys 17 Preparation of a data This international collaboration involves the dissemination of information on PV systems in base on the performance the various member countries, and conversion of performance data from Israeli PV systems of PV systems in Israel, into a format compatible with a data base developed within the framework of the within the framework of International Energy Agency Task 2 PV specialist working group. Task 1 includes gathering Israel’s participation in and dissemination of information about PV systems and components in the various member the IEA Photovoltaics countries. Task 2 is concerned with performance data and analysis of PV systems in the Program Tasks 1 and 2 various member countries. We prepare data on Israeli PV systems, insert the data into an Faiman, Berman international data base and perform comparative analysis of PV systems using an analysis package developed by the working group. (Funding: Ministry of National Infrastructures).

A 1996 satellite photograph of Israel and it’s neighboring n countries. Israel is the geographic a e crossroads of three dryland n a regions. The Sahara-Arabian r desert belt extends across Egypt’s r e

t western desert through the Sinai i

d peninsula, the Negev and Jordan. L

e The northern Mediterranean M region extends from the coast of E n the PA’s Gaza Strip, through the r Asian steppes e A Israeli and Lebanese coasts. The h t

Asian steppes extend from central r R o Israel northward through Jordan N

and Syria. S I

Sede-Boqer

- A r a b i a n a r a a h S

The sand dunes on the international border line between Israel and Egypt [arrow] change from a light whitish color to a slightly darker hew as they cross into the Negev, which is covered by a microbial crust on stabilized sand dunes. This crust is an important natural element in the prevention of the expansion of deserts. Because the Negev is, by and large, closed to large-scale movement of people and herds, it is covered by the microbial crust. The microbial crust phenomenon is also relevant in developed countries. In areas that usually have quite a lot of rainfall and are cultivated intensively every year, the crust never forms. If a sequence of droughts occurs, since there is no crust on the topsoil, the dust is carried into the air, and can cause severe dust storms. The ‘Dust Bowl’ was just such a phenomenon in the USA.

energy physics 18 Research Interests

Sergey Biryukov Ph.D. Joint Institute for Nuclear Research, Dubna, 1995; Researcher Grade B Applied solar energy; System design and analysis of system performance; Influence of environment on thermal and photovoltaic conversion efficiency; Aerosol physics; Hydrodynamics, electrostatics and electrodynamics of interactions between windborne dust and collector surfaces. Phone: 972-8-659-6737 • Fax: 972-8-659-6936 • E-mail: [email protected]

Georgy I.Burde Ph.D. Perm University, USSR, 1972; Associate Professor Dynamic meteorology; Fluid dynamics (boundary layer theory, hydrodynamic stability, numerical methods in fluid dynamics, multiphase flows, environmental fluid dynamics); Heat and mass transfer, convective stability; Partial differential equations of mathematical physics. Phone: 972-8-659-6847 • Fax: 972-8-659-6921 • E-mail: [email protected]

David Faiman Ph.D. University of Illinois, 1969; Professor Applied solar energy; Radiation measurement; Spectral studies; Photovoltaic materials, devices and systems; Solar-thermal systems. Phone: 972-8-659-6933 • Fax: 972-8-659-6736 • E-mail: [email protected]

Daniel Feuermann Ph.D. Ben-Gurion University, 1985; Researcher Grade B Application of non-imaging optics to illumination and irradiation problems in high-tech industry. Analysis of closed system greenhouses. Energy in buildings. High-flux infrared radiation and solar energy concentrators - approaching the thermodynamic limit to optical concentration with practical, compact devices. Tailoring illumination optical systems to prescribed flux distributions at maximum radiative efficiency. Phone: 972-8-659-6927 • Fax: 972-8-659-6921 • E-mail: [email protected]

Anatoly Gitelson Ph.D. State University of Rostov, USSR, 1972; Professor Physical aspects of remote sensing; Radiative transfer; Remote sensing of environment (ocean, coastal and inland waters, vegetation and atmosphere) in visible, near infrared and microwave ranges of the spectrum. Phone: 972-8-659-6858 • Fax: 972-8-659-6909 • E-mail: [email protected]

Jeffrey M. Gordon Ph.D. Brown University, USA,1976; Professor Applied optics and radiative transfer: Solar energy - Development of new solar concentrators based on nonimaging optics, ranging from low-concentration for stationary collectors to dual-stage designs for very high flux devices. Biomedical optics - Design of sculpted optical fiber tips for improving the efficacy and efficiency of laser surgery; Invention of solar surgery and its prodigious potential for supplanting expensive surgical lasers; Design of optical systems for Israeli high-tech industries in medical diagnostic systems. Irreversible thermodynamics: Development of universal predictive and diagnostic thermodynamic models for cooling systems such as reciprocating, centrifugal and absorption chillers. New ultra-high-efficiency designs for solar cooling. Illumination optics: Design and invention of new high-efficiency reflector shapes for lighting that also insure excellent angular control, involving the tailoring of reflector optics to prescribed target flux maps, for conventional lighting and infrared applications. Phone: 972-8-659-6923 • Fax: 972-8-659-6921 • E-mail: [email protected]

Arnon Karnieli Ph.D. University of Arizona, 1988; Researcher Grade B Remote sensing: Spatial and spectral data analysis; Application of remote sensing to environment and earth resources problems especially in arid and semiarid regions; Geographic information system; Digital elevation model; Image processing. Phone: 972-8-659-6855 • Fax: 972-8-659-6704 • E-mail: [email protected] physicenergys 19 Eugene Katz Ph.D. Moscow Institute of Steel & Alloys, 1990; Researcher Fields of Interest: Applied solar energy; Structural defects in semiconductors; Porous silicon; Photovoltaic materials; Fullerenes. Phone: 972-8-659-6739 • Fax: 972-8-659-6736 • E-mail:[email protected]

Ehud Meron Ph.D. Weizmann Institute,1986; Associate Professor Nonlinear dynamics; Pattern formation; Applications to physical, chemical and ecological systems. Phone: 972-8-659-6926 • Fax: 972-8-659-6921 • E-mail: [email protected]

Zvi Y. Offer Ph.D. University of Bucharest, 1979; Senior Lecturer Geomorphology; Relationship between the meteorological parameters, relief morphometry and airborne particles in the Negev Desert (deflation, erosion, transport, sedimentation, composition, aerosols, atmospheric pollution); Practical applications. Phone: 972-8-659-6849 • Fax: 972-8-659-6921 • E-mail: [email protected]

Leonid Progozhin Ph.D. Ben-Gurion University, 1995; Researcher Grade A Free boundary and variational problems; Numerical analysis; Models of dissipative systems; Granular Mechanics; Applied superconductivity. Phone: 972-8-659-6922 • Fax: 972-8-659-6921• E-mail: [email protected]

Isaak Rubinstein Ph.D. Weizmann Institute, 1978; Professor Theory of non-linear transport processes in continuous media mass and momentum transfer in electrolyte solutions; Electrochemistry of synthetic ion-exchange membranes with applications to desalination; Semiconductor transport; Chemical engineering. Phone: 972-8-659-6924 • Fax: 972-8-659-6921 • E-mail: [email protected]

Boris Zaltzman Ph.D. Novosibirsk State University, Russia, 1989; Senior Lecturer Incumbent of the Mendel Wasserman Career Development Chair in Desert Studies Theory of continuous nonlinear transport processes in heat and mass transfer; Ionic transport in electrolytes and semiconductor transport, including free boundary problems in these systems. Phone: 972-8-659-6928 • Fax: 972-8-659-6921 • E-mail: [email protected]

AbrahaM Zangvil Ph.D. University of California,-Los Angeles,1975; Associate Professor Incumbent of the Edward and Bertha Rose Chair in Desert Meteorology Dynamic and synoptic meteorology; Synoptic climatology; Rainfall; Relationships between rainfall and the large scale moisture field; Climate change; Connection between climate change and synoptic mesoscale weather systems. Phone: 972-8-659-6845 • Fax: 972-8-659-6921 • E-mail: [email protected]

Yair Zarmi Ph.D. Weizmann Institute, 1970; Professor Incumbent of the Phyllis and Kurt Kilstock Chair in Environmental Physics of Arid Zones Stochastic aspects of solar research; Nonlinear dynamics; Irreversible thermodynamic analysis of heat and mass transfer processes. Phone: 972-8-659-6920 • Fax: 972-8-659-6921 • E-mail: [email protected]

Amos Zemel Ph.D. Weizmann Institute, 1981; Associate Professor Statistical properties of solar radiation; Dynamic optimization methodology and applications: Optimal exploitation of natural resources under uncertainty; R&D investment strategies in environmental projects; The relations between ecological and economic models. Phone: 972-8-659-6925 • Fax: 972-8-659-6921 • E-mail: [email protected]

energy physics 20 Publications Arkin, Y., C. Ichoku, A. Karnieli. Fault traces in an arid valley floor revealed by radar surface roughness classification, Arava Valley Israel. Canadian Journal of Remote Sensing 25:302-310 (1999) Bär M., A. Hagberg, E. Meron and U.Thiele. Stratified spatiotemporal chaos in anisotropic reaction-diffusion systems. Phys. Rev. Lett. 83:2664-2667 (1999). Biryukov S., D.Faiman and A.Goldfeld. An optical system for the quantitative study of particulate contamination on solar collector surfaces. Solar Energy 66:371 (1999) Burde, G.I. Semigeostrophic frontogenesis in the presence of Newtonian cooling. Jour. of Atmos. Sci. 56:3774-3788 (1999) Elphick C., A. Hagberg and E. Meron. Multi-phase patterns in periodically forced oscillatory systems. Phys. Rev. E59:5285-5291 (1999) Faiman D. Sizing PV systems for southern England: computing kWh from kWp. Proc. Instn. Civ. Engrs Mun. Engr 133:123 (1999) Fedotov A, N. Drozdov, E. A. Katz, Ju. Iliashuk, A. Mazanik and A. Ulyashin. Transformation of electrical activity of extended defects in silicon polycrystals under annealing and hydrogen plasma treatment. Physica Status Solidi A171:353 (1999) Fedotov A, A. Masanik, E.A. Katz, Yu. Ilyashuk and A. Drozdovsky. Electrical activity of tilt and twist grain boundaries in silicon. Solid State Phenomena 67-68:15 (1999) Feuermann, D., J.M. Gordon and H. Ries. High-flux solar concentration with imaging designs. Solar Energy 65:83-89 (1999) Feuermann, D. and J.M. Gordon. Solar fiber-optic mini-dishes: A new approach to the efficient collection of sunlight. Solar Energy 65:159-170 (1999) Gitelson, A.A., J.F. Schalles, D.C. Rundquist, F. R. Schiebe, Y.Z. Yacobi. Comparative reflectance properties of algal cultures with manipulated densities. J. Applied Phycology 4:345-354 (1999) Gitelson, A.A., C. Buschmann and H.K. Lichtenthaler. The Chlorophyll Fluorescence Ratio F735/F700 as an accurate measure of the chlorophyll content in plants. Remote Sensing of Environment 69:296-302 (1999) Gordon, J.M., K.C. Ng and H.T. Chua. Simple thermodynamic diagrams for real refrigeration systems. Journal of Applied Physics 85:641-646 (1999) Gordon, J.M. and K.C. Ng. High efficiency solar cooling. Solar Energy 68:23-31 (1999). Ichoku, C., M.O. Andreae, T.W. Andreae, F.X. Meixner, G.Schebeske, P. Formenti, W. Maenhaut, J. Cafmeyer, J. Ptasinski, A. Karnieli and L. Orlovsky. Interrelationship between aerosol characteristics and light scattering during late winter in an eastern Mediterranean arid environment. Journal of Geophysical Research 104:371-393 (1999) Kahn, P. B. and Y. Zarmi. Time dependence of operators in anharmonic quantum oscillators: Explicit perturbative analysis. J. Math. Phys. 40:4658-4663 (1999) Karas, S., and A. Zangvil. A preliminary analysis of disturbance tracks over the Mediterranean Basin.Theoretical and Applied Climatology 64:239-248 (1999) Karnieli, A., G.J. Kidron, C. Glaesser and E. Ben-Dor. Spectral characteristics of cyanobacteria soil crust in semiarid environment. Remote Sensing of Environment 69:67-75 (1999) Katz, E. A. Fullerene-based thin films as a novel polycrystalline semiconductor. Solid State Phenomena 67-68:435 (1999) Katz E.A., A.I. Shames, D. Faiman, S.Shtutina, Y. Cohen, S. Goren, W. Kempinski and L. Piekara-Sady. Do structural defects affect semiconducting properties of fullerene thin films? Physica B:273-274:932 (1999) Prigozhin, L. Nonlinear dynamics of Aeolian sand ripples. Phys. Rev. E60:729 (1999) Meron E. Self-organization in interface dynamics and urban development. Disc. Dyn. Nat. Soc. 3:125-136 (1999) Merzlyak, M.N., A.A. Gitelson, O.B. Chivkunova, and Y.R. Rakitin. Non-destructive optical detection of pigment changes during leaf senescence and fruit ripening. Physiologia Plantarum 106:135-141 (1999) Primicerio M., I. Rubinstein and B. Zaltzman. Electrodiffusional free boundary problem in a bipolar membrane (semiconductor diode) at a reverse bias for constant current. Quarterly Appl. Math. 57:637-659 (1999) Rubinstein I., and B. Zaltzman. Electroconvective mechanisms in concentration polarization at electrodialysis membranes. In: Membrane Surfaces (Ed. T.S. Soerensen) Marcel Dekker pp 591-621 (1999) Rubinstein I. and B.Zaltzman. Diffusional mechanism of strong selection in Ostwald ripening. Phys. Rev. E 61:709-717 (2000) Saltz, D., H.Schmidt, M. Rowen, A. Karnieli, D. Ward and I. Schmidt. Assessing grazing impacts by remote sensing in hyper-arid environments. Journal of Range Management 52:500-507(1999)

physicenergys 21 Department of SOLAR Energy and Environmental Physics

Technical staff Dov Bokovza Svetlana Gillerman Mali EIchler Shlomo Kabalo David Klepach Melincheck Volodya

Secretarial staff Mazal Adar Shoshana Dann Lilian Na’aman

Visiting Scientists Bjarne Andresen, University of Copenhagen, Denmark Jerzey Cierniewski, Agricultural University, Poznan, Poland Ray Dicker, Australia Cornelia Glaesser, Martin Luther University, Germany Dirk Goossens, Agricultural University, Wageningen, the Netherlands Garik Gutman, NASA/HQ, USA. Peter B. Kahn, State University of New York, Stony Brook, ,NY Helmut Lichtenthaler, University of Karlsruhe, Germany Mark Merzlyak, Moscow State University, Russia Rachel Pinker, University of Maryland, USA Harald Ries, Optics and Energy Consulting Inc., Munich, Germany Marcus Salazar, University of Bourgogne, France

Postdoctoral Fellows Jost von Hardenberg, Torino, Italy Charles Ichoku, Universite Pierre et Marie Curie, France

Graduate Students Yael Cohen Giorgio Dall’Olmo Wiessam Essa Stefanie Herman Svetlana Karas Erik Moderegger Kathy Pearlmutter Zhiaho Qin Shmuel Schijvarg Heike Schmidt Robi Stark Louis Traore Yehezkel Yizhaq Arik Yochelis Bayarjargal Yu Alex Weksler Hagit Zioni Yoav Zur Yossi Zvieli

energy physics 22 MARCO AND LOUISE MITRANI DEPARTMENT OF DESERT ECOLOGY2

Clockwise from upper left: The ibex (Capra ibex Black widow spiders The poplar (Populus Bacteria that use nubiana) lives in the (Latrodectus revivensis) euphratica) is found at polyethylene as their sole mountains of the Negev, are a dominant water sources all over carbon source may in the Rift Valley and component of Israel and a few places in provide a solution to Judean desert. web-building spiders in the Negev highlands, disposing of polyethylene the Negev highlands. including Ein Avdat in waste used in protected Nahal Zin. agriculture in the Arava Valley. MARCO AND LOUISE MITRANI DEPARTMENT OF DESERT ECOLOGY Prof. Berry Pinshow, Chairperson

Researchers in the Mitrani Department of Desert Ecology use deserts as model ecosystems for advancing the study of ecology in general, and the ecology of Israeli deserts in particular. Our findings can aid the conservation of desert ecosystems and can be applied to the prudent and sustainable development of desert regions. A major departmental project deals with the conservation and maintenance of biodiversity in arid lands. This research includes studies to assess environmental heterogeneity (both physical and biological), ecological transformations (natural and man-caused), and biotic interactions (such as predation, parasitism, and competition for resources). The roles of scale and the mechanisms involved in creating and maintaining the diverse patterns of various desert plants and animals are also major topics of investigation. Research conducted by departmental staff and students includes investigations in physiological ecology, behavioral ecology and life histories, population ecology and genetics, Poplar tree (Populus euphratica) and community and landscape ecology. Studies in applied ecology, in collaboration with the at Ein Avdat near the Sede-Boqer Jewish National Fund and other organizations, investigate the implications of regional Campus. development projects, methods of arresting desertification, and the rehabilitation of landscapes degraded by human activity. The Mitrani Department facilities include an animal care unit, a reference herbarium, areas for garden experiments in loess and sandy desert soils, outdoor insect houses, and research sites representing a variety of desert habitats. Three peripheral research centers are affiliated with the Department: The Ramon Science Center (Mitzpe Ramon), the Hatzeva Research and Development Center (Hatzeva, Arava valley), and the Jewish National Fund Desertification and Restoration Ecology Research Center (Sede-Boqer Campus). Phone: 972-8-659-6771 • Fax: 972-8-659-6772 • E-mail: [email protected] Academic Staff Abramsky, Zvika1 Ayal, Yoram Bouskila, Amos2 Kotler, Burt P. Lubin, Yael D. Novoplansky, Ariel Pinshow, Berry1 Safriel, Uriel N. Saltz, David Shachak, Moshe Ward, David Ziv, Yaron2 ASsociate Staff Yarom, Ilan Zaady, Eli

1 Joint appt. with BGU’s Dept. of Life Sciences 2 Home department – BGU’s Dept. of Life Sciences

desert ecology 24 Research Activities

Physiological Ecology

Desert organisms often have specialized physiological responses that are not observed in species residing in temperate climates. Currently, studies by Department researchers focus on the respiratory physiology, water loss, and energy budgets of desert birds and small mammals. Although migrating birds are not necessarily adapted to arid-land conditions, they are also of interest as hundreds of species make desert stopovers during their annual migrations. In this context studies on birds have focused on the physiological limitations on long-distance flight. Other physiological aspects of bird migration are also studied.

Carbon isotope ratios in We hypothesized that an animal’s past and present diet can be distinguished through the exhaled CO indicate 13 12 2 C/ C signatures of dietary components found in exhaled CO2. We tested our hypothesis metabolic substrate use 13 by feeding 12 pigeons corn (a C4 plant) for 30 days, after which their breath C was – and therefore past and 13.63‰ (± 0.30). We then fed 6 of them wheat (a CO3 plant) while the others continued to present diets in birds eat corn. After 48 h the exhaled 13C from corn-fed pigeons was unchanged, while that from Pinshow wheat-fed pigeons was –20.5 ‰. Three wheat-fed pigeons were then fasted for three days, after which their exhaled α13C was –14.96 ‰, while it was –13.57 ‰ in corn-fed pigeons, and –22.22 ‰ in pigeons fed only wheat. Thus, it is apparent that 13C/12C ratios of exhaled

CO2 can be used to make inferences concerning metabolic substrate and hence present diet, past diet, and changes in diet from past to present. Breath CO2 analysis can be accomplished without harming the animal or having to recapture it successively and is applicable to rare and endangered species. (Funding: United States-Israel Binational Science Foundation). With: Kent Hatch, Ben-Gurion University

Effects of fasting on Some birds regularly undergo extended fasts and many maintain high-metabolic activity, such in-flight fuel catabolism as migratory flight, while fasting. We investigated the effects of fasting on energy substrate of pigeons metabolism in flight by depriving trained tippler pigeons (Columba livia) of food for 2 - 48 h Pinshow preceding flights of 4 h. Immediately after flight, blood concentrations of uric acid and b-hydroxybutyrate were increased, indicating elevated protein and lipid catabolism during flight. Lighter birds and birds fasted for longer periods before a flight lost less mass during a 4-h flight than heavier ones and ones that fasted for shorter periods. Birds that lost more body mass during flight had lower blood b-hydroxybutyrate concentrations, suggesting lower in-flight lipid oxidation. Flying pigeons apparently did not compensate for lower lipid catabolism with increased proteolysis. Changes in in-flight protein catabolism were not correlated with either fast duration or pre-flight body mass. We reasoned that pigeons lost more mass in-flight after feeding than after fasting because recently fed birds catabolized more glycogen. Thus, pre-flight fast duration is an important determinant of the fuels used in flight. (Funding: United States-Israel Binational Science Foundation). With: Lenny Gannes, Princeton University; Kent Hatch, Ben-Gurion University

Nitrogen requirements Nectarivorous birds are represented by three major radiations: honeyeaters and sunbirds in of an old world the Old World, and hummingbirds in the New. Costa’s hummingbirds and New Holland nectarivore, the honeyeaters have unusually low protein requirements that have been related to the species’ orange-tufted sunbird low-protein, high-sugar diets. Therefore, we hypothesised that orange-tufted sunbirds Nectarina Osea (Nectarinia osea) would likewise have low maintenance protein requirements and low rates Pinshow of endogenous nitrogen loss. To test this hypothesis, we measured nitrogen balance, total endogenous nitrogen loss and body mass changes in captive birds, using insects as a protein source. In addition we made separate estimates of endogenous urinary and faecal nitrogen for orange-tufted sunbirds. Nitrogen balance was less than one half of that predicted for birds of the same mass, while total endogenous nitrogen loss is less than one third of the allometrically predicted value. Thus orange-tufted sunbirds follow the same pattern of low protein requirements found in hummingbirds and honeyeaters. Metabolic faecal nitrogen and endogenous urinary nitrogen of sunbirds were similar to those found for nectarivorous desert ecology 25 marsupials which have the lowest measured values for mammals. Low metabolic faecal nitrogen is attributable to a fibreless easily digestible liquid diet, while low endogenous urinary nitrogen probably results from efficient protein use. (Funding: Israel Science Foundation). With: Lizanne Roxburgh, Ben-Gurion University

Test for physiological During northward migration blackcaps arrive at stopover sites in Israel's Negev Desert with limitation to nutrient reduced mass of organs that are important in food digestion and assimilation. Blackcaps that assimilation in a stay to refuel (largely on fruits) do not gain mass rapidly until after 3 days at the stopover long-distance passerine site. We hypothesized that 1) it may take several days to rebuild these reduced organs, 2) migrant at a springtime during this recovery interval high feeding rates might not be possible, and 3) this could be the stopover site basis for the absence of immediate body mass gain in blackcaps at stopover sites. To test Pinshow predictions from this hypothesis we used an established fasting protocol to create a group of blackcaps with reduced intestinal and liver mass, compared with ad libitum-fed controls. Migrants were captured and caged in the laboratory where they were habituated to a fruit mash diet for 8 days. One experimental group was then fasted two days, one was fed at a restricted level (one-third ad libitum food intake) for four days, and one group was held as ad libitum-fed controls. The fasted and restricted birds were then allowed to feed again ad libitum. Birds that were experimentally fasted progressively increased their daily assimilation rate and achieved the highest rate (one-third higher than controls) 3 days after the end of their fast. Birds that were restricted achieved high rates immediately once ad libitum food was provided. Increased assimilation rate was achieved via hyperphagia and not increased assimilation efficiency. The response of the fasted birds supports the hypothesis that there may be physiological constraints to the rate of refueling during migratory stopover. (Funding: US-Israel Binational Science Foundation; Fulbright Foundation). With: W.H. Karasov, University of Wisconsin, Madison

Behavioral Ecology and Life Histories

In the ecological growth facility, Mitrani researchers investigate Organisms apply various mechanisms to cope with temporal and spatial changes in resource the growth ‘decisions’ of plants abundance. They may, on the one hand, adjust their foraging strategies, i.e., behavior, and on under different environmental the other hand, they may modify their demographic strategies, namely, aspects of growth, regimes. reproduction, and seed dispersal. In deserts, environmental variation may be substantial and resources meager. Mitrani researchers examine the growth ‘decisions’ of plants under different environmental regimes; the ways that insects and spiders make foraging decisions and the life-history consequences of these decisions; and how foraging behavior can be used to explain the interactions among species in desert ecosystems.

Plasticity of Allocation of resources to newly developing organs depends on the actual availability of developmental limited resources and the probability that these organs will successfully complete their life hierarchies in plants cycle. A central question is, what are the environmental factors and the internal controls that Novoplansky govern the hierarchies and sizes of newly developing organs. Many plant organs are comprised of smaller functional units. For example, first-order branches would be functionally meaningless without their photosynthetic leaves. Such hierarchical construction can be readily found in both the vegetative and the reproductive structures of most plants. While allocation to relatively small organs allows swift materialization and low risk of invested resources, the development of relatively large organs may offer greater efficiency of resource use. The size of the developing organs is thus expected to represent an inherent trade-off between efficiency and risk in resource utilization. Accordingly, it is expected that the determination of the hierarchy and the size of any given organ would not only depend on resource availability and the vigor of the plant but also on the plant’s evolutionary background (e.g. general probability of catastrophes), and on information concerning its specific environment such as the time left to the end of the season, and the expected future availability of limiting resources. With T. Sachs, The Hebrew University of Jerusalem; G. Jelschke, Jena University, Germany. desert ecology 26 Genetic variability in The genetic variability of drought resistance was examined in plant populations near the core and peripheral center (core) and at the periphery of their distributions. Clover (Trifolium purpureum) and plant populations: cooksfoot (Dactylis glomerata) were collected in the field from three core and four peripheral relevance to drought populations each. The specimens were grown in the greenhouse under high or low water survival availability throughout the growth season. While no consistent differences in the levels of Novoplansky, Safriel genetic variability were observed in core and peripheral populations, plants from sites within the same regions varied considerably in almost all cases. This may mean that the populations studied may each represent a unique genetic background. We expect to examine the genetic variations of populations in northern temperate climates and those in actual desert environments, and to compare these with populations of semiarid species examined here. With: A. Cahaner, Hebrew University of Jerusalem.

Effects of resource Although the question of whether competition intensity increases or is unchanging along pulsing on individual productivity gradients has been highly controversial for a number of years, empirical results performance and bearing on this question are quite variable and no consistent answer has yet emerged. We competitive hierarchies suggest that explicit consideration of resource dynamics within and between productivity in plants levels could clarify both existing theoretical predictions and the experimental evidence used Novoplansky to test these predictions. When soil resources are temporally variable, plants will experience two distinct phases of resource availability: relatively short pulse periods when resources are high and most growth and resource accumulation occurs and longer interpulse periods when resources are more restricted and most mortality due to resource deficits takes place. We suggest that competition for limited resources takes place largely during pulse periods, while stress tolerance largely determines survival during interpulse periods. As productivity increases, the frequency of pulses (as well as or in place of their magnitude) often increases and the duration of interpulse periods decreases. While competitive effects on growth should occur during pulses at both high and low productivity, we suggest that competition for soil resources is unimportant in determining individual survival during interpulse intervals. For the longer interpulse intervals at lower productivity, the lack of competitive influence on survival should further extend to lack of effects on population persistence. This hypothesis predicts that relative competitive effects on growth should be similar at high and low productivity, while competitive effects on survival and on population abundance and community structure should increase with increasing productivity. Further, because gradients in productivity due to water are more likely to fit the assumptions of this hypothesis than are gradients due to nutrients, we also predict that competition intensity is more likely to increase along water productivity gradients than along nutrient productivity gradients. With: D. Goldberg, University of Michigan; A. Sher, BIDR

Root-root and This study is aimed at studying the hypothesis that root communication plays a major role in root-object determining the directional responses and spatial distribution of roots. The foci of the study interactions: close are the directional responses of roots when encountering other (self or non-self) roots or encounters of the second inanimate objects. An experimental system was developed in which plants with two identical and the third kinds roots are grown so each one of their roots is confronted with self roots on one side and Novoplansky with non-self roots on the other side or when confronted by various physical obstacles. Preliminary results have shown that the roots of peas and beans are capable of avoiding nearby physical obstacles and prefer to branch towards neighboring non-self roots. Other experiments test the hypotheses that a) roots are capable of perceiving and avoiding inanimate objects by responding to self-inhibition substance(s) that are secreted by the roots and are accumulated near physical obstacles; b) Plants use self/non-self recognition to minimize self and maximize non-self competitive interactions. The proposed study is expected to contribute to the understanding of the unexplored complexity of root-root and root-obstacle interactions and to shed light on their population and community-level implications. With: M. Gersani, Ben-Gurion University

desert ecology 27 Populations and Communities

The interactions between desert herbivores and vegetation or between animal predators and their prey are complex. An improved understanding of arid environments and attempts to ensure their preservation require detailed investigations of population structures and dynamics as well as the interactions among indigenous species in desert communities. One Mitrani group investigates how vegetation structure and predation determine the species composition of darkling beetles; a second collaboration studies complex interactions among spider species; a third group probes the structure of desert rodent communities.

Complex interactions In the desert, complex interactions may exist between predators and their prey. Spiders may among spider predators account for nearly half the biomass of arthropod populations in deserts. The abundance of and spider prey five species of spiders living in the Negev desert was investigated. Two of them (Poecilochroa Lubin senilis and Thyene sp.) are predators of one or more of the other three species (Mogrus sp., Stegodyphus lineatus and Latrodectus revivensis). We found that Poecilochroa senilis attacks predominantly Mogrus, but will accept Stegodyphus, an alternative prey that is also attacked by Thyene. Predation pressure on Mogrus, the more vulnerable species, is reduced by its seasonal migration into a different habitat. In other interactions, in winter, Poecilochroa spiders readily prey on Latrodectus spiderlings inside their cocoons. However, in summer, adult Latrodectus may trap and attack P. senilis. (Funding: Israel Science Foundation). With: M. Whitehouse, University of Queensland, Brisbane, Australia

Foraging Games Between Predator-prey interactions often constitute a foraging game in which prey individuals manage Owls And Gerbils: risk from predators and predator individuals manage fear in their prey. A tool of risk Temporal Dynamics Of management available to clever prey includes apprehension, the redirection of attention Resource Depletion And from foraging to predator detection. One such foraging game occurs between gerbils and Apprehension In Gerbils owls on the sand dunes of the Negev desert. Here, interacting species of gerbils compete for Kotler patches of seeds that are renewed daily by afternoon winds. In such a situation, gerbils are expected to deplete resource patches over the course of the night, owls are expected to hunt when gerbil activity is highest, and gerbils are expected to be most apprehensive when owls are most active and most lethal. We tested these predictions for gerbils in two field experiments using seed trays to measure patch depletion and apprehension over the course of the night, between the bush and open microhabitats, and at four moon phases (new, half waxing, full, and half waning). The gerbils depleted seed resources gradually during the course of the night. Gerbils depleted seed resources more quickly in the bush microhabitat than the open, and more quickly at new moon than at other moon phases. Moon phase interacted with timing of activity. Gerbil activity at new moon was high throughout most of the night, but decreased towards dawn. In contrast, activity at full moon was generally low, but increased towards dawn. The two gerbil species, Gerbillus andersoni allenbyi and G. pyramidum, partitioned the night, with G. pyramidum visiting resource patches earlier in the night and encountering a richer, but more risky environment, and G. a. allenbyi foraging later in an environment characterized by fewer seed resources, but lower risk. The same pattern In the aviary, researchers extended over moon phases, with G. pyramidum foraging relatively more at full and waning investigate predator behavior of barn owls (Tyto alba.) half moon. This resulted in the most extreme temporal partitioning occurring at new and waxing half moon. Apprehension by gerbils was highest early in the night when seed resources were highest and gerbil activity most intense. Also, apprehension was higher at full moon than new moon when predators were most lethal. Finally, apprehension was higher in the open microhabitat early in the night, but this difference disappeared as resources depleted during the night, suggesting the role of owl attacks early on, but perhaps relatively more attention directed towards snakes towards dawn. Apprehension thus appears to be related to the forager’s activity, as well as conditions that affect predator lethality and encounter rates with predators. The environmental conditions, resource depletion, the decisions of the gerbils regarding level of activity, location of activity, and level of apprehension, and the decisions of the predators regarding level and timing of activity are all tied up in the foraging game. This game affects three trophic levels, including the effect of the desert ecology 28 gerbils on the availability and distribution of seeds, the competitive interaction between the two gerbil species, and the predator-prey interaction between gerbils and owls. (Funding: U.S.-Israel Binational Science Foundation) With: J. S. Brown, University of Illinois at Chicago; S. R. X. Dall, Cambridge University; S. Gresser, University of Sydney; D. Ganey, Emporia State University; A Bouskila, BIDR

Examining parental Provisioning of young in the nest by parent birds is a classic example of central-place foraging; investment in themselves it is also a time when crucial life history decisions are made. Food delivery has fitness benefits and their chicks: through its effects on nestling survival and growth. It also has survival costs in terms of the differential food time and energy spent by the parents while provisioning and their increased exposure to allocation by parent predators. Previous theoretical and empirical studies of parental allocation decisions have sunbirds generally dealt with sharing by parent birds of standard food items between themselves and Pinshow their chicks. However, food types may differ in suitability for transport back to the nest and/or in nutrient content. This may have consequences for both foraging and allocation decisions made by parent birds. Specifically, the availability of energetically profitable food items that the parent itself eats should influence the total rate at which it can deliver other food items to the nest. We found that while parent orange-tufted sunbirds (Nectarinia osea) consume flower nectar and arthropod prey, they supply their chicks with exclusively arthropod prey. Thus, manipulation of the nectar source can be used to test hypotheses regarding strategies of parental investment, foraging, and the trade-off between self-feeding and provisioning. We used orange-tufted sunbirds to test the hypothesis that parents change the total amount of food delivered to their young according to the energy content of the food they consume. Pairs with two or three chicks were provided with feeders containing low, medium or high concentration sugar solutions. As sugar concentration increased, 1) both parents (especially the females) delivered more arthropods to the nest; 2) males increased their nest-guarding effort; and 3) inter-brood interval decreased. Nestling food Female black widow spider intake, growth and survival all increased with increasing sugar concentration and with (Latrodectus revivensis) with her egg sac. These spiders feed on a decreasing brood size. We concluded that increased energy intake by parent sunbirds affords wide range of surface-dwelling them the extra time and/or energy to invest more in their young, with consequent positive arthropods, including scorpions effects on their reproductive output. (Funding: Mitrani Center for Desert Ecology). and solifuges many times their size. With: Shai Markman, BIDR; John Wright, University of Wales, Bangor

Community structure of Using the theory of density-dependent habitat selection, we have spent almost a decade desert rodents studying the interactions of two gerbils, Gerbillus allenbyi and G. pyramidum, in the sandy Abramsky habitats of the Negev desert. We have successfully measured the gerbils’ interspecific and victim isoclines, the latter by using trained owls. We also determined the relative contribution of predation and competition to fixing population densities. Presently, the energetic costs of several biotic interactions are being measured, including competition within and between gerbil species, risks of predation, and habitat selection. We are also investigating the long-term influence of risk of predation on rodent population dynamics and interactions, as well as its indirect effects on other seed-eating organisms and on annual plants. (Funding: US-Israel Binational Science Foundation; Israel Science Foundation). With: M. Rosenzweig, O. Ovadia, G. Ben-Natan, and A. Bar, Ben-Gurion University

desert ecology 29 Conservation Ecology

The spreading desertification in many areas of the world, including the south of Israel, has been well documented. This phenomenon, along with man-induced disturbances, can lead to the extinction of populations and to the reduction of genetic variation in the populations that remain. Mitrani Department researchers investigate genetic and phenotypic variation in plants, the conservation as well as the reintroduction of endangered mammalian species, and the conservation and restoration of acacia savannas and of the Carmel forest ecosystem.

Conservation priorities It is hypothesized that the most genetically diverse populations within a species’ range occur based on genetic within an area of transition between ecosystems where a sharp environmental gradient diversity across an exists – the ecotone. Many of the Israeli animal and plant species occur along a steep ecological gradient eco-geographical gradient extending from mesic Mediterranean zones in the north to steppe Safriel and desert regions in the south. To test the hypothesis, the genetic variability as expressed by allozyme diversity of one such species, the Chukar Partridge, Alectoris chukar was sampled. Based on 32 allozyme loci, the genetic diversity of chukars increased significantly along the gradient from populations in Mediterranean regions to those at the ecotone in the northern Negev desert. It may be therefore recommended that for protecting the highest within-species diversities, higher conservation priority be assigned to the Mediterranean-Negev ecotone area. With: S. Kark, P. Alkon and E. Randi

Assessing grazing impact Assessing vegetation status via remote sensing techniques using various vegetation indices by remote sensing in has been successfully applied to semi-arid and arid environments. We tested the feasibility of hyper-arid applying such techniques for assessing grazing impact in hyper-arid environments with a high environments variance in soil type over space. An anticlinal erosional cirque called Makhtesh Ramon in the Saltz Negev desert, Israel, was selected for the study. The cirque is typified by low rainfall (40-90 mm per year), a variety of soil substrates and is subject to grazing by a herd of Asiatic wild asses (Equus hemionus) reintroduced into the cirque between 1984 and 1987. As a control, we used an ungrazed dry riverbed south of the cirque that runs parallel to the riverbed draining the cirque. We used five common vegetation indices derived from Landsat 5 satellite Thematic Mapper (TM). Four images were used, representing dry and wet seasons in above- and below-average rainfall years (1995 and 1987, respectively). To test whether we can detect changes in plant community structure via satellite data we correlated vegetation indices from the TM to ground measurements made along the altitudinal gradient of the cirque. To test whether differences in plant cover could be detected, we correlated the vegetation indices with ground measurements of cover in and out of the cirque (grazed and ungrazed areas). Although ground measurements showed that community structure changed following grazing with altitudinal gradient and ground cover 30% lower inside the cirque than outside the cirque, none of the five vegetation indices correlated with the ground measurements. Transformed Soil Adjusted Vegetation Index (TSAVI) and Normalized Difference Vegetation Index (NDVI) produced the best results. We hypothesize that the low vegetation cover that typifies hyper-arid environments increases the noise to signal ratio. Thus, a 30% decline in vegetation cover in this case is only an absolute decline of 4% from 15.8 to 11.2%. Because TM is sensitive to absolute cover rather than the relative differences, it is difficult to demonstrate differences among TM images. Using ANOVA to test the effect of season and grazing status on TSAVI and NDVI, we found a significant interaction between season and grazing status in 1995 with indices declining more from wet to dry season inside the cirque than outside the cirque. No such pattern was found in 1987. These data suggest that satellite imagery may detect changes in plant cover over time but cannot serve as a direct index of plant cover in hyper-arid conditions.

desert ecology 30 Large mammalian High mortality, poor germination, and the poor survival of young native acacia trees in many herbivores and the Middle Eastern regions may result in the loss of some five other plant species, which depend conservation of acacia on the acacias for nitrogen and shade. We studied the effects of large mammalian herbivores stands in arid regions of on the establishment of young Acacia raddiana and A. tortilis in the Arava Valley between the the Middle East Red Sea and the Dead Sea, Israel. Seed accumulation under trees was high when large Ward mammalian herbivores such as gazelles and camels were excluded, and direct observations confirmed that these mammals were the main seed dispersers of these Acacia species. Insect seed predators (bruchid beetles) damage more than 95% of seeds not consumed by ungulates. Moreover, seed germination was facilitated by passage through the mammalian ungulate gut. Under present conditions, several years of high rainfall are necessary for the successful establishment of young trees. Under severe browsing pressure, growth of juvenile trees was delayed and smaller size trees were over-represented. There was no evidence, however, of negative effects of this browsing on the long-term demography of acacia trees. We conclude that large mammalian herbivores are essential components of arid acacia savannas, and that wild domestic ungulates must be included in future conservation programs. (Funding: German Ministry of Environmental Affairs, Israel Ministry of Science, and Keren Kayemet L’Yisrael (JNF).

Ecosystem Studies

Ecosystem studies address the complex of a community and its environment functioning as a single ecological unit. Dealing with problems on that very inclusive ecosystem approach, Mitrani scientists are studying the interactions between organisms at several levels of the food chain, providing insights into the dynamic processes that determine the structure and function of desert ecosystems, as well as the impact of man on these ecosystems.

Desert ecosystems Various aspects of the interactions of animal and plant communities with their environments Shachak are under investigation. These include studies of: organisms acting as ecosystem engineers in the Negev (with C. Jones, Institute of Ecosystem Studies [IES]); the dynamics of patchy vegetation in semiarid systems (with G. Lovett, IES); the effects of grazing on patchiness, resources, and organisms in a semiarid landscape (with A. Perevelotsky, Volcani Institute, Israel); the structure and function of sink-limited systems (with S. Pickett and P. Groffman, IES; and A. Karnieli, B. Boeken, and E. Zaady, BIDR); human-induced changes of the relationship among patchiness, resource flow, and biological productivity and diversity (with S. Pickett, IES); the role of invertebrates in ecosystem functioning in arid lands (with A. Wilby, BIDR); and, seed flow in a semiarid landscape (with H. Kugel, Hebrew University of Jerusalem, and B. Boeken, BIDR).

desert ecology 31 The Ramon Science Center Prof. David Ward, Head

The Ramon Science Center conducts long-term research on the ecology and geology of the Makhtesh Ramon and surrounding environment in the central Negev desert. The center is situated in the town of Mizpe Ramon, about 35 kilometers south of the Jacob Blaustein Institute for Desert Research in Sede-Boqer and is affiliated with the Mitrani Department of Desert Ecology. Makhtesh Ramon is a large erosion crater some 40 kilometers long and about 8 kilometers wide, surrounded by 400 meter-high natural walls. Initially established as a geological park because of its remarkable diversity of geological structures and habitats, this crater now forms the central part of Israel’s largest nature reserve – the Negev Mountains National Park. Makhtesh Ramon is home to a wide variety of desert animals and plants, some of which are found nowhere else. Of particular ecological interest is the fact that the crater forms a natural boundary between two major biogeographic zones, the steppe (Irano-Turanian) and the true (Sahara-Arabian) desert. As such, the crater is an extraordinary natural laboratory for the study of ecological interactions of the two floras and faunas. The academic staff of the Ramon Science Center includes three geologists and three ecologists. Academic STaff Avni, Yoav Krasnov, Boris Plakht, Josef Sheinkman, Vladimir Shenbrot, Georgy Ward, David

Phone: 972-8-658-8764 • Fax: 972-8-658-6369

Adjunct Researchers

Prof. Emanuel Mazor, Weizmann Institute of Science Dr. David Saltz, BIDR

Satellite photo of Makhtesh Ramon, a large erosion crater in the Negev highlands. Forming a natural boundary between the Irano-Turanian steppe region in the north-east and the Sahara-Arabian desert which lies to the south, Makhtesh Ramon presents researchers with unusual opportunities for geological and ecological investigations.

desert ecology 32 Research Activities

Geology

Mapping of Quaternary This work represents an attempt to construct Quaternary maps in a genetic-chronological deposits in Makhtesh order. Two maps depicting Quaternary geology of Makhtesh Hazera and Makhtesh Hatira are Hatira and Makhtesh prepared at the scale of 1:50,000. The major mapping unit is by genetic type of sediment. Each Hazera genetic type is further subdivided according to age. Quaternary mapping of Makhtesh Hazera Plakht and Makhtesh Hatira is based on: (1) development of a morphostratigraphic scheme and definition of genetic types of sediments (including construction of geological-geomorphological cross- sections in different portions of valleys, construction of longitudinal profiles of river beds and terraces and detailed study of pediments as integral components of the landform system) and complex analysis of alluvium and loess as a tool for stratigraphic correlation (lithological analysis, the study of paleosoils and absolute dating of terrace alluvium).

Morpho– and As a key to the paleogeographic resconstruction of the Negev, we are investigating and chronostratigraphy of mapping, at a scale of 1:50,000, the Quaternary units in the middle reaches of Nahal Zin. the Quaternary of the This allows us to express the spatial distribution of Quaternary sediments and to determine middle Nahal Zin the relative time-scale of regional Quaternary history. The study includes Plakht, Sheinkman morphostratigraphy of the river valley, study of the alluvium composition and sampling for absolute age determination.

estimating Determining the connections between landforms and composing rocks in the erosion-accumulative Makhtesh/Nahal Zin/Dead Sea geomorphosystem allows us to estimate activity in the Central erosion-accumulation in the Central Negev. We studied the staircases of terraces Negev composing the Nahal Zin and Nahal Hatira valley and elaborated the morphostratigraphic Sheinkman scheme. Our investigation shows that the -130-m level of the maximum ingression of Dead Sea in the Nahal Zin canyon compares to the –180-m level in the formerly printed materials. The complex facial composition of ancient lake and fluvial sediments were determined, and data collected on the first absolute ages of the sediments.

Ongoing destruction In southern Israel, gully erosion creating badland topography is a well-known phenomenon process of loess land developed within loess soils and fine alluvial sediments. This phenomenon becomes critical in reducing pastoral and the Negev Highlands where potential agricultural fields are limited to narrow valleys. agriculture uses: Negev During the last 15 years, we monitored and studied the mechanism and the rate of gully Highlands migration in several locations in the region south of Beer-Sheva. and found that the Avni, Plakht, Ward development of a deep and narrow gully concentrates the runoff and restricts the irrigation effect of the floods from the whole width of the valley. As a result, a reduction of about 80% of the floral biomass was observed and the agriculture potential was severely damaged. These parameters indicate ongoing aridization of the area that is proceeding at a rate of several meters per year for each gully. Preliminary results relate the ongoing destruction of the loess cover of the Negev Highland valleys to a dynamic change in the rock/soil ratio during the Holocene. With: A. Yair, Hebrew University of Jerusalem

Synoptic patterns, storm The purpose of this three-year project is to study the synoptic patterns and the storm tracks tracks and distribution that cause extreme flooding in the Negev highlands region. Special concern will be given to of rainfall causing the the storms and floods caused by the "Red Sea low pressure" that is responsible for the major extreme floods in the flood events known in the region. One of the aims of the research is to evaluate and analyze Negev Mountains the floods and synoptic data collected in the last 40 years in the region. Ongoing monitoring Avni, Ward of present and future events will be done during the course of the research project. With: Y. Enzel and R. Cahana, Hebrew University of Jerusalem

desert ecology 33 Ecology

Urban ecology of a The purpose of this complex study of geology, geomorphology, botany and zoology is to settlement in close represent the ecology of the town of Mitzpe Ramon and its surroundings, the Makhtesh proximity to a Ramon Nature Reserve, in order to determine rational methods for land use and nature reserve conservation of the desert environment both inside the town and in the adjacent nature Ward, Mazor, Plakht, reserve. Particular attention is being devoted to the influence of the marble quarries on the Krasnov, Avni, Shenbrot environment of the town. We suggest alternatives, which do not disturb the natural environment, to the present-day quarries.

Monitoring of the biota One of the principal purposes of nature reserves is to estimate what degree of protection is of Ramon park Nature needed to insure the required level of nature conservation, and to evaluate the results of Reserve using management practice. The solution of this problem includes developing the principles of the tenebrionid beetles monitoring process, which are urgently needed for nature reserves and for particularly Krasnov sensitive nature zones as, for example, Makhtesh Ramon. Recording the changes in abundance, diversity and biology of plants and animals is vital for decision-making in conservation. The monitoring of living organisms is becoming accepted as a more informative method than that of monitoring physical or chemical variables when assessing the effect of environmental change on ecosystems. The principal objective of the monitoring is not to find solutions to methods of management, but to derive information on the biota state and the extent of change in it. It is then up to the managers and biologists to determine the causes of change and thence determine how to prevent changes from getting worse and how to reverse the situation. Since it is impractical and impossible to monitor all components of the reserve biota, it is necessary to select just a few components, which will serve as bioindicators for the state of nature in the reserve. We elaborated monitoring protocol using tenebrionid beetles as indicators of the biota state and continue to perform routine monitoring of this taxon in Makhtesh Ramon and the vicinity.

Ecological and Populations of rodents isolated on islands often show systematic differences in their physiological demography, reproduction, behavior, and morphology when compared to mainland parameters of Gerbillus populations. These differences, termed "the island syndrome", include many distinctive gerbillus from isolated characteristics. In Israel, Gerbillus gerbillus (Rodentia:Gerbillidae) represents a pattern of population distribution which is similar to the mainland-island pattern. It occurs in two main areas, namely Krasnov, Shenbrot in Holot Agur, Holot Shunra and Holot Nachal Secher in the northwest Negev and in Holot Samar in the Arava Valley. In addition, G. gerbillus inhabits small isolated sand dunes in the eastern part of Makhtesh Ramon. This pattern of distribution provides a good opportunity for studying the island syndrome of the isolated population of this rodent. Our research deals with the comparative aspects of the ecology, physiology, behavior and genetics of different populations of G. gerbillus. We compare G. gerbillus from an isolated population with two mainland populations. The aim of the research is to evaluate genetic, physiological, behavioral and ecological specificity of individuals in the isolated population of G. gerbillus and to reveal the possible connections among the "mainland" and "island" populations, the history of the species distribution in the region, and the degree of the isolation of Makhtesh Ramon population. With: I. Choshniak and P. Sinai, Tel Aviv University

Respiratory gas exchange Measurements of respiratory gas exchange on fleas at similar stages of development at 25oC and ventilatory allowed us to determine and developm a set of standardized parameters for quantifying both characteristics in fleas metabolic and ventilation characteristics of the prepupa and pupal stages as well as the newly Xenopsylla conformis emerged adult and feeding adult stages. Flea-respiratory gas exchange involved measurement and Xenopsylla ramesis of CO2 emission using a high resolution flow-through respirometry system. Fleas were Krasnov initially measured individually but later in groups to minimize error associated with instrument drift. When measured in groups, fleas soon settled and remained quiet in the respirometer chamber. No significant differences were found between individual and group recordings of fleas. Cocoon stages of known age were measured in the intact cocoons. After the recording, cocoons were dissected and the developmental stages inside identified and desert ecology 34 weighed. Vco2 has been measured for all developmental stages of X. conformis and for the newly emerged adults of X. ramensis. Continuous ventilation was found in adult and preimago stages. In X. conformis, the life cycle stage with the highest energy requirements is the feeding adults. High metabolic rate in this hematophagus stage is probably associated with blood-meal digestion and in females, oogenesis and ovipostion. Lowest energy requirements are characteristic of the nonfeeding off-host cocoon stages: prepupa, pupa and premerged adults. Such low metabolic rates are expected in the cocoon stages as they form the main resting stage for many flea species. Mass specific metabolic rate of the unfed stages of X. ramensis did not differ significantly from those of X. conformis. Smaller size of X. ramensis in

comparison to X. conformis resulted in higher CO2 emission rates per individual flea. With: I, Khokhlova, Desert Animal Adaptations and Husbandr;, L. Fielden, Truman University, USA

Characterization of Whole-body permeability measurements at 25oC and >5% RH estimate water loss via whole body permeability trans-cuticular and respiratory avenues. These measurements determine "leakiness" of the in flea Xenopsylla two flea species as well as susceptibility of the different life cycle stages to dehydration. Data conformis have been collected for newly emerged adults of X. conformis. Fleas were placed in groups (n Krasnov ≥10) in perforated microcentrifuge tubes at 25oC in a drierite dessicator (>.5% RH). Mass loss measurements were made at 12 h intervals and water loss rates estimated. Water loss rates are high and adults show little tolerance to dessicating conditions. Approximately 50% of the fleas were dead after 24 hrs and no fleas survived more than three days. With: L. Fielden, Truman University, USA

Flea fauna of We investigated 14 rodent species from 18 localities yielding fourteen species of fleas. Southern Israel Nosopsyllus i. theodori is reported from Gerbillus gerbillus, Gerbillus henleyi, and Mus musculus in Krasnov, Shenbrot Israel for the first time. Additional records of Coptopsylla africana in Israel substantiate the presence of this species in Israel. With: M. Hastriter, Bringham Young University, USA S. Medvedev, Sociological Institute, St. Petersburg, Russia

Rodent and snail The project is devoted to development of an Intelligent Biodiversity Information System for biodiversity in different the central Negev desert. The system will allow decision makers to identify patterns of habitats of the southern biodiversity at spatial scales ranging from local sites of 100x100 m to the entire Central Israel Negev, and to evaluate local and regional losses in biodiversity expected from potential Shenbrot, Krasnov future scenarios of habitat destruction and development programs. The system under development is based on empirically-derived species response models that predict probabilities of species occurrences at a site from information on climatological and edaphic factors. Data for model calibration are being obtained from an extensive sampling project covering the main climatological and edaphic gradients of the central Negev (the faunal data on rodents and snails) and maps already available in a digital form (rainfall, temperature, topography, geology, soils). With: R. Kadmon and Y. Heller, Hebrew University of Jerusalem

Habitat dependence of The jird Meriones crassus, which occupies several habitats in the central Negev, demonstrates the architecture and changes in its flea composition (Xenopsylla conformis versus Xenopsylla ramesis) among microclimate of habitats along the rainfall gradient. The working hypothesis is that this replacement is Meriones crassus correlated with host-habitat factors, specifically temperature and humidity. To check this burrows hypothesis, the structure and microclimate (temperature and humidity) of jird burrows were Shenbrot, Krasnov compared in two different habitats. Significant between-habitat differences were found in the general length of burrow tunnels, the number of burrow openings and in the burrow air humidity.

desert ecology 35 population and Since 1993 we have been monitoring the central Negev rodent populations on 24 sample community dynamics of grids established in Makhtesh Ramon and its vicinity. The aim of this long-term program is to Central Negev rodents estimate the influence of environmental fluctuations on populations of individual species and Shenbrot on the whole community in a system of habitat mosaic within a complex landscape.

Genetic diversity and There is widespread concern over mortality of native Acacia trees in the Negev desert, water stress in isolated Israel. Mortality varies widely, and may reach as high as 61% in populations of adult trees. The Negev desert populations threat of extinction is becoming evident in these Acacia spp. due to high mortality and rare of Acacia raddiana recruitment of seedlings. It is hypothesized that diminished genetic diversity has resulted Ward from these populations’ decline. The present study focused on Acacia raddiana because it is the most widespread species among the three native Acacias. We selected five sites with the highest mortality and three sites with the lowest mortality out of 75 sites surveyed. Random Amplified Polymorphic DNA (RAPD) markers were used to assess the relationships and genetic diversity among these populations. We investigated whether mortality is related to current water stress in these populations using a Scholander pressure chamber. There is considerable genetic variability among populations and a high degree of polymorphism within populations. Low genetic polymorphism is not associated with high mortality populations. We found that high mortality populations have significantly more negative water potentials than low mortality populations. There was a negative correlation between water stress and genetic polymorphism, indicating that genetic polymorphism may be important in withstanding environmental stress. With: M. Shtresha, Ben-Gurion University

Water stress in Many populations of native Acacia raddiana trees in the Negev desert suffer from high Acacia raddiana mortality. Road-building techniques that cut off water to trees in downstream populations Ward and pumping of aquifers for agriculture have been mooted as causes of this mortality. We studied the water relations of nine isolated populations of these trees using a Scholander pressure chamber and stable carbon isotopes in order to determine whether current water stress could be the cause of this mortality. We found that high mortality populations have significantly more negative water potentials, lower relative water contents and lower cell water volumes at full turgor than low mortality populations. These results show that mortality is correlated with current inter-population differences in water stress. However, we found no significant difference in water potential between trees upstream and downstream of roads, indicating that this is not the current cause of water stress. Furthermore, greater water stress in trees after a dry winter than in the previous summer indicates that these trees are largely drawing on surface floods for water and seldom use aquifer water. Thus, aquifer pumping is an unlikely cause of mortality. Hence, water stress is linked to mortality in these trees; our results indicate that irregular water stress (perhaps in drought years only) is the cause of this mortality. With: M. Shtresha, Ben-Gurion University

Soil factors as Flash floods during winter cause erosive activities in the basins and adjacent agricultural areas indicators of in the semi-arid parts of the Negev desert of Israel. This has led to the formation of waterfalls desertification in an (gullies) that erode streams. Consequently, this has led to the loss of soil nutrients over time. agro-ecosystem in the Soil erosion in conjunction with human activities has greatly contributed to desertification in northern Negev this part of the Negev. We set out to examine the effects of soil erosion and agricultural Ward, Avni practices in seventeen eroded sites in the northern Negev desert. Our presumption was that soil erosion and agricultural activities would reduce soil quality. In all the parameters investigated there were significant differences between sites. Areas above (uneroded) and below (eroded) gullies and distances (5, 10 and 20m) from waterfalls showed significant differences at all sites under investigation. Salinity was highest in the nature reserve sites and irrigated areas because of accumulation of bases resulting from reduced leaching and continuous supplies of heavy metals from brackish water used in the irrigation system, respectively. Organic carbon increased along a moisture gradient, being lowest in areas receiving 200 mm and highest where rainfall is over 300 mm per year. Nature reserves had desert ecology 36 higher organic carbon than cultivated areas. Nitrogen showed significant differences both between sites and eroded versus uneroded areas. Biomass of plants in a bioassay showed a positive correlation with the amount of organic carbon, an indicator of a reduction in soil quality. Water holding capacity was higher in nature reserve soils than in cultivated areas, whereas eroded sites contained bigger soil particles than uneroded ones. With T. Akuja

The population of the In the Negev Highlands, several hundreds of Pistacia atlantica trees are widely distributed Pistacia Atlantica as a along the valleys, especially in the range of 700-1000 m.a.s.l. The present research analyzes tourism resource in the the population of the Pistacia atlantica in Nahal Loz, central Negev highlands, to determine Makhtesim region – the following points: 1) the distribution of the young trees relative to the older ones in order destruction and to evaluate the vitality of the population; 2) the distribution of the sex ratio in the population; conservation patterns 3) the geomorphological characteristics of the tree locations; 4) the effect of erosion on the Avni tree population – especially the relations between the young trees and the erosion features like gullies development; and 5) the rule of the erosion over the last hundreds of years based on the position of old trees relative to the erosive features.The distribution of Pistacia atlantica in Nahal Loz has been affected by erosion in the last few years, putting the trees in danger of extinction. The recruitment potential of the trees however still seems to overcome this problem. There are enough young trees for replacement, and the distribution of the sexes appears balanced enough. The next stage of the research will focus on analyzing the role of erosion on the destruction of the Pistacia population, and developing methods for conservation.

desert ecology 37 HAZEVA RESEARCH AND DEVELOPMENT CENTER (HRDC) Dr. Ilan Yarom, Scientific Director

The Hazeva Research and Development Center (HRDC) is located in the central Arava Rift Valley, between the Dead Sea and Eilat. The Arava Rift Valley, home to some of the most pristine habitats in Israel, offers singular opportunities for research. There is an extraordinary confluence of natural ecosystems in the area with a beautiful and fragile mixture of plants and animals originating from different biogeographical zones: African Acacia trees, the Arabian babbler (an Asian song-bird), and the common wolf whose habitat extends to Europe. Many species cannot be found elsewhere in Israel. The nearby Shezaf Nature Reserve is about 9,500 acres and serves as a natural laboratory for scientific research. The ibex (Capra ibex nubiana) has The Ministry of Science and the Central Arava Regional Council are the main sponsors of been the focus of several HRDC and since 1996 HRDC has been academically affiliated with Ben-Gurion University of ecological studies. the Negev’s Jacob Blaustein Institute for Desert Research. The major areas of research at HRDC are: biodiversity, conservation of natural resources, ecological tourism, sustainable agriculture, and regional development. Researchers from academic institutions in Israel and around the world collaborate on research activities. HRDC’s 1999 budget was approximately $200,000. An additional $200,000 was secured from research grants in 1999.

Hazeva Research and Development Center c/o Hazeva Field School, Mobile Post Office Ha’Arava 86815, Israel Phone: 972-8-658-1641 • Fax: 972-8-658-2068 • E-mail: [email protected] Research Staff Dr. Ilan Yarom, Entomologist and Scientific Director. Dr. Rivka Ofir, Cell biologist and molecular geneticist Dr. Vasiliy Kravchenko, Entomologist, Research fellow Dr. Avner Anava, Zoologist; Postdoctoral Fellow Gideon Wasserberg, Ph.D. candidate (Ben-Gurion University) Research Activities

Insects in a changing Until now, there have been few studies on the insect fauna of the Arava. This is the first desert environment: A comprehensive multi-year effort aimed at understanding the biodiversity of the entomofauna study of the biodiversity of the Arava Rift Valley. Special attention is given to finding potential pests and promising and documentation of natural enemies that may serve as biological agents in future biological control or IPM the entomofauna of the strategies employed in the agriculture fields of the region. Insects are collected by staff Arava valley members and visiting entomologists throughout the year using various methods including Yarom aerial collecting, Malaise traps, light traps and others. The material is preserved by regular methods and identified by local taxonomists and colleagues around the world. Most of the material, including type specimens of the new species, will be deposited at the National Collection of Insects at the Department of Zoology, Tel Aviv University. With: V. Kravchenko, HRDC

Biodiversity of Tamarix This joint Israeli-German, three-year interdisciplinary project serves as a model for the study and associated insects in of human impact on biodiversity. This unique ecosystem comprised of species of Tamarix and natural and disturbed associated insects is being studied in natural and disturbed habitats. Habitats in the Arava are habitats in Israel also being compared with those in the coastal plain and Dead Sea area. This is a pioneering Yarom study of biodiversity changes at the ecosystem level for the entire Mediterranean basin. It will contribute to knowledge of the biology and ecology of Tamarix -based ecosystems and to the understanding of the mutual relationships of Tamarix plants with their associated insects at all trophic levels. With: D. Gerling, A. Freidberg, A. Eshel, Tel Aviv University; C. Zebitz, University of Hohenheim, Stuttgart,

desert Germany ecology 38 Ecology of fresh water A new system of water reservoirs was built in the Arava in recent years. The purpose of the reservoirs in the Arava reservoirs is to capture floodwater in the desert wadis for irrigation and to recharge the region, limnological and underground water basin. The goal of this study is twofold: 1) to identify the dynamics of the ecological effects in limnological processes of the captured water; 2) to identify the ecological changes caused by reservoirs and building the reservoirs, both around the reservoirs and downstream. Preliminary results downstream show remarkable differences between the two reservoirs under investigation: The Yarom downstream reservoir (Iddan reservoir) is much more eutrophic than the upstream reservoir (Zukim reservoir). We suspect that intensive agricultural fields located between the two reservoirs, but absent upstream from the Zukim reservoir, contribute to accumulation of nutrients in Iddan reservoir. We found out that there is a rapid microalgae growth in Iddan reservoir vs. macroalgae in Zukim reservoir. With: S. Gafny, Tel Aviv University

impact of flash flood Our goals are to clarify the relationships between flash-flood water and shallow ground interception on Arava water and to examine the impact of a massive environmental disturbance (catching flood shallow groundwater water) on the natural balance of the water system in the Arava. The study employs Yarom geochemical and isotope characterization of shallow ground water near water reservoirs, their temporal and spatial changes, and developing a model for evaluating the relationships between floodwater, captured water, and ground water. With: A. Bein and A. Burg, Geological Survey of Israel

development in the Coetaneous leishmaniasis ("Jericho rose lesion") is a common human disease in the Arava Arava and its effect on valley. Although coetaneous leishmaniasis is not lethal, the lesion may leave a noticeable scar. relationships between It is caused by a parasite and transmitted from local rodents to humans by sand flies. We host and vector of study the major environmental factors that affect the populations of the carrier rodent, such coetaneous as population dynamics and ecology, patterns of dispersal and activity, epidemiology of the leishmaniasis rodent population and the influence of human activity on the rodent populations and sand Yarom flies (the vector). With: G. Waserberg, Z. Abramsky, Ben-Gurion University; A. Warburg, Hebrew University, Jerusalem.

The fat-sand-rat The fat-sand-rat is a diurnal rodent that lives in small colonies. The goal of this study is to (Psammomys obesus) as a develop a new attraction for ecological tourism, much like the native Arabian babbler, which potential new tourist is well known as a social bird and attracts students of all kinds from Israel and abroad. The attraction for the researchers are working in two directions: 1) to accustom the gerbils to the presence of Arava human observers; 2) to study the behavior of the gerbils, their physiology, and other Anava information for preparing an ecotourism program. With: I. Yarom, HRDC; M. Kam, and A.A. Degen, Ben-Gurion University

Phytochemicals in the The research focuses on four projects: Arava plants: Screening 1. Collecting desert plant extracts that will serve as a library of natural products for for their screening phytochemicals for use against various biological causes of human diseases. pharmaceutical 2. High Throughput Screening (HTS) of phytochemicals for activating or repressing the potential "killing proteases" (Caspases) involved in programmed cell death (apoptosis). HTS of the first Ofir 100 desert plant extracts resulted in the identification of 10 plants containing phytochemicals capable of activating caspase-3 activity in cancer cells (leading to cytotoxicity accompanied by DNA Ladder). 3. HTS of natural products against serotonin re-uptake: potential treatment for depression in pre- and postmenopausal women. Serotonin plays a major role in depression at times of changing hormone levels in women. Phytochemicals will be screened for their effect on the uptake of serotonin by recombinant human serotonin transporter. 4. HTS of Indian plant extracts for cytotoxic activity against cancer cells and for pro- apoptotic activity. Thirty extracts prepared from plants used by local Indian doctors as medicine were screened for pro-apoptotic activity. Two plants contain compounds capable of activating caspase-3 and killing human cancer cells grown in vitro. Plants with functional activity may be considered for future cultivation as a potential new crop in the Arava. ecologdeserty 39 Microbial degradation The use of isolated bacteria that are able to use polyethylene as the sole carbon source is of polyethylene waste in being tested in a pilot project in the Arava. The goal is to develop a biotechnological method the Arava Valley for using these bacteria for degrading the large mound of polyethylene waste accumulated Ofir from agricultural use of polyethylene. With: A. Sivan, Institutes for Applied Research, Ben-Gurion University

Desertification and Restoration Ecology Research Center Dr. Eli Zaady, Resident Scientist

The Jewish National Fund (JNF), motivated by the need for research to support its dryland development projects, established the Desertification and Restoration Ecology Research Center jointly with the BIDR. The Center promotes interdisciplinary research into the causes of desertification, develops means of preventing it, and methods for restoring already desertified areas. Research Activities

Cooperative monitoring Desertification is a world-wide problem in arid lands that is made worse by population for long-term growth, urban development, and inappropriate agricultural techniques. Implementing a land sustainable land use in management program based on sustainable land use techniques can prevent desertification. the Middle East Sustainable land use relies on land quality indicators to identify problems and measure Zaady trends. Research is needed to fully understand how land quality indicators change over long periods under varying conditions. Sustainable land use is of particular importance in the Middle East. Population and economic growth are straining the environment's ability to support human activity. These trends are particularly acute in the "fertile crescent" extending from Egypt to Lebanon. The Middle East peace process recognized the importance of the environment in a stable peace by establishing a working group on the environment. The commonality of the problem presents an opportunity for regional scientists to collaborate in the collection, exchange, and analysis of environmental data. The Cooperative Monitoring Center (CMC), Sandia Laboratories, in association with the US National Science Foundation's International Long-Term Ecological Research (ILTER) program, initiated a project to measure fundamental parameters affecting sustainable land use on an ecological rather than national basis. The project brings together Palestinian, Israeli, and US scientists at Hebron University, the Ministry of Environmental Affairs of the Palestinian Authority, the Mitrani Center for Desert Ecology of Ben-Gurion University, the Jewish National Fund, the Volcani Center of the Israel Ministry of Agriculture, and the University of New Mexico. Meteorological data is fundamental to environmental research and is inadequately measured along the rainfall and biodiversity gradient extending from the Negev desert to the plateaus of the West Bank. A jointly-operated network of monitoring stations to collect and exchange measurements of meteorological and soil conditions was established at two Israeli and two Palestinian environmental research sites. The ILTER program provided the scientific context for the project, guidelines for monitoring and an international framework for sharing environmental data. The CMC provided the monitoring hardware as well as expertise in network and Internet communications. The regional partners provided the sites and research staff to operate the meteorological stations. UNM provided data and operational experience from a similar site in the U.S. A long-term goal of the project is for the Palestinian sites to join the ILTER program along with the Israeli sites.

desert ecology 40 Soil factors as Soil erosion is an all-inclusive term describing the deflation of the landscape by wind and indicators of water. Flash floods during winter cause erosive activities in the basins and adjacent desertification processes agricultural areas in the semi-arid parts of the Negev desert of Israel. This has led to in an agro-ecosystem in formation of waterfalls, which erode streams and cause the loss of soil nutrients over time. the northern Negev Soil erosion in conjunction with human activities has greatly contributed to desertification in desert this part of the Negev. We set out to examine the effects of soil erosion and agricultural Zaady practices in twelve eroded sites in the northern Negev Desert. Our contention was that soil erosion and agricultural activities would reduce soil quality. The results showed, in all the parameters investigated, that there were significant differences between sites. Areas above, below and at various distances from waterfalls showed significant differences. Ecological sites had higher organic carbon than cultivated areas, meaning that land degradation is taking place in the adjacent farmlands. Biomass of plants in bioassay showed a positive correlation with the amount of organic carbon, an indicator of reduction of soil quality in the adjoining cultivated areas. There is a need to further characterize the soil and increase the number of sites in the study area in order to conclusively determine soil quality and recommend corrective measures with a view to combating desertification. With: Y. Gutterman and D. Ward, BIDR

microphytic soil crust This investigation is part of the ‘Savannization Project’, a program aimed at combating communities desertification initiated by the Jewish National Fund in cooperation with scientists from Zaady Israel and the USA. We examined the processes of recovery of the microphytic soil crust after disturbances. The disturbances were caused by construction of pits and mounds, by scraping the soil surface and by applying herbicides. A central assumption of the Savannization Project is that plant and animal production and diversity in arid regions depend on the distribution and abundance of microphytic soil crusts, which are major sources of water and nutrients for higher plants. Results show that soil crust recovery in the Negev takes about seven to ten years. During this time, soil infiltration and soil erosion decrease and moss density increases. Since natural recovery of soil crusts is not a very long process, we recommend that for a few years after a heavy disturbance, managers should prevent The microphytic soil crust in the Negev highlands near Sede-Boqer human activities and grazing in order to allow the crust to recover. This is important as (100mm average annual rainfall). productivity and diversity in the Negev are concentrated mainly in the shrub patches, which depend upon the supply of resources from the crust patches.

Patterns of cO exchange 2 The objective of this research was to determine whether CO2 exchange rates could be used in biological soil crusts as an indicator for determining the state of development and species or functional of successional age composition of biological soil crusts in different successional stages. In order to do so, we Zaady quantified the CO2 exchange rates, i.e., CO2 assimilation and respiration, in samples from different microhabitats at two different sites in the Negev desert. The data sets obtained in

the course of this study show substantial net CO2 assimilation rates, which are in a range similar to dark respiration rates. We found a substantial gradient of CO2 exchange for both respiration and photosynthesis in biological soil crusts of successional age. Hence, as ecotypes containing such biological soil crusts with dominant photosynthetically active organisms are a widespread phenomenon in desert, boreal and arctic systems, their contribution to the global cycling of trace gases and elements can be significant for global budgets. With: J. Kesselmeier, Max-Planck-Institut fur Chemie, Mainz, Germany.

contribution of aeolian We investigated the dynamics of airborne particles in the northern Negev desert and in the particles to microphytic Negev highland region, and evaluated their contribution to microphytic soil crust soil crust patches development. Results show that aeolian accumulation and deposition on the south-facing Zaady slopes of the watershed were significantly higher than on the north-facing slope, but the highest accumulation was obtained in the wadi. The size classes of the airborne particles show that almost no damage was caused by dust deposition, and that most of the particles were fixed by the microphytic crusts and contributed to the soil depth. With: Z. Y. Offer, BIDR, Meteorology, Dept. of Energy and Environmental Physics. desert ecology 41 The relationships In this study, we measured some of the physiological and geomorphological characters of the between lizard different sandy surface substrates available to the lizards. We then compared the distribution distribution and of lizard burrows among the different substrates to the distribution of available sites. All four microphytic soil crust parameters measured showed a similar pattern of decrease from the well developed successional trend in permanent crusts to the loose sand. The lizards strongly preferred the temporary crust, arid sandy landscape where 80%-94% of the burrows were dug. These results may have important implications for Zaady land management, because sandy areas that are over-trampled are often converted into crustless sand. On the other hand, sandy areas inhabited by low densities of wildlife and with no livestock trampling, develop crusts with almost no disturbance and eventually turn into hard permanent crust that might not be suitable for small digging vertebrates. With: A. Bouskila, BIDR

The Nitrogen cycle in In a series of ongoing studies, we examined and characterized several aspects of the nitrogen dryland ecosystems cycle in dryland ecosystems. Zaady, Shachak 1. When comparing the N-fixation potential of different microphytic crust and macrophytic patch soil/litter types, we found that free-living N-fixing bacteria are important if desert patchiness is taken into consideration. Higher rates of N-fixation were observed in soil from macrophytic patches than in the soil crust material. The generally high C content of the macrophytic patch soil-litter, and the particularly high C-to-N ratio of the largest size class of this material, appear to facilitate N fixation in macrophytic patches. 2. In order to a) evaluate the potential for microbial immobilization and denitrification to compete with plants for N,; and b) determine the effect of litter on nutrient cycling processes in desert soils, we sought to quantify available N production within macrophytic patches and on the soil crust patches following rewetting events. Findings indicate that litter plays a strong role in conserving N following wetting events in Negev soils. Amounts of soil NH4+ and NO3- and microbial biomass N were reduced in litter-amended treatments, suggesting that significant quantities of N were sequestered in litter. Immobilization and release of N by litter may be especially important in the N cycle in desert ecosystems. With: P. Groffman, Institute of Ecosystem Studies, USA. effect of microphytes on The objective of this study was to compare reflectance values of higher plants with those of the spectral reflectance lower plants in drylands. During the wet season, when microphytic crusts are green, their of vegetation reflectance values are similar to those of higher plants, while in the dry season, they are in drylands similar to those of soil. We found that the reflectance of lower plant communities may lead Zaady, Shachak to misinterpretation of the vegetation dynamics and overestimation of ecosystem productivity. From the remote sensing point of view, the biogenic crusts of microphytic communities should be considered as soil during the dry season and as vegetation during the wet season. With: A. Karnieli, BIDR

The effects of grazing on The aim of this study was to quantify the effects of grazing on the ecological system, abiotic and biotic especially soil parameters and vegetation. We monitored the diversity and composition of parameters in semi-arid the plant community, herbaceous biomass, soil moisture, soil organic matter, habitat ecosystem: a case study structure, and quality of the vegetation for grazers (protein content and digestion). from the northern Monitoring was in both grazed and in ungrazed plots. Our results showed that grazing had Negev desert, Israel. immediate effects on the plant community and habitat structure: the density of plant species Zaady, Shachak decreased, vegetation community composition was affected and exposed soil surface increased. When plant diversity, soil fertility, and soil moisture were considered, no correlation was found in relation to grazing. Therefore, the results helped to determine management patterns for effective runoff cultivation and minimum soil erosion, as well as minimum disturbance of plant diversity and productivity. The significance of the research is that it demonstrates that livestock grazing can be effective as a management tool while imposing limited damage to the ecosystem. With: A. Perevolotsky, Volcani Center.

desert ecology 42 The effect of herbicides Our objectives were to examine the influences of chemical disturbances in a patchy system on flow of water, soil, on 1) the flow of water; 2) soil erosion; and 3) nutrient flows. We found that herbicides and nutrients disturb the microphytic soil crust and alter the functioning of the desert ecological system. Zaady, Shachak The destruction of the weeds did not significantly increase runoff, but rather caused damage to the microphytic community, resulting in the loss of soil and organic matter. The use of herbicides in open areas that are covered with microphytic crust is not recommended. It can be used for purposes of annual removal and increasing infiltration in small areas under trees.

Infiltration through We examined the role of soil crusts in infiltration processes in three contrasting three contrasting environments in the northern, central and central-western Negev, Israel. Removal of a thin biological soil crusts in cyanobacterial-dominant crust from a sandy dune at Nizzana in the central-western Negev, patterned landscapes in a well-developed lichen-dominant and a cyanobacterial-dominant crust from a loess-covered the Negev, Israel hill slope at Sayeret Shaked in the northern Negev resulted in a three- to five-fold increase Zaady, Shachak in sorptivity and steady-state infiltration under both ponding and tension. Removal of a depositional crust colonised by cyanobacteria from a loess floodplain at Sede Zin in the central Negev resulted in increased infiltration under tension, but no significant effect under ponding. We attribute the lack of effect under ponding to exposure of surface silts to water, which resulted in clogging of matrix pores and surface sealing. We maintain that removal of the crusts in all three landscapes would influence resource flows, particularly redistribution of runoff water, which is essential for the maintenance of desert soil-surface patterning. It would also have marked effects on germination, establishment, and survival of vascular plants and soil biota, leading ultimately to desertification. With: J. D. Eldridge, University of New South Wales, Sydney, Australia.

desert ecology 43 Research Interests Zvika Abramsky Ph.D. Colorado State University, 1976; Professor Incumbent of The Abraham and Bessie Zacks Chair in Desert Ecology Community ecology of desert rodents: Applying the theory of density-dependent habitat selection to measure the magnitude and energetic costs of biotic interactions (competition within and between species and predator-prey interactions). Phone: 972-8-646-1342 • Fax: 972-8-647-2890 • E-mail: [email protected]

Yoav Avni Ph.D. Hebrew University of Jerusalem, 1998; Researcher Geology: Morphotectonics; Erosion processes; Palaeogeographic reconstructions. Phone: 972-8-658-8754 • FAX: 972-8-658-6369 • E-mail: [email protected]

Yoram Ayal Ph.D. Hebrew University of Jerusalem, 1978; Researcher Grade B Community ecology in relation to primary productivity; Desert community structure; Dynamics of parasitoid-host interactions from the individual to the population; Dynamics of insect-plant interactions. Phone: 972-8-659-6774 • Fax: 972-8-659-6772 • E-mail: [email protected]

Amos Bouskila Ph.D. University of California at Davis, 1993; Lecturer Behavioral and community ecology; Behaviors related to predation; Conservation of reptile species and habitats; Mathematical models for behavioral studies. Phone: 972-8-659-6775/646-1278 • Fax: 972-8-659-6772 • E-mail: [email protected]

Burt P. Kotler Ph.D. University of Arizona, 1983; Associate Professor Community, evolutionary, and behavioral ecology; Optimal foraging and habitat use; Trade-off between food and safety, implications of information available to foragers; Foraging games between predators and their prey; Mechanisms of coexistence among desert seed-eating birds and mammals; Applying foraging theory and mechanisms of species coexistence to conservation. Phone: 972-8-659-6785 • Fax: 972-8-659-6772 • E-mail: [email protected]

Boris Krasnov Ph.D. Moscow State University, 1986; Researcher Grade B Animal ecology: Population and community ecology of small mammals; Animal behavior; Community ecology of ground-dwelling arthropods; Host-ectoparasite relationships. Phone: 972-8-658-8764 • FAX: 972-8-658-6369 • E-mail: [email protected]

Yael D. Lubin Ph.D. University of Florida, 1972; Associate Professor Behavioral and evolutionary ecology of arachnids, particularly spiders: Behavioral adaptations to desert conditions, mating strategies, maternal care of young, social behavior, dispersal and population structure; Influence of habitat structure on spider species diversity. Phone: 972-8-659-6782 • Fax: 972-8-659-6772 • E-mail: [email protected]

Ariel Novoplansky Ph.D. Hebrew University of Jerusalem, 1990; Lecturer Evolutionary ecology of plants; Plant morphogenesis; Phenotypic plasticity of plants; Life-history tactics and strategies of plants; Information perception and processing by plants; Genetics of drought-responsive genes; Improving plant response to CO2 fertilization; Ecological implications of the wind dispersal of pine seeds. Phone: 972-8-659-6820 • Fax: 972-8-659-6821 • E-mail: [email protected]

Rivka Ofir Ph.D. Ben-Gurion Universiy of the Negev, 1985; Researcher Grade C Molecular biology; Cell biology; Phytochemicals; SIgnal transduction; normal and cancer cells; immunology. Phone: 972-8-659-6773 • Fax: 972-8-658-2068 • E-mail: [email protected]

Berry Pinshow Ph.D. Duke University, 1975; Professor Physiological ecology; Energy and water exchange between animals and the environment; Physiology of thermoregulation and osmoregulation in desert animals; Avian respiration, thermoregulation, and osmoregulation, and their role in flight duration, particularly with respect to migrating birds; Biogeography of birds in the Negev; Body composition in migrating passerines; Blood-gas transport. Phone: 972-8-659-6773 • Fax: 972-8-659-6772 • E-mail: [email protected] desert ecology 44 Josef Plakht Ph.D. Moscow State University, 1978; Researcher Grade B Geomorphology: Geomorphological and Quaternary mapping, stratigraphy and palaeo-geography of the Quaternary. Phone: 972-8-658-8764 • Fax: 972-8-658-6369 • E-mail: [email protected]

Uriel N. Safriel Ph.D. Oxford University, 1967; Professor Avian ecology; Conservation ecology; Ecology of desertification and global climatic change, effects thereof on forage grasses and on the Chukar partridge; Ecological implications of the wind dispersal of pine seeds. Phone: 972-8-659-6700 • Fax: 972-8-659-6703 • E-mail: [email protected]

David Saltz Ph.D. Colorado State University, 1988; Senior Lecturer Wildlife management and conservation biology; Various aspects of wildlife population dynamics, including ungulate ecology; Mountain gazelles and harvesting; Ecology of small populations; Reintroduction of Arabian oryx and Persian fallow deer; Space-use patterns of wolves in the Golan; Human impact on wildlife; Ecology of ibex populations. Phone: 972-8-659-6778 • Fax: 972-8-659-6772 • E-mail: [email protected]

Moshe Shachak Ph.D. Hebrew University of Jerusalem, 1976; Associate Professor Watershed ecology of arid lands; Ecology of desertification; Ecological management; Ecological systems; Role of animals in the functioning of arid ecological systems. Phone: 972-8-659-6786 • Fax: 972-8-659-6772 • E-mail: [email protected]

Georgy Shenbrot Ph.D. Moscow State University, 1980; Researcher Zoology: Community ecology of desert animals; Endangered and rare species protection. Phone: 972-8-658-8764 • FAX: 972-8-658-6369 • E-mail: [email protected]

Vladimir Sheinkman Ph.D. Institute of Geography of the Russian Academy of Sciences, 1981; Associate Researcher Geography: Quaternary geology and geomorphology. Phone: 972-8-658-8764 • Fax: 972-8-658-6369 • E-mail: [email protected]

David WarD Ph.D. University of Natal, 1987; Associate Professor Co-evolution of plant-herbivore systems; Defensive and growth responses of plants to herbivores; Relative effects of mammalian and insect herbivores on plant communities; Conservation of multi-species herbivory systems and endangered plants. Phone: 972-8-659-6781 • Fax: 972-8-659-6772 • E-mail: [email protected]

Ilan Yarom Ph.D. University of Kansas, 1995; Researcher Grade C Entomology; Biodiversity; Systematics and taxonomy of flies; Biology, ecology and control of agricultural pests; Desert ecology; Environmental impact of modern settlement on drylands. Phone: 972-8-658-1641 • Fax: 972-8-658-2068 • E-mail: [email protected].

Eli Zaady Ph.D. Hebrew University of Jerusalem, 1992; Researcher Grade C Nutrient flows in dryland ecosystems; Soil desertification and restoration; Rhizosphere ecology; Soil microbiology and microbial ecology; Landscape and microphyte ecology. Phone: 972-8-659-6784 • Fax: 972-8-659-6772 • E-mail: [email protected]

Yaron Ziv Ph.D. University of Arizona, 1998; Lecturer Population Ecology: species interactions and Coexistence; Habitat selection; Foraging behavior. Community ecology: Patterns of species; Diversity and community structure; the role of habitat distribution and arrangement in community organization.Species-area relationship. Landscape ecology: Effects of the physical environment on the organization of communities. Conservation biology: Use of landscape-scale modeling for providing management policies regarding nature reserves and endangered species and communities. Phone: 972-8-646-1373 • Fax: 972-8-647-2890 • E-mail: [email protected]

desert ecology 45 Publications

Adams, N. J., B. Pinshow, L. Z. Gannes and H. Biebach. Body temperatures in free-flying pigeons. J. Comp. Physiol. B 169:195-199 (1999) Amir, N., M. E. A Whitehouse and Y. Lubin. Food consumption and competition in a communally feeding social spider, Stegodyphus dumicola (Eresidae). Journal of Arachnology (in press) Ayal Y., M. Broza and M.P. Pener. Geographical distribution and habitat segregation of bushcrickets (Orthoptera : Tettigoniidae) in Israel. Israel Journal of Zoology 45:64-76 (1999) Crouch, T., Y. Lubin and M.Bodasing. Dispersal in the social spider Stegodyphus mimosarum Pavesi 1883 (Araneae: Eresidae). Durban Museum Novitates 23: 52-55 (1998) Eldridge, J. D., E. Zaady, M.Shachak, and C. Myers. Control of desertification by microphytic crusts in a Negev desert shrubland. Desertification and Soil Processes: Sixth International Rangeland Congress Proceedings 1:111-113 (1999) Garb, J., B.P. Kotler. and J.S. Brown.. Consequences of seed size in foraging and species interactions among Negev Desert granivores. Oikos 88:291-300 (1999) Giladi, I. and B. Pinshow. Evaporative and excretory water loss during free flight in pigeons. J. Comp. Physiol. B. 169:311-318 (1999) Groffman, P., E. Zaady and M. Shachak. Microbial contribution to biodiversity at organism, landscape and ecosystem scales. In: Biodiversity in Drylands; Towards a Unified Framework and Identification Research Needs. pp 32-39. Ben-Gurion University, Beer-Sheva, Israel (1999) Hoekstra T. and M.Shachak. (Eds.) Arid Lands Management - Toward Ecological Sustainability. Univ.of Illinios Press (1999) Johannesen, J. and Y. Lubin. Group founding and breeding structure in the subsocial spider Stegodyphus lineatus (Eresidae). Heredity, 82:677-686 (1999) Kotler, B.P. and J.S. Brown. Mechanisms of coexistence of optimal foragers as determinants of the local abundance and distributions of desert granivores. J. Mammalogy 80:361-374 (1999) Kotler, B.P., J.S. Brown and M. Hickie. Fox squirrels as futures traders: feeding behavior in response to food storability. Amer. Midl. Nat. 142:77-86 (1999) Kotler, B.P., J.S. Brown and M. Knight. Habitat and patch use in hyraxes: there's no place like home? Ecology Letters 3:82-88 (1999) Krasnov, B., M. Hastriter, S. Medvedev, G. Shenbrot, I. Khokhlova and V. Vaschenok. Additional records of fleas (Siphonaptera) on wild rodents in the southern part of Israel. Israel Journal of Zoology 45:333-340 (1999) Levacov, R. and E.Zaady. The effect of herbicides on resources flow in patchy Negev desert landscape. Ecology and Environment (In Hebrew, abstract in English) 5:112-121 (1999) Markman, S., B. Pinshow and J. Wright. Orange-tufted sunbirds do not feed nectar to their chicks. Auk 116:257-259 (1999) Morris, D.W., J.S. Brown and B.P. Kotler. The geographical ecology of mammals. J. Mammalogy 80:361-374 (1999) Pasquet, A., R. Leborgne and Y. Lubin. Optimal foraging, predation risk and life history of a desert spider, Stegodyphus lineatus (Eresidae). Behavioural Ecology, 10:115-121 (1999) Rosenzweig, M. L. and Y. Ziv. The echo pattern of species diversity pattern and process in flagrante delicto. Ecography 22:614-628 (1999) Saltz, D. A long-term systematic approach to reintroductions: the Persian fallow deer and Arabian oryx in Israel. Animal Conservation 1:245-252 (1998) Saltz, D., H. Schmidt, M. Rowen, A. Karnieli, D. Ward and I. Schmidt. The feasibility of applying remote sensing techniques for assessing grazing impacts in hyper-arid environments. J. Range Management 52:500-507 (1999) Saltz, D., M. Shachak, M. Caldwell, S. T. A. Picket, H. Tsoar, J. Dawson, Y. Yom Tov, M. Weltz and R. Farrow. The study and management of dryland population systems. In: Arid Lands Management - Towards Ecological Sustainability (Eds. T. W. Hoekstra and M. Shachak) pp 75-96 University of Illinois Press (1999) Schneider, J. and Y. Lubin. Intersexual conflict in spiders. Oikos (Special issue: Costs of Reproduction, Ed. H. Ylonen), 83:496-506 (1998) Shachak, M., S. T. A. Pickett, B. Boeken and E. Zaady. Managing patchiness, ecological flows, productivity, and diversity in dry lands: Concepts and applications in the Negev desert. In: Arid Lands Management – Toward Ecological Sustainability. (Eds. T. Hoekstra and M. Shachak) pp 254-263 Univ. of Illinois Press, Urbana. 1999 Shenbrot, G., B. Krasnov, and I. Khokhlova. Notes on the biology of the bushy-tailed bird, Sekeetamys calurus, in the central Negev, Israel. Mammalia 63: 374-377 (1999) Shem-Tov, S., E. Zaady, M. P. Groffman and Y .Gutterman. Soil carbon content along rainfall gradient and germination: a potential mechanism for regulating of Plantago coronopus. Soil Biology and Biochemistry 31:1209-1217 (1999)

desert ecology 46 Tielman, I. B., J. B. Williams, G. Michaeli and B. Pinshow. The role of the nasal passages in the water economy of Crested larks and Desert larks. Physiol. Zool. 72:219-227 (1999) Ward, D., D. Saltz, M. Rowen and I. Schmidt. Effects of grazing by re-introduced Equus hemionus on the vegetation in a Negev erosion cirque. Journal of Vegetation. Science: 10:579-586 (1999) Whitehouse, M.A.E. and Y. Lubin. Strategic interference competition by individuals in social spider foraging groups. Animal Behaviour 58:677-688 (1999) Zaady, E. Nitrogen cycle and the Negev desert patchiness. Ecology and Environment (In Hebrew, abstract in English) 5:70-76 (1999) Zaady, E.The role of microphytic soil crusts in desert ecosystems. Ecology and Environment (In Hebrew, abstract in English) 5:77-84 (1999) Zaady, E., R. Eliasaf, R. Yonatan, L. Dvash and A. Perevolotsky. The response of plant community to grazing: Plant and soil parameters that are affected by grazing. Ecology and Environment (In Hebrew, abstract in English), 5:167-179 (1999) Ziv, Y., and J. A. Smallwood. Gerbils and pocket mice - interspecific competition and the temporal niche. In: Activity Patterns in Small Mammals - a Comparative Ecological Approach (Eds. H. S. Halle and N. C. Stenseth) Ecological Studies pp 141 ff. Springer-Verlag, Berlin (2000)

desert ecology 47 Mitrani Department of Desert Ecology

Technical staff Yael Bar-Ilan - Hazeva Research Station Moris Melnokov - Hazeva Research Station Sol Brand Iris Musly Ofer Eitan Sonia Rosin Marc Goldberg Galit Shiran Dr. Vasiliy Kravchenko- Hazeva Research Station Dror Tschory Michal Laniado - Ramon Science Center Jum’aa Zanun Regina Levacov Natali Zeevi - Hazeva Research Station Zafrir Levi

Secretarial staff Yael Kaplan Tamar Livne - Hazeva Research Station Rinat Lukats Orli Plotkin - Hazeva Research Station Avi Shushan - Ramon Science Center Galit Sudery

Visiting Scientists Dr. Joel Brown, University of Illinois at Chicago, USA Amber Budden, University of Wales, Bangor - Hazeva Research Station Dr. Tanza Crouch, Durban Natural Science Museum, South Africa Prof. Perry Eason, University of Louisville, USA Prof. Deborah Goldberg, University of Michigan, USA Adam Green, University of Wisconsin, Madison Vladimir Gromov, Russian Academy of Science, Russia – Ramon Science Center Dr. José Gruenzweig, University of Alaska, USA Prof. Ted Hammel, Indiana University, USA Irina Insarova, Moscow State University, Russia – Ramon Science Center Prof. Gotfried Jetschke, University of Jena, Germany Dr. Miklos Kertesz, Institute of Ecology and Botany of the Hungarian Academy of Sciences, Hungary Günter Müller, The Museum of Munich, and the Hebrew University of Jerusalem - Hazeva Research Station Dr. Beata Oborny, Lorand Eotvos University, Budapest, Hungary Mirjam Papke, University of Hamburg, Germany Prof. Henry Prange, Indiana University, USA Dr. Eric Rextad, University of Alaska, USA Prof. David Robershaw, Cornell University, USA Dr. Jutta Schneider, University of Mainz, Germany Sergei Semenov, Moscow State University, Russia Ramon Science Center Prof. Deborah Smith, University of Kansas, USA Dr. Andrei Tchabovsky, Severtzov Institute of Ecology and Evolution of Russian Academy of Science Dr. Peter Turchin, University of Connecticut, USA Prof. Roy Turkington, University of British Colombia, Canada Dr. Linda Wiener, St. John’s College, USA Prof. Ron Ydenberg, Department of Biological Sciences, Simon Fraser University, USA

desert ecology 48 Postdoctoral Dr. Avner Anava - Hazeva Research Station Fellows Dr. Sasha Dall Dr. Ali Harari Dr. Greg Johnston Dr. Carmi Korine Dr. Thomas Rödel Dr. Anna Sher Dr. Phillip Taylor Dr. Ian van Tets Dr. Mary Whitehouse Dr. Andrew Wilby

Graduate Students Tania Acuna Hagai Halel Natalia Ruiz Aram Aviram Sharon Halevi Hila Shamir Noa Avni Bruce Kahn Ehud Shani Alona Bachi Moses Kirega Eyal Shochat Mitchell Baker Anat Levi Madan Shrestha Michal Ben Dror Eliezer Lichtenstein Gil Stav Gil Ben Natan Chris Lortie Eric Summer Betina Berendonck Alex Maklakov Sergei Volis Pablo Blinder Regev Manor Gideon Wasserberg Gil Bohrer Nir Maoz Kerstin Wiegand Shlomi Brandwin Shai Markman Nimrod Yisraeli Rami Buchnik Keren Or Hila Zachor Ayelet Danino Yarden Oren Fenchan Zhang Anat De Mush Ofer Ovadia Merav Ziv Dini Deutsh Guy Peer Ido Zurim Tamar Erez Steven Pousty Girmay Gebru Noam Ra’anan Adam Green Ornea Reisman-Berman Esther Guggenheim Lizzane Roxburg Dror Hablena Nir Sapir

desert ecology 49