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Most of rural people in Iran living in small villages were subsisting on small scale farming or animal husbandry in an arid environment. Farms and houses belonged to the landowners (malik or arbab) who lived usually in urban places. That is, most of inhabitants in villages were sharecroppers (ra'iyat) or share-tenants (ijareh-Kunandeh) and their families. They were largely dependent on the landowners or landlords not only economically but also socially even after the Land Reform, which started in 1963 and had apparently cleaned out share croppers and share-tenants. On the other hand, both urban and rural population of Iran increased rapidly after the World War II, and migration from rural areas to urban places was also noteworthy. The migration is thought to be stronger related to limitation in population carrying capacity of the villages The author had a survey trip to a village on the north slope of the Zagros mountains. and investigated the effects of socio-economic stratification on the population carrying capacity of the village as well as the capacity of the families for sustaining their members.

The Rio Salado catchment is located in the southern Atacama Desert. The area is distinctly arid and no ground-water reserves originating from local recharge exist. To obtain water for a new copper ore processing plant, brines are being utilized. The complex hydrogeology of the brines from their origin in the Andes to their emergence as springs in the vicinity of El Salado is described. The surface and ground-water discharges indicate that the long-term supply of brine will be adequate for the processing plant. A design for abstraction incorporating three filter drains with wooden pump-housings has been adopted to combat corrosion, incrustation and flood damage.

Experiments with Prunus armeniaca were carried out under conditions of constant temperature but varying air humidity. Experiments were also contucted with a constant water vapor difference between the evaporating sites in a leaf and the air, but with varying leaf temperature. These served as a basis for predicting the daily course of total diffusion resistance under the natural climatic conditions of a desert. For the simulation, the rsults of the experiments at constant conditions with only one variable factor are fitted with empirical equations which serve as "calibration curves" to predict the change in diffusion resistance caused by a change in humidity and temperature calculated from the meteorological data of a desert day. The simulation shows that for P. armeniaca humidity and temperature are the dominating factors in controlling the daily course of diffusion resistance. For meteorologically very different days the simulation allows the increase in diffusion resistance in the morning to be predicted with an accuracy of 90%-105% as compared to directly observed measurements. In the afternoon, especially after extreme climatic conditions during the morning, the deviation between predicted and observed values of diffusion resistance may be greater, but not more than -20% to -30%. This possibly indicates the existence of an additional factor of significance which was not included in the simulation. The two peaked curves of net photosynthesis and transpiration characteristic of plants living under arid conditions can be explained in this species by the humidity-and temperature-controlled stomatal response. This stomatal regulation leads to a decreasing total daily transpirational water loss on a dry day as compared to a moist one. The significance of this controlling mechanism for the primary production and the water relations of P. armeniaca is discussed.

Summary Nubian sandstone exposures in sub-humid, semi-arid, and arid environments have given rise to red, sandy but in other respects very different soils. Soils have a fairly well developed profile only in the sub-humid zone, including a textural B horizon and are free of soluble salts and carbonates. In the semi-arid and arid zones, profile differentiation is weak or non-existent. Soils are shallow and contain carbonates, and in the arid zone also soluble salts, including gypsum. Kaolinite is the only clay mineral which is common to all the nubian sandstone parent materials. It is the major clay mineral in the sub-humid zone soil. In the semi-arid soils smectite is a second major clay component. In the arid zone both smectite and palygorskite, in minor amounts, accompany kaolinite. Both smectite and palygorskite are probably pedogenic neoformation products. Material of aeolian origin has probably been introduced into the silt and fine sand fractions of both the semi-arid and arid soils. Some contamination of the clay fractions may have also occurred.

Pushkar, near Ajmer, Rajasthan, lies in the dry zone to the east of the Indian desert. In the vicinity there is evidence for three arid phases, during the latter part of the Pleistocene, each repre...

The Ah horizons of a Brown–Dark Brown–Black–Dark Gray–Gray Luvisolic sequence of Canadian grassland and forest soils were studied. Clay-associated humus was present in greater proportions in the grassland than in forest soils, particularly in the grassland soils of the more arid regions. Amounts of alkali-pyrophosphate-extractable humus increased in the Brown to Gray Luvisolic sequence. Alkali-pyrophosphate-extractable humic acid (HA-A) contents were greatest in the Black and Dark Gray soils. C:H ratios, extinction coefficients at 280 nm (E280), and resistance to acid hydrolysis of the HA-A and clay-associated HA-B increased in the Brown to Gray Luvisolic sequence. Free radical concentrations were least for the Brown and Dark Brown soils, moderate for the Black and greatest for the Gray Luvisolic soils. The data suggest an increase in the proportion of aromatic components in the humic acids in going from the Brown to the Gray Luvisolic soils. An objective, multivariate similarity analysis based on 22 humus characteristics showed a relationship between soil zone or soil environment and the nature of the soil's humus.

A B S T R A C T Section Ximenesia is native to the southwestern United States and northern Mexico. Two of its taxa, Verbesina encelioides subsp. exauriculata and V. nana, are more western and occur in arid or semiarid regions, whereas the third taxon, V. encelioides subsp. encelioides, is more eastern and occurs in relatively moist regions. A crossing program revealed the absence of isolating barriers between the subspecies of V. encelioides. It is suggested that V. encelioides and V. nana are effectively isolated genetically by differences in ploidy. The study of several morphological characters of both field-collected and garden-grown populations indicates that differential adaptation for aridity has been of primary importance in the evolution of section Ximenesia. The taxa occupying arid regions show a reduction of transpiring surface, reduced reproductive capacity, and reduced dispersibility. IN THE MOST RECENT taxonomic treatment of section Ximenesia (Coleman, 1966a), two species were recognized. Verbesina encelioides (Cav.) Benth. & Hook., an annual, taprooted diploid (n = 17), was divided into two subspecies. Subspecies encelioides is eastern and lowland, occurring primarily in eastern Oklahoma, eastern Texas, and lowland northeastern Mexico. Subspecies exauriculata (Rob. & Greenm.) Coleman is western and highland and occurs throughout

Kangaroo is taken as a general term embracing all members of the marsupial family Macropodidae, although special reference is made to the larger species Megaleia rufa, Macropus robustus, M. giganteus and M. fuliginosus. The origin and evolution of the Metatheria is traced from their divergence from the Eutheria during the early Cretaceous. The entry of Metatheria into Australia probably took place during the Eocene via Antarctica. During the Pliocene there was a marked radiation, within this stock, of forms adapted for grazing. The biology of modem species is considered in relation to their distribution in and adaptation for hot, arid areas with seasonally poor quality food. Kangaroos are efficient homeotherms and their main avenue of heat loss at high temperatures is by panting, with sweating and saliva-spreading in extreme conditions. Their low level of oxygen metabolism is of advantage in hot arid conditions. post-partum fertilization is maintained in the uterus during pouch-suckling of another young, may be an adaptation to allow replacement of young lost by accident or drought, but it may also be 3 general reproductive adaptation of marsupials. The water relations of kangaroos demonstrate a high degree of adaptation to an arid environment. The marsupial characteristic of low body water turnover is combined with high total body water and the capacity to survive weight loss during dehydration typical of ruminant and ruminant-like animals. In addition, desert kangaroos exhibit the ability of many other desert-adapted mammals to reduce water loss by evaporation and from urine and faeces during dehydration, and to recycle urea when nitrogen and water are in short supply. The large kangaroos are well adapted to the utilization of poor quality food, with ruminant-type digestion and nitrogen and water conservation by urea recycling. The diet of large kangaroos includes a large proportion of grass, and does not generally overlap greatly with that of sheep. In kangaroos of arid and semi-arid areas, food, water and shelter are important factors controlling distribution, with food the most important. Reproduction in kangaroos is greatly affected by the severe environmental conditions imposed by drought. The onset of sexual maturity in females is delayed, there is increased mortality of pouch-young due to failure of lactation, and if drought continues, females enter anoestrus and breeding ceases. Embryonic diapause, whereby a dormant embryo from a The family Macropodidae includes some of the most social marsupials. The large, partly diurnal grazing animals of open habitat generally exhibit some form of group cohesion, with a low level of social organization. In the natural regulation of numbers, predators and disease appear relatively unimportant. Rainfall via its effect on food supply is a most important factor controlling numbers. Other such factors are habitat destruction, which is most significant for small species, and commercial exploitation by shooting, which is most significant for large species. However, regulations arein force to control shooting of the large species and there is little likelihood of their extinction from this cause alone.

Northern Belize lies in the northeastern quadrant of the central rainforest zone of the area formerly occupied by Classic Maya civilization, adjacent to the ecological frontier with the northern zone, the arid karstic plain of northern Yucatan. It is bounded on the east by the Caribbean, and is traversed by two of the major rivers of the Maya lowlands, the Rio Hondo and Rio Nuevo, the upper tributaries of which drain the Maya heartland of south Campeche and northeastern Peten.

Even at first glance, one can see remarkable similarities in the topography, geography and patterns of land use of the west coast republics of South America and of the states of Australia which stretch along that continent's eastern and southeastern shores. Not only are the latitudinal parameters comparable, but similarities in climate and patterns of agriculture abound. The resemblances are particularly defined as we consider the geographical extravagance of Chile and compare it alone to the eastern edge of Australia. The desert north of Chile has as its counterpart the arid lands of the island continent's interior, while the semi-arid Norte Chico is much like the area immediately inland from the Australian Dividing Range. Central Chile's Mediterranean climate finds its mirror image in the Riverina, and the rain forest of eastern Australia is much like the deep and tangled woods of Chile's south-west coast. Finally even green and mountainous Chiloe finds a transPacific image in rugged Tasmania.1 Apparently, climate and geography molded both Chile and Australia as producers of primary products for the world markets. Such parallel evolution would suggest that there would be little trade and exchange between the areas, yet trade did indeed develop and came to be significant during several decades of the nineteenth century. This study considers the economic relations which existed between the Republic of Chile and the areas of Australia encompassed by the contemporary states of New South Wales, Queensland and Victoria.2

In arid and semi-arid regions it is important to pay attention to climatic factors in locating and planning new settlements. Physical factors such as large differences in elevation over short distances, proximity to a large lake or the combination of the two factors, cause improvement of the climate. The central Jordan Valley and the Dead Sea could be a suitable area for proving these assumptions. A topo-climatological research has been performed in this region to help the planners in finding the best locations for new settlements. By using a “discomfort index”, which is based on temperature and humidity, the influence of the above mentioned physical factors on local climate modification has been verified. Also, its importance in the improvement of the location of new settlements has been shown.

Ford, J. 1974. Speciation in Australian birds adapted to arid habitats. Emu 74: 161–168.Several stages of speciation can now be identified in some birds occurring mainly in the mulga habitat of the...

SummaryWool samples from 49 ewes representing four breeds of sheep, Ossimi, Rahmani, Barki and Merino were used to study the seasonal variation in wool growth. The first three breeds are of the local carpet-wool types of Egypt.Consistent differences were found between breeds in diameter and length of fibres (i.e. genetic effects). These effects were not modified by the environment (i.e. time of year) although the latter had different effects on diameter than on length. Medullation, however, was not consistent from breed to breed in all seasons (i.e. there was genotype x environment interaction). It is concluded that seasonality in wool growth exists under the semi-arid conditions of Egypt in local breeds but to a lesser extent in imported Merino sheep.

Eleven plant sociations are reported from the McMurdo Sound region of continental Antarctica, and they are grouped in the Alga, Fruticose and Foliose Lichen; Crustaceous Lichen; and Short Moss Turf and Cushion subformations of the Antarctic Non-vascular Cryptogam Tundra formation. Their inclusion necessitated only minor modification of a vegetation classification developed in the maritime Antarctic.The most widespread vegetation consisted of sparsely developed communities of turf- and cushion-forming mosses in habitats ranging from dry cinder slopes to sand and gravel in seepage areas and by meltwater streams. The bryophyte colonies seldom exceeded 4 cm in depth, and although total plant cover within the communities locally reached 85%, it was more frequently under 5%. The Sarconeunim association appeared to tolerate more arid conditions than the Bryum association, whose communities occasionally merged with algal sociations occupying certain of the streams. Exposed rock habitats normally supported at most small scattered thalli of crustaceous lichens, well-developed lichen communities being rare.

Observations of the temperature gradients, moisture content, size distribution of the sand, and tritium, deuterium and oxygen-18 content of the moisture in the sand dunes in a very arid region show that a significant portion of an annual rainfall of about 80 mm infiltrates through the sand dunes and can be a source of major recharge to the aquifer formation outcrops covered by the sand dunes. The mechanism of water movement seems to be related closely to the vertical temperature gradients in the sand. The water infiltrating to the dunes is highly enriched with respect to stable isotopes of oxygen and hydrogen providing a natural label for this type of water.

Over much of arid Western Australia a red and brown hardpan occurs on broad plains; it may lie either on the surface or buried beneath a shallow mantle of soil. It is proposed that, because of its lithological character and its considerable thickness and extent, it should be given the name of Wiluna Hardpan. The proposed type section is north of Wiluna, near Bulloo Downs homestead, where headward erosion of the Ashburton River is exposing sections 30 m deep. Although both ferruginous and calcareous cement may be present, Wiluna Hardpan is largely indurated with silica. It is younger than laterite, but broadly contemporaneous with calcrete and Robe Pisolite. Initially it was probably geographically restricted by a coincidence of suitable conditions of low relief and a climate resulting in episodic flooding and desiccation. Its present distribution is partly controlled by current erosional and depositional processes.

The tendency for avian clutch size to decrease with latitude is well documented (Lack, 1947, 1948; Lack and Moreau, 1965; Moreau, 1944; Skutch, 1949, 1967a). Most of the hypotheses proposed to explain this phenomenon suggest that energy (either food itself or the time used to gather it) is in some way limiting. Lack (1947, 1948, 1966) indicates that mean clutch size represents the largest number of young for which parents can find adequate food. Because shorter days (Lack, 1947) and heavy rains (Foster, 1974a) decrease the number of daylight hours available for feeding, tropical birds presumably can feed fewer young than can temperate forms. Ricklefs (1970) postulates that increased intersp,ecific competition among tropical as compared to temperate predators causes a reduction in food abundance (insects) and thus results in low productivity of predators, i.e., low clutch size among birds. Cody (1966) suggests that tropical birds must devote proportionally mo,re energy to improving predator avoidance and competitive ability than do temperate forms, even at the expense of energy for reproduction, because both predation and competition are higher in the tropics. In view of the above, the large number of avian species in the New World and African tropics which molt while breeding is of interest. Although most investigators have considered molt-breeding overlap only incidental to other studies, this phenomenon has now been reported (Foster, 1974b) for 122 tropical species (excluding all Australian arid region birds). Molt, which usually is temporally independent of breeding is an energetically demanding process. Thus species which overlap molt and breeding form something of a paradox. These birds appear to have additional energy available during the breeding period which could be devoted to reproduction but is not. Organisms which do not utilize for breeding all energy potentially available for that process presumably should be at a selective disadvantage. The purpose of the present paper is to define a set of circumstances in which the channelling of energy into molt, even at the expense of breeding, may be selectively advantageous.

Atriplex buchananii is a C, plant endemic in New Zealand. Its distribution is discontinuous in inland Central Otago and coastal in Southland, Otago, Canterbury, and Wellington. It occupies sites that are arid and subject to saltladen winds or with saline soils. Bladders occur on both surfaces of leaves of all ages. The leaf has Kranz-type anatomy but there are no obvious differences in ultrastructure between chloroplasts of the bundle sheath and the mesophyll cells.

SummaryVarieties of beans (Phaseolus vulgaris L.) were grown under both greenhouse and field conditions to determine the causes of inter-varietal differences in susceptibility to sodium toxicity injury. Varieties varied greatly in plant growth and survival on sodic soils under arid conditions. Environmental conditions were very important in determining differences in survival. Chemical analysis of plant parts indicated that varieties accumulated different amounts of sodium in the roots, stems and leaves. Sodium concentration in stems and leaves of sodium-tolerant varieties was controlled to a low level at lower degrees of injury.

A statistical assay of the available 14C dates for the Sahara Desert region is presented. Palaeoclimatic conclusions have been drawn from two frequency distributions for the Late Glacial and Holocene. The statistical results fit very well the geomorphic and sedimentologic observations of the Tibesti Mts., periods with large data populations coinciding with humid phases; those with only a few data represent arid and/or erosional phases. Consequently, the peaks of the histograms correspond to phases of clayey, and the gaps to those of sandy, accumulation.

The influences of chlorides on cement and concrete is discussed. It is stressed that chlorides enhance sulphate attack. Severe conditions which accelerate corrosion in hot arid areas are described. Laboratory experiments on the behaviour of clinker and normal Portland cement immersed in corrosive solutions for a period of 8 years are described. A scheme for chloride attack processes is described. Two of the general conclusions are: 1. (1) The penetration and adsorption of chlorides into Portland cement is much higher than that of sulphates. 2. (2) Climatic factors have a decisive influence on the character and magnitude of corrosion.

Bromeliaceae exhibits a wide range of habitat preferences, ranging from mesic terrestrial to arid epiphytic. Much of this diversity is facilitated by adaptations which aid salt procurement and increase mineral use efficiency in the forest canopy. Three major nutritional strategies exist in the family: the one employed by numerous terrestrial species of subfamilies Bromelioideae and Pitcairnioideae seems to differ very little from that serving many rooted terrestrials in other families; the tank and atmospheric strategies, however, are based on much more specialized nutritional modes which are derived from the former. Each is dependent on a broad constellation of structural and functional features involving many parts of the plant body and all phases of the life cycle. Tank nutrition is most effective on moist sites, while the atmospheric forms are adapted to drier, less fertile situations. Relationships among these nutritional strategies and the major taxonomic units of Bromeliaceae are proposed.

A brief review is made of methods of soil age determination. Radiocarbon dating is considered to be the most reliable. The analysis of such dates permits the creation of a concept of absolute and relative soil ages. The two main regularities observed are: (1) the upper horizons of a majority of soils are younger than the lower ones (exclusive of the humus-illuvial podzols); (2) forest (“podzolic”) soils are younger than steppe (“chernozem”) soils. At the same time, the first regularity is absent in arable soils, where a sharp increase of soil age is observed at the lower boundary of plowing. Recent data on tropical black clays reveal a great age of humus throughout their profiles due apparently to peculiarities of the clay. A very interesting coincidence in calculation of the rates of accumulation of mantle with the total dust content in the atmosphere is discussed. The existence of a planetary dust turnover is proposed, as well as its consequence— rejuvenation of the soils in temperate humid areas and their aging in arid tropics and subtropics. Insufficiency of data does not permit final conclusions, but the main trends of soil age investigations are indicated.

Two multivariate techniques for evaluation of ring-width and climatic relation- ships are described. One technique employs multiple regression on principal components of climate. Response functions are obtained which express in mathematical form the relative effect of monthly temperature and monthly precipitation during a 14-month period on ring- width variations. Response functions are calculated for 127 coniferous tree sites in western North America. The other technique is a cluster analysis which is used to identify similarities among the response functions and classify them on the basis of their similarities and differ- ences. Higher-than-average precipitation most commonly results in higher-than-average growth, though on cold sites the effects of precipitation during the cooler parts of the year are some- times lacking or inverse. Precipitation is directly related to growth throughout the entire year for 32% of the sites, representing many that have been used in dendrochronology. In the remaining 68% of the sites the effects of precipitation vary from season to season. Tempera- ture is most commonly inversely related to ring width during autumn, spring, and summer. Inverse relationships occur in mid-winter for trees on the warmest sites and on certain high- altitude sites. However temperature effects are often direct ones, especially during winter and for many sites at high altitudes, high latitudes, or on north-facing slopes. Site factors appear most responsible for variations in the growth responses. Aspect of slope appears to be the most critical, followed by altitude and latitude. There are fewer differences between species than between factors of the site, although certain species such as bristlecone pine have a more or less unique growth response. Some speculations are offered on the effects of the sites and their microenvironments on biological processes linking the climatic variables and growth. The variety of ring-width responses to variations in climatic factors suggest that more physiological study of trees on extreme sites may reveal unique growth-environment rela- tionships that have not been observed on more optimum sites. The median percent of tree- growth variance accounted for by climate is approximately 60 to 65%. With such a high percentage of variation related to climate, ring-width variability, if adequately sampled, dated, and calibrated with climate, can be used successfully to estimate past climate, even though all linkages of cause and effect have not been demonstrated by physiological research. It is pro- posed for reconstruction of past climate that many ring-width chronologies be used with diverse tree-growth responses, because the differences can be handled by multivariate tech- niques and provide more information on various climatic factors than chronologies with the same growth response. It is also proposed that response functions have applications in the modeling of productivity in forest ecosystems. They can be used to ascertain the effects of climatic variation on tree growth and to help in extrapolating information gathered in one area to other tree sites.

Summary An attempt was made to determine the species composition, density and biomass density of lizards in some of the principal land units in South Turkana. Thirteen species were recorded. Density estimates were determined from quadrat sampling in representative habitats. Because the number of lizards active was found to vary with time of day and temperature, minimum density estimates were obtained by confining counts to peak activity periods. Biomass density was calculated from the product of species density and the mean population weight measured from shot specimens. The biomass density estimate of the lizard fauna was found to be about 4–5% of the large mammal fauna, and appreciably more in the more arid land units. The species composition of South Turkana lizards show affinities to the Somali fauna, though not to the extent of the East Rudolf fauna, suggesting a more recent penetration of arid–adapted species.

The results from stratigraphy, radiocarbon dating and pollen analysis of three salt-lake deposits at Sambhar, Lunkaransar and Didwana in western Raj'asthan, and one freshwater lake deposit at Pushkar in the Aravalli Hills, are described in conjunction with pollen analysis of some archaeological soil samples from the Indus Valley site at Kalibangan in northern Rajasthan. The salt-lake deposits studied are stratigraphically divisible into (a) pre-lacustrine, (b) lacustrine and (c) post-lacustrine sections. The pre-lacustrine section is characterized by a thick bed of aeolian sand underlying lacustrine sediments, while the lacustrine and post-lacustrine sections are broadly circumscribed by laminated clay and nonlaminated silt respectively. The pollen record from the four lake profiles studied is divided into local pollen zones. Four regional pollen assemblage zones are delineated for the area west of the Aravalli Range in Rajasthan. The environmental history deduced from the pollen record is divisible into phases I-V, of which phases II-V follow the regional pollen assemblage zones. Phase I is stratigraphically determined, and is representative of severe arid environments under which the sand dunes, now stabilized, are suggested to have been active. The plant microfossils first appear in phase II with the deposition of lacustrine sediments dated to around 10000 b . p . The vegetation comprises an openland steppe which is rich in grasses, Artemisia and sedges and poor in halophytes. Artemisa, Typha angustata, Mimosa rubicaulis and Oldenlandia , which now grow under areas of comparatively higher average annual rainfall (above 50 cm), appear to have flourished in the semi-arid belt, while the first two plant taxa had encroached even as far as the arid belt, both suggesting that a general westward shift of the rainfall belts had taken place. Vegetation destruction through burning by man is suggested to have started together with the first occurrence of Cerealia-type pollen at about 7500 b . c . and continued thereafter throughout phases III and IV. The increase in swamp vegetation and the intensification of vegetation cover inland together with the maxima of all mesophytic elements in phase IV ( ca. 3000 b .c . to ca. 1000 b .c .) indicate an increase in the rainfall, apart from a short relatively drier time about 1800-1500 b . c . at Sambhar which correlates with the decline of the Indus culture in northwest India. Phase IV is immediately followed by aridity for which there is stratigraphic evidence that the salt lakes started drying. At Pushkar, there is evidence that the vegetation showed a marked change in the Aravallis. The onset of this aridity is suggested to have been widespread. The climate did not ameliorate until about phase V (? early centuries a .d . to present) at which time the Rangmahal culture perhaps flourished in Rajasthan, the remains of which imply good water supply. In conclusion it is suggested that the Rajasthan desert is primarily natural, its history punctuated by at least one more vegetated, humid period during the Holocene, the climatic control of which as indicated by the vegetation history is consistent with climatic events elsewhere in the world.

The results of analysis of Earth Resources Technology Satellite imagery of Israel and its vicinity are presented in the fields of arid regions vegetation studies, oceanography, atmospheric and cloud studies, pollution observations, geology, and geomorphology. Assessment of usefulness of the four spectral bands of the Multi-Spectral Scanner, which produced the imagery, is presented.

A model is presented which describes the transition from mixed rainfall-dependent agriculture with animal husbandry to specialized modes of production based upon irrigated agriculture and nomadic pastoralism. This model emphasizes selective pressures for mixed farming before irrigation agriculture had expanded in the arid alluvial zones of Mesopotamia, and selective pressures for specialization after irrigation agriculture had become established in that zone. It goes on to describe dynamic interaction between specialized groups once such specialization has become institutionalized.

Trends and periodicities in the annual rainfall of 31 meteorological sub-divisions of India based on data for over 60 years have been examined by various latest techniques like Mann-Kendall rank method, low-pass filter and power spectrum analysis. It is seen that the frequency distribution of annual rainfall for the period of 1901 to 1960 is not normally distributed in some sub-divisions of the country. Positive trend is noticed over central India and the adjoining parts of the peninsula and also over two smaller areas in north-west and north-east India. Only over some parts of eastern India there is negative trend. Increase in mean rainfall for 30 years shows a gradient from the west coast to the interior parts of the country with a maximum over the west coast. The spectral analysis of the annual rainfall of these sub-divisions shows a significant cycle of range 8.5 to 12.0 years which is mainly seen in and around the arid and semi-arid regions of Rajasthan, some central parts of India and extreme south peninsula. A cycle of 2.0 to 3.5 years is also observed over large parts of the country mainly over north-west India, central parts of peninsula and some parts of northeast India.

SUMMARYA field experiment was conducted for two years to study the influence of type of seed bed and various mulcheson yield and nutrient uptake by pearl millet, and on moisture conservation, under the semi-arid conditions of Delhi. A flat seedbed stored more moisture, gave significantly higher yield of pearl millet, and increased the uptake of N, P and K, compared withridge and furrow beds. Mulches were effective in conserving moisture, with straw mulch significantly better than dust mulch inits effect on crop yield and nutrient uptake.

Tree-ring data contribute to a better understanding of the nature of past climatic variations. Annual ring records several thousand years long can be constructed for a few areas, but interpretation of them requires the development of new approaches. For example, a single record of average ring width in the upper tree line environment provides a guide to past temperature fluctuations. However, comparison of this record with another, that of the arid lower forest border, from the same area permits characterization of associated precipitation and temperature anomalies that may, in turn, be linked to features of the general circulation. Other approaches that promise to be very fruitful include study of the variation of ring-width statistics through time, investigation of the physical and chemical properties of wood, and combined multivariate analysis of data for a variety of paleoclimatic indicators.

Israel is a participant in the Earth Resources Technology Satellite Program (ERTS). The imagery of Israel and vicinity taken by the Multi Spectral Scanner of the ERTS-1 Satellite has been the subject of analysis in a multidisciplinary research program. The objectives of the program are mapping of agricultural crops, mainly wheat and orange groves, mapping of natural vegetation, and studies for Israeli hydrology, arid regions research, geology, and oceanography. Cases of water, air, and soil pollution have been observed in the imagery on several dates, and are reported in this paper. These are: oil slicks in the Gulf of Suez and possibly near Haifa; smoke plumes, extending over some 100 km in a nearly straight line along the Gulf of Suez, and soil pollution caused by copper mine effluents in the Arava Valley in Israel. The images of these cases of pollution are presented and ‘space signatures’, i.e., the radiometric spectral characteristics of these cases of pollution as seen from space are also given.

Evapotranspiration from a flood-irrigated rice crop in a semi-arid region, was determined with lysimeters at distances nominally 15, 60, 290 and 790 m downwind from an edge. Results were consistent with an expression of the form E = ax−p + b. It is suggested that, as a consequence, the evapotranspiration at any position in such a field may be obtained, at least in principle, from the evapotranspiration measured at a single point, together with measures of net radiation and wet bulb temperature. Finally, it is indicated that for many purposes evapotranspiration measured at the centre of a uniform field is an adequate approximation to the mean for the whole field, without applying a correction for advection.

Nowhere else does aridity beset so large an area and affect so many contiguous nations as in Africa and the Middle East, yet the problems confronting these states do not stem solely from environmental constraints but also from cultural traditions and social characteristics of the people. Insufficient water sharply circumscribes economic activity and population distribution is directly related to presence or absence of water; enormous evaporative loss from impounded water further complicates efforts at redistribution of that vital resource. Man has learned, however, to cope with such environmental handicaps; plant domestication in the Middle East in the Neolithic reflects successful coping with distinctly seasonal precipitation regimes. Annual rates of population increase in the region are high and likely to remain so in the foreseeable future. A dispersed, rural population with a high dependency ratio poses obstacles to governments seeking to improve the quality of life and to meet rising expecta...

The belts of savanna lying to the south of the Sahara are described. Evidence is then presented which suggests that these have been created from forest by shifting cultivation and the use of fire: they have probably developed contemporaneously with the evolution of Man and increase in human population. The effect of climatic changes in creating desert are discussed, and the conclusion is reached that present conditions in much of the Sahara have been engendered almost entirely by human activities. These include felling of trees for firewood and charcoal, or to make their leaves accessible to stock in times of drought and, even more important, overgrazing—especially by goats. Finally, it is suggested that, in the long term, agriculture may not be the most promising way of developing arid regions. Overstocking the savanna and desert must inevitably lead to disaster.

This paper extends the argument that cattle ranching and ranchers can be better understood by viewing the ranch resource as generating both production and consumption outputs. It was found that nonmonetary outputs of ranch ownership are the most significant factors in explaining high sale prices of Arizona ranches. Land fundamentalism, rural fundamentalism, and conspicuous consumption/speculative attitudes are the most important of these consumption outputs. The analysis suggests that small town viability and growth in the arid Southwest, and possibly in the West as a whole, may be more likely to occur if rural development policies are not predicated on the economic impact of surrounding ranches.

This paper attempts to reconstruct the regional history of uplift and climate since the Cretaceous from the terrace deposits and equivalent features in the Middle Ugab Valley, and from their relationship to adjacent erosion surfaces. Pre-Karroo planation was not advanced, but by earliest Tertiary times the “African” Surface, with characteristic inselberge, had been formed. This surface is preserved on the divide to the south and as a summit plane north of the Ugab, although modified by Tertiary warping along the Otavi axis. The pre-Middle Eocene Ugab occupied a broad valley on this surface. Within the valley three levels are recognised. The Main Terrace surface lies 500 feet above the present river and contains up to 300 feet of sands and conglomerates capped by calcareous sandstones and resting on a weathered Eocene (“Pedestal”) surface. These deposits indicate aridity during the Tertiary period. Their dissection followed upon end-Tertiary uplift with a semi-arid climate and produced the Lower T...

Two of the most conspicuously abundant birds during the summer in the Sonoran desert regions of southern Arizona and northern Mexico are White-winged Doves (Zenaida asiatica) and Inca Doves (Scardafella inca). These doves have nearly identical general distributions extending over arid parts of the southwestern United States and south through Mexico into Central America. However, within this range Inca Doves are confined to desert towns and villages while White-winged Doves occur throughout the deserts (Ridgway, 1916; Bent, 1932). In addition there are seasonal differences in distribution at least within the United States, with the strong-flying White-winged Doves represented only as spring and summer residents while the relatively sedentary Inca Doves are continuously resident (Bent, 1932). In their enlightening review article on the water economy of land birds, Bartholomew and Cade (1963) indicate an apparent direct relationship between body weight and efficiency of osmotic homeostasis. The differences in body weight between White-winged Doves (ca. 140 g) and Inca Doves (ca. 40 g), together with differences in habitat preference and mobility in the same desert macroenvironment, afforded an excellent opportunity to test the proposed relationship between body weight and water economy in two closely related land birds. Therefore, this study undertakes to examine the water relations of White-winged and Inca doves in light of taxonomic affinity, similarity of macroenvironment, and differences in body size, mobility, and microenvironmental preferences.

Man's relation to and dependence upon other forms of life are nowhere illustrated more vividly than in the field of his health. He has known for some time that certain of his most devastating diseases are transmitted to him by mosquitoes, fleas, lice, ticks, and various vertebrates. He is beginning to realize that in many cases these vectors obtain their initial infections from other vertebrate animals which are the natural hosts of the disease organisms. But although he is aware that many members of the animal kingdom thus form a tremendous disease reservoir which may serve as a continuing source of human infection (Meyer 1931), he is as yet largely ignorant of the complex epidemiological interrelationships which this fact implies. For a number of years the George Williams Hooper Foundation has directed research into various aspects of this problem. Part of the Foundation's program has been an investigation of the host-parasite-disease relationships existing in a natural mammalian community. The following report describes this investigation. No such study pretends to be complete or to do more than scratch the surface of this field of inquiry. However, in reporting on the ectoparasites obtained over six years from the maminals of a restricted area, we have tried to indicate some of the potentialities that such a community provides for the maintenance and spread of disease organisms dependent upon arthropod transmission. Throughout this study, attention was focused primarily on the California ground squirrel, Citellus beecheyi, which has long been known as a factor in the epidemiology of plague (Wherry 1908). This squirrel is one of the commonest rodents in California and is usually an important member of any natural community in which it is found; in many areas of the state it is a serious agricultural pest. It was accordingly selected for intensive study to determine its role as a reservoir of disease. In the choice of a site for this investigation, therefore, important considerations were an abundance of ground squirrels, an absence of human activity which would disturb natural conditions, and accessibility throughout the year. These prerequisites were provided by the environs of the Calaveras Dam, in the Livermore Hills of the central Coast Range, eight miles south of Sunol, Alameda County, California. The terrain is rugged there; some hills reach an elevation of 2000 feet, and the bottoms of some canyons are no more than 500 feet above sea level. Grassland predominates, with trees and brush growing chiefly on the northern exposures and in ravines. The climate of the region is somewhat arid. May, June, July, August, and September are largely rainless, and most of the precipitation occurs in November, December, January, and February. Rainfall in this latter period of the study varied from 17.4 to 25.2 inches per year. Conditions are influenced by the moderate weather prevailing on the coast. High morning fogs are frequent in early summer, and a heavy dew accumulates on the low vegetation nearly every night in April and May. The minimum and maximum temperatures recorded were 190 and 1090 F. respectively. Mean monthly temperatures of 65 0

Tree—ring samples of Pseudotsuga menziesii (Mirb.) Franco, Pinus ponderosa Laws., and Pinus edulis Engelm. for 1860 through 1962 were obtained from sites along a vegetational gradient, ranging from forest interior sites to semiarid lower forest border sites. Samples were analyzed using a stratified nested plot design. Near the lower forest border tree rings are narrowest, the variability in the relative ring—width response from year to year is greatest, and the variance in common or the correlation between radii and between trees is highest. This variability is more highly related to climatic fluctuations than the variability in highest. This variability is more highly related to climatic fluctuations that the variability in forest interior trees and may be attributed to longer and more frequent periods during which water stress is limiting to physiological processes in the trees. Hence, at the arid forest border tree—ring chronologies contain the most consistent, but variable, growth responses and provide the best record of climatic fluctuations. The semiarid lower forest border trees exhibit a high frequency of partial growth layers. Chronologies from the forest interior exhibit very few partial growth layers. Crossdating between both types of sites and among many individuals of different species makes absolute dating not only possible but exceedingly reliable. Such tree—ring analyses may have considerable application to the evaluation of ecological forest gradients.

The arid plateau of the Judaean wilderness drops on the east to the trough of the Dead Sea in a long range of sheer cliffs, which are pierced about 32 miles south of the mouth of the Jordan by the ravine of the Wad-el-Hâfâf. On its northern flank a huge mass of their red limestone has split away to form an isolated flat-topped crag standing 1700 feet above the Dead Sea about a mile and a half from its western shore.

THIS study reports on the use of tritiated water (HTO) to determine total body water and the kinetics of the water pool in captive Roadrunners (Geacoccyx californianus). The Roadrunner is an interesting subject for the study of water turnover, as it occurs in the most arid regions of North America (Grinnell, 1907), consumes primarily animal material (Bryant, 1916), will drink water in the field (Sutton, 19140), but apparently does not require it (Miller and Stebbins, 1964; Ohmart, field observ.). In addition, data on its water losses and requirements are available (Calder and Schmidt-Nielsen, 1967; Calder and Bentley, 1967; Calder, 1968a, 1968b). To our knowledge, this is the first reported attempt to use the HTO (tritiated water) technique to determine body water loss in nondomesticated or desert dwelling birds under two different environmental conditions.

SUMMARYThe effects of irrigation on the yields of wheat and cotton were studied on a sandy clay loam soil, with a water-table at 7 ft below ground, under the arid conditions of Lyallpur. The conventional practice of providing 19-acre in. of water to Mexican wheat and 25-acre in. to American cotton proved to be a wasteful and unproductive practice on such soils. High yields of both these crops could be obtained without any subsequent watering after an initial 4-in. irrigation applied for seedbed preparation and sowing, while one 3-in. irrigation after sowing was needed to obtain maximum yields.

Tetranychus sinhai Baker (Acarina, Tetranychidae), a new pest was observed to infest barley, wheat, and rye crops in the Prairie Provinces of Canada. In barley, typical symptoms of the mite attack are manifested by a darkening of leaves, followed by yellowing and wilting from the bend of the leaf to its tip. The increase in number of mites per leaf was reflected by the showing of advanced symptoms on leaves. One hundred and sixty-five barley varieties from different parts of the world were examined for their reaction to T. sinhai infestation in the field. Of these 15 were found to be resistant, 47 moderately resistant, 88 moderately susceptible, and 15 susceptible. In general, the barley varieties grown in arid regions of the world appeared to be more resistant to T. sinhai infestation.The most commonly grown barley varieties in Canada, Parkland, and Montcalm, were moderately susceptible. Only two North American varieties, Canadian Lake Shore–C.I. 2750, and Gem C.I. 7243 showed high resistance to T. sinhai infestation.

Alluvial deposits of the sloping plains below the foothills of the Himalaya consist of thick permeable beds of cobbles, pebbles, coarse sands, and minor clay bands in the Bhabar zone, a northwest-southeast-trending belt of relatively arid country whose southern limit is marked by a line of springs. In the flatter swampy terrain of the Tarai belt below the spring line, the deposits are predominantly hard clays and kankar with intercalated sand and gravel lenses and beds in which ground water occurs under artesian conditions. Exploratory drilling has shown that adequate supplies of good- quality water are also available in the Bhabar zone from perched ground- water bodies as well as the deep water-table aquifer.