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1

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Ecosystem Management of Desertified Shrublands in Israel (1998)

Shachak, Moshe ; Sachs, Menachem ; Moshe, Itshak

Springer

Ecosystems 1 (1998), S. 475-483

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ISSN: 1435-0629

Keywords: Key words: desertification; ecosystem leakage; ecosystem management; microphytic soil crust; Negev; shrubland; surface runoff.

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: ABSTRACT The objectives of this study were to understand the ecological processes and possible management strategies in desertified shrublands. We hypothesized that biological production and diversity in desertified shrublands in the Negev in Israel are low due to water, soil, and nutrient leakage from the ecosystem. We designed a series of field experiments in order to examine (a) whether source–sink relationships exist between the crusted soil and the shrub patches, (b) whether resources (water, soil, and nutrients) leak from the system, and (c) whether management, which changes the landscape mosaic by introducing new sink patches that reduce leakage of resources, may increase productivity and diversity. The results indicate that the low number of shrub patches, which serve as sinks for resources, leads to water, soil, and nutrient leakage from the ecosystem. This leakage reduces ecosystem production and diversity. We found that artificially created pits, which act as sinks for resources, decrease leakage and increase biomass production and annual plant species diversity. Based on the experimental results, we developed conceptual models for shrubland desertification and ecosystem management. The models are based on a source–sink relationship between two patch types characteristic of shrublands. The models relate landscape productivity to the number of sink patches and suggest that, in cases where there are too few sinks, artificially created sink patches should be added. Management methods were developed to reduce resource leakage in the desertified shrubland of the Negev. Methods included construction of man-made pits in the landscape that add resource-enriched patches to the landscape. These patches are used to create parks consisting of clusters of trees integrated into a matrix of shrubs and herbaceous vegetation. The managed parks are used for recreational purposes and for rangeland.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s100219900043

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2

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Fertilization of the desert soil by rock-eating snails (1990)

Jones, Clive G. ; Shachak, Moshe

[s.l.] : Nature Publishing Group

Nature 346 (1990), S. 839-841

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ISSN: 1476-4687

Source: Nature Archives 1869 - 2009

Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics

Notes: [Auszug] FIG. 1 The rocky Central Negev Desert Highlands, Israel, showing higher plants growing in patches of soil adjacent to limestone rock. The two substrates support different plant communities. Endolithic lichens live within the upper few mm of the limestone rocks, which cover 70% of the desert area; ...

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1038/346839a0

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3

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Harvester ant response to spatial and temporal heterogeneity in seed availability: pattern in the process of granivory (2000)

Wilby, Andrew ; Shachak, Moshe

Springer

Oecologia 125 (2000), S. 495-503

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ISSN: 1432-1939

Keywords: Animal-landscape interactions Israel Negev Desert Seed predation

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract. The influence of temporal and spatial heterogeneity in seed availability on the foraging behaviour of the harvester ant Messor arenarius was studied in an arid shrubland in the Negev Desert, Israel. The study investigated the implications of behavioural responses to heterogeneity in seed availability for the seed predation process and the potential for feedback effects on vegetation. Vegetation and seed rain were monitored across two landscape patch types (shrub patches and inter-shrub patches) in 1997. Shrub patches were shown to have higher plant and seed-rain density than inter-shrub patches. Patch use and seed selection by M. arenarius foragers were monitored through the spring, summer and autumn of 1997. After a pulse of seed production in the spring, the ants exhibited very narrow diet breadth, specialising on a single annual grass species, Stipa capensis. At this time, ants were foraging and collecting seeds mainly from inter-shrub patches. In the summer, diet breadth broadened and use of shrub patches increased, although the rate of seed collection per unit area was approximately equal in the two patch types. The increase in the use of shrub patches was due to colony-level selection of foraging areas with relatively high shrub cover and an increase in the use of shrub patches by individual foragers. In the autumn, a pulse of seed production by the shrub species Atractylis serratuloides and Noaea mucronata led to a reduction in diet breadth as foragers specialised on these species. During this period, foragers exhibited a large increase in the proportion of time spent in shrub patches and in the proportion of food items collected from shrub patches. The seasonal patterns in foraging behaviour showed linked changes in seed selection and patch use resulting in important differences in the seed predation process between the two landscape patch types. For much of the study period, there was higher seed predation pressure on the inter-shrub patches, which were of relatively low productivity compared with the shrub patches. This suggests that the seed predation process may help maintain the spatial heterogeneity in the density of ephemeral plants in the landscape.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004420000478

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4

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An algae — Desert snail food chain: Energy flow and soil turnover (1980)

Shachak, Moshe ; Steinberger, Yosef

Springer

Oecologia 46 (1980), S. 402-411

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ISSN: 1432-1939

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The feeding ecology of adult desert snails (Sphincterochila zonata), inhabiting a loess plain in the Negev Desert, was studied during a 7-year period. Energy flow and soil turnover determinations were made at the individual and population level on the basis of field observations and data derived from laboratory simulations. Sphincterochila zonata were only active on 8–27 winter days annually, otherwise they were dormant. The snails fed exclusively on algae that grew on the soil surface following rain. The mean annual dry-weight biomass of algae was 197.4(±118.1) gr·m-2. The dry weight biomass of snails ranged from 0.02–0.14 gr·m-2. Annual production in the food chain varied substantially from year to year (1–1539 Kj·m-2), but the net annual energy balance of the snails was always positive. Soil crust turnover, resulting from grazing of snails on algae, was estimated at 142 kg·hectare-1 during the study period. The annual magnitude of energy flow and soil turnover is determined by the soil surface moisture regime which in turn, is a function of rainfall patterns. Sphincterochila zonata may serve an important role in Negev ecosystems by dispersing soil algae and altering soil structure. The snails are not subject to substanding predation by rodents but may occasionally serve as an important food source for migrating birds.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00346271

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5

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Relationship among settling, demography and habitat selection: an approach and a case study (1988)

Shachak, Moshe ; Brand, Sol

Springer

Oecologia 76 (1988), S. 620-626

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ISSN: 1432-1939

Keywords: Habitat selection ; Site selection ; Settling ; Demography ; Desert isopods

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary We explore the demographic consequences of site selection by animals on their abundance among habitats. We found that pre and post settling survivorship are important links between the behavioral decisions where to settle and the distribution of a population among habitats. This was demonstrated for 10 generations of the desert isopod, Hemilepistus reaumuri, in three habitats in the Negev Desert, Israel. The populations exhibit low survivorship before settling (≈12%) and high survivorship (≈55%) after settling. According to our model this implies high site selection. Theoretical considerations and the case study led us to suggest the following relationship among settling, demography and habitat selection: 1) Individuals search for suitable settling sites to inhabit and reproduce. 2) Their decision where and when to settle is a cost benefit decision. They weigh the benefit of searching for a high quality site against mortality due to increased searching time. 3) The individual's decision to settle determines the pre and post settling survivorship pattern. 4) Survivorship pattern dictates density pattern in time and space. 5) Density pattern in a given habitat determines its quality for the individual. 6) Settling selection among habitats and the number of safe sites controls the distribution of densities among habitats.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00397879

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6

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Energy allocation and life history strategy of the desert isopod H. reaumuri (1980)

Shachak, Moshe

Springer

Oecologia 45 (1980), S. 404-413

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ISSN: 1432-1939

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Population characteristics of the desert isopod H. reaumuri and its energy allocation during each penophase were investigated in the Negev desert, Israel. It was found that on the individual level, 52% of the energy is allocated to the prereproductive, and 48% to the reproductive phenophases. On the population level, only 10–23% is devoted to isopods which are involved in reproduction. Assuming that the energy allocation pattern in H. reaumuri is the consequence of its life history strategy, two unique evolutionary lines were suggested. One suggestion is the evolution of the family mode of life which increases the probability of the individual's survival. This is due to parental investment and co-operation between siblings. The other suggestion is the evolution of high energy utilization for burrowing, in order to solve the low and unpredictable nature of water resources in the desert.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00540214

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7

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The relationship between sit and wait foraging strategy and dispersal in the desert scorpion, Scorpio maurus palmatus (1983)

Shachak, Moshe ; Brand, Sol

Springer

Oecologia 60 (1983), S. 371-377

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ISSN: 1432-1939

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract We examine the role of the sit and wait foraging strategy and of the stability and predictability of the biotic environment in shaping population biology and life history traits of the desert scorpion, Scorpio maurus palmatus. The study was carried out in a loessial plain in the Negev desert, Israel. We used a grid system (5x80 m) within the Hammada scoparia plant association. The area was divided into 1,600 squares (50x50 cm) and the presence (within ±5 cm) and width of each scorpion burrow was recorded for eight years (1973–1980). It was found that: (1) Dispersal is a common phenomenon for all S. maurus palmatus age groups and takes place only after a heavy rainfall when soil moisture is high. (2) Dispersion patterns change from clumped to random as a function of age. (3) Dispersal is age specific and density dependent. (4) During the dry seasons a high percentage of the population goes into the resting stage. In order to integrate the above findings, a graphical model was constructed with the main assumption that the S. maurus palmatus prey availability relationship is a decreasing function between the scorpion burrow and its food resources. Data and model analysis led to the conclusion that the desert scorpion, S. maurus palmatus, is confronted with a relatively predictable physical environmeent and unpredictable biological environment. Two alternative strategies are available for S. maurus palmatus to overcome prey unpredictability; dispersal during the rainy season and inactivity during the dry seasons. We suggest that many other burrowing desert animals may face the problem of unpredictability of biological resources. Thus it seems that the S. maurus palmatus biological relationship model can be applied, with modifications, to a wide spectrum of desert burrowing animals.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00376854

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8

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Porcupine disturbances and vegetation pattern along a resource gradient in a desert (1991)

Shachak, Moshe ; Brand, Sol ; Gutterman, Yitzchak

Springer

Oecologia 88 (1991), S. 141-147

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ISSN: 1432-1939

Keywords: Annual plants ; Disturbance ; Negev Desert ; Porcupine ; Resource shift

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary In the Negev Desert, Israel, the Indian crested porcupine, Hystrix indica, digs similar sized, discrete, elongated pits (257±21.3 cm3; n=144) while foraging for below-ground plant storage organs. In these digs, soil moisture content is higher than in the surrounding soil matrix. The digs disturb population and community structure due to porcupine consumption or damage of 18 species of plants, and repopulation by 55 plant species. Over the past 14 years we have studied dig dynamics on a rocky hillslope with three distinct habitats as regards soil moisture content. Midslope soil moisture is the highest, decreasing towards upper and lower slope. We have counted a total of 6,609 digs in the area: 2141 on the upper, 3211 in the middle and 1257 on the lower part of the slope. The number of digs at midslope is significantly higher than on the other parts of the slope (ANOVA; P〈0.0001). There is a significant (P〈0.05) correlation between the mean number of porcupine digs and the cumulative rainfall amount for the 2 years prior to dig formation. To study plant repopulation in digs, all plants in 144 digs along the slope and from equal sized plots in the undistarbed soil matrix were collected. In all, 288 samples with 20 584 plants were collected, 2042 from the matrix and 18,542 from digs. Of the 55 species, we focused on the abundance patterns of Filago desertorum, Picris cyanocarpa and Bromus rubens, which made up 69.5% of all the individuals in the digs and 68.3% in the matrix. Our results showed that all three species increased in abundance in the digs as compared to the matrix. F. desertorum density increased by a factor of 2.9, P. cyanocarpa by 9.5 and B. rubens by 12.0. There were species-specific responses in abundance to the location of the digs along the moisture gradient. The only species whose abundance responded to the moisture gradient was F. desertorum. P. cyanocarpa demonstrated peak abundance in the location with the poorest moisture regime, while B. rubens showed peak abundance at the intermediate part of the moisture gradient. We suggest a scheme for integrating the increase in density and the species-specific responses to the digs along a water gradient based on R.H. Whittaker's view of individual species abundances along an environmental gradient.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00328415

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