Research Projects

Contact Us


Mailing Address:
The Robert H. Smith Institute of
Plant Sciences and Genetics
in Agriculture
POB 12, Rehovot 76100, Israel

Administrator: Neomi Maimon 
Tel: 972-8-948-9251,
Fax: 972-8-948-9899,

Director: Prof. David Weiss
Tel: 972-8-948-9436
Fax: 972-8-948-9899


Current Projects

Consequences of Invasive Prosopis Species for Ecosystems around the Dead Sea

Consequences of invasive Prosopis species for ecosystems functioning around the Dead Sea and strategies to prevent future invasions

In many drylands, key invasive plant species belong to the genus Prosopis spp. (mesquite) known to have a negative impact on native biodiversity and on water availability to native trees and shrubs with shallower root system. Moreover, mesquite has a potential to increase soil erosion rates due to modified root structure, and more nitrogen supplied to the newly colonized ecosystems may significantly impair water quality.

In Israel, exotic Prosopis species are widely used as ornamental plants and have been purposely planted in arid and semi-arid regions since the 1960s.  A recent survey reported that multiple planted populations of Prosopis became invasive and currently invade 690 km2 of the Dead Sea area, Negev desert, Jordan Valley and the Arava Valley.

Despite the increasing presence and very high risk of invasiveness, the impact of Prosopis encroachment on ecosystems and the environmental conditions prone to invasions in Israel are currently unknown, although consequences for plant communities and function of ecosystems were anticipated. There is a major knowledge gap in our understanding of the environmental factors conducive to invasion by exotic Prosopis species in Israel and the ecosystem consequences of such invasion events.

The objectives of the project are as follows:

a) To understand the edaphic, hydrologic, geophysical and climatic conditions conductive to the invasion by Prosopis spp.

b) To assess ecophysiological performance and traits related to successful Prosopis invasions by comparing the performance of Prosopis individuals to native Acacia trees.

c) To evaluate the ecosystem-scale changes imposed by Prosopis invasion on the carbon and nitrogen cycles, and the composition of plant communities;

d) To develop practical guidelines for the effective prevention of further invasion by Prosopis spp. around the Dead Sea.



Ilya Gelfand, French Associates Institute for Agriculture and Biotechnology of Drylands, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev



Alon Levinzon (MSc student)

Dryland-specific Mechanisms of Organic Matter Decay

Dryland-specific mechanisms of organic matter decay and their contribution to the CO2 flux from decomposition in dry shrubland ecosystems

Litter degradation is a key process in the carbon cycle. To date, there is a lack of understanding of the mechanisms underlying decomposition of organic matter in arid and semi-arid zones. There are a few factors involved in this process that drive various decay mechanisms, as follows: (1) Litter quality or traits (nutrients and their ratio, structural components, morphological traits, and more), (2) humidity and water, driving microbial degradation, (3) UV and short-wave visible radiation (280-550 nm) driving photochemical degradation, (4) high temperature, driving thermal degradation. Notably, these decay mechanisms frequently interact and additional factors can come into play, such as litter position.

This research will analyze the profile of changes in litter traits and CO2 fluxes induced by single and combined decay mechanisms. Furthermore, the project will quantify in an extended field study the decay-derived CO2 flux and turnover time of ‘dead’ carbon at the ecosystem scale.

The overarching goal of this research is to determine the climatic impacts on the CO2 flux derived from decomposition of organic materials in dryland ecosystems and to assess the contribution of the various decay mechanisms on the CO2 flux.

Information on climate effects will enable improved projections of the decay-derived CO2 flux in drylands under a changed climate. Changes in litter functional traits during decomposition as affected by climate and litter type will shed new light on the functioning of the decay mechanisms. Information on the relative contributions of the decay mechanisms will further enhance our understanding of the control over decomposition and the concomitant CO2 emissions from drylands.


Shai Schechter (PhD student)


Plant-Microbiota Affairs during Leaf Senescence and Decay

Plant-Microbiota Affairs during Leaf Senescence and Decay 2018 - 2020

Leaf senescence is a central, well-coordinated process in the life of plants and comprises the first stage of leaf litter decomposition that ultimately recycles carbon and nutrients. Microorganisms are known to participate in leaf litter decomposition, but little is known on the role of microbiota in leaf senescence and the initiation of decay immediately following tissue death. In this work, we aim to study the involvement of leaf microbiota in senescence and early breakdown of cell components in leaves by combining microbial, chemical and ecological approaches, using microscopic and chemical tools at various scales. We will study sorghum (Sorghum bicolor) – a staple food for millions of people and fodder for farm animals across the world. Importantly, the selection of grass as a model plant will allow us analyzing mature, senescing, dead and decomposing tissue along a developmental axis on the same leaf and under identical conditions. Specifically, we will correlate microscale mapping of leaf topography, chemical composition and water content, with the microscale microbial organization on the leaf and with isotopic composition of CO2 emission, over time and across space along the axis of the senescing and decaying sorghum leaf. This study has the potential to reveal novel interactions between microbiota, plant developmental processes, and ecologically significant mechanisms. It will shed light on the dynamics of bacterial organization and may reveal new roles that plant microbiota plays in leaf senescence and early decay, which are key processes in the carbon and nutrient cycles in natural and agricultural systems.

Rivka Elbaum, Faculty of Agriculture, Food and Environment, the Hebrew University of Jerusalem, Rehovot, Israel
Nadav Kashtan, Faculty of Agriculture, Food and Environment, the Hebrew University of Jerusalem, Rehovot, Israel


Grazing to Mitigate Climate Change Effects on Native Oaks

Development of an Ecohydrological Grazing Strategy to Mitigate Drought Effects in Species-Rich Mediterranean Woodlands Threatened by Climate Change 2018 - 2020

Oaks (Quercus calliprinos) woodlands growing in marginal water limited habitats of Israel are under serious threat of oak decline induced by climate change. Livestock grazing is one of the few tools available for effective, large-scale vegetation management in drylands, but our understanding of the impact of grazing on the water relations, growth and survival of trees under drought is very limited.

The overarching objective of this project is to assess the impact of grazing on water relations and performance of oak trees as keystone species in the climate-vulnerable transition zone of Israel. This project also aims to assess oak populations growing in marginal, water-limited habitats to develop a set of environmental and biological indicators of their vulnerability to drought. In this project an eco-hydrological model which describes woodland structure, and oak performance and survival along aridity and grazing gradients will be developed.

Yagil Osem, Agricultural Research Organization, Bet Dagan, Israel

Omri Hasson (PhD student)

Grazing Effects on Forest Trees

Impact of Grazing on Water Relations, Nutrition and Productivity of Needle and Broad-Leaved Trees in Forests and Woodlands 2018 - 2020

Drought events in the Mediterranean region have been documented with increasing regularity over the past two decades. Livestock grazing is widespread in the extensive coniferous forests of Israel, both as a husbandry practice and as an important tool for reducing understory biomass and subsequently the risk of wildfires. It is believed that grazing plays a role in alleviating drought stress in trees by eliminating understory competition for limited water resources. However, despite its prevalence as a management tool, little is known about the effect of grazing on the physiological status of pine trees.

The aim of this project is to research the effect of livestock grazing (cattle, goats and sheep) on tree growth, and water and nutrient relations, to determine the relationship between grazing and planting density, and to observe the effect of grazing on natural forest regeneration in semi-arid coniferous forests. The study is set up at three different sites (Yatir, Sataf, and Mt. Horshan), over a range of growing conditions and accompanying vegetation types typical of the Eastern Mediterranean. All three sites contain plots fenced off to prevent grazing, adjacent to control plots that are subject to seasonal grazing of various types, over a range of different stand densities.

This research will help determine the effects of livestock grazing on the physiological function of pine trees under a variety of growth conditions common to this part of the world. Additionally, it will contribute to understanding the relationship between grazing, forest thinning practices, and forest regeneration. These results will play a role in developing new integrated forest management strategies and help ascertain whether livestock grazing can be effectively utilized to mitigate water shortage and ensure survival of forests in semi-arid areas threatened by future climate change.

Yagil Osem, Agricultural Research Organization, Bet Dagan, Israel

Levi Burrows (MSc student)




Tree Water Balance in a Semiarid Pine Forest

Tree Water Balance in a Semiarid Pine Forest and Rates of Survival Under Global Climate Change 2017 - 2019

Past Projects

Coupling of the Canopy and the Root System in Trees

Coupling of the Canopy and the Root System through Carbon and Nitrogen Dynamics in Tropical Trees 2014 - 2017

Trees in tropical forests are considered the largest component of the terrestrial biosphere carbon cycle. Yet little is known about carbon related coupling between the canopy and the root system. The factors that determine tree carbon assimilation and respiration activities, and thus affecting the dynamics of the carbon cycle, are not yet fully appreciated. Mainly, the mechanisms of the coupling between the activity of the autotrophic and heterotrophic parts of the trees are still in debate. The interrelation between the photosynthesizing canopy, the source of carbohydrates, and the respiring root system, one of the sinks of carbohydrates, is not well understood because of the lack of access to the root system.

This research aims to investigate the canopy-root interrelation using a unique method of directly approaching roots in an aeroponics facility, the Sarah Racine Root Research Laboratory at Tel Aviv University, Tel Aviv, Israel. The Root Laboratory is a temperature controlled greenhouse, divided into compartments, each of which is further divided into an above-ground space of 2.8-4.5 m height and a fully accessible belowground space of 6 m depth. By flux measurements and carbon isotope labeling the type and velocity of coupling between canopy activity and root response can be studied. Two possible mechanisms couple plant photosynthetic activity with root respiration. Firstly, the direct transport of assimilates from leaves through the phloem to the roots. Secondly, the indirect physiochemical effect on root activity through pressure-concentration waves, which increases the turgor in the phloem. The latter mechanism has been suggested on theoretical grounds, but has yet to be shown in plants.

Eshel A, Grünzweig JM. 2013. Root-shoot allometry of tropical forest trees determined in a large-scale aeroponic system. Annals of Botany 112, 291-296.

Nina Buchmann, ETH Zurich, Switzerland

Israel Oren (PhD student)

Partner organizations:
ETH Zurich, Switzerland


Drought Resistance Strategies of Woodland Species

Strategies, Function and Vulnerability of Key Mediterranean Woodland Species under Drought 2012 - 2017

Summary: An increase in temperatures and a decrease in precipitation are predicted in the Mediterranean Basin as a part of climate-change scenarios. The Mediterranean region is particularly vulnerable to climate change because the structure and function of its vegetation systems are considered to be limited by water. Mortality of dominant tree species (Quercus calliprinos, Phillyrea longifolia and Pistacia lentiscus) has been lately reported in Ramat Hanadiv Nature Park in southern Mt. Carmel region. This mortality is assumed to be related to several years of reduced precipitation and, possibly, increased summer temperature. The objective of the study is to understand the possible consequences of climate change in Mediterranean woodlands in terms of function, structure and dynamics of the main woody species and the whole ecosystem.

The research questions/goals include:

1) Ecophysiological assessment of the relationships between water availability and the function of the different tree/shrub species. How do the dominant tree species respond to water stress?

2) Identifying principle mechanisms of coping with drought within the different species (e.g. avoidance in time or space, tolerance)

3) Is the water availability the main factor determining the vegetation structure and function? How should we expect ecosystem functions and structure to be effected by future drier conditions?

4) How grazing affects the water status and the physiology of these species? Can grazing be used to alleviate water stress and decrease mortality?

Yagil Osem, Agricultural Research Organization, Bet Dagan, Israel

Päivi Väänänen (PhD student)

Partner organizations:
Ramat Hanadiv Nature Park




Long-Term Biogeochemical Monitoring in Shrubland

Long-Term Biogeochemical Monitoring in the Mediterranean Shrubland of Ramat Hanadiv 2010 - 2017


Ecosystem functioning is comprised of processes, such as plant growth and organic matter decay, by which elements are transferred among different components of the system (organisms, soil). Through element cycling (the biogeochemical cycles) carbon and nutrients are absorbed by plants from the atmosphere and the soil, respectively, and are recycled through decomposition and mineralization processes in the soil. There is considerable knowledge on species composition in Mediterranean ecosystems, but we have a poor understanding about the biogeochemical cycles and their regulation by land management and climatic variables in these systems. The biogeochemical monitoring in Ramat Hanadiv aims at assessing the long-term changes in the status and function of the Mediterranean ecosystem. The monitoring activity is performed in the Phillyrea latifolia-dominated shrubland, and it evaluates the impact of land management by goat grazing and the regulation by climate and the main vegetation components on key processes in the cycling of elements. These processes include the nutrient status of the vegetation, plant litter production and its decomposition.

Yael Navon, Ramat Hanadiv Nature Park

Partner organizations:
Ramat Hanadiv Nature Park




Impact of Pines on the Understory in Mature Forests

A Case Study of the Divergent Impact of Pinus Halepensis and Pinus Brutia on the Understory in Mature Forests 2013 - 2015

Humidity Effects on Microbial Respiration in Drylands

Impact of Dew and Atmospheric Water Vapor on Heterotrophic Respiration in Arid and Semi-Arid Ecosystems 2012 - 2015

The decay of dead plant material (litter) and soil organic matter releases CO2from ecosystems back to the atmosphere, a process termed heterotrophic respiration (Rh). Heterotrophic respiration is a key process in storage of soil organic carbon and in modulating the fluxes of CO2 to and from ecosystems, and thus global atmospheric CO2 concentrations. The factors controlling Rh in the vast drylands of the globe are only partly known, especially during dry periods. Absorption of moisture from atmospheric water vapor was recently described to enhance plant-litter decay, but neither water vapor nor other non-rainfall water sources, such as dew were investigated regarding their effects on Rh. Moreover, solar radiation was shown to induce CO2 production in plant litter, but the contribution of this CO2 source to the carbon cycle of ecosystems was not investigated. The overarching goal of this project is to evaluate the impact of novel drivers of Rh and their significance for the ecosystem carbon balance in drylands of two continents. A series of parallel field and lab studies at a semi-arid and an arid site in each country will provide a mechanistic insight into CO2 fluxes from soil and litter as induced by non-rainfall moisture sources. Moreover, the contribution of CO2 production by solar radiation to ecosystem carbon balance will be determined. The role of water vapor, dew and solar radiation as drivers of CO2 production might become increasingly important, as many drylands are experiencing enhanced drought as a consequence of global climate change.

Gliksman D, Rey A, Seligmann R, Dumbur R, Sperling O, Navon Y, Haenel S, De Angelis P, Arnone JA, III, Grünzweig JM. 2016. Biotic degradation at night, abiotic degradation at day: positive feedbacks on litter decomposition in drylands. Global Change Biology (accepted for publication).

John A. Arnone III, Desert Research Institute, Reno NV, USA

Partner organizations:
United States – Israel Binational Science Foundation


Canopy-Root Interrelations in Tropical Forest Trees

Canopy-Root Interrelations in Tropical Forest Trees with a Fully Accessible Root System 2012 - 2014


Development of Forest Trees with Enhanced Drought Tolerance

Development of Forest Trees with Enhanced Drought Tolerance – Improving Selection by Combining Physiological and Morphological Methods for Examination of Trees Responses to Drought Under Controlled Conditions and in the Field 2011 - 2013


Global climate-change scenarios in the Mediterranean region forecast rising temperatures, reduced rainfall amounts and a generally drier climate. The rapidly changing climatic conditions might put perennial species, particularly trees, in danger because of their inherent slow adaptation rates. For afforestation in drylands under a changed climate, there is a need for more drought tolerant trees.

This study focusses on a combination of physiological and morphological methods for selection of genotypes with enhanced drought tolerance. Model tree species used for afforestation in Israel are the evergreen conifer Aleppo pine (Pinus halepensis) and the deciduous broad-leaved Atlantic pistachio (Pistacia atlantica). Mother trees showing features of adaptation to drought in dry southern Israel serve as seed sources for this project. Seeds of each mother plant are evaluated for indices of drought tolerance by three different approaches:

1) transpiration under drought treatment as assessed by lysimeters on the whole-plant level;

2) sensitivity to xylem embolism as determined by ultrasonic acoustic emission;

3) growth rate of an efficient root system as assessed under standard and drought conditions.

Drought tolerance of seed sources tested under controlled conditions will also be evaluated in the field. The findings of this project will assist in selecting drought tolerant seed sources for afforestation under a future drier climate. In addition, the studies will deepen our understanding in the ecophysiological and morphological processes related to drought tolerance in trees.

Collaboration: Rony Wallach, the Hebrew University of Jerusalem, Rehovot, Israel 
Menachem Moshelion, the Hebrew University of Jerusalem, Rehovot, Israel

Co-workers: Dana Sarid (MSc student)

Partner organizations: Ministry of Agriculture and Rural Development KKL – Jewish National Fund



Development of Mature Conifer Forests and Their Understory

Trends in the Development of Mature Conifer Forests and Mechanisms for the Conservation of Biodiversity in the Emerging Understory 2009 - 2012


Summary: Pine forests planted in Israel on barren and deserted land have resulted in mixed forests with diverse understory. However, heavy forest thinning or complete pine felling might lead to the development of a dense oak-dominated monocultures and reduced biodiversity. Understanding the processes promoting the establishment of a native woody understory in relation to the management of pine canopy is essential to predict future co-existence of the species, and to establish knowledge and tools for managing mixed species forests. The primary objectives of this study are to:

1) Produce a quantitative assessment of pine management on the growth, structure, composition and diversity of the understory.

2) Determination of the abiotic mechanisms which control the understory development as shown by growth and composition.

To understand those mechanisms we will study microclimate and biogeochemical cycling as affected by woody species under various developmental stages of mature pine forest. Those stages are part of 50-60 years old forests in the Western Galilee and range from dense to thinned and cleared stands. The history of plots will be studied, and surveys on the recent status of understory composition, structure and plant diversity will be carried out. This research will help improve forest planning and management, while reaching sustainability goals, such as biodiversity, patchiness and rare-species conservation. Furthermore, they will lead to better understanding of the abiotic processes and mechanisms involved in proliferation of the understory. Beyond that, the study can help develop new forest management tools to predict vegetation dynamics and achieve ecosystem sustainability goals.

Co-workers: Kalil Adar (PhD student) Rita Dumbur (Lab technician)

Partner organizations: KKL – Jewish National Fund



Tree Density Effects on Litter Decomposition in Pine Forests

Litter Decomposition and Nutrient Dynamics in Aleppo Pine Forests under Different Tree Densities and Climatic Conditions 2011 - 2013

Organic matter was removed from planted forests in Israel during the past decades management measures, such as thinning, pruning and grazing. Removal of biomass and plant litter might deplete nutrients in those ecosystems, thus reducing productivity and carbon sequestration. Plant litter provides additional ecosystem services, such as reduction of soil erosion, attenuation of extreme microclimatic soil condition, and conservation of biodiversity through habitat variation. Our understanding of the impact of plant litter and its decay on pine forests in Israel is basic at most. Moreover, there is a lack of information concerning effects of climate, stand conditions, and litter quality (chemical composition) on litter decomposition in dryland forests. The objective of this study is to assess the impact of climatic conditions and tree density on litter decomposition, nutrient dynamics and soil microclimate in 45-year old Aleppo pine forests. We study decomposition and chemical change of leaf litter and wood chips in long-term ecological research (LTER) plots of a semi-arid and a sub-humid forest over different seasons and years. In addition, soil moisture beneath manipulated litter layers, and nutrient dynamics in litter and soil are monitored. Findings of this project will assist in developing sustainable management strategies for enhancing ecosystem services in dryland forests.



Daniel Gliksman (PhD student)

Partner organizations:
KKL – Jewish National Fund



CO2 Emissions from Plant Litter in the Rainless Season


Potential Microbial Activity and CO2 Emission During Plant-Litter Decomposition in a Mediterranean Ecosystem During the Rainless Season 2010 - 2011




Plant-litter decomposition is an essential step in the carbon cycle, and, thus, significantly affects the atmospheric CO2 concentration. In the vast dryland regions of the globe, litter decays year-round, though much less is known about decomposition during the rainless dry season than during the wet season. Recently, absorption of atmospheric water vapor was described as a primary driver of decomposition during rainless seasons, but the mechanism by which litter decays under this driver is unknown so far. The objective of the proposed study is to assess microbial activity contributing to plant-litter decay and nutrient cycling in dry areas during the rainless season. Studies with various types of plant litter in a Mediterranean shrubland and in the lab will assess microbial degradation of litter using extracellular enzyme activity and CO2emission. Since the rate of microbial decay and of CO2 emission can increase with litter nitrogen content, we will estimate nitrogen fixation rates on litter, a component of the nitrogen cycle that has been neglected so far. Decomposition driven by water-vapor absorption will become more prominent in a future warmer and drier world. Hence, the proposed study has implications for predicting regional and global CO2 fluxes under global climate change by coupled climate carbon-cycle models.

Publications: Gliksman D, Rey A, Seligmann R, Dumbur R, Sperling O, Navon Y, Haenel S, De Angelis P, Arnone JA, III, Grünzweig JM. 2016. Biotic degradation at night, abiotic degradation at day: positive feedbacks on litter decomposition in drylands. Global Change Biology (accepted for publication).

Co-workers: Daniel Gliksman (PhD student)

Partner organizations: Ring Center for Inter-Disciplinary Environmental Research



Harnessing Mediterranean Plants for Climate Change Mitigation

Harnessing the Biodiversity of Mediterranean Plants for Mitigating the Effects of Climate Change and Desertification 2008 - 2011


The main objective of this project was to select plant material of the native tree species Populus euphratica, and to develop sustainable technologies for afforestation and carbon sequestration in arid regions. The genus Populus is largely used as a model for research on biology of tree species, and it is of economic interest for production of wood materials and bio-energy. To be able to identify suitable plant material, we studied the ecophysiological basis of natural populations of P. euphratica in Israel. This species is adapted to extreme conditions, mainly related to extreme temperatures and salinization of soils and water. In this project, we characterized trees for their tolerance to salt stress, and developed ecophysiological “markers” for identification of such tolerance responses in natural populations. Unraveling the natural diversity among P. euphratica populations that have developed stress tolerance mechanisms allows to select the best plant material for afforestation purposes relying on irrigation with marginal water, such saline and reclaimed waste water.

Collaboration: Arie Altman, the Hebrew University of Jerusalem, Rehovot, Israel

Co-workers: Eliad Sassoni (MSc student) Tamar Weinberg (MSc student)

Partner organizations: The Italian Ministry of Environment, Land and Sea Tel Aviv University




Climate Change in the Mediterranean (CIRCE Project)

Climate Change and Impact Research: The Mediterranean Environment (CIRCE) 2007 - 2011


The FP6 project Climate Change and Impact Research: the Mediterranean Environment (CIRCE) aims at developing for the first time an assessment of the climate change impacts in the Mediterranean area. The objectives of the project are:

  • To predict and to quantify physical impacts of climate change in the Mediterranean area
  • To evaluate the consequences of climate change for the society and the economy of the populations located in the Mediterranean area
  • To develop an integrated approach to understand combined effects of climate change
  • To identify adaptation and mitigation strategies in collaboration with regional stakeholders


Talmon Y, Sternberg M, Grünzweig JM. 2011. Impact of rainfall manipulations and biotic controls on soil respiration in Mediterranean and desert ecosystems along an aridity gradient. Global Change Biology 17, 1108-1118.

Navarro A et al. Regional Assessment of Climate Change in the Mediterranean (synthesis to be published)

Co-workers: Dina Kanas (project technician)

Partner organizations: European Commission's Sixth Framework Programme



Biodiversity and Carbon Sequestration

Biodiversity and Carbon Sequestration: a Field Study Simulating Loss of Plant Species from Mediterranean Grassland 2007 - 2010


The current loss of biodiversity on a global scale may be a major threat to the composition and functioning of ecosystems, and to the services mankind derives from nature. Most terrestrial ecosystems are based on vegetation as the main autotrophic component, and, therefore, functioning of these systems depends to a high degree on plant diversity. Many recent studies investigated effects of biodiversity loss on carbon dynamics by focusing on biomass accumulation and primary productivity. However, field data are rare that provide means for predicting carbon sequestration (the full carbon balance) as influenced by loss of plant diversity. This project proposed a field study in Mediterranean grassland to investigate effects of diversity loss on carbon sequestration. Reduction in diversity was simulated by establishing replicated experimental plant assemblages of decreasing species richness in old-field soil. Carbon sequestration was quantified by measuring net ecosystem CO2 fluxes with a static chamber technique. The main objectives of this study were

1) to quantify the effect of plant diversity loss on net ecosystem carbon balance in Mediterranean grassland, and assess potentially functional mechanisms;

2) to determine plant diversity effects on components of net ecosystem productivity, mainly net primary production and decomposition of soil organic matter;

3) to analyze the relationship between diversity effects on the carbon cycle and functional traits of the plant species involved;

4) to estimate the impact of plant diversity loss on microclimatic factors (water availability, temperature), and consequently on C balance and its components.

Partner organizations: Israel Science Foundation



Biogeochemical Cycles of the Phillyrea latifolia Shrubland

Study of Major Processes in the Biogeochemical Cycles of the Phillyrea latifolia Shrubland in Ramat Hanadiv 2007 - 2010


The fluxes of matter and energy among the different components of an ecosystem are instrumental in ecosystem characterization and functioning. Despite their importance, those processes were rarely studied in Israel. The objectives of this research were

1) to assess spatial and temporal changes in major processes of the biogeochemical cycles in a Mediterranean ecosystem,

2) elaborate biotic and abiotic factors regulating those changes.

The project was carried out in a shrubland dominated by Phillyrea latifolia in Ramat Hanadiv, north-central Israel. Studies focused on biomass and plant litter production, litter decomposition and nutrient dynamics at microsites, including shrubs and intershrub patches. This project enabled studying variation in major ecosystem processes in space and time, and assessing factors leading to variation.


Dirks I, Navon Y, Kanas D, Dumbur R and Grünzweig JM. 2010. Atmospheric water vapor as driver of litter decomposition in Mediterranean shrubland and grassland during rainless seasons. Global Change Biology 16, 2799-2812.

Yael Navon (postdoc) 
Rita Dumbur (lab technician)

Partner organizations:
Ramat Hanadiv Nature Park



Biodiversity and Carbon Storage Responses to Land Use Change

Evaluation of Universal Patterns of Biodiversity and Carbon Storage Responses to Land Use Change: A Comparative Study with Temperate and Mediterranean Ecosystems 2006 - 2010


Human land-use change results in disturbance of landscapes and ecosystems on large areas of the Earth, thus affecting environmental resources and ecosystem services. Human land use is the main factor for loss of biodiversity on a global scale. To date, most effects of land use on plant communities and ecosystem services have been tested under distinct disturbance regimes in a single biogeographical region. Comparing various types of land use under different degrees of intensity across biomes might reveal universal patterns of ecosystem responses that are unknown so far. This project that jointly investigates land-use impacts on plant communities, biodiversity and C storage in Germany and Israel using data from field plots in both countries analyzed by a statistical habitat model. The main objective of this project is to find universal patterns of responses to change in land use, and to predict consequences for plant biodiversity and ecosystem C storage across land-use types and biogeographical regions. Verifying a functional relation between sets of biological attributes, environmental resources and land management allows predicting biodiversity for a wide range of systems and landscapes by knowing land use and resource regimes. Relationships between C stocks and plant traits, resources and management also enable us to find the sources for changes in C storage following land-use change, a causal connection that is unknown in most cases. Results from this study add new insights on the generality of responses of vegetation and C cycling to environmental changes.


Dirks I, Navon Y, Kanas D, Dumbur R and Grünzweig JM. 2010. Atmospheric water vapor as driver of litter decomposition in Mediterranean shrubland and grassland during rainless seasons. Global Change Biology 16, 2799-2812.

Michael Kleyer, University of Oldenburg, Oldenburg, Germany

Inga Dirks (PhD student)

Partner organizations:
State of Lower-Saxony and the Volkswagen Foundation, Hannover, Germany



Carbon Fluxes under Simulated Climate Change and N Deposition

Carbon Fluxes under Simulated Climate Change and Nitrogen Deposition in Mediterranean and Desert Ecosystems 2006 - 2009


Alterations in land-use and atmospheric composition brought by human activity have been associated with recent changes in the climate system and in nitrogen deposition to the Earth surface. Such changes might affect natural ecosystems and their ability to sequester carbon and to regulate water fluxes. The impact of a long-term precipitation change, the main concerns for the dry regions of the world, and of nitrogen additions on ecosystem carbon cycling and water relations is practically unknown. The objectives of two studies on these topics were to quantify CO2 and water fluxes in Mediterranean and desert shrubland under different realistic scenarios of changes in precipitation and nitrogen deposition, to assess effects of climate variables and nitrogen on these fluxes and to evaluate possible interactions between ecosystem processes linked to carbon dynamics and water. A study on climate-change impacts was conducted at 4 study sites along a precipitation gradient from mesic (800 mm mean annual rain fall) to arid (90 mm) climatic zones. Field manipulations to simulate scenarios of increasing and decreasing of 30% of the average annual rain fall, was situated at the dry Mediterranean (540 mm) and the semiarid (300 mm) climatic zones, the two central stations along the gradient. Another study quantified net ecosystem CO2 exchange and evapotranspiration at patch-scale in a desert ecosystem under precipitation and nitrogen manipulations. These projects contribute to a better understanding of global-change effects on carbon cycling, water relations and the interaction between carbon and water in Mediterranean and arid ecosystems. Results from this research might improve predictions of future changes in the carbon cycle and in water relations under changed climate and nitrogen deposition. In addition, the project might contribute to the development of scientific tools to management of carbon and water in drought-affected ecosystems.

Talmon Y, Sternberg M, Grünzweig JM. 2011. Impact of rainfall manipulations and biotic controls on soil respiration in Mediterranean and desert ecosystems along an aridity gradient. Global Change Biology 17, 1108-1118.

John A. Arnone III, Desert Research Institute, Reno NV, USA 
Marcelo Sternberg, Tel Aviv University, Tel Aviv, Israel

Ophir Tal (postdoc) 
Yiftach Talmon (MSc student)

Partner organizations:
International Arid Land Consortium


Biomass and Plant Diversity in the Understory of a Semiarid Forest

Impact of Biotic and Abiotic Factors on Understory Biomass and Species Richness in Aleppo Pine Forests of the Northern Negev 2006 - 2008


Plant biodiversity in Mediterranean forests is represented by their understory vegetation, which contains both woody species and annuals. This work focused on forests planted in Aleppo pine (Pinus halepensis) in the transition zone between the Mediterranean area and the desert area. This region is characterized by its high plant species richness, but Aleppo pines are not part of the natural vegetation in this area and their effect on the local vegetation remains unclear. The main goal of this study was to characterize richness and cover of understory vegetation in pine forests of southern Israel, and to examine abiotic and biotic factors that control understory parameters. This study was carried out in two forests, in the Lachish area, Amatzya forest (400 mm precipitation), and in the south Hebron mountains, Yatir forest (280 mm). These are mature forests, in which Aleppo pine is a planted species that was introduced into the habitat. Study plots were selected on north and south aspects, and varied in tree density. Data collection included canopy, understory and soil variables. Multivariance analysis was performed to find connections between species distribution and environmental factors that might explain its variation.

Tamar Amit (MSc student)

Partner organizations:
KKL – Jewish National Fund



Effect of Maternal CO2 on Seed Quality and Offspring Performance

Effect of Maternal CO2 Concentration on Seed Quality and Offspring Performance in a Semi-Arid Mediterranean Community 2005 - 2007


Atmospheric CO2 enrichment has a direct effect on plants (elevated CO2 effects), beside its indirect influence through global warming. Elevated CO2 often increases photosynthesis and decreases water use, but has variable impacts on growth and reproduction. While numerous native and agricultural species have been tested for responses of seed production to elevated CO2, information on seed quality and particularly on growth of a second generation is very sparse.


In this study, maternal effects on seeds from annual plants of the northern Negev are tested under uniform ambient conditions. Seeds have been produced at three different CO2 concentrations (between pre-industrial and future CO2), and seed quality as well as growth and development of offspring originating from these seeds were investigated. Results show that elevated CO2 has an inter-generational influence on plants, but this effect differs among species and functional plant groups. Notably, severity of a fungal disease in the largest species of this annual community was affected by maternal CO2 treatments in some years. Thus, biodiversity of plant communities could be strongly altered by rising CO2 through maternal effects.


Grünzweig JM, Dumbur R. 2012. Seed traits, seed-reserve utilization and offspring performance across pre-industrial to future CO2 concentrations in a Mediterranean community. Oikos; doi: 10.1111/j.1600-0706.2011.19770.x (in press).

Grünzweig JM. 2011. Potential maternal effects of elevated atmospheric CO2on development and disease severity in a Mediterranean legume. Frontiers in Plant Science 2, 30; doi: 10.3389/fpls.2011.00030.



The Carbon Cycle in a Semi-Arid Pine Forest

The Carbon Cycle and its Biological and Environmental Drivers in a Semi-Arid Pine Forest 2004 - 2009


Forests are the main ecosystem types on Earth engaged in carbon sequestration which reduces the CO2 concentration in the atmosphere. However, the rate of carbon sequestration, and the environmental and biological factors affecting the rate of this process are not well understood. This is particularly true for forests of the hot and dry areas of the world, despite the potentially large contribution of these vast areas to global CO2 balance. This long-term project led by the Weizmann Institute of Science investigates the potential of carbon sequestration in semi-arid forests, using Yatir forest in the northern Negev as a model. Studies on large stands of Aleppo pine (Pinus halepensis) assess net ecosystem CO2 production and its main flux components and drivers; leaf-level photosynthesis and transpiration; leaf, trunk and soil respiration; changes in ecosystem carbon and nitrogen stocks following afforestation; carbon-nitrogen-water interrelations. This project provides field data to improve estimates of regional and global carbon budgets, and enhances our understanding of potential future climate effects on forest carbon dynamics.


Gelfand I, Grünzweig JM, Yakir D. 2012. Slowing of nitrogen cycling and increasing nitrogen use efficiency following afforestation of semi-arid shrubland. Oecologia 168, 563-575..

Sprintsin M, Cohen S, Maseyk K, Rotenberg E, Grünzweig JM, Karnieli A, Berliner P, Yakir D. 2011. Long term and seasonal courses of leaf area index in a semi-arid forest plantation. Agricultural and Forest Meteorology, 151, 565-574.

Grünzweig JM, Hemming D, Maseyk K, Lin T, Rotenberg E, Raz-Yaseef N, Falloon PD and Yakir D. 2009. Water limitation to soil CO2 efflux in a pine forest at the semi-arid ‘timberline’. Journal of Geophysical Research 114, G03008.

Maseyk KS, Grünzweig JM, Rotenberg E and Yakir D. 2008. Respiration acclimation contributes to high carbon-use efficiency in a seasonally dry pine forest. Global Change Biology 14, 1553-1567.

Maseyk KS, Lin T, Rotenberg E, Grünzweig JM, Schwartz A and Yakir D. 2008. Physiology-phenology interactions in a productive semi-arid pine forest. New Phytologist 178, 603-616.

Grünzweig JM, Gelfand I, Fried Y and Yakir D. 2007. Biogeochemical factors contributing to enhanced carbon storage following afforestation of a semi-arid shrubland. Biogeosciences 4, 891-904.

Grünzweig JM, Lin T, Rotenberg E, Schwartz A and Yakir Y. 2003. Carbon sequestration in arid-land forest. Global Change Biology 9, 791-799.

Dan Yakir, Weizmann Institute of Science, Rehovot, Israel