Desert Fringes Research Articles

GEOMORPHOLOGICAL EVIDENCE OF INTENSE PREHISTORIC SOIL EROSION IN THE HIGHLANDS OF CENTRAL JORDAN

Soils and alluvial sediments in two wadi systems provide preliminary evidence of intense prehistoric soil erosion in the Plateau of Central Jordan. Magnetic susceptibility, color, secondary carbonate morphology, and soil structure suggest that, at the end of the Pleistocene, red Mediterranean soils (terra rossa soils) extended into areas that today are dry steppes on desert fringes. The chronological correlation between alluvial depositional events and cultural phases in the context of climatic change in the Levant suggests that climatic fluctuations at the end of the Pleistocene, which were characterized by gradual drying and warming, triggered several consecutive cycles of soil erosion. There is also evidence to suggest that the advent of early farming in the early Holocene played an important role in the continuation of soil erosion processes. The results of this preliminary research suggest that studies of ancient soil erosion in this region, red Mediterranean soils are a useful chronological and pedological datum to be correlated with alluvial and colluvial deposits. [Key words: soil erosion, alluvial sequences, red Mediterranean soils, Levant, Jordan, Middle East, soil properties.]

Micromorphological indications on the nature of the Late Quaternary Paleosols in the southern coastal plain of Israel

The nature of alternating layers of clayey soil material and calcareous soil material in the desert fringe area is discussed. In earlier work by other researchers, these soil materials were considered as representing different climatic environments: the clayey layers a wet period and the calcareous layers a dry period. Based on a pedogenic approach supported by micromorphological indications, however, it is concluded that the clayey layers together with the calcareous layers form a single pedogenic unit developed in the same climatic environment. The calcareous layers are in fact calcic horizons accumulated from the overlying leached clayey material and their appearance is similar to the modern Brown Grumusolic soils that occur in the semiarid area of the coastal plain. A sequence of four superimposed Brown Grumusolic paleosols, developed during the last glacial period, was recognized. In the western part of the coastal plain, Quartzic Brown soils and Husmas soils which developed on sand dunes occur. The former has an argilic horizon with a calcic horizon below. Microcalcites of eolian dust origin are homogeneously distributed in the plasma, the soil representing a monogenetic soil type developed during a semiarid climate. The latter is a Reddish Brown Mediterranean polygenetic soil with leached soil material, in which the calcic horizon accumulated from a loessial soil cover that settled during a drier climate. Both soils also developed during the last glacial period. In the eastern coastal plain, older paleosols which developed on sand dunes occur below the Brown Grumusolic soils. One type is a polygenetic leached Quartzic Gray Brown paleosol, not recognized in previous studies, which overlies a Red Hamra soil (sandy Red Mediterranean soil).

Identification of sand sources and transport pathways at the Kelso Dunes, California, using thermal infrared remote sensing

The Kelso dune field is located in the eastern Mojave Desert, California, at the terminus of a sand-transport pathway, which has its primary source at the Mojave River Wash 50 km to the west. Initial examination of 1984 airborne thermal infrared multispectral scanner (TIMS) data showed significant spectral variations that indicate potential mineralogic heterogeneities within the active dunes. This result prompted the collection of a suite of 48 sand samples in 1990, and the acquiring of new TIMS data in 1995. This new data set was used to test a newly developed linear spectral retrieval algorithm in conjunction with a spectral library of end-member minerals. Results of this analysis produced images of end-member minerals that showed marked variations within the dunes. In addition, standard petrographic techniques revealed that the dunes contain mineralogic variations and were much less quartz rich (∼42%) than previously reported (∼70%–90%). Point-count results agreed with the spectral data to within an average of 5.3% for TIMS-derived and 3.1% for laboratory-derived mineralogic abundances. High concentrations of several of the end-member minerals on the surrounding alluvial fans indicate a potential nearby source for these minerals. Most evident is the presence of potassium feldspar from the fan that emanates from the Providence Mountains east of the dunes. This previously unidentified potential sand input is not visible with other remote sensing techniques and was confirmed with additional field sampling. Much of the quartz and some plagioclase feldspar, however, appear to have been transported from the Mojave River Wash source as previously reported. This study also validates the potential of using thermal remote sensing from future satellite-based instruments to globally monitor desert fringe areas susceptible to the changing conditions of sand encroachment.

Environmental change over two decades since dredging and excavation of the lower Boro River, Okavango Delta, Botswana

The Okavango Delta, southern Africa's largest wetland, is situated on the fringe of the semi‐arid Kalahari Desert. It is a large alluvial fan, occupying a graben structure which is an extension of the East African Rift system. Of the 16 km3 of water which enters the Delta each year, 96% is lost to the atmosphere by evapotranspiration, 2% to groundwater and only 2% leaves as surface flow. In order to increase surface outflow to meet human needs, the distal Boro channel–floodplain system was dredged, excavated and bunded between 1971 and 1974. The immediate impact of these measures was the destruction of in‐channel flora. After 20 years, the aquatic flora has recovered in the excavated channel. However, little recovery has occurred along the channel reach which was dredged. Moreover, there has been significant encroachment of terrestrial species onto the floodplain in the region of the dredged channel. In addition, dredging created a nick point which has been migrating upstream by headward erosion since dredging ceased. The average rate of advance of the nick point has been about 500 m per year. Incision associated with nick point migration has produced a channel which is indistinguishable in form from the dredged channel and, like the dredged channel, is almost completely devoid of in‐channel aquatic flora. The adverse environmental impact of dredging has therefore continued to propagate in an upstream direction, although the height of the nick point has decreased, suggesting a natural attenuation process. This is likely to result in eventual elimination of the nick point.

Use of Solute Chemistry and Isotopes to Identify Sources of Ground‐Water Recharge in the Nile Aquifer System, Upper Egypt

AbstractTwelve ground‐water samples were collected in the Nag Hammadi area, from Quaternary and Plio‐Pleistocene age aquifers. The isotopic data indicate that the main recharge source of the Quaternary aquifer is the recent River Nile water, which is isotopically enriched from evaporation in Lake Nasser. Sources of recharge to the Plio‐Pleistocene aquifer are: (1) Old Nile water depleted in isotope composition, which was trapped in the geological formation, characterized by low permeability and clay lenses prior to the construction of the Aswan High Dam; and (2) The leakage of palaeo water from the deep aquifer system through main faults which bisect the study area. The variation in the chemistry of ground water is thought to be related to mixing between the different water sources and leaching of fertilizers in the newly reclaimed areas in the desert fringes.

Sufi and Scholar on the Desert Edge. Muhammad ben 'Ali al-Sanusi and His Brotherhood

The Sanusiya was one of the most influential Islamic movements in North Africa and the Sahara in the nineteenth century. It organised the Beduin of the desert and desert fringes into a Sufi movement that combined religious piety with trade. Later, it played a key role in the resistance to French and Italian colonialism. The basis of the movement was laid by the Maghrebi scholar Muhammad b. Ali al-Sanusi (1787-1859), who saw his task as being to advance the growth and spread of Islamic learning, in particular the study of Law and the prophetic tradition. This study of al-Sanusi focuses on the scholarly tradition of which he was part, and the heritage of his numerous books and the organisation of the Sufi order in North Africa. The book discusses his role in the Sufi network of Ahmad Ibn ldris and of the scholarly milieu of the Qarawiyin in Fez, giving an overview of the Sanusiya order in the mid-nineteenth century. It also presents al-Sanusi's writings.

Apologia for ‘the Sabaean cultural-political area’

Firstly, I accept Beeston's proposal to refer ‘to linguistic data as Minaic, Sabaic, Qatabanic and Hadramitic, leaving Minaean etc. for non-linguistic contexts’ (Beeston, 1987a: 13). His argument (at least with respect to the distinction between the ‘Sabaean’ and the ‘Sabaic’) looks entirely convincing:The Sabaeans were the inhabitants of the area around Ma'rib. But they shared a common language(no doubt with dialectal varieties) with the peoples of the desert fringes between Ma'rib and Wadial-Jawf, of a considerable part of Wadi al-Jawf itself, and of the high plateaux lying in the angle of those two areas—Arḥab, Qā‘ al-Bawn, Qā‘ Ṣany‘ā’ etc. It is dubious whether these other peoples would have called themselves Sabaeans,1 and it might be preferable therefore to term the language Sabaic rather than Sabaean’ (Beeston, 1979: 115).

Streamflow droughts of northern Nigerian rivers

Several types of streamflow droughts in northern Nigeria can be distinguished, including short droughts which cluster in the rainy season, long droughts which span the dry season, and multiyear droughts. The latter are not analysed in this paper because of limited record length. The duration of short droughts follow a Weibull distribution while the durations of long droughts are normally distributed. As drought duration and deficit are highly correlated, similar probability distributions apply to the deficits. The starting date of droughts can be described by normal distributions. It is suggested that while the occupants of the desert fringe have adapted to long droughts that last the dry seasons, improved knowledge of short drought occurrences is beneficial to the planning of activities for the rainy period.

The Horse and Slave Trade Between the Western Sahara and Senegambia

Following the late fifteenth- and sixteenth-century cavalry revolution in Senegambia, the horse and slave trade became a major sector of the desert-edge political economy. Black African states imported horses from North Africa and the western Sahara in exchange for slaves. Over time, under conditions of increasing aridity, the zone of desert horse-breeding was pushed south, and through crossbreeding with the small disease-resistant indigenous horses of the savanna, new breeds were created. Although the savanna remained an epidemiologically hostile environment for the larger and more desirable horses bred in North Africa, in the high desert and along the desert fringe, Black African states continued to import horses in exchange for slaves into the period of French colonial rule.The evidence assembled on the horse trade into northern Senegambia raises the difficult issue of the relative quantitative importance of the Atlantic and Saharan/North African slave trades and calls into question the assumption that the Atlantic slave trade was the larger of the two. Most available evidence concerns the Wolof kingdoms of Waalo and Kajoor. It suggests that the volume of slaves exported north into the desert from Waalo in the late seventeenth century was probably at least ten times as great as the volume of slaves exported into the Atlantic slave trade. For both Waalo and Kajoor, this ratio declined during the first half of the eighteenth century as slave exports into the Atlantic markets increased. The second half of the eighteenth century saw an increase in predatory raiding from the desert which produced an additional flow of north-bound slaves. For Waalo and Kajoor – and probably for the other Black African states of northern Senegambia – the flow of slaves north to Saharan and North African markets probably remained the larger of the two export volumes over the eighteenth century. This northward flow of slaves continued strong after the abolition of the Atlantic slave trade and was only shut down with the imposition of French colonial authority.

Impact of the Reuse of Domestic Waste Water for Irrigation on Ground Water Quality

Egypt planned to reclaim large areas in both the Eastern and Western desert fringes of the Nile Delta with an increasing use of sewage effluent from Greater Cairo. The Gabal el Asfar farm which has been irrigated with raw to primary treated sewage effluent for a period of seventy five years was selected as a pilot area to investigate the groundwater quality. This farm covering 3000 feddan (1250 ha), is located in the sandy area northeast of Cairo. The main objective of the study was to assess the impact of agricultural application of sewage effluent on groundwater quality. Observation wells were constructed and field and laboratory measurements were carried out in and around the Gabal el Asfar area. The water balance and mass balances have been assessed. The study yielded useful recommendations to decrease the impact on groundwater quality and possible risks in Gabal el Asfar, concerning 1) type and amount of pollution from sewage effluent, 2) design criteria to control possible spreading of pollutants, and finally 3) the use of groundwater in the area. The following comprises the main conclusions:*Irrigation with sewage effluent had a positive impact on salinity of the initially brackish groundwater. On the contrary, groundwater quality is negatively affected from sewage effluent with regard to nitrogen contents (ammonium and nitrate), phosphate, heavy metals and faecal coliforms.*The drinking water limit for nitrate is sometimes exceeded. Moreover, faecal coliforms are found in water from all shallow handpumps in the area. The general suitability of the groundwater is therefore limited while the use of handpumps for drinking water purposes should be avoided. High boron contents of sewage effluent indicate a risk for crops sensitive to boron.*The accumulation of heavy metals and phosphorus in the soil adversely affects the soil system.*Pretreatment of sewage effluent in Gabal el Asfar should be improved to limit the pollution of the aquifer. Industrial discharge in sewage effluent should be avoided.*Groundwater recharged by sewage effluent is mainly collected by drains in or at the borders of the area, so spreading of pollutants out of the area is largely controlled.

Late Quaternary Geological History of the Dead Sea Area, Israel

A 34.5 m borehole, which was drilled near the Dead Sea coast (altitude -394 m) in the southern part of the fan delta of Wadi Zeelim, reveals the geological history of that area from the latest Pleistocene to present. The depositional time frame is based on six 14C dates and two U-Th dates. An erosional (or nondepositional) period is implied by the hiatus between 21,100 yr B.P. (U-Th age, depth 33 m) and 11,315 yr B.P. (14C age, depth 32 m). A subsequent arid phase is recorded by a 6.5-m-thick layer of halite; based on 14C dates this phase relates to the abrupt Younger Dryas cold period reported in temperate to polar regions. The fragility of the environment in this region is indicated by the fact that the region experienced such a severe, short aridification phase (less than 1000 yr), evidence of which is found widely in the desert fringes of the Middle East and North Africa. The aragonite found in most of the Holocene section indicates that the well site was covered by the lake for most of the Holocene. Exceptions are the intervals at 0-3 and 10-14 m depths which represent low stands of the lake.

Aerial Seed Banks in the Central Namib: Distribution of Serotinous Plants in Relation to Climate and Habitat

Distribution of serotinous plants in the central Namib and adjacent areas was correlated with climatic parameters (rain quantity, variability and frequency and prevailing type of precipitation) and habitat in a Binary Multiple Regression model. The desert fringe with (a) high variability of rain (60-70% of annual mean), (b) low quantities of rain (50-100 mmyr1), and (c) prevailing precipitation type rain rather than fog, proved most conducive to serotiny. Serotinous plants were most common in habitats where run-off accumulated, such as foothills of mountains, pans and channels, and on plains. Temporal and spatial variation of water availability, as well as intense rains and run-off, both inducing seed dispersal by water, might explain the abundance of serotinous plants at the desert fringe.

Composition and history of ground water in the western Nile Delta

A hydrochemical and environmental isotope investigation was conducted in the Nile Delta and adjacent desert fringes within the framework of a routine hydrogeological mapping project. The aim of the study was to obtain additional insight into the historical groundwater flow pattern, to differentiate between fossil ground water and contemporaneous recharge by Nile water. An inventory of existing chemical analyses was made (252 data points) and an additional 27 new samples were taken, which were also analysed for stable isotope ( δ 18 O and δ 2 H) content and, for nine samples, 14C and tritium. In the majority of analyses, irrespective of total salinity, an enrichment in sodium was observed relative to the concentration resulting from direct mixing of Nile water with sewater. The Na-rich water is thought to have originated in the extreme arid period from 14000 to 10000 years B.P. (last phase of the Weichsel glaciation) in which, by direct evaporation of (scarce) rain, trona minerals were formed at the surface, and the ground water in phreatic aquifers gradually became saline. The succeeding humid phase from 8000 to 5000 years B.P. when sea-level was relatively high, caused freshening on the desert fringes only, because the Delta floodplain was covered by clay. The present arid phase, which started at around 3500 years B.P., also marked the start of widespread floodplain irrigation. Groundwater levels on the desert fringes dropped as a result of both aquifer depletion by discharge to the Qattara Depression in the west and climatic effects. This in turn initiated a freshening process in the Quaternary and Moghra aquifer of the Delta. Nile water has since then reached Wadi Natrun, 55 km to the west of the western floodplain border.

Settlement and Agriculture on an Ancient Desert Frontier

During late antiquity, large-scale settlement existed in the Negev for almost a thousand years. Comparison with desert settlements in North Africa reveals that the Negev settlement was not unique and that its antecedents were Mediterranean practices. The principal processes that caused the rise, flourishing, and decline of desert settlement are examined. SETTLEMENT in arid areas was neither common nor easily implemented until modern transportation and water-supply technologies were developed. Nonetheless, the central and southern sections of the Negev, located in the southern portion of what is now Israel, were settled for almost one thousand years, from the second century B.C. to the seventh century A.D., under the Nabateans, the Romans, and the Byzantines. The remains of towns, farmhouses, agricultural field systems, cisterns, and wells have impressed travelers and scholars since the beginning of modern research and exploration during the nineteenth century. The most prominent remains are six well-built towns: Elusa, the largest urban center in the region and perhaps its capital, Nessana, Shivta, Rehovot ba-Negev, Avdat, and Mamshit (Fig. 1). These urban centers have been studied by archaeologists, and the history of the Negev has been described mainly in terms of their findings and the few historical records (Gutwein 1981; Negev 1983, 1986). Settlement in the Negev reached its climax during the Byzantine period, from the fourth to seventh century A.D., when most of the buildings in the centers were constructed, large churches were founded, and an agricultural complex, focused chiefly on production of cereals, wine, and olive oil, flourished. The fall of the settlements came as an indirect outcome of the Arab conquest in A.D. 638. During that conquest, the Negev settlements neither were destroyed nor suffered violence. However, the conquest led to the decay of the towns and rural settlements, and they were gradually abandoned during the late seventh and early eighth centuries A.D. (Negev 1986). The settlements in the Negev and their desert agriculture are outstanding features in the history of the region. During no other period was the Negev so densely occupied and populated. The characteristics of this settlement inevitably raise several historical-geographical questions. First, was settlement unique, or was it part of a broad pattern associated with late antiquity? Second, did the Negev settlement scheme originate in the desert, or was it an example of an aspect of Mediterranean life adapted to desert conditions? Third, did the rise, flourishing, and decline of desert settlement stem from * DR. RUBIN is a lecturer in geography at the Hebrew University of Jerusalem, Jerusalem, Israel. This content downloaded from 207.46.13.128 on Wed, 07 Sep 2016 06:14:16 UTC All use subject to http://about.jstor.org/terms THE GEOGRAPHICAL REVIEW FIG. 1-Ancient urban centers in the Negev. conditions unique to the desert or from external forces generated by colonial and imperial goals? In the balance of this article, I attempt to answer these questions. Previous research has revealed no essential similarity between settlement in the Negev and that in southern Arabia, but close parallels existed between the Negev settlement pattern and those in the North African desert fringes of Tripolitania, Mauritania, and Numidia (Fig. 2). A comparison of the characteristics of the Negev and North African settlements is the framework for addressing the large question of desert settlement and its political-geographical origins. 198 This content downloaded from 207.46.13.128 on Wed, 07 Sep 2016 06:14:16 UTC All use subject to http://about.jstor.org/terms ANCIENT NEGEV SETTLEMENT 199

Germination Response of Artemisia tridentata (Asteraceae) to Light and Chill: Patterns of Between-Population Variation

Artemisia tridentata Nutt. is the dominant shrub over much of semiarid North America. It consists of several subspecies and includes ecotypes that occur over a range of habitats from warm desert fringes to montane forest and meadow communities. Fifteen seed collections representing the three common subspecies and a spectrum of habitats were subjected to a series of laboratory light and chill treatments. Recently harvested seeds were mostly nondormant at 15 C but required light for full germination. Removal of the pericarp, afterripening in dry storage, and short chill treatments all resulted in a reduction in light requirement. When examined on a by-collection basis, seed germination response variables were significantly correlated with each other and with mean January temperature at the seed collection site, an index of winter severity. Collections from colder sites were 16%-36% dormant in the light at 15 C and nearly 100% light-requiring, while collections from warm desert fringes were nondormant in light and only 50%-70% light-requiring. Cold winter collections required up to 98 d to germinate to 50% at 1 C in light, whereas warm winter collections germinated to 50% in as little as 16 d. There was no clear relationship between germination behavior and subspecific identity. The observed climate-correlated variation in germination response to light and chill appears to be of adaptive significance, but a genetic basis for patterns of infraspecific variation in germination response in this species has not yet been demonstrated.

The History and Archaeology of Ooldea Soak and Mission

Ooldea Soak is located on the southern fringe of the Great Victoria Desert, about 250 km northwest of Ceduna, South Australia. As one of the few permanent sources of freshwater in the region, it was an important drought refuge for desert Aborigines in prehistoric times and an important meeting place and ceremonial trade centre. In the late 19th century Ooldea served as a depot for a number of explorers, including Giles, Tietkins and Maurice. After 191 7 the Soak became an important watering point on the Trans-Australian Railway. The construction of the railway brought many of the desert Aborigines into contact with whites for the first time and many of the desert people eventually left their homelands and sought refuge at Ooldea. Daisy Bates came to Ooldea in 191 9 and camped near the siding, 6 km south of the Soak. She remained there for 15 years, providing food and medical treatment to the Aborigines. A United Aborigines Mission operated at the Soak from 1933 until its closure in 1952, when the Aborigines were transferred to Yalata Reserve near the coast. The Ooldea area is rich in Aboriginal and European archaeological remains. Preliminary field surveys and recording at Ooldea Soak and Mission and Bates' campsite were conducted in 1988 by ANUTech Pty Ltd, as part of a study of the history and archaeology of the Ooldea area for the Aboriginal Heritage Branch, Department of Environment and Planning, South Australia (Gara et al. 1988). The archaeology of Bates' Ooldea campsite is described elsewhere (Colley et al. 1989: this volume). This paper outlines results of a preliminary archaeological survey at Ooldea Soak and Mission and presents a summary of the ethnography and history of the area.

Farming on the desert fringe—a case study of State Farms in Xinjiang, China

Since 1949, the Xinjiang region in north-west China has been subjected to massive development initiatives and transmigration from the eastern seaboard. A consequence has been the introduction of new technologies in irrigated agriculture to areas on the desert fringe. Large scale (100,000 ha) State Farms have been developed in the semi-desert with variable success.

Drought-related changes to geomorphologic processes in central Mali

Geomorphologic evidence exists for repetitive drought conditions in the African Sahel; within this framework of broad climatic changes through time, the 1968- 1985 drought episodes are not abnormal. The impact of recent drought on the economies and environments of Sahelian nations has been substantial, however, and the recovery capabilities off severely damaged lands are not well known. Study of the geomorphology and surface processes across a portion of Mali provides some constraints on the responses of desert fringe fluvial systems to changing environmental conditions. Multi-temporal orbital image data were used in combination with field investigation to map drought-affected soils, and to document changes to both fluvial and aeolian processes across the region of study. A combination of statistical methods yields consistent evidence of net albedo increases associated with particular landforms and surface processes over a nine-year interval. Although aeolian processes are a significant transport mechanism for removal and redistribution of soil materials, both orbital data and field study indicate that fluvial erosion is responsible for much of the primary topsoil loss and landform modification in this portion of the Sahel.

Rates and modes of dust accretion and deposition in an arid region—the Negev, Israel

Summary Rates of dust accretion and deposition are dependent on the amount of available dust and the trap efficiency of a particular site. Several types of dust-trapping terrains are widespread in deserts: (1) Gravelly (Serir) surfaces that turn with time into Reg soils; (2) vegetated surfaces in the desert fringe that may turn into löessial terrains; (3) stabilized sand dunes; (4) playa surfaces. Loessial terrains exhibit a high rate of dust accretion during the late Pleistocene—0.07–0.15 mm a −1 on the interfluves and ≤0.5 mm a −1 along the flood plains. Gravelly surfaces usually trap about 0.1 mm a −1 of dust initially but the rates decrease to several μm a −1 due to plugging with dust and salts and may ultimately remain constant as a gravel-free B horizon develops. The amounts of imported dust, from both local and distant sources, have changed during the Quaternary due to climatic fluctuations. Roofless ancient building—most efficient dust traps—show that although large amounts of dust were available (much of it from local sources) during the late Holocene, there was not intensive dust accretion during this period due to increasing aridity and decreasing trap efficiency. Wash and gullying led to destruction of the once widespread efficient trapping terrains.

The mechanics and geological implications of dust transport and deposition in deserts with particular reference to loess formation and dune sand diagenesis in the northern Negev, Israel

Summary Entrainment, transport and deposition of dust in and around deserts has major geological implications. A consideration of the mechanics of dust transport and deposition shows that ‘desert loess’ can only accumulate in vegetated desert fringe areas which are relatively close to a major source of dust. Dust deposition can also contribute to the stabilization of active sand dunes, and infiltrated dust plays an important role in the early diagenesis of a wide range of desert sediments.