History, Satellite Imagery and the Flora of Israel (Phytogeography)
1.2.1. Research on the vegetation of Israel
The earliest surveys of Israel’s vegetal landscape were published in the 19th century. In the book HaAsif, edited by N. Sokolov and printed in Hebrew in Warsaw (1887), there is a long chapter entitled “Plants of Eretz Israel,” by a tourist of that time, R. Y. Edlstein. He described several vegetal landscapes along his route, pointing out crops and plants useful to man and his livestock and comparing them to the plants and landscapes with which he was familiar in Europe and North Africa. The names of the chapters themselves are interesting: “Is It Fat or Slim?”; “The Wonder Land”; “Glory of Jaffa and the Sharon”; “The Judean Mts. and Jerusalem”; “Jericho the Town of Date Palms”; “The Dead Sea and Hebron”; “The Lebanon”; “Beirut and the Sharon around It.”
Among the early 20th-century residents of Eretz Israel, Aaron Aaronsohn and Alexander Eig were the botanical pioneers. They were devoted to traveling the country as far as possible and observing and describing its many landscapes. Aaronsohn did not manage to publish his work; it was summarized and published in Hebrew and French by Oppenheimer and Evenari (1941). Eig wrote much of his work in French and in English. In 1946, several years after Eig’s early death, Michael Zohary published a considerable part of his research, mainly that concerning the vegetation of the country. Zohary himself continued studying Israel’s vegetation and published some of his research in scientific articles. He dealt with the vegetation at the “class” level, describing it in his books in Hebrew and English. These books, primarily his Introduction to Geobotany, and Geobotany (both in Hebrew) were the basis of my own and many others’ knowledge of Israel’s vegetation.
When I began my MSc. degree, I decided to focus on the vegetation of Mishor Yamin, near Dimona, for my thesis. Up until I completed my study (Danin et al., 1964), climate had been regarded as the main factor influencing the distribution of plant communities. Mishor Yamin is a unique system: sandstone and conglomerates of the Neogene era fill up the syncline between the Hathira and Hazera anticlines. I concluded that the main environmental factor influencing the distribution of plant communities here was the depth of loose sand above hard sandstone (Fig. 1.2.26). This was one of the first studies to consider the influence of the substratum on the distribution of vegetation. The boundaries of the associations were indicated on aerial photographs; the associations were delimited by observing patches the dominant plants.
The study of Avraham Bourbine (1963) at the Sodom Salinas was part of the project of “Negev Vegetation Mapping”, a project initiated and managed by Prof. Gideon Orshan. In the southern Dead Sea basin, Bourbine discovered plant communities resistant to wet salinity. He found that soil salinity, soil texture and depth of water were the main factors influencing distribution of vegetation. Aerial photographs were used here to delineate the association boundaries. Though Bourbine’s studies were not published in any scientific journals, his M.Sc. thesis was of help to agriculturists who were developing farms in the area.
Based on the principles established by Yaacov Lipkin (1971), Dvora Rudich wrote her M.Sc. thesis on the vegetation around Hazeva in the Arava Valley, which she mapped. The areas under study were divided into homogeneous geomorphological units. Aerial photographs were used here as well, and the patterns of wadis network were used to differentiate the mapping units of the vegetation. Each mapping unit was found to have a typical sequence of associations growing along the wadis. Rudich’s work was published in the “Israel Journal of Botany” (Rudich & Danin, 1978).
The M.Sc. theses of Ruhama Berliner and Aviva Rabinovitch, and the latter’s Ph.D. thesis on the vegetation of the Galilee, published in Hebrew as Rock, Soil and Vegetation in the Galilee (1986), added considerably to our knowledge of the vegetation of this relatively rainy area. Their research delved deeply into the relationship between vegetation and soil. They found that the levels of phosphorous and magnesium in the soil and rock were of primary importance in the composition of the vegetation. Soils lacking phosphorous are covered with bathas of Sarcopoterium spinosum, while phosphorous-rich soils feature herbaceous plants such as Avena sterilis, Triticum dicoccoides, and Hordeum spontaneum. The vegetation of the Judean Hills (shfela) was mapped by Gil Sapir, who found that climatic and edaphic factors influence the distribution of vegetation there. Amos Sabakh mapped the vegetation of the Samarian Desert, where he noted climatic, microclimatic, and edaphic factors influencing vegetation distribution. Neither Sapir’s nor Sabakh’s M.Sc. theses were published.
1.2.2. Israel in Satellite Images
Satellite images of Israel reveal a prominent line: the Mediterranean coastline, where the light color of sands subject to a xeric, unique moisture regime differs from the adjacent fertile soils east of their contact line (Fig. 1.2.7). There are other prominent lines along the country’s international borders, highlighting the different kinds of land management in the neighboring states. The borderline with Egypt, for instance, in northeastern Sinai and the Haluza sands, stands out sharply (Fig. 1.2.8). This borderline passes through an area of sand dunes and stable sand fields covered with a crust of cyanobacteria and mosses. This crust needs protection from trampling by people and livestock in order to survive. East of the borderline, in Israel, that crust is protected against traffic; on the west Egyptian Sinai it is not. These differences can be seen on the ground, from aerial photographs, and in satellite images. Over time, a difference in the reflective quality of the Israeli areas and the Egyptian ones became noticeable south of the Haluza sands, even in places where the soil is not sandy.
Elsewhere in the country, satellite images depict prominent lines between Israel and Syria in the Golan (Figs. 1.2.9, 1.2.10), between Israel and Lebanon (Fig. 1.2.9), between the western Negev and the Gaza area, and in the Judean Mountains and foothills (Figs. 1.2.11, 1.2.12). The impact of climate, important and obvious as it is in the field, is relatively hard to see in satellite images. This may be explained by the gradual changes along climatic gradients. The transition between edaphic and management conditions can be seen along lines a few meters wide, such as for instance, in areas divided by barbed wire fence. Large rock-type units delineating boundaries in Jordan and in Sinai are prominent in satellite images. Borders in the landscapes of old sandstone with magmatic rock, and with limestone and other rock types, can be recognized easily.
1.2.3. The flora of Israel (phytogeography)
When dealing with plant cover of an area one should differentiate between two terms:
A. Vegetation = the vegetal landscape of a certain area, dealing with the physiognomy of the area. Many people relate to the vegetal landscape without considering the whole list of species occurring in that or other area of vegetation.
B. Flora = the whole list of species occurring in the study area, their world distribution areas, the plant families they belong to, etc.
Books dealing with the plants of the country and Jordan are known as “Flora Palaestina” and “Analytical Flora of Eretz Israel.” For example: the vegetation of maquis and forests of sclerophylous evergreen trees such as Quercus calliprinos, Ceratonia siliqua or olive develop in areas where the mean annual rainfall is 400-1000 mm, falling mainly in the cold winter. The summer is warm and dry. Such conditions occur around the Mediterranean Sea, but also in California, Chile, South Africa and Australia. The Mediterranean flora occurs only around the Mediterranean Sea.
There are oak species (Qurcus), red bud (Cercis), and species from other genera but there is not even one species of native shrub or tree common to both Israel and California. The genera building the same landscapes in Australia belong to the genera Acacia and Eucalyptus. The genera building the sclerophylous woodlands in S. Africa and in Chile belong to families and genera differing from those growing in other areas with a Mediterranean climate. In one of his articles, Dr. Peter Raven discussed the floristic differences between the five areas and explained that the Mediterranean climate developed some 1-2 million years ago. At that time, due to plate tectonics, there was no floristic link between the five areas. Hence, their flora differs significantly. On the other hand, due to the adaptation of plants to the environment, plants from different floristic resources look the same. This phenomenon is known as “convergence.” The phytogeography of Israel is discussed in several scientific articles and will be discussed here in brief. The basic unit in the phytogeographic research is the “areal” or “distribution area.” Based on congruence of areal boundaries of many species, former phytogeographers recognized the geographical plant region. Four such regions meet in Israel: 1. Mediterranean, 2. Irano-Turanian, 3. Saharo-Arabian, and 4. Sudanian. This situation exists because of the highly diverse types of climate, rocks and soils. The part of a region in a country, of which the boundaries are political, is known as phytogeographical territory. A plant species may belong to one or more region. We shall use the term “chorotype” (the distribution type) for the region or regions in which the specific plant grows. For example, more than 50% of the plants growing in the Mediterranean territory of Israel are confined to the Mediterranean region and their chorotype is M. The territory marked by M(M-IT) has M-species in the first place and the chorotype M-IT as second in frequency.
18.104.22.168. Renewed phytogeographical analyses
The phytogeographical map of M. Zohary (in his book “Geobotany,” and in the first part of “Flora Palaestina”), is simple; the four territories mentioned above are presented there. When the list of plants was analyzed while mapping the plant communities of the Negev Highlands (Danin, 1970, doctorate), I found many discrepancies between the location of sites in Zohary’s phytogeographical map and the chorotypes spectrum.
The plants chorotypes were following those written in Flora Palaestina. Thus the associations dominated by Artemisia sieberi (a typical Irano-Turanian species) have Saharo-Arabian dominating species in their list of companions. Following this contradiction I decided to go deeper into the question and made a phytogeographical analysis for each 5 X 5 km square of the country, where I listed more than 40 species. I combined neighboring squares that had similar phytogeographical spectrums and follow statistical justification. I consulted with a friend – Dr. Dan Simberloff, who was staying in Israel at that time. He presented a course in our department criticizing methods used by many investigators. Consulting with him decreased the statistical criticism of the manuscript. Thus a new phytogeographical map of Israel and Sinai was formed (Fig. 1.2.13) with seven territories:
1.M – Mediterranean
2.M(M-IT) – Mediterranean with Mediterranean-Irano-Turanian as the second most important chorotype
3.IT – Irano-Turanian which is in fact IT(SA, M)
4.SA(IT) – Saharo-Arabian with Irano-Turanian as the second most important chorotype
5.SA(S) – Saharo-Arabian with Sudanian as the second most important chorotype
6.SA(M) – Saharo-Arabian with Mediterranean as the second most important chorotype
7.S(SA) – Sudanian with Saharo-Arabian as the second most important chorotype.
In an undetailed phytogeographical map of the study area there will be two parts: the Mediterranean and the Saharo Arabian. The boundary between them follows the south-eastern boundary of the M(M-IT) territory (Fig. 1.2.13).
22.214.171.124. A phytogeographical analysis according to geographical subdivisions
While preparing the revised distribution atlas of Flora Palaestina (Danin, 2004) I prepared Fig. 1.2.14. The phytogeographical spectrum of the list of species in each of the 31 geographical districts was established. The geographical division of the country was assembled during dozens of years of botanical investigations in the country. The division of western Jordan into four districts (Gilead, Ammon, Moav, and Edom) was presented by Smith (1936). The present division of the study area is based on the map in Zohary (1966) with minute changes derived from my own research. The latter investigations doubled the phytogeographical information presented in the four parts of Flora Palaestina (Feinbrun 1978, 1986; Zohary 1966, 1972). While participating in a phytogeographical conference in St. Petersburg (1995) I saw that the area of Israel in the maps of Asia is minute. The difficulty in marking 31 districts in such a map led me to try and minimize the geographical districts and base it on floristic variables. Phytogeographical analyses of 31 lists of species of the districts were carried out (Fig. 1.2.14). There is a high similarity in the phytogeographical spectrum drawn by the quantitative relationship of the four principal chorotypes (M, M-IT, IT, SA).
In light of the conclusions resulting from the phytogeographical analysis, I tried to divide Israel into five territories: 1. Mediterranean maquis and bathas, 2. Semi-steppe bathas, 3. Shrub-steppes, 4. Deserts, 5. Montane vegetation of Mt. Hermon (Fig. 1.2.15). These maps were integrated into each species in my website at the botanical garden and then into the present website. Due to difficulties in communication with the programmers involved with my websites, the maps continue to confuse the users because they represent “half way maps.” I look forward to the completion of this geographical information.
126.96.36.199. A transect from The Judean Mountains to Moav
The transect in the Judean Desert (Fig. 1.2.16) presents three variables: 1. Rocks type, 2. Codes of the plant communities, 3. Colored columns representing the phytogeographical spectrum. Keys to the first two parameters can be seen in our scientific article (Danin et al. 1975). The colored columns are a souvenir for me from a lecture I gave in the northeastern coastal area of the Dead Sea. Following the initiative of Seffi Hanegbi and his associates, we gave a short conference for tourist guides from Israel, Jordan and Palestine, in the hope of promoting peace activities in our area. I prepared Figs. 1.2.16 and 1.2.17 for a lecture on the phytogeography of that part of the Middle East. The westernmost column in the two figures includes Mt. Scopus and displays the M chorotype as the most frequent one; second in importance is the M-IT chorotype. The value of the SA chorotype is minute in the west. Along the slopes of the Judean Desert the importance of the M decreases gently whereas that of the M-IT and the IT remain relatively constant. The SA chorotype is more or less complementary to the M from west to east. A mirror picture is seen on the ascent from the Dead Sea to the Jordanian plateau near Mt. Nebo (Fig. 1.2.17). However, the importance of the M-IT is higher here and the M chorotype has lower values. A prominent phytogeographical phenomenon which does not have significant expression in the phytogeographical analysis, is the presence of Sudanian trees and shrubs. These are present in wadis in the hot areas of the eastern Judean Desert and near springs in the Dead Sea Valley. The most prominent are Ziziphus spina-christi, Acacia raddiana, Acacia tortilis, Phoenix dactylifera and Moringa peregrina. This landscape unit is known in vegetation maps as “savannoid vegetation with desert shrubs.” These trees dominate in their countries of origin in a wide array of conditions; in our area they receive the necessary quantities of water in wadis and near springs. They are accompanied by Sudanian perennial grasses in Africa; in the Dead Sea Valley and the Arava Valley, the Sudanian trees are accompanied by Saharo-Arabian desert shrubs and semi-shrubs.
Danin, A. 1976. Plant species diversity under desert Conditions. I. Annual species diversity in the Dead Sea Valley. Oecologia (Berl.) 22: 251 259.
Danin, A. and Barbour, M.G. 1982. Microsuccession of cryptogams and phanerogams in the Dead Sea area, Israel. Flora 172: 173 179.
Danin, A. and Ganor, E. 1997. Trapping of airborne dust by Eig’s meadowgrass (Poa eigii) in the Judean Desert, Israel. J. Arid Env. 35: 77-86.
Danin, A., Orshan, G. and Zohary, M. 1975. The vegetation of the Northern Negev and the Judean Desert of Israel. Israel J. Bot. 24: 118 172.
Feinbrun-Dothan N. 1978. Flora Palaestina part III. Israel Acad. Sci. Human. Jerusalem. 481 pp.
Feinbrun-Dothan N. 1986. Ibid, part IV. 463 pp.
Smith, G.A. 1936. A Historical Atlas of the Holy Land. 2nd ed. London: Hodder and Stoughton. P. 54.
Zohary, M. 1966. Flora Palaestina. part I. Israel Acad. Sci. Human.
Zohary, M. 1972. Ibid. part II. Jerusalem.