Eastern Mediterranean hydroclimate over the late glacial and Holocene, reconstructed from the sediments of Nar lake, central Turkey, using stable isotopes and carbonate mineralogy

There is a lack of high-resolution records of hydroclimate variability in the Eastern Mediterranean from the late glacial and early Holocene. More knowledge of the speed of climate shifts and the degree to which they were synchronous with changes in the North Atlantic or elsewhere is required to understand better the controls on Eastern Mediterranean climate. Using endogenic carbonate from a sediment sequence from Nar Gölü, a maar lake in central Turkey, dated by varve counting and uranium-thorium methods, we present high-resolution (∼25 years) oxygen (δ18O) and carbon isotope records, supported by carbonate mineralogy data, spanning the late glacial and Holocene. δ18Ocarbonate at Nar Gölü has been shown previously to be a strong proxy for regional water balance. After a dry period (i.e. evaporation far exceeding precipitation) in the Younger Dryas, the data show a transition into the relatively wetter early Holocene. In the early Holocene there are two drier periods that appear to peak at ∼9.3 ka and ∼8.2 ka, coincident with cooling ‘events’ seen in North Atlantic records. After this, and as seen in other records from the Eastern Mediterranean, there is a millennial-scale drying trend through the Mid Holocene Transition. The relatively dry late Holocene is punctuated by centennial-scale drought intervals, at the times of 4.2 ka ‘event’ and Late Bronze Age societal ‘collapse’. Overall, we show that central Turkey is drier when the North Atlantic is cooler, throughout this record and at multiple timescales, thought to be due to a weakening of the westerly storm track resulting from reduced cyclogenesis in the North Atlantic. However, some features, such as the Mid Holocene Transition and the fact the early Holocene dry episodes at Nar Gölü are of a longer duration than the more discrete ‘events’ seen in North Atlantic records, imply there are additional controls on Eastern Mediterranean hydroclimate

Impact of Microhabitats on the Heterogeneity of Seedling Emergence in a Mediterranean Coastal Sand Dunes Community

Seedling emergence and establishment was monitored in 3 microhabitats during growing seasons in a Mediterranean coastal sand dune community in Poleg Stream Nature Reserve, Israel. Seedling emergence varied temporally among the 3 microhabitats, with a delay in the timing of seedling emergence in shrub understoreys due to lower soil average temperatures and lower irradiance. In contrast, seedling emergence on trails was advanced because of more intense irradiance and higher soil temperatures on their more exposed soil surfaces. Microhabitats showed significant differences in individual densities, species diversity, and species richness of total seedlings (

Impact of spatial patterns on arthropod assemblages following natural dune stabilization under extreme arid conditions

Background: The cessation of anthropogenic activities in mobile sand dune ecosystems under xeric arid conditions has resulted in the gradual stabilization of dunes over the course of five decades.&nbsp;Our objective was to analyze the spatial patterns of arthropod assemblages along a gradient of different stabilization levels, which represents the different stages of dune stabilization - from the shifting crest of the dune to the stabilized crusted interdune.The study was carried out at the sand dunes of the northwestern Negev in Israel. Data was collected using dry pitfall traps over two consecutive years during the spring along northern windward aspects. Four dunes were chosen, characterized by three significant landscape units: shifting crest, semi-stabilized slope and stabilized interdune.Results: We identified three significant assemblages of arthropods along the gradient. The shifting dune crests are populated by psammophilic species found almost exclusively in sandy habitats in Egypt and the western Negev in Israel. The crusted, stabilized inter-dunes are populated mainly by loess-dwelling species, which are common in most of the Negev loess plains and have a wide distribution range, and the semi-stabilized slopes host species of both extreme landscape units but is distinguished by four species that show significant affinity to it.&nbsp;Conclusions: Our results demonstrate functional arthropod heterogeneity and emphasize the risk of regional species homogenization. Heterogeneity is a key property in maintaining sand dune biodiversity. Homogenization, as a result of sand stabilization, may lead to loss of psammophilic species.&nbsp;</p

Chalcolithic Agricultural Life at Grar, Northern Negev, Israel: Dry Farmed Cereals and Dung-Fueled Hearths

Abstract: It is commonly assumed that during the Chalcolithic period in the northern Negev (4700-3800 BC in southern Israel) fi elds were located on fl oodplains and runoff irrigation was practiced. Here we present a study conducted at Grar, a Chalcolithic site located on a loess plateau on the banks of Nahal Grar, in which we quantitatively studied the phytolith assemblages in two separate excavation areas. The sediments at the site include large amounts of phytoliths indicating that large amounts of vegetal matter had been brought to the site. The phytolith assemblages are composed mainly of grass phytoliths. The amount of dendriform phytoliths indicates that domestic cereals, wheat and/ or barley, comprise part of the phytolith assemblage at the site. The ratio of phytoliths originating from the leaves and/ or stems of cereals and other grasses to those originating from infl orescences is large relative to ratios reported in studies from Neolithic and Iron Age sites, indicating that the straw from cereals was used on site for various tasks. The number of long cells in silica skeleton phytoliths from infl orescences only, indicates that the crops were dry farmed. Three superimposed in situ hearths fueled by livestock dung had also been identifi ed at the site. Overall, this study shows that agricultural practices during the Chalcolithic were varied, including both dry farming and use of runoff irrigation. The dung fueled hearths are probably among the few unequivocal indications for the early use of animal secondary products during the Chalcolithic in the southern Levant.Résumé: Il est généralement admis qu’au Chalcolithique (4700-3800 avant J.-C.) dans le Nord-Néguev, les champs sont situés dans des plaines inondables et que s’y pratique une irrigation par eaux de ruissellement. Nous présentons ici une étude menée à Grar, site chalcolithique se trouvant sur le plateau de loess des rives du Nahal Grar, pour laquelle ont été examinés quantitativement des assemblages phytolithiques de deux aires de fouille distinctes. Les sédiments sont composés d’importantes quantités de phytolithes, vestiges de toute la matière végétale qui s’est progressivement accumulée sur le site. Ces assemblages phytolithiques sont principalement constitués de phytolithes d’herbe, même si la présence de phytolithes dendriformes prouve que les céréales domestiquées, le blé et/ ou l’orge, en font aussi partie. Le ratio des phytolithes issus de tiges et/ ou de feuilles de céréales et d’autres herbes sur ceux issus d’infl orescences est élevé comparativement aux ratios mentionnés dans les études des sites néolithiques et de l’âge de Fer, ce qui montre que la paille de céréales a connu diverses utilisations sur ce site. Le nombre de cellules longues dans les squelettes siliceux des phytolithes issus d’infl orescences seules indique que les céréales étaient issues de cultures sèches. Ainsi, ont été retrouvés in situ trois foyers successifs, avec du fumier pour combustible. D’une manière générale, cette étude montre qu’au Chalcolithique, il existe différentes pratiques agricoles, dont la culture sèche et l’irrigation par ruissellement. En outre, l’utilisation de fumier comme combustible représente probablement l’une des rares preuves de l’utilisation de produits secondaires à cette période dans le Levant Sud.Katz Ofir, Gilead I., Bar Kutiel Pua, Shahack-Gross Ruth. Chalcolithic Agricultural Life at Grar, Northern Negev, Israel: Dry Farmed Cereals and Dung-Fueled Hearths. In: Paléorient, 2007, vol. 33, n°2. pp. 101-116

Asynchrony Drives Plant and Animal Community Stability in Mediterranean Coastal Dunes

Substantial evidence now suggests that a positive diversity–stability relationship exists. Yet few studies examine the facets of biodiversity that contribute to this relationship, and empirical research is predominantly conducted on grassland communities under controlled conditions. We investigate the roles of species richness, environmental condition (vegetation cover), asynchrony, and weighted population stability in driving community stability across multiple taxa. We used data from a Long-term Ecological Research project to investigate temporal stability of annual plants, beetles, reptiles, and rodents in Nizzanim Coastal Sand Dune Nature Reserve in Israel. All four taxa had a strong positive relationship between asynchrony and community stability. Only rodents showed a positive richness–stability relationship. Perennial plant cover had a significant relationship with community stability for three taxa, but the direction of the correlation varied. Asynchrony had a stronger relationship with perennial plant cover than it did with richness for both plants and beetles. We suggest that community stability is driven by asynchrony for flora as well as fauna. Stability appears to be determined by species’ interactions and their responses to the environment, and not always by diversity. This has important consequences for understanding the effects of environmental degradation on ecosystem stability and productivity, which have destabilizing consequences beyond biodiversity loss