During the last few years more than 200 publications related to GLOWA Jordan River have been published either in peer reviewed journals or as books or book chapters. You can download the regularly updated list of publications: GLOWA JR publication list
Here our newest scientific publications:
Siewert W. & Tielbörger K. 2010: Dispersal-Dormancy Relationships in Annual Plants: Putting Model Predictions to the Test.
Abstract. Bet hedging is a means to increase fitness in environments that vary unpredictably in space and time. In such environments, models predict a trade-off between the bet-hedging strategies dispersal and dormancy, while the increasing importance of risk reduction with decreasing predictability should lead to an increase in dispersal and dormancy along gradients of environmental predictability. However, so far there has been no experimental study to test these predictions in the field. Here, we used a set of novel field experiments that enabled us to quantify and separate seedling recruitment from three sources: local reproduction, dormancy, and dispersal. The study included the entire plant community from five environments differing considerably in predictability. Evidence for both the existence of a trade‐off between dispersal and dormancy within environments and their increased use in unpredictable environments was very weak. The importance of dispersal for population and community dynamics in our system was extremely low relative to dormancy and local reproduction. This indicates that the role of dispersal for buffering environmental variation may be negligible compared with other risk‐reducing strategies. Our findings highlight the urgent need for multispecies and multisite experiments in empirical tests of theoretical predictions.
Talmon Y., Sternberg M., Grünzweig J.M. 2010: Impact of rainfall manipulations and biotic controls on soil respiration in Mediterranean and desert ecosystems along an aridity gradient.
Abstract. Spatially heterogeneous ecosystems form a majority of land types in the vast drylands of the globe. To evaluate climate-change effects on CO2 fluxes in such ecosystems, it is critical to understand the relative responses of each ecosystem component (microsite). We investigated soil respiration (Rs) at four sites along an aridity gradient (90– 780mm mean annual precipitation, MAP) during almost 2 years. In addition, Rs was measured in rainfall manipulations plots at the two central sites where ~30% droughting and water supplementation treatments were used over 5 years. Annual Rs was higher by 23% under shrub canopies compared with herbaceous gaps between shrubs, but Rs at both microsites responded similarly to rainfall reduction. Decreasing precipitation and soil water content along the aridity gradient and across rainfall manipulations resulted in a progressive decline in Rs at both microsites, i.e. the drier the conditions, the larger was the effect of reduction in water availability on Rs. Annual Rs on the ecosystem scale decreased at a slope of 256MAPgCm−2yr−1mm−1 (r2 =0.97). The reduction in Rs amounted to 77% along the aridity gradient and to 16% across rainfall manipulations. Soil organic carbon (SOC) decreased with declining precipitation, and variation in SOC stocks explained 77% of the variation in annual Rs across sites, rainfall manipulations and microsites. This study shows that rainfall manipulations over several years are a useful tool for experimentally predicting climate-change effects on CO2 fluxes for time scales (such as approximated by aridity gradients) that are beyond common research periods. Rainfall reduction decreases rates of Rs not only by lowering biological activity, but also by drastically reducing shrub cover. We postulate that future climate change in heterogeneous ecosystems, such as Mediterranean and deserts shrublands will have a major impact on Rs by feedbacks through changes in vegetation structure.doi: 10.1111/j.1365–2486.2010.02285.x
Tielbörger K. & Petrù M. 2010: An experimental test for effects of the maternal environment on delayed germination.
Abstract. (1) Recent models on bet-hedging germination in annual plants assume a negative relationship between the proportion of offspring that germinate and the quality of the maternal environment. An increase in the proportion of seeds remaining dormant in the next year, when produced in seasons with high reproduction may result from selection that avoids overcrowding in the following year. (2) We present the first empirical test of this prediction by utilizing a field experiment in Israel which manipulated the entire maternal environment. We subjected semi-arid and Mediterranean annual plant communities to different rainfall treatments: control, reduced and increased rainfall. We then related maternal environment quality to offspring germination fractions for three focal species in two consecutive seasons. (3) There was a negative relationship between the quality of the maternal environment and offspring germination fraction in four out of twelve cases. The negative relationship was stronger for the least competitive species and in the environment with high competition intensity, supporting the role of competition for the observed pattern. (4) Our results suggest that competition with all neighbours is more likely to explain the pattern than sib competition. (5) Synthesis. Our findings provide the first experimental evidence of a highly reliable cue (productivity of maternal environment) that allows for plants to respond to their future biotic environment. There is an urgent need for testing predictions of theoretical models in natural populations and for incorporating the role of density dependence in studies of bet-hedging germination.
Rotenberg E. & Yakir D. 2010: Contribution of Semi-Arid Forests to the Climate System.
Abstract. Forests both take up CO2 and enhance absorption of solar radiation, with contrasting effects on global temperature. Based on a 9-year study in the forests’ dry timberline, we show that substantial carbon sequestration (cooling effect) is maintained in the large dry transition zone(precipitation from 200 to 600 millimeters) by shifts in peak photosynthetic activities from summer to early spring, and this is counteracted by longwave radiation (L) supression (warming effect), doubling the forestation shortwave (S) albedo effect. Several decades of carbon accumulation are required to balance the twofold S + L effect. Desertification over the past several decades, however, contributed negative forcing at Earth’s surface equivalent to ~20% of the global anthropogenic CO2 effect over the same period, moderating warming trends.
Almasri M.N & McNeill L.S. 2009: Optimal planning of wastewater reuse using the suitability approach: A conceptual framework for the West Bank, Palestine. Desalination, 248: 428–435
Abstract. Recently, wastewater reuse is receiving a great deal of focus and interest among planners and decision makers in the West Bank, Palestine. This interest in wastewater reuse is motivated by the shortage in water resources accessibility due to the unstable political situation in the region. Much of the recent dispute that took place at the national level and among the stakeholders and planners revolved around issues related to the priorities of wastewater reuse in terms of location implementation of reuse schemes. The paper illustrates the conceptual framework for developing such a map and elaborates on the factors that dictate map development. Examples of such factors are discussed. The paper’s outcomes show that the development of the map requires a multidisciplinary expertise and the work necessitates the collaboration among experts from different fields.
McNeill L.S., Almasri M.N. and Mizyed N. 2009: A sustainable approach for reusing treated wastewater in agricultural irrigation in the West Bank – Palestine. Desalination, 248:315–321
Abstract. There is a critical lack of sanitation in the West Bank (Palestine).Most domestic sewage is disposed of into unlined cesspits or septic tanks, or directly discharged to the environment without treatment. Water resources in the West Bank are limited, and nearly 70% of the water is used for agricultural irrigation. Reuse of treated (reclaimed) wastewater has great potential to alleviate these problems and improve crop yield, but there are many challenges to implementing wastewater reuse. This paper presents a case study in the West Bank town of Tubas, which currently has no sewage collection system or treatment. This study includes traditional engineering design and will address socio-cultural issues through a detailed survey of public perceptions about reclaimed wastewater and an education plan for the various stakeholders in the town. This approach should lead to a wastewater reuse system that is beneficial to Tubas as well as sustainable.
Har-Edom O-L. & Sternberg M. 2009: Invasive species and climate change: Conyza canadensis (L.) Cronquist as a tool for assessing the invasibility of natural plant communities along an aridity gradient.
Abstract. The predicted reduction in precipitation in the eastern Mediterranean due to climate change may expose the natural plant communities to invasive species. We assessed whether natural plant communities along an aridity gradient in Israel were resistant to invasion by considering differences in abiotic conditions and community characteristics in these regions. We considered Conyza canadensis as a model plant as it is a common invader in the region. We examined the mechanisms and functional traits of both the plant communities and C. canadensis that promote or discourage invasion. Study sites represented a rainfall gradient with four ecosystem types: mesic Mediterranean, Mediterranean, semiarid and arid. Our results showed that the mechanisms of community invasion resistance varied along the aridity gradient. At the arid and semiarid sites, water deficiency impaired the establishment of C. canadensis. At the mesic Mediterranean site, plant competition had a negative effect on C. canadensis performance, thus greatly reducing the likelihood of its establishment. We conclude that a decrease in regional precipitation due to climate change may not affect intrinsic resistance characteristics of natural plant communities to invasion in the area.
Menzel et al. 2009:
Modelling the effects of land-use and land-cover change on water availability in the Jordan River region.
Abstract. Within the GLOWA Jordan River project, a first-time overview of the current and possible future land and water conditions of a major part of the Eastern Mediterranean region (ca. 100 000 km2) is given. First, we applied the hydrological model TRAIN to simulate current water availability (runoff and groundwater recharge) and irrigation water demand on a 1 km×1 km spatial resolution. The results demonstrate the scarcity of water resources in the study region, with extremely low values of water availability in the semi-arid and arid parts. Then, a set of four divergent scenarios on the future of water has been developed using a stakeholder driven approach. Relevant drivers for land-use/land-cover change were fed into the LandSHIFT.R model to produce land-use and land-cover maps for the different scenarios. These maps were used as input to TRAIN in order to generate scenarios of water availability and irrigation water demand for the region. For this study, two intermediate scenarios were selected, with projected developments ranging between optimistic and pessimistic futures (with regard to social and economic conditions in the region). Given that climate conditions remain unchanged, the simulations show both increases and decreases in water availability, depending on the future pattern of natural and agricultural vegetation and the related dominance of hydrological processes.