Ancient to recent-past runoff harvesting agriculture in the hyper-arid Arava Valley: OSL dating and insights

Runoff harvesting agriculture was prevalent in ancient times across the southern Levant. In modern Israel, remnants of this agricultural adaptation strategy are widespread mostly in the semi-arid and arid Negev. Extensive literature has thoroughly described the farming systems of this region. However, runoff agriculture in the dryer, hyper-arid regions of the Arava Valley and southern Negev (excluding the Uvda Valley), has scarcely been researched. A recent study revealed remnants of simple stone terraces in several wadis (ephemeral stream channels) throughout the central Arava Valley that have not yet been dated. The objective of this study was to use the Optically Stimulated Luminescence (OSL) method to date sediments trapped in the stone terraces. The results revealed dominance of terraces dated to the Ottoman period (1516–1917 CE). Few samples were dated to the earlier Late Islamic period (1099–1516 CE) or Byzantine period (324–638 CE), and to the later, modern period of the mid-20th century. Generally, these periods coincide with relatively moister regional climatic conditions, which prevailed in the 4th, 11th–12th, and late 19th centuries CE. Yet, our findings also concur with periods of effective governance by central administrations. Therefore, results of this study fit the concept that runoff agriculture practiced in peripheral areas in ancient to recent-past times was co-determined by climatic settings and geo-political conditions, which enabled human inhabitation in these regions.

Changes in biogeochemistry recorded in the Lisan formation and the Dead Sea Basin

<p>Terrestrial climate archives provide a rich array of information on regional climate dynamics that often can link to global climate change.  A range of new metal and coupled isotope proxies is helping to unlock the most information from terrestrial archives and this paleoclimate information. The Jordon-Arava valley, tectonically active since the early Neogene, is one of the world’s largest pull-apart basins.  Throughout the Pleistocene to the Holocene, the valley contained a series of lacustrine water bodies.  As the valley is located on the boundary between the African-Arabian deserts and the Mediterranean regional climatic zone, studies of past conditions in these lacustrine bodies allows the reconstruction of changes in the regional hydrological cycle.  Lacustrine sediments, such as those found in the Jordon-Arava valley, record paleoclimatic information similar to that found within marine sedimentary archives and often at much higher resolution, from millennial to even annual timescales. The Lisan Formation is a 40-80m thick Pleistocene marl, which was deposited in Lake Lisan, which existed over the last glacial cycle in the Jordan-Arava Valley. The Lisan Formation contains a significant quantity of annually-precipitated primary aragonite, which has not recrystallised to calcite, allowing for direct U-Th dating, which has led to an exceptional age model for the Lisan Formation.</p><p>Here we discuss the measurement of the sulfur and oxygen isotopic composition of gypsum in the Lisan formation, as well as the generation of sulfur nodules within the formation that are not found in the sediment cores of the Dead Sea. We use this data to explore how sediment diagenesis, relating to changes in biogeochemistry, changes as a function of climate change over the last glacial cycle. We then present the calcium isotopic composition of the gypsum and interbedded aragonite, and show how the aragonite calcium isotopic composition covaries with lake level, and thus offers profound insight into the regional hydrological cycle in the Jordon-Arava Valley.</p>

Drainage reversal toward cliffs induced by lateral lithologic differences

Drainage reversals, an end-member case of drainage reorganization, often occur toward cliffs. Reversals are commonly identified by the presence of barbed tributaries, with a junction angle >90°, that preserve the antecedent drainage geometry. The processes that form reversed drainages are largely unknown. Particularly, barbed tributaries cannot form through a spatially uniform migration of the cliff and drainage divide, which would be expected to erase the antecedent drainage pattern, and tectonic tilting toward the cliff that could reverse the flow direction is inconsistent with geodynamic models of large-scale escarpment, where many reversals are documented. Here, we propose a new mechanism for drainage reversal, where the slope imbalance across a cliff, together with the high erodibility of sediments that fill cliff-truncated valleys, result in faster divide migration along valleys compared to interfluves. We demonstrate this mechanism along channels that drain toward the escarpment of the Arava Valley in Israel. Reversal is established by observations of barbed tributaries and opposite-grading terraces. We show that drainage reversal occurs when erodible valley fill exists, and that the reversal extent correlates with the thickness of this fill, in agreement with the predictions of the proposed mechanism. This new reversal mechanism demonstrates that valley fill could play an acute role in fluvial reorganization processes, and that reversals could occur independently of tectonic tilting.

The Potential of Enriched Fertilization in Overcoming Nutritional Deficiency in Grafted Melons

Melon plants grafted on Cucurbita rootstock may suffer from nutritional deficiencies due to reduced absorption and translocation of minerals to the foliage. Melon (Cucumis melo L.) cv. 6023 was grafted onto two interspecific Cucurbita rootstocks (Cucurbita maxima × Cucurbita moschata) ‘TZ-148’ and ‘Gad’. Nongrafted melons were used as controls. Two fertilization field experiments were conducted in walk-in tunnels in the northern Arava valley of southern Israel. Two fertigation regimes were used: 1) standard and 2) enriched for magnesium (Mg; 150 mg·L−1), manganese (Mn; 7.5 mg·L−1), and zinc (Zn; 0.75 mg·L−1) to increase the concentrations of the lacking elements. The enriched fertigation significantly increased Mn, Zn, and Mg contents in the leaf tissue. Concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sodium (Na), chloride (Cl), iron (Fe), and boron (B) were unaffected by the enriched fertilizer. There were no deficiency symptoms in grafted plants supplied with the enriched fertilizer.