Effects of body mass and temperature on standard metabolic rate of the herbivorous desert lizardUromastyx philbyi

The standard metabolic rate ofUromastyx philbyiwas measured at 20–40 °C, using constant pressure manometric respirometers. Standard metabolic rate was mass-dependent. Values for the mass exponent ‘b’ ranged from 0·75 at 20 °C to 0·82 at 40 °C. Standard metabolic rate increased as temperature increased with high Q₁₀values at low temperatures (20–25 °C). Low standard metabolic rates in this species are probably an adaptation to herbivory in hot desert environments.     

The role of dew as a moisture source for sand microbiotic crusts in the Negev Desert, Israel

Dew and fog were measured periodically during the years 1992–1995 at the Hallamish dune field, western Negev Desert (average annual rain precipitation ca. 95 mm). A major portion of the dunes are covered by cyanobacterial and moss-dominated microbiotic crusts. Chlorophyll- a measurements and microscopic examination were carried out in order to detect the possible changes in crust biomass and phenological changes of the mosses following the occurrence of dew and fog. Dew and/or fog were present in over 50% of the late summer and fall mornings with an average yield of 0·1 mm on cloth attached to glass plates. This corresponds to ca. 0·03 mm for the upper 0·5 cm of the crust, and is less than the 0·1 mm threshold which implies liquid water and which was also found necessary for net photosynthesis of the cyanobacterial crust. This threshold was met only during heavy dew or fog events, during which 10–40% of the crust surface area was moistened. It was estimated that dew and fog could account for upto 3·2–9·4% of the total annual time of crust wetness and consequently activity due to liquid water. Nevertheless, microscopic examination of the dominant moss species at Nizzana, Bryum dunense, disclosed phenological changes, mainly resulting in growth of vegetative reproduction organs (bulbils), and sexual organs, gametangia (antheridia and archegonia). B.dunense may thus be adapted to the utilization of dew and fog precipitation for the production of nearly mature sexual organs. The moss may thus be capable of already utilizing the first winter rains for fertilization and sporophyte formation.     

Temporal and spatial changes of temperature and precipitation in Hexi Corridor during 1955–2011

This study is focused on the northwestern part of Gansu Province, namely the Hexi Corridor. The aim is to address the question of whether any trend in the annual and monthly series of temperature and precipitation during the period 1955-2011 appears at the scale of this region. The temperature and precipitation variation and abrupt change were examined by means of linear regression, five-year moving average, non-parameter Mann-Kendall test, accumulated variance analysis and Pettitt test method. Conclusions provide evidence of warming and wetting across the Hexi Corridor. The mean annual temperature in Hexi Corridor increased significantly in recent 57 years, and the increasing rate was 0.27℃/10a. The abrupt change phenomenon of the annual temperature was detected mainly in 1986. The seasonal average temperature in this region exhibited an evident upward trend and the uptrend rate for the standard value of winter temperature indicated the largerst of four seasons. The annual precipitation in the Hexi Corridor area displayed an obviously increasing trend and the uptrend rate was 3.95 mm/10a. However, the annual precipitation in each basin of the Hexi Corridor area did not passed the significance test. The rainy season precipitation fluctuating as same as the annual one presented insignificant uptrend. No consistent abrupt change was detected in precipitation in this study area, but the rainy season precipitation abrupt change was mainly observed in 1968.     

Nonlinearity of ecogeomorphic processes along Mediterranean-arid transect

The study was conducted along a climatic transect extending from the Judaean mountains (mean annual rainfall, 700 mm; annual mean temperature, 17 °C) to the Dead Sea (mean annual rainfall, <100 mm; annual mean temperature, 23 °C).A high correlation was found between climatic conditions and factors and processes of the ecogeomorphological system. The values of certain factors and processes, such as soluble salt content and overland flow, increase with increasing aridity, whereas those of others, such as soil organic matter content, clay content, aggregate size and stability and infiltration rate, diminish with increasing aridity. These trends express the long-term effect of the prevailing mean climatic conditions in the research stations, conditions that led to the development of various types of soil and of plant communities.It was also found that for many of the factors and processes examined, such as organic matter content, salt concentration, aggregate stability, infiltration rate and overland flow yield, the rates of change with respect to position along the transect are not linear, and that a climatic threshold value exists in the zone with a mean annual rainfall of about 300 mm and in which the P/T ratio is about 17, which creates a sharp boundary between arid and Mediterranean ecogeomorphological systems. While in arid systems, erosion occurs mainly through physical–mechanical processes, under Mediterranean systems, it is governed mainly by chemical and biological processes.The significance of the existence of a sharp boundary between the arid and the Mediterranean zones is that even a relatively slight increase in the annual mean temperature and/or a slight decrease in the mean annual rainfall is liable to shift the boundary towards the Mediterranean zone and accelerate desertification processes.     

Smith Canyon dune field, Washington, U.S.A: relation to glacial outburst floods, the Mazama eruption, and Holocene paleoclimate

Sedimentary deposits from the Smith Canyon dune field, south-central Columbia Basin, Washington, U.S.A. document climatically-influenced Late Pleistocene and Holocene aeolian and fluvial deposition in a region impacted by glacial outburst floods and tephra falls. The depositional history is summarized by five environmentally distinctive and climatically sensitive sedimentary units (temporal limits estimated): Unit 1 (c. 15·5–8 ka), pedogenically altered glacial outburst flood and minor aeolian silt and clay; Unit 2 (c. 8–6·9 ka), fluvial and minor aeolian sand; Unit 3 (c. 6·9–6·8 ka), flood-induced fluvial sand with gravel-sized tephra clasts; Unit 4 (c. 6·8–3·9 ka), aeolian dune sand; Unit 5 (c. 3·9 ka to present), pedogenically altered, stabilized dune sand. Estimated age ranges are based on stratigraphic position, tephrochronology, and correlation with temporally constrained strata from elsewhere in the region.     

Phenology, and seed production and germination of seven endemic Mimosa species (Fabaceae-Mimosoideae) of the Tehuacán-Cuicatlán Valley, Mexico

We report on the phenology, seed production, and three assays (field, greenhouse and laboratory) to detect the optimal temperature for germination (OPT) and the temperature with fastest germination rate (TFASG) of seven Mimosa species, all endemic to Mexico: Mimosa adenantheroides (M. Martens and Galeotti) Benth., M. calcicola B. L. Rob., M. lacerata Rose, M. luisana Brandegee, M polyantha Benth., M. purpusii Brandegee and M. texana (A. Gray) Small var. filipes (Britton and Rose) Barneby. Flowering and fruiting take place during the wet season (May–September). Though flowering periods overlap among species, no hybrid species were found. The reproductive strategy includes a large number of seeds produced (4000–15000 per plant); however, a high percentage (30–75%) is not viable due to bruchid predation (Acanthoscelides mexicanus (Sharp) and Stator pruininus Horn). In the laboratory, OPT was established at (23°C)24°C(27–28°C) and TFASG at (20°C)25°C(30°C), with 100% of germination in six of the seven Mimosa species. In the field, the maximum germination rate (MAXG) was 92% to 100%, whereas in the greenhouse this value was 56% to 80%. Our results show that heat and moisture do not necessarily stress Mimosa seedling germination, but shade seems to be an important factor influencing germination.     

Microclimate, freezing tolerance, and cold acclimation along an elevation gradient for seedlings of the Great Basin Desert shrub, Artemisia tridentata

Vegetation, microclimate, seedling frequency, freezing tolerance, and cold acclimation were compared for seedlings of Artemisia tridentata collected from 1775, 2175, and 2575 m elevation in the eastern Sierra Nevada, California. Data were used to test the hypothesis that ecotypic differences in stress physiology are important for seedling survival along gradients from desert to montane ecosystems. The vegetation canopy cover and A. tridentata seedling frequency were greatest at 2575 m, compared to 1775 and 2175 m. Snow cover ameliorated temperatures near the soil surface for part of the winter and depth varied across elevations. Freezing tolerance was compared for seedlings maintained in growth chambers at day/night air temperatures of 25°C/15°C. The temperature at which electrolyte leakage and Photosystem II function (F_V/F_M) from leaves were half-maximum was approximately −13·5°C for leaves of seedlings from all three elevations. Shifting day/night air temperatures from 25°C/15°C to 15°C/5°C initiated about 1·5° of acclimation by plants from all three altitudes, with seedlings from the highest elevation exhibiting the greatest acclimation change. Measurements of ambient air and canopy temperatures at the three elevations indicated that wintertime average low temperatures were consistent with the measured degree of freezing tolerance. At small spatial scales used in this study, pollen and seed dispersal between study sites may have precluded resolution of ecotypic differences. Patterns of freezing tolerance and cold acclimation may depend on a combination of mesoclimate and microclimate temperatures, canopy cover, snow depth, and snow melt patterns.     

近31 a河西走廊地区深层地温变化及突变分析

根据河西走廊地区深层地温观测时间最长、资料完整的酒泉、张掖及武威3个地面气象站1980年1月～2011年2月的逐月80、160、320 cm地温资料,运用线性拟合、滑动平均和Mann-Kendall方法进行趋势和突变分析。研究表明：近31 a来河西走廊地区80、160、320 cm深层地温均呈显著的波动上升趋势,其中各深层地温夏季增温速率最大,春季次之,冬季最小,各季各深层地温均发生了暖突变。各深层地温年时间序列中存在3 a波动周期,且表现为前期冷,后期暖的演变趋势,线性增温速率显著,80 cm地温增温速率0.55 ℃/10 a,暖突变出现在1994年;160 cm地温增温速率0.59 ℃/10 a,暖突变出现在1995年;320 cm地温增温速率0.60 ℃/10 a,暖突变出现在1996年。说明年深层地温随着深度的增加,暖突变出现时间存在滞后现象。气温对深层地温的影响作用明显,深层地温受气温升高的影响也呈升高趋势。但随着深度的增加气温与地温的相关性略有降低,这是由于深层地温的变化存在滞后性所致。     

Recovery of topsoil physicochemical properties in revegetated sites in the sand-burial ecosystems of the Tengger Desert, northern China

Recovery in soil properties and processes after sand burial in the Tengger Desert, northern China, was documented at five different-aged revegetated sites (1956, 1964, 1973, 1982, and 1991) and at a reference site with native vegetation, which had never been damaged by sand burial and was enclosed for grazing. The proportions of silt and clay, depth of topsoil and biological soil crusts, and concentrations of soil organic C, K, total N and total P increased with years since revegetation. Most characteristics of topsoil (0–5 cm) characteristics had recovered to 60% of those measured at the reference site by 50 years after sand-binding vegetation had been established. Exceptions were electrical conductivity and contents of sand, silt, CaCO₃ and organic C, which recovered to 20–40% of the values at the reference site. The difference in annual recovery rates of soil properties between the two most recently revegetated sites (0–14 years) was greater than the difference between the two oldest revegetated sites (43–50 years). Best-fit asymptote models showed that the estimated times for the soil properties in the 50-year-old site to reach the same levels as in the reference site (i.e. an undisturbed, native steppified desert ecosystem) would be between 23 and 245 years, but for some properties even maximum recovery after > 50 years still fell significantly short of the level at the reference site. These results suggest that soil recovery is a slow process in an extremely arid desert environment, and therefore the conservation of soil habitat is a crucial issue for land managers.     

Large rockslides in the Southern Central Andes of Chile (32–34.5°S): Tectonic control and significance for Quaternary landscape evolution

The distribution and age of large (> 0.1 km²) Pliocene to recent rockslides in the Chilean Cordillera Principal (32–34.5 S), the Southern Central Andes, has been analyzed to determine the rockslide triggering mechanisms and impact on regional landscape evolution. Most of the rockslides appear in the western Cordillera Principal and cluster along major geological structures. Variographic analyses show spatial correlation between rockslides, geological structures and shallow seismicity. A relative chronosequence was calibrated with existing ¹⁴C and ⁴⁰Ar/³⁹Ar dates and new cosmogenic nuclide exposure ages for selected rockslides. Rockslide-induced sediment yield was estimated with empirical relations for rockslide area distributions. Throughout the Quaternary, rockslides have delivered sediment to streams at rates equivalent to denudation rates of 0.10 ±0.06 mm a^− 1, while estimates using short term (20 a) seismicity records are 0.3_− 0.2^+ 0.6 mm a^− 1. The estimates of sediment transfer and the spatial distribution of rockslides reflect a landscape in which tectonic and geological controls on denudation are more significant than climate.     

Extractable and total Fe and Mn contents of three sand dune soils in NW Nigeria

The profile distribution of total, diethylene triamine penta-acetic acid (DTPA)- and 0·1 HCl-extractable Fe and Mn were determined in 12 pedons formed on three contiguous sand dunes in the semi-arid savanna of Nigeria. The total Fe and Mn contents varied from 100 to 3750 and 40 to 11,375 μg g⁻¹, respectively. Values of 0·1 HCl-extractable Fe and Mn varied from 8·0 to 123 and 1·5 to 43·5 μg g⁻¹, respectively. The corresponding values of DTPA-extractable Fe and Mn were 4·5 to 16·0 and 1·0 to 38·8 μg g⁻¹. Total Fe and Mn correlated significantly with clay in nearly all the dunes (p≤ 0·01) but were not significantly correlated with organic matter. The 0·1 HCl-extractable Mn had a positive significant correlation with soil pH (r= 0·58*) in Illela dunes but a negative significant correlation with pH in the Sangiwa dunes (r= −0·75***). The values of extractable Fe and Mn in the sand dune soils are above the critical limits reported in other literature, thus deficiencies of these micronutrients do not pose a problem to crop production in the study area.     

Late Quaternary systematic stream offsets caused by repeated large seismic events along the Kunlun fault, northern Tibet

The Kunlun fault is one of the largest strike-slip faults in northern Tibet, China. In this paper, we focus upon the Kusai Lake–Kunlun Pass segment of the fault to understand the geomorphic development of offset streams caused by repeated large seismic events, based on tectono-geomorphic analysis of high-resolution satellite remote sensing images combined with field studies. The results indicate that systematic left-lateral stream offsets appear at various scales across the fault zone: Lateral offsets of small gullies caused by the 2001 M_w 7.8 Kunlun earthquake vary typically from 3 m to 6 m, meanwhile streams with cumulative offsets of 10 m, 25–30 m, 50–70 m, 250–300 m and 750–1400 m have resulted from repeated large seismic events during the late Quaternary. An average slip rate of 10 ± 1 mm/year has been estimated from the lateral stream offsets and ¹⁴C ages of alluvial fan surfaces incised by the streams. A three-dimensional model showing tectono-geomorphic features along a left-lateral strike-slip fault is also presented. The Kusai Lake–Kunlun Pass segment provides an opportunity to understand the relationship between geomorphic features produced by individual large seismic events and long-term geomorphic development caused by repeated large seismic events along a major strike-slip fault.     

Germination of Callitris seeds in relation to temperature, water stress, priming, and hydration–dehydration cycles

The effects of temperature, water stress, hydration–dehydration cycles and seed priming on the germination of Callitris verrucosa and Callitris preissii, two Australian semi-arid coniferous tree species, were investigated. Optimum germination occurred at 18°C, with a minimum germination time of 8–9 days for both species. At this temperature, germination was inhibited at osmotic potentials lower than −1·0 MPa, but the capacity to germinate at low osmotic stress increased as the temperature decreased. Seed priming and hydration–dehydration cycles did not reduce seed viability, and Callitris seeds appear to retain the physiological changes induced by short-term hydration, as the time to the onset of germination was decreased to about 3 days. The capacity of Callitris seeds for incremental germination is likely to increase overall germination success in a low rainfall environment.     

地形对民勤沙尘暴发生发展影响的模拟研究——以一次特强沙尘暴为例

河西走廊是中国西北路径冷空气的必经之地,其狭管地形加之丰富的沙尘源地,使其成为中国沙尘暴多发区;民勤位于走廊中段,地处巴丹吉林和腾格里两大沙漠的接壤地带,正好位于雅布赖山和龙首山形成的山口下游方。河西走廊加上民勤周边这种双狭管的特殊地形,使得民勤又成为河西走廊沙尘暴的多发区以及中国的生态环境极度脆弱区。本文以2010年4月24日河西走廊一次特强沙尘暴（部分时段能见度为0,达到了黑风标准）为例,利用GRAPES_SDM沙尘模式对这次沙尘暴进行了数值模拟,并重点对民勤周边山地采取改变高度和范围等方式,模拟研究了地形对过境民勤的风速、地面起沙通量、沙尘浓度以及沙尘输送的影响。结果表明：（1）民勤周边地形高度降低的情况下,地面风速减弱,携沙气流遇到地形阻挡,沿着坡地爬升,部分沙尘可以翻越地形到背风坡,此时的地形特征将减弱沙尘扩散强度;（2）民勤周边地形高度增高,风速小于地形不变时的风速,气流发生明显的绕流,改变沙尘扩散方向;（3）改变民勤周边山体地形位置,狭管效应减弱,地面风速明显减小,沙尘影响范围较控制试验向南及东南方向扩展;（4）河西走廊南部祁连山高度改变对沙尘的影响程度大于民勤北部雅布赖山的改变,这与祁连山的山体面积和高度明显大于雅布赖山有关,说明河西走廊“狭管”地形是民勤沙尘暴之所以多发的重要原因,民勤周边的小型“狭管”地形又使得民勤成为走廊中沙尘暴最为严重的区域。（5）地形改变将减小地表起沙量,从而减小沙尘浓度,也即减弱沙尘暴的发生发展。     

Seed germination of seven Sahelian legume species

As part of the restoration of degraded land south of the Sahara, an experimental study has been carried out on the germinative properties of the seeds of seven Sahelian leguminous species (Cassia obtusifolia, Cassia occidentalis, Indigofera astragalina, Indigofera senegalensis, Indigofera tinctoria, Sesbania pachycarpa and Tephrosia purpurea). Analysis of the effects of temperature, pretreatment and water potential has enabled definition of their optimum germination conditions. For the temperature range studied (20–40°C), germination capacity was significantly greater between 30 and 35°C for all species. All species except Cassia obtusifolia developed a very strong integumental inhibition which was easily eliminated by mechanical scarification or immersion in concentrated sulphuric acid (H₂SO₄, 95%). Study of the influence of water potential on germination showed that these species are able to germinate at relatively low water potentials. Different patterns of response to water stress are highlighted and explained by the different behaviours of these species in the semi-arid conditions of the Sahelian environment.     

Evaluation of annual radiation and windiness over a playa: possibility of harvesting the solar and wind energies

We set up an automatic weather station over a playa (the flat floor of an undrained desert basin that becomes at times a shallow lake), approximately 65 km east–west by 130 km north–south, located at the U.S. Army Dugway Proving Ground (40°08′N, 113°27′W, 1124 m above mean sea level) in north-western Utah, U.S.A., in 1999. This station measured the incoming (R_si) and outgoing (R_so) solar or shortwave radiation using two CM21 Kipp & Zonen pyranometers (one inverted), the incoming (R_li or atmospheric) and outgoing (R_lo or terrestrial) longwave radiation, using two CG1 KippZonen pyrgeometers (one inverted), and the net (R_n) radiation using a Q*7 net radiometer (Radiation Energy Balance System, REBS). We also measured the 10-m wind speed (U₁₀) and direction (R.M. Young wind monitor) and precipitation (Campbell Sci., Inc.). The measurements were taken every 2 s, averaged into 20-min, continuously, throughout the year. The annual (August 1999 – August 2000) comparisons of global or solar radiation and windiness with two other stations in central (Hunter) and northern (Logan) Utah, indicate higher solar radiation (R_si,Dugway=7797 MJ m⁻² period⁻¹vs. R_{si, Hunter}=7021 MJ m⁻² period⁻¹ and R_{si, Logan}=6865 MJ m⁻² period⁻¹) and much higher annual mean windiness (U_Dugway=387 km day⁻¹vs. U_Hunter=275 km day⁻¹ and U_Logan=174 km day⁻¹) throughout the period over the playa. These data reveal the possibility of simultaneously harvesting these two sources of clean energies at this vast and uniform playa.     

沙尘事件对兰州河谷大气环境PM10的影响

利用1999—2001年兰州河谷大气中空气污染物的监测数据,结合河西地区沙尘事件频次,分析了兰州河谷大气环境PM10含量的季节变化特征及其成因。结果表明,源于河西地区的沙尘暴对兰州市空气中PM10含量有重要影响,PM10浓度在冬春季较高,在夏季较低。1985—2001年16 a来河西走廊中东部沙尘事件年均约为37.6 d,兰州河谷年均沙尘事件约为24.4 d,两者表现出显著的相关性（R=0.67,P=0.003）。2001年兰州河谷1 h平均沙尘PM10浓度统计分析显示:PM10含量大于1.0 mg·m-3 的峰值,主要由河西地区沙尘暴过程引起,而PM10含量0.5~1.0 mg·m-3之间的峰值,主要由工业污染物SO2、NOx及颗粒物的排放引起。要长期有效地改善兰州市大气环境质量,不仅要科学地制定本地污染物的减排措施,还要考虑周围地区生态环境的建设。     

Short-term changes in the magnitude, frequency and temporal distribution of floods in the Eastern Mediterranean region during the last 45 years — Nahal Oren, Mt. Carmel, Israel

Short-term changes in Eastern Mediterranean precipitation affecting flow regime were documented in Nahal Oren, a 35 km² ephemeral stream in Mt. Carmel, a 500 m high mountain ridge located at the NW coast of Israel. The rainy winter of the Mediterranean type climate (Csa) in Mt. Carmel is characterized by average annual rainfall of 550 mm at the coastal plain to 750 mm at the highest elevation while the summer is hot and dry. Stream flow generates after accumulated rainfall of 120–150 mm while “large floods”, defined as flows with peak discharge of > 5 m³ s^− 1 and/or > 150,000 m³ in volume, are generated in response to rainfall of over 100 mm. Hence, large floods in Nahal Oren stream occur not earlier than December. Precipitation and flow data were divided into two sub-periods: 1957–1969 and 1991–2003 and compared to each other. The results indicate a clear increase in the frequency of large floods, their magnitudes and volumes during the second period with no parallel change in the annual precipitation. Similarly, an increase in storm rainfall–runoff ratio from < 5% to > 15% and a decrease in the threshold rainfall for channel flow by 16–25% were documented. These short-term variations in flooding behavior are explained by the clear decrease in the length of the rainy season and by the resulting significant shortening in the duration of the dry-spells. The increase in the number of large rainfall events and the large floods in each hydrological year together with the increasing number of years with no floods indicate strengthening of their uncertainty of behavior.     

The comparative influence of past management and rainfall on range herbaceous standing crop in east-central Argentina: 14 years of observations

Impacts of six initial treatments and rainfall on maximum above-ground herbaceous standing crop were assessed in 1978 and annually from 1984 to 1992 in rangelands of east-central semi-arid Argentina. Treatments applied in 1977–1978 were: (1) untreated control; (2) burning; (3) herbicide application (shrub control); (4) Old Field 1 or (5) Old Field 2 (areas previously exposed to different degrees of mechanical soil disturbance for 25 years); and (6) overgrazing. Domestic herbivores were excluded thereafter from all treatments until 1993.During 1984–1992, total above-ground herbaceous standing crop often remained greater in both Old Fields than in the other treatments; highest mean values were 2336 and 1640 kg ha⁻¹for Old Field 1 and Old Field 2 treatments, respectively. Lowest total above-ground standing crops in all treatments (M = 296–475 kg ha⁻¹) occurred in 1989, the year with the lowest annual rainfall (257·5 mm). Desirable perennial grasses contributed most (44–100%) to total herbaceous standing crop in all treatments during the study period. Most of this standing crop was made up of the cool-season grassesPiptochaetium napostaense, Poa ligularis, Stipa clarazii, S. papposaandS. tenuis. Annual rainfall was closely related (p< 0·05) to total herbaceous and desirable perennial grass standing crops in most treatments, and accounted for most of the variation in herbage production between years.     

Water requirements for cultivatingSalicornia bigeloviiTorr. with seawater on sand in a coastal desert environment

The forage and oilseed halophyte,Salicornia bigeloviiTorr., was grown in gravity-drained lysimeters set in open plots of the same crop over two seasons in a coastal desert environment in Sonora, Mexico. The lysimeters were irrigated daily with seawater (40 g l⁻¹salts) at rates ranging from 46–225% of potential evaporation. Biomass and seed yields increased with increasing irrigation depth over the range of treatments. Biomass yields ranged from 13·6–23·1 t DM ha⁻¹, equivalent to conventional forage crops, on seasonal water application depths of 2·3–3·8 m, but were markedly lower at lower irrigation depths. Increasing the irrigation depth lowered the soil solution salinity, resulting in greater growth and water use, and hence leaching fractions that were nearly even over irrigation treatments, averaging 0·5. Evapo-transpiration rose in direct proportion to the irrigation depth. Potential evaporation was estimated by site pan evaporation and by the Blaney-Criddle and Penman models using climatological data; the methods agreed within 15%. The ratio of evapo-transpiration to potential evaporation increased over the growing season and approached 1·5 by pan on the highest irrigation treatment due to the combined effects of high transpiration and high evaporation from the permanently moist soil surface. The best field predictor of biomass yield was the salinity of the soil moisture in the top 15 cm of soil profile, which constitutes the root zone for this crop. Root zone salinity must be kept at 70–75 g l⁻¹for high yields. Although irrigation and drainage requirements were high compared to conventional crops, seawater irrigation appears to be feasible in medium sand and could augment crop production along coastal deserts. The possibility of using this crop for animal production is discussed.