Eco-geographic study of Mahaleb ( Prunus mahaleb. L) in the middle 1 and northern parts of the eastern Mediterranean 2

5 Background: Mahaleb still exists in most of the eastern Mediterranean 6 forests associated with Cilician fir (Abies cilicica) and Lebanon cedar 7 (Cedrus libani). However, there is an importance of conservation of its 8 germplasm in hereditary banks due to their degradation in natural habitats, 9 as well as there is growing interest in expanding Mahaleb cultivation due to 10 its low requirements and endurance of harsh environments. 11 Methods : The study used the approaches of the autecology concepts to study 12 Mahaleb in situ. The field surveys have been conducted on an investigated 13 homogeneous area of about 100m 2 to 400m 2 as a (relevé area). 14 Results: Mahaleb occurs in its habitat in isolated individuals form and 15 fragile structures of populations that were largely believed to have been in 16 clumped or linear populations. The spatial distribution is restricted to small 17 isolated zones in half-open, treeless or rocky outcrops areas of deciduous 18 forests or rugged areas of barren mountains. The root sprouting seems to be 19 the dominant mode of recruitment. However, all sites showed missing age 20

classes that may indicate human infringement or the failure of recruitment in 21 some years. The spatial distribution showed that Mahaleb exists in different 22 environmental and climatic conditions regarding soil, landscape, rainfall, 23 temperature. This can be attributed to its possession of genetic capabilities 24 that enable it to adapt to varying environmental conditions in addition to the 25 presence of different genotypes or higher taxa such as subspecies or even it 26 may reflect the differences of environmental resilience inside some species 27 themselves. 28 Conclusions: this reflecting Mahaleb's high ability to withstand 29 environmental, thermal, and water stresses. Notable, strong, long roots were 30 found at different depths of soils, some within the joints of the rocks, and 31 this strengthens its role in protecting soil conservation. The geo-distribution 32 of Mahaleb suggests different genotypes or higher taxa such as subspecies 33 or even the differences of environmental resilience inside some species 34 themselves. 35 It is also necessary to predict new potential areas for growth Mahaleb in the 36 eastern Mediterranean to increase production either by introducing its 37 cultivation in unconventional areas or by enhancing its productivity in the 38 areas currently cultivated, which appears to be an important issue soon. 39 Keywords: Prunus mahaleb,drought,genetic erosion,40 Mediterranean. 41 * Correspondence: hussamhmhusien@gmail.com 42 Background 43 East Mediterranean region and Western Asia countries are considered the 44 origin habitat of Mahaleb (Prunus mahaleb L., Cerasus mahaleb L. Mill., 45 mahleb cherry or St. Lucie cherry EN., mahlab Arb.) (Zohary 1962;Ruiz, 46 1989;Rallo 1995;Scholz and Scholz 1995;Blanca and Diaz 1999;Katzer 47 2002). Besides, it is adjudged to be native in northwestern Europe or at 48 least it is naturalized there (National Research Council 1991). The 49 occurrence of small and spatially isolated populations in Switzerland forms 50 the northern range edge that can Mahaleb reaches (Kollmann and 51 Pflugshaupt 2005). The isolation of these old rare species is often the result 52 of environmental change (Huenneke 1991) such as climate cooling that 53 followed the warmest time of the post-glacial period (Burga and Perret 54 1998;Kollmann and Pflugshaupt 2005). Many studies consider Mahaleb 55 to be one of the ancestors of cherry, where in many countries; it is used as 56 seedling rootstock to grafting sweet cherry (P. avium L.) and sour cherry 57 (P. ceracus L.). It is considered a strong rootstock due to its tolerance to 58 drought and high calcium carbonate content in the soil (Nabulsi 2004); it 59 is also found in most well-drained soils (Guitian 1993) and poor soils on 60 open rocky slopes as well as in sunny or partially sunny places (Bean 1981;61 Huxley 1992). Socias (1996)  were between its wild forms, the weight of the fruit, the length of the leaf 70 neck, and the leaf area index. 71 The wild condition exists in most of the eastern Mediterranean forests 72 associated with Cilician fir (Abies cilicica) and Lebanon cedar (Cedrus 73 libani), on 2000 m elevation (Mouterde 1970, Barkuda andAudat 1983;74 Barkuda et al. 2002). Currently, there is growing interest in expanding 75 Mahaleb cultivation in promising agricultural areas due to its low 76 agricultural requirements and endurance of harsh environments. For 77 instance, in Syria there are 5737 hectares of cultivated land containing 78 around 1.3 million trees most of which are not in the fruiting stage. 79 However, the production of kernels around 25 tons annually ranking Syria 80 in the advanced position (The annual agricultural statistical abstract 2016). 81 In addition to the economic feasibility of cultivating where farmers found 82 an economic benefit from cultivating it because of the demand for it for its 83 nutritional and medical value and for being part of many industries. Its 84 kernel oil contained a high level of polyunsaturated fatty acids especially, 85 α-eleostearic, which is a conjugated fatty acid rarely found in vegetable 86 (Sbihi et al., 2014) and for the future, it may be important for clinical 87 nutrition and the food and pharmaceutical industries (Özçelik et al. 2012). 88 Phenotype differences of Mahaleb were studied in Turkey and Italy as a 89 valuable genetic material for seed breeding programs (Gass 1996); several 90 clones of drought and carbonates tolerance clones were selected for arid 91 calcareous soils (Baumann 1977;Giorgio et al. 1992;Giorgio and 92 Standardi 1993). The Eastern Mediterranean where is characterized by 93 historical degradation as a result of habitat damage due to frequent fires, 94 wood extraction, and overgrazing. In particular, Mahaleb is suffering from 95 tremendous depletion in genetic resources in their origin habitats (Nabulsi 96 2004). However, Tawaklna et al. (2011) found and studied 22 phenotypes 97 of wild mahaleb in Syria. 98 This study aims to know the autecology of Mahaleb and to study its 99 landscape ecology in different ecosystems in the middle and northern parts 100 of the eastern facade of the Mediterranean. 101

Study area 103
A comprehensive field survey and a spatial investigation were carried out 104 on the locations where wild or cultivated Mahaleb exist in both the natural 105 forests and some mountain areas where the remnants of the perennial wild 106 trees still grow, in order to study Mahaleb in its natural habitats. As well 107 as, in some sites that are planted and irrigated by local farmers. Information 108 regarding the locations was retrieved from a variety of sources: available 109 documents and literature, official statistics from the National Statistical 110 Agencies, and the local inhabitants ( Fig. 1). 111 Survey methodology was adopted according to Maxted (1997), where the 115 location of the Mahaleb in each study area was initially investigated. 116 Homogeneous areas of about 100m 2 to 400m 2 were selected as (relevé 117 area) and the following parameters were recorded and studied (Chalabi, 118 1980;Sankary 1988 that is defined as follows (Braun-Blanquet 1928;1964;Whittaker 1973;132 Mueller-Dombois and Ellenberg 1974;Chalabi 1980;Nader 1985): 133 5: the species covers more than 3/4 of the relevé area (more than 75%). 134 4: covers from 1/2 to 3/4 the relevé area. 135 3: covers from 1/4 to 1/2 the relevé area. Soil samples were taken from topsoil (depth of 0 to 30 cm) for laboratory 144 analysis, where they were air-dried and then mashed, and then the parts> 145 2 mm were sifted in the sieve, and then conducted on the parts with a 146 diameter> 2 mm, the following physical and chemical analyses: 147 The particle-size analysis was performed by the hydrometer method with 148 the application of sodium-hexametaphosphate (Na6P6O18) as a chemical 149 dispersion agent, Soil Survey Division Staff (1993). 150 The Walkley-Black method (1934), modified by Nelson and Sommers 151 (1982) was used to determine the soil organic matter. 152 Electrical Conductivity (EC) was measured in the suspension of H2O (1:2), 153 Soil Conservation Service (1992). 154 Soil reaction (pH) was measured in the suspension of H2O (1:1), Soil 155 Conservation Service (1992). 156 Total Nitrogen was estimated by (Kjeldahl 1883) and McRae (1988). 157 Total potassium was estimated by (Jackson 1956). 158 Available phosphorus was estimated by (Olsen 1954). 159 Calcium carbonate content was determined by (Balázs et al. 2005 Quarterly precipitation pattern, Seasonal Trend (K), Precipitation 174 Covariance Variance (C.V). 175 The pluviothermic quotient of Emberger (1955) and Daget (1977) was 176 used to determine the bioclimate and variant of each study site. where: Q the pluviothermic quotient, P is the average annual precipitation 179 in mm, M is the mean of the maximal temperature of the hottest month 180 in ᴏ C (degree absolute) and m is the mean of the minimal temperature of 181 the coldest month ᴏ C (degree absolute). 182 According to the Q2 values, five categories of humidity could be 183 distinguished (Table 1). 184 As the role of the minimum temperature of species distribution has been 187 pointed out by Larcher (1983) and Woodward (1987). Therefore, (Quézel 188 et al. 1985;Daget et al. 1988; Barbero et al. 1992) have suggested winter 189 variants according to the values of m (Table 2). 190  Sankary (1988) (Table 3). 205 Aridity Index estimated using the calculation of the degree of continentally 206 (Gorczynski 1922;Abbas 1990 To develop a digital map of Mahaleb distribution, a digital database was 214 established using GIS (Hijmans et al. 2005). The data were analyzed 215 statistically using the Statistical Analyses System (SAS). 216

217
The results of the eco-geographic survey confirmed that Mahaleb is present 218 where the EU-Mediterranean climate prevails. Its occurrence was 219 monitored in the middle and northern parts of the eastern facade of the 220 Mediterranean. In six locations where its were observed in wild conditions, 221 and in four sites it was in cultivated conditions. However, it is disappeared 222 completely from some locations, where it was strongly believed to exist. 223 The topographical features of the sites of Mahaleb diffusion varied, as they 224 appeared on steep slopes, between rocks, and in the flat agricultural plains, 225 associated with a variety of plants. The following is a brief description of 226 Physical and chemical properties of the soil of the studied sites: 228 Soil textures varied from sandy loam (Lsr7), sandy clay loam (Lse1), clay 229 loamy in both (SD) and (Hj), and clay in the rest of the locations (Table 3). 230 Table 3 Soil particle size distribution. 231 The chemical and fertility properties of the soils in which Mahaleb is 232 occurring have varied widely (Table 4). 233 Table 4 Chemical analysis of study sites soils. 234 Results of the climatic study of the studied sites: 235 The results showed that the average prevailing temperature in the sites 236 ranged between 7.78 and 34.8 °C, while the (WTI) ranged between glacial 237 to cold, and the (WI) between glacial winter to a cold winter (Table 5). 238 Table 5 WTI and WI for the study sites. 239 The annual rainfall ranging from 257.7 to 1425.1 mm, with (C.V) between 240 0.223 and 0.37 and standard error is 126.6. The seasonal pattern of 241 precipitation is winter-spring-autumn-summer (Table 6). 242 Table 6 The character of rainfall of the study sites. 243 According to the pluviothermic quotient of Emberger, Mahaleb occurs in 244 bioclimatic stages from humid cold to semi-arid fresh with frequent to 245 occasional frost frequency (F.F) (Fig. 2). 246

Fig. 2. The distribution of study sites on Emberger's climagram. 247
The indicators of the drought showed that the thermal average of Mahaleb 248 ranges between 12 and 19. 249 The degree of continentally that can serve as aridity index ranges between 250 24 and 38.08; i.e. from continental to semi-continental to coastal with a 251 range exceeding 14. Spatial continental values ranged from 49.05 at (REs) 252 to 14. 49 at (Lse1) ( Table 7). 253 Table 7 The mean thermal and continental mean values for each studied 254 genotypes that reflects various environmental conditions (Vivero et al. 279 2001). Although this occurrence is not widespread, it supports previous 280 studies that confirmed that some countries of western Asia such as Syria, 281 Turkey, Iran, Iraq, and Lebanon are also the original homeland of Mahaleb. 282 Where can be found in wild conditions in the forest and mountainous areas 283 (Mouterde 1970;Chalabi 1980;Nahal et al. 1989;Ghazal 1994;Ghazal 284 Asswad 1998;Chikhali 2000). No individuals of Mahaleb were observed 285 in Orontes plain and in Jisr al-Shughur contrary to what some previous 286 studies indicated (Mouterde 1970;Barkoudeh and Audat 1983). Besides, 287 its presence was very rare in the Anti-Lebanon mountain range and the 288 Qalamoun Mountains, where cherry cultivation abounds in abundance, and 289 this may be due to the use of wild trees as assets for grafting cherries. This 290 illustrates the extent of the genetic erosion to which Mahaleb was exposed 291 by human activities such as changing the agricultural system in its natural 292 habitats, as well as the overgrazing and logging of old trees and seedlings 293 alike. 294 Soil data indicates that the growth of Mahaleb occurs in soils of various 295 textures, and this is in line with the findings of each of Bean (1981) and 296 Huxley (1992). The degree of soil interaction (pH) appeared different, with 297 a range of 1.64. This indicates the resilience of Mahaleb towards the soil 298 pH, where it was found in soils of different pH, ranging from a slightly 299 acid (SD) to a moderately alkaline (Im), this corresponds to what Bean 300 (1981) and Huxley (1992) indicated that it favors slightly acid soils and 301 suffering from chlorosis in the soil of moderately acid or higher. Soil 302 salinity was low in most locations, while the most prominent variation was 303 in the calcium carbonate that directly affects the mobility of trace elements 304 in the soil, especially iron. Mahaleb has shown some resilience indicators 305 as it tolerates high levels of calcium in the soil, whether in the seedling 306 phase or whole trees. Where the calcium carbonate ratios in the soil of the 307 studied sites ranged between 4.38% at the site (SD) and 42.08% at the site 308 (Ak3) between 4.38% at the site (SD) and 42.08% at the site (Ak3). The 309 percentage of organic matter content in the studied site soil varied. The 310 highest was in the site (Lse1), (REw), and (Lsr7) with values of 4.79%, 311 4.52%, and 4.42%, respectively, while the lowest was in the site (Ak3) 312 reached 0.57%. This indicates that it is of low nutritional requirement and 313 grows in both fertile and poor soils. Site soil was characterized by a 314 significant total nitrogen content; the maximum was 1.01% in (Lsr7). The 315 content of available phosphorus was rated as good; (Sd) was the heights 316 with (55.1 mg.kg -1 ). As well as, good content of available potash, the 317 maximum was (428.2 mg.kg -1 ) in (Rg). However, the site (Ak3) was poor 318 with available potash (126.6 mg.kg -1 ). Notable, strong, long root systems 319 were observed growing in soils of different depths, even within the joints 320 of the rocks, and this strengthens its role in protecting the soil from water 321 erosion. According to the pluviothermic quotient of Emberger, it can be 322 concluded that Mahaleb is one of the plants that occur in a different 323 bioclimatic stage where the pluviothermic (Q2) accedes 34. The indicators 324 of the drought showed that the thermal average of Mahaleb ranges between 325 12 and 19. This suggests that the biological zero of these variates ranges 326 between 10 and 20 °C. The degree of continentally expresses a high ability 327 of (tree and seedling) to withstand environmental, thermal, and water 328 stresses. 329 The variety of soil properties and diversity of climate parameters where 330 Mahaleb occurs indicates that this geo-environmental diversity may be 331 reflected in the presence of different genotypes or higher taxa such as 332 subspecies or even it may reflect the differences of environmental 333 resilience inside some species themselves. 334 The only study that was implemented by Tawaklna et al. (2011), where 22 335 wild phenotypes were identified and described, six of them which are 336 superior in the morphological characterization were selected. Further 337 studies must build on the same study, even though it did not rely on a sound 338 approach to the description of Mahaleb. Rather, it relied on the 339 methodology for the description of cherries approved by the International 340 Plant Genetic Resources Institute (IPGRI) because the description of 341 Mahaleb simply does not exist yet. Moreover, the study did not find 342 possible correlations between phenotypes and eco-geographic conditions. 343

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Mahaleb in the Mediterranean has been present since ancient times where 345 its seeds were still used in nutrition and industry. It is used as a rootstock 346 of cherry trees due to the strength of its roots and its tolerance to drought 347 and the high carbonation in the soil. It can be found in wild and cultivated 348 conditions. 349 Mahaleb has developed over time a phenomenon of acclimatization 350 towards the surrounding environmental factors, such as terrestrial and 351 climatic environmental stresses. Its smooth, shiny leaves formed a way to 352 reflect sunlight, thereby avoiding its direct thermal effect, on the one hand, 353 and reducing evapotranspiration intensity on the other hand . 354 The environmental resilience of Mahaleb has created important roles in the 355 eastern Mediterranean forest that can play in progressive succession as 356 medium-sized trees within the climax community and as shrubs in the 357 reactionary succession within the deteriorating forest apogee community . 358 In cultivated land, there is an increasing interest in the cultivation of 359 Mahaleb in the last decades, as a promising tree in the hilly and 360 mountainous areas as a tree capable of withstanding the harsh environment 361 in addition to its good economic returns, low requirements, and resistance 362 to diseases, so its cultivation has spread steadily. Also, its wide 363 environmental range indicates the presence of many phenotypes suited for 364 promising agricultural areas. To achieve this, detailed studies should be 365 conducted to determine the critical (biotic and abiotic) stress boundaries of 366 Mahaleb trees in their natural habitats to elect acclimatized clones in each 367 environmental region. 368 It is also necessary to predict new potential areas for growth Mahaleb in 369 the eastern Mediterranean to increase production either by introducing its 370 cultivation in unconventional areas or by enhancing its productivity in the 371 areas currently cultivated, which appears to be an important issue soon. 372

Declarations 373
Ethics approval and consent to participate 374 Not applicable. 375

Consent for publication 376
Not applicable. 377

Availability of data and material 378
All data generated or analysed during this study are included in this 379 published article. 380

Competing interests 381
The authors declare that they have no competing interests. 382