In most areas of the Negev Highlands, the Judean Desert, Sinai, and southwestern Jordan that receive 80-250 mm. mean annual rainfall, semi-shrubs grow in a diffused pattern, creating shrub-steppes. The most common dominants in these steppes are Artemisia sieberi, Noaea mucronata, and Gymnocarpos decander. During the spring of rainy years, the shrub-steppes may look like ornamental gardens with flowering tulips (Fig. 1.3.64, 1.3.65), Iris species and others. The phytomass produced by annuals in these plant communities on stony-rocky shallow soils is always rather small when compared with that of fine-grained, deep soils (Fig. 1.3.66). The latter soil types hold much of their water close to the soil surface; hence a lot of it is lost through direct evaporation.
The minute quantities of salts (8 ppm.) carried by clouds and later by rain from the Mediterranean Sea climate systems remain in the soil and accumulate there (Yaalon, 1963). The soil may therefore be too dry or too saline for the growth of annuals in normal or dry years but in rainy years, after efficient leaching of the soil, plant communities dominated by a single annual salt-resistant species develop above the leached saline soil. These species include Spergularia diandra and Gymnarrhena micrantha (Fig. 1.3.67), Mesembryanthemum nodiflorum (Fig. 1.3.68), Aizoon hispanicum, and Nasturtiopsis coronopifolia (Fig. 1.3.69).
Nearly monospecific communities of semi-shrubs exist, each of them best adapted to the local, specific saline conditions (Danin, 1978). The most common dominants in these conditions are Reaumuria hirtella (Figs. 1.3.70, 1.3.71), Reaumuria negevensis, Salsola vermiculata (Fig. 1.3.72), Bassia arabica, and Atriplex glauca on chalk- and marl-derived soils; Peganum harmala, Anabasis syriaca and Haloxylon scoparium (Fig. 1.3.73) are the shrubby dominants on loess-derived soils. During dry years these areas are almost devoid of any plant cover. In rainy years, however, beautifully showy geophytes such as Leontice leontopetalum (Fig. 1.3.74) and Ixiolirion tataricum (Fig. 1.3.75) thrive. In areas where bits of sand weres sedimented together, the loess may resemble a flower garden in the valleys among shrub-steppe hills (Fig. 1.3.76). Areas that have been plowed shallowly and planted with wheat or barley become contaminated with weed communities typified by Achillea santolina (Fig. 1.3.77) and Hyoscyamus reticulatus (Fig. 1.3.78).
Outcrops of smooth-faced hard limestone (Fig. 1.3.79) support plants that may differ a great deal from those on other soil types. On such outcrops, the vegetation is typically characterized by Chiliadenus iphionoides, C. montanus, Globularia arabica, Stachys aegyptiaca, Polygala negevensis, Tanacetum sinaicum, and Capparis aegyptia. Isolated populations of dozens of Mediterranean relics and many rare desert plants are found in these habitats in the Negev, the Judean Desert, Sinai, and Jordan. The semi-shrub Sarcopoterium spinosum, and the geophytes Narcissus tazetta (Fig. 1.3.80) and Sternbergia clusiana (Fig. 1.3.81) represent this phenomenon in the Negev (Danin, 1972, 1983, 1999), and several new species have been discovered there (Fig. 1.3.82).
Shrubs of Retama raetam and Achillea fragrantissima are the dominants in hard limestone wadis. Atriplex halimus prevails in this kind of habitat, where the catchment area is built up from the salty soils on chalk, clay or marl. At lower elevations Acacia raddiana (Fig. 1.3.83), A. pachyceras, Tamarix nilotica (Fig. 1.3.84), and T. aphylla occur as well. Many small springs exist in the limestone hills of western Sinai and the sandstone hills of southwest Jordan. Most of these springs can be detected from afar by their date palms (Phoenix dactylifera), which are confined to sites with high water tables of fresh water. The palms are accompanied by Nitraria retusa, Juncus arabicus, Phragmites australis, and Cressa cretica (Fig. 1.3.85). In many wadis there are canyons, which may have long-lasting pools supplied by floodwaters; these support a rich flora of hydrophytes such as Zannichellia palustris and Potamogeton spp., and green algae such as Chara spp.