Desert Vegetation

פורסם: August 27th, 2012 | עודכן: 14/01/15

4. Desert vegetation

East of the area where [Salsola vermiculata] and [Reaumuria hirtella] prevail, and at a lower altitude, the dominant shrubby halophyte on chalk outcrops is [Suaeda asphaltica]. Associations dominated by the latter belong to the vegetation class Anabasietea articulatae. This Suaeda is endemic to Israel and grows in a longitudinal strip from the Judean Desert near Jericho southwards to Nahal Zin near Sde Boker. S. asphaltica is one of the plants most resistant to soil salinity. Like other halophytes it forms monospecific stands (Figs. 8.1.26, 8.1.27). There are continuous carpets of [Poa eigii] among the Suaeda shrubs on north-facing slopes; in rainy years there are many herbaceous companions. Goat and sheep trails are common in all the stands of this plant community. These trails result from the walking habits of the herds (Fig. 8.1.28).

The animals walk in single file on the same path and the result of trampling during moist days is a minute change of the microtopography with clear footprints of the goats and sheep (Fig. 8.1.29). The Suaeda shrubs also recycle salts and in the green slope of that plant community (Fig. 8.1.26) there are patches devoid of plants below the shrubs like those seen under the S. vermiculata shrubs (8.1.24). The Suaeda shrubs absorb salty water from the soil, dilute the salts in their succulent leaves (Figs. 8.1.30, 8.1.31) which they shed gradually towards the summer (Fig. 8.1.32). The dry leaves, flowers, and stems accumulate below the shrubs on the slopes. Hence, the plant-less patches are elliptic and not circular (Fig. 8.1.33). The Poa eigii carpets trap dust [ here as well].

In our study (Danin & Ganor, 1997) we found that soil depth was 60cm in the north-facing slope, where S. asphaltica dominates. The soil does not contain chalk stones although the entire hill is made up of this rock. In the south-facing slope the dominant shrub is [Zygophyllum dumosum]; the soil is shallow and rich in chalk stones. In this way an important issue in pedology of desert areas is revealed.

Fig.8.1.26: Suaeda asphaltica community on a north-facing slope near Mizpe Yericho. The area below each shrub is devoid of the Poa eigii companion

Fig.8.1.27: Suaeda asphaltica community on a steep north-facing slope below Mizpe Yericho. Sheep and goats walking on the same paths for many years caused this special landscape. Atriplex halimus prevails in the large wadis

Fig.8.1.28: Sheep and goats walking in single file in the Judean Desert

Fig.8.1.29: Sheep and goat path in a Poa eigii carpet with foot-prints of the herds

Fig.8.1.30: A Suaeda asphaltica shrub in bloom

Fig.8.1.31: Detail: Suaeda asphaltica branches carrying flowers on the leaf petioles

Fig.8.1.32: Suaeda asphaltica which shed its leaves last summer, starts to develop a new crown in winter

Fig.8.1.33: A Suaeda asphaltica shrub in a carpet of Poa eigii near the “Sea Level” sign. Recycling of salts by the shrubs prevents the growth of companions below them