Har Tayasim: Soils and Rocks; Batha & Maquis
2. Har Tayasim
Har Tayasim has been a nature reserve for more than 55 years. For this reason, management of the area and vegetation development differs from that of the Judean Mts., Mt. Carmel, and Galilee. Cutting, overgrazing and trampling by man and his domestic animals stopped more than 50 years ago. Since then, the disturbances are restricted to making roads and parking lots, gardening associated with the memorial monument, tree planting, cutting of invasive pine trees, and preparations for the annual Memorial Day. The top of the mountain is formed by three geological formations, and the phenomena of plant-soil relationships may be applied in order to understand vegetation distribution in the Judean Mts. and on the ridges of northern Israel.
2.1. Soils and Rocks
Har Tayasim is situated near the highest point of the Judean Mountains anticline. Hence, the rock layers are more or less horizontal. Three rock formations from the Cenomanian are exposed here (Figs. 2.2.1, 2.2.2), each with its typical landscape, soils, and plant communities. The distribution of the latter is highly correlated with rock and soil types (Fig. 2.2.2). Unit 1, the deepest in the profile, is Bet Meir Formation. It is built up of alternate layers of limestone and soft marl or clay (Figs. 2.2.3, 2.2.4). In places where human interference did not cease, the layer pattern is clearer (Fig. 2.2.4). In a different site in the Judean Mts., human activity in a similar rock sequence was applied by building stone walls and making terraces to preserve agricultural land (Fig. 2.2.5).
Motza Formation (unit 2) was named after the the marl quarries near Motza (5 km W of Jerusalem). This marl was used in the preparation of fire-resistant bricks at the "Red House Factory" of Motza. The landscape formed by Motza Formation on hilltops in the Judean Mts. is shown in Fig. 2.2.6, where two red arrows indicate the transition from Bet-Meir to Motza Formation. Human activity in this area, near Batir Village, continues in the same manner as the regular area management in the Judean Mts. belonging to the Palestinian authority. Large terraces constructed on these landscapes of Motza Formation may be seen clearly near the indication "2" in the aerial photograph (Fig. 2.2.2). A dense batha (= dwarf shrub formation) of Cistus, Fumana, Satureja and Thymbra already existed there in 1952, the year this photograph was taken (Fig. 2.2.7). In addition to special soil properties, Motza Formation is characterized by having a microbiotic crust of cyanobacteria, algae, lichens and mosses (Fig. 2.2.8).
It is assumed that this crust has a considerable influence on the nitrogen regime in the soil and consequently on vegetation composition. Soil analyses of the Light Rendzina developed on Motza Formation showed that much of the nitrogen there is in the ammonia ions (NH4) state. In the past, I have suggested to future researchers, and I now suggest again: it is possible that the nitrogen status is associated with development of the microbiotic crust that seals the soil and reduces its aeration. When oxygen is deficient, the nitrogen changes into an ammonia state, through microbial activity. The chemical reaction of the ammonia-rich soil solution decreases the solubility and the availability of essential nutrients. These special edaphic factors influence the unique composition of vegetation on Light Rendzina.
Aminadav Formation (unit 3) is recognized in the aerial photograph (Fig. 2.2.2) as a dark triangle surrounded by typical areas of Motza Formation (unit 2). Hard rock outcrops protrude in a ground view of Aminadav Formation (Fig. 2.2.9). The rocky nature of this formation is expressed in the paucity of agricultural land and in the success of the oak-pistachio maquis covering the rocky terrain. The soil developing here is Terra Rossa, leached and poor in nutrients. The transition from the young unit 3 to the older unit 2 takes place along a topographic descent from unit 3 (in Fig. 2.2.2) northwards, through the Air Force monument to the Motza Formation terraces. However, the transition southwards from unit 3 to unit 2 takes place at the same altitude (Fig. 2.2.10). Amongst the broken arrows in Fig. 2.2.2, there is a geological fault, where the block south of it (unit 2) was raised, in relation to the unit 3 outcrop. Later the area became one hill "carved" by erosive forces. The transition between the geological formations is evident in the replacement of light and dull vegetation by tall, green arboreal vegetation (cf. 2 & 3 labels on Fig. 2.2.10). These areas differ in soil type, which is Light Rendzina in one, and Terra Rossa in the other.
2.2. Batha of Sarcopoterium spinosum and Maquis of Quercus calliprinos
The interesting issues in the chapter on vegetation are the characterization of plant communities, and processes of associative replacement on various rock types as time passes. In many components the vegetation of unit 3 resembles that of the rocky terrain of Ramat Bet Hakerem. Plant succession was described there in detail. Some 20-30 years ago it was possible to see batha patches of Sarcopoterium spinosum on the Terra Rossa of unit 3 (Fig. 2.2.11). Exposed areas in that batha were rich in herbaceous species including several species of clovers. Carpets of Linum pubescens (Fig. 2.2.12) and other species could be seen there. Experimental study has shown that annuals growing on Terra Rossa suppress the seedlings of S. spinosum by drying up the soils in their sites. Peripheral growth of S. spinosum shrubs in margins of formerly ploughed terraces leads to rejection of the annuals (Fig. 2.2.13) and enables the establishment of new S. spinosum seedlings. One of the rare plants which grew in the rock crevices of Aminadav formation was Sternbergia colchiciflora. Following the expansion and growth of the oak and pistachio (Quercus calliprinos and Pistacia palaestina) maquis, accompanied by the Syrian pear (Pyrus syriaca – Fig. 2.2.9), the small companion plants disappeared. The aerial photograph of 1952 (Fig. 2.2.2) shows clearly that maquis trees survived in the rocky area from the period when it was farmed by Arabs (before 1948). Following the cessation of cutting and grazing, trees gradually grew up in the areas shaded by maquis. New young oak trees established themselves in the shade of Q. calliprinos trees. By their shade, they displaced the annuals and the semi shrubs. An increasing quantity of humus accumulates in the shade of Cistus shrubs and may protect the oak acorns from direct desiccation and they germinate in winter. When growing up, these oaks rejected the shrubs in the shade of which they germinated and became established. Open spaces in the maquis of the reserve during the first few dozen years became impenetrable due to the dense growth of vines such as the thorny Smilax aspera (Fig. 2.2.14).