We can differentiate between four different principal methods, all based on three 

 fundamental natural laws: 



1. Liebig's Law of the Minimum 



2. The Geo- ecological Law of Distribution (/. Ecol. 35) 



3. The Biological Rules of Climatic Extremes (Pal. /. Bot. Rebovot Ser. 7) 



Three of the methods are based on the surprising regularity of shifts in amplitude 

 in respect to shifts in climatic factors. These shifts in amplitude have long been 

 known, but only recently have they been analysed by statistical and mathematical me- 

 thods. Here nature shows us, and I must stress this again and again, that the vegeta- 

 tion of a region is a much more sensitive indicator of its climate than a collection of 

 meteorological data describing isolated single factors. The four methods provide the 

 key to the code we are attempting to read. Let us take the example of the Laurel tree. 

 In the graph we can see a geographical shift in its amplitude with respect to the IE - 

 factor, that is in relation to insulation and exposure. In areas with an annual precipi- 

 tation of 600- 700 mm., Laurus nobilis occurs only on very steep slopes with a small 

 insolation; that is, only on steep north, north-east, and north-west slopes. Between 

 the 700 and 800mm. isohyetals it occurs on much less steep north slopes, and even on 

 steep west and east slopes. Between 800 and 900mm. the Laurel occurs on south slopes 

 with a 5° slope, and at over 900 mm. of rainfall, the IE -factor ceases to be a factor in- 

 fluencing the geographical distribution of the species. This indicates that the plant is 

 already at the climatic optimum of its geographical distribution. This is a clear example 

 of the Geo -ecological Law of Distribution. This law, in abbreviated form, states, that 

 micro - distribution (that is the topographical distribution of a species or ecotype) is a 

 parallel function of macro -distribution or geographical distribution, since both are det- 

 .rmined by the same ecological amplitudes. 



Next comes the method of geographical shifts in amplitude in relation to the depth 

 of the groundwater table, and finally the method of topographical shifts in amplitude in 

 relation to the IE -factor. The depth to the water table can be determined in a case 

 when it is not too far removed from the ground surface: also average precipitation. 

 Since records from rain gauges are almost always inadequate in arid regions the possi- 

 bilities of exact determination of isohyetals offered by these four methods are of special 

 significance. 



My last mentioned example provides corroborative evidence, since I found out only 

 two years after the completion of ecological tests, that I had by chance conducted my 

 experiments in the vicinity of a rain gauge with a record of more than 20 years. After 

 considering the coefficients necessary to correct for sandy soil and elevation, the me- 

 thod of overlapping amplitudes indicated that average precipitation during the past 30- 

 40 years had been 130- 145mm. per year. Two years after the publication of these re- 

 sults, the record of a border station 2km. from the location of my test appeared, giving 

 a mean annual rainfall of 136.1mm. Since then I have had several other confirmations 

 of the accuracy of this method. 



We are coming to recognize more and more that the vegetation of each region indi- 

 cates its climate with much greater accuracy and sensitivity than meteorological data. 

 The three fundamental laws and the four applied methods teach us to decipher the code in 



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