Plant Biodiversity, Phytosociology and Latitudinal Ranges in Sahara Meridional and Sahelian Regions

International Journal of Geobotanical Research, Vol. nº 6. 2016. pp. 37-55

Plant biodiversity, phytosociology and latitudinal ranges in Sahara meridional and Sahelian regions

(1) (2) (3) (1) (4) Manuel COSTA , Arnoldo SANTOS , Lleonard LLORENS , Pilar SORIANO & Herminio BOIRA

(1) Jardin Botánico. Valencia. Spain (2) Jardin Aclimatacion de la Orotava. Tenerife. Spain (3) Universitat Illes Balears. Spain (4) Instituto Agroforestal Mediterráneo. Universidad Politécnica. Valencia. Spain

Abstract: Phytosociological aspects and latitudinal distribution of the main species of Southern and Western Sahara are analysed. From the statistical analysis of the matrix of 98 vegetation samples, five new associations for W. and S. Sahara are proposed. Differential ecological characteristics and distribution areas are reported. Ass.Tetraenetum gaetulae include subhalophilous species in coastal areas and dunes of the W Sahara (Mauritanie). Launaeo nudicaulis-Pergularietum tomentosae include characteristic species of the ergs in W Sahara; Boscio salicifoliae-Combretum micranthi constitute a transit community from the savannah to the desert with an irregular belt in the Sahelian-Sudanian area; associations Salvadoro persicae-Leptadenietum pyrotechnicae and Fagonio olivieri-Aervetum javanicae are typical plant communities in the ergs, regs and general plain sand areas of the meridional Sahara. A relation of the species and communities with latitudinal ranges, climatic data and soil characteristics has been established. A new phytosociological class, Panico turgidi-Acacietea raddianae, and order, Panico turgidi–Acacietalia raddianae, are proposed by grouping the last four associations. The differential values of the taxonomic biodiversity index and biotypes among the Sahelian, Saharan-Sudanian and hyperdesertic Saharan-Sudanian regions are also reported. Ethnobotanical aspects, such as plant use, nutritional, medicinal and domestic resources, are cited. Keywords: Sahara, erg, regs, phytosociology, corology, biodiversity.

Introduction Previous works into plant geography, particularly of sandy dunes and regs, have led to floristic catalogues Studies about Saharan vegetation (Quézel, 1958, 1965, 1969) emphasise that no flora has been defined to different with synthetic assays for interpretation purposes. biogeographical regions, nor clear bioclimatic differen- As pointed out in several studies (Quézel & Simon- tiation. Extreme dry conditions allow certain bioindicator neau, 1962; Killian, 1960), the proposal of one phytoso- species to colonise on sandy dunes, soil (ergs), rocky ciological scheme from floristic affinities of vegetation sandbanks (regs, desert area covered with coarse gravel samples and published floristic catalogues presents great and small stones) and mountain slopes. difficulty. The numerous studies conducted on meridional Saha- The principal biogeographic delimitation of desert ran vegetation have focused principally on areas of high zones has been established from the mean values of mountains, their valleys, and formations about isolated annual precipitations of around 200 mm. When consi- wet areas. The best known flora and communities corres- dering the immense domain of the Saharan Arabian de- pond to the massifs of Tibesti (Marie & Monod, 1950), sert and other factors that determine water balance, the L’ Air (Bruneau de Mire et Guillet, H., 1956); L’ Enedi limits can also be defined by 100-mm isohyets (Ozenda, (Guillet, H., 1968) W. Sahara (Guinochet, M. et Quézel, 1983). These limits do not presuppose any exact corres- 1954; P. Quézel, P. et Simonneau, P. 1960, 1962). Never- pondence with the chorology of certain plant species, theless, phytosociological studies done in big sandy areas and other ecological factors, like soil properties or geo- (ergs, regs, oueds, etc.) have considered a relatively small morphology, can determine their extension and form. sampling area, and have been limited to isolated pro- Numerous studies have been done on the bioclimatic posals of communities without the floristic relations that and floristic Saharan domain, and many have defined its allow phytosociological relations and syntaxonomical northern area (Barry et Celles1973; Barry et Faurel 1974; unities to be established. Rossetti 1963; Monod 1957).

Corresponding author: Herminio Boira. Instituto. Agroforestal Mediterráneo. CPI. Universidad Politécnica de Valencia. Cno. Vera 14, 46022 . Valencia. (Spain). email: [email protected].. ISSN: 22536302 (print)/ISSN: 22536515 (on line) ©Editaefa DOI: 10.5616/ijgr 160004 38 M. Costa, A. Santos, L. Llorens, P. Soriano & H. Boira

Presence of the Atlas mountain range, especially its (Capot-Rey 1952). Bioclimatic islands appear exceptio- southern faces, determines that Saharan conditions settle nally in the mountains of central Sahara (Aïr, Adrar Ifo- abruptly along the whole Morocco-Algerian slope. To ghas, Ennedi, etc.) the south of Djelfa (Algeria), the high reliefs (1600 m) Absence of mountains along the whole frontier with maintain moderate precipitation and temperature condi- tropical forest determines a progressive change towards tions, and permit presence of aleppo pine (P. halepensis) typical Saharan vegetation over a wide area of the tran- and typical Mediterranean health (garriga) sition Sahelian-Sudanian region in which man tropical However at a short distance and at lower latitudes, savannah species, such as Acacia sp., plant grasses and climatic variables begin to define a desert climate. In La- palms (Capot-Rey 1952) are frequent, and sometimes ghouat (N. Sahara, Algeria), annual precipitation values dominant. Fewer studies have been conducted in this area are 150 mm and temperatures reach an average mean of than those done on the northern limit. However, we intend around 25ºC, while the mean precipitation value in Lar- to establish a limit by following the dispersion areas of geau (N. Chad) does not reach 20 mm. species like Cornulaca monacantha (S limit) and Cenchrus When applying the xerothermicity index (Bagnouls ciliaris (N limit) and, if applicable, they coincide consi- and Gaussen, 1953) to this fringe, the limit of the Sahara derably with the 150 -m isohyet. on its northern slope can be determined by the index This work aims to establish the principal plant asso- curve 300, and comes very close to previous limits. Ho- wever, we consider that new bioclimatic indices should ciations of S and W Sahara regions, bioclimatic typifica- be applied as they would establish a better relationship of tion and their phytosociological relationships with their species and vegetation with temperature, precipitation floristic and biogeographic data. and seasonality. Study area From the chorological view point, several authors (Ozenda 1983; Capot-Rey 1952; Le Houérou 1968) have Floristic and biogeographic data were obtained from proposed the fringe at which esparto grass (Stipa tena- eight itineraries (N–S) across Western and Southern Sa- cissima) disappears, or that at which fructification of hara through four expeditions between 1996 and 2005 date palms (Phoenix dactylifera) is not complete at the (Fig. 1), including the Sahelian-Sudanian and Saharan- northern limit of the Sahara. These references possess a Arabian regions of Niger, Mauritania, Mali, N. Burkina relative value due to both the biological plasticity of Faso and Chad (African subkingdom, Good, 1964; Ri- other species and the irregularity of the physical environ- vas-Martínez & al., 1999). The characteristic taxa of the mental. Sudanian-Sahelian and Saharan-Arabian units were de- The semiarid southern border of the Sahara in wes- termined and data on their latitudinal limits are reported. tern and central Africa has more imprecise limits. From Use of biodiversity, evaluated in the floristic and the bioclimatic viewpoint, enough consent has been biological data, is the object of the ethnobotanical refe- reached to admit the 200-mm isohyet as a boundary line rence.

Figure 1. Study transects across the Sahelian-Sudanian and Saharan- Arabian regions of Mauritania, Mali, Burkina Faso, Niger and Chad.

Plant biodiversity, phytosociology and latitudinal ranges in Sahara meridional and Sahelian regions 39

Material and methods 30-year record period. Floristic α-biodiversity (Shannon & Weaver, 1949) The areas of both vegetation samples (Fig. 1) and the was calculated from the abundance values of species main bioindicator taxa were recorded by GPS devices in (Raunkaier, 1937). UTM units. Data were processed to establish latitudinal The references of the plant resources used for popu- dispersion ranges, the extreme values for each species lation and indigenous tribes were based on both the bi- and the delimitation of the associations area. Plant names bliography and the observed or directly obtained data. in text follow The Plant List. Vegetation samples were collected by the Sigmatistic method (Braun-Blanquet, Results 1964). In spite of the difficulty of applying this method The study, which was carried out in two biogeogra- to Saharan vegetation (Ozenda, 1983), a syntaxonomical phic regions, was related to the ?bioclimatic characteris- outline based on numerical data processing and the com- tics according to the thermicity index (It= 813), and also munity proposed in previous works was obtained. The to the general ombrothermic (Io= 0.05-3.28) and ombro- phytosociological analysis was carried out with specific thermic dry period (Iod = 0.0-0.06) (Rivas-Martínez & osftware (Pc.-Ord V. 6, Twinspan, 2011) after elimina- 2 al., 1999). The Saharan-Sudanian region has a bioclimate ting all the inventories of poorly present species, which that is tropical xeric, infratropical semiarid (Fig. 2), with did not contribute significant information, and after loose forest, thorny tree and shrubs (savannah, Sahel). applying euclidean distances and Ward´s method for the The Saharan-Arabian region has a Mediterranean hyper- linkage groups of relevés. desertic (Mehd), inframediterrannean (ime) macroclima- The edaphohygrophilous communities of “gueltas” te, and also a bioclimate between hyperarid (har) and ul- and plains were also excluded as mountain vegetation. trahyperarid (uha). In this bioclimate, vegetation corres- Vegetation areas were characterised by bioclimatic ponds to infratropical hyperarid desert with sparse vege- indicator indices, such as thermicity (It) and ombro- tation (S and W Sahara) or perennial halophytic steppes thermic (Io, Iod ) (Rivas-Martínez 2008). The values of 2 in littoral areas of the W Sahara (Rivas-Martínez 2008). the bioclimatic indices were calculated from the climatic Samples of vegetation have been reported in 160 data that corresponded to eight localities in the studied inventories, including 140 species. areas (Agadez, Bilma and Niamey (Niger), Uagadugu

(Burkina), Bamako (Mali), Tinduf (Argelia), Atar and Nouadhibou, (Mauritania), Faya-Largeau (Chad) using a

Figure 2. Characteristic bioclimograms of the studied areas in the Saheliana-Sudaniana (Tropical xeric, Niamey) and meridional Saharan-Arabian (Tropical hyperxeric, Bilma) regions

Biogeographical trends carpa often present together with other elements also from the savannah, like Hyparrhenia hirta and Eleusine The mean values and range of species’ latitudinal dis- indica, among others. A more restricted distribution of tribution (e.s.) was calculated from the GPS-recorded Commiphora pedunculata and Caralluma dalzielii can coordinates in the inventories (Fig. 3). be found in areas of central and western Sahel. The most significant taxa in the Shaelian-Sudanian Species, such as Acacia seyal, Boscia senegalensis region (13º-16ºLN) belong to the driest facies of the sa- and Capparis deciduas, surpass 16ºLN. in spite of their vannah forest: Cenchrus biflorus, Faidherbia albida, optimum sahelian, around which the northern limit Leptadenia lancifolia, Hyphaene thebaica, Acacia nilo- seems to be established. This is because they grow pre- tica, Boscia octandra and Bauhinia reticulata. They are ferably in the centre-oriental areas of the studied territory accompanied in transition areas by characteristic species (Mali, Chad), where the Sahelian-Sudanian domain of the tropical savannah, with species of the family northwardly draws a lobe, which reaches 18º LN, exclu- Combretaceae (Combretum micranthum, Combretum ding the massif of Ennedi. These chorological conside- glutinosum, Guiera senegalensis and Anogeissus leio- rations reaffirmed the limits shown on the vegetation

40 M. Costa, A. Santos, L. Llorens, P. Soriano & H. Boira map of southern Sahara (Quézel et al. 1964). The Saharan-Arabian region, as a synthesis of clima- The transition from the Sahelian-Sudanian region to te, flora and vegetation, is characterised by the domain of the Saharan-Arabian one (Fig. 2) is gradual and, except species with a wide latitudinal spectrum. Nevertheless, the western area of Mauritania, characteristic savannah the optimal area lies between 16º and 20ºLN. Further species do not surpass 16ºLN. north, species become poor and flora is represented by In the vegetation samples and records of this region, limited taxa with a marked hyperxeric character (Salsola frequent pan-Saharan species are strongly present when vermiculata, Nucularia perrinii, Cornulaca monacantha latitudes surpass 16ºLN. (Acacia tortilis, Balanites and Fagonia olivieri) which, according to our records, aegyptiaca, Maerua crassifolia Acacia flava, Citrullus reach 22.5ºLN in the areas surroundings Taudemi (Mali). lanatus, Leptadenia pyrotechnica and Stipagrostis plumosa).

Figure 3. Latitudinal ranges of principal species of the Sahelian and Saharan meridional vegetation. (*) Characteristic species of sintaxonomic unities

Figure 4. Biotypes ranges (a) and floristic biodiversity (b) in Saharan and Sahelian vegetation. MF, macrophanerophytes; F, phanerophytes; NF, nanophanerophytes; Ch, chamephytes; H, hemicriptophytes; T, terophytes

Plant biodiversity, phytosociology and latitudinal ranges in Sahara meridional and Sahelian regions 41

The typical species of the Saharan area are Ziziphus raddiana. These plants are tolerant to different xeric bio- lotus, Chrozophora brocchiana, Salvadora persica, climates and possess a high capacity as nitrogen-fixing Aristida caerulescens, Stipagrostis pungens, Calotropis agents and improve degraded soil (E. Le Floch, M. Grou- procera and Indigofera stenophylla. zis, 2003). In the western regions of the Sahara (Mauritania), the With very little floristic affinity to the previous four transition from the savannah to desert areas occurs with associations, the community with Tetraena gaetula, Ta- less presence of differential species, according to the flo- marix amplexicaulis and Nitraria retusa, along the coas- ristic records obtained. The oceanic influence stresses the tal dunes of Mauritania, is characteristic of sandy and dryness conditions and allows the presence of Saharo- saline habitats. Macaronesian and Mediterranean species. Unlike central The vegetation of NW Sahara (Mauritanie) shows regions, three biogeographical unities range from north major floristic differences with previous ones, among to south: a) Saharo-Mediterranean, with characteristic which Launaea nudicaulis and Pergularia tomentosa are species like Ziziphus jujuba, Lycium intricatum, Ziziphus highlighted. lotus, Launaea nudicaulis and Caylusea hexagyna. From the results based on floristic distances, five new Unlike previous reports (Monod, 1944; Barry & al., 1987), associations are proposed: Tetraenetum gaetulae, Lau- these regions in the present study reached southern limits naeo nudicaulis-Pergularietum tomentosae Boscio Sali- at around 20ºLN, close to the coast; b) Saharan-Arabian cifoliae-Combretum micranthi, Salvadoro persicae-Lep- regions (18ºLN - 20ºLN.); c) the Sahelian-Sudanian re- tadenietum pyrotechnicae and Fagonio olivieri-Aervetum gion, between Mauritania and Senegal, which extends javaniae The last four are included in the Ord. Panico along more regular limits (up to 15ºLN). turgidi-Acacietalia raddianae (nova), Cl. Panico turgidi- Acacietea raddianae (nova). Chorology and Biodiversity I. SARCOCORNIETEA FRUTICOSAE Br.-Bl. &Tüxen ex A. & Despite the extreme environmental conditions, floris- O. Bolòs 1950 tic Saharan-Arabian biodiversity (Fig. 4) reached values of 2.01, and 2.11 for Sahelian-Sudanian biodiversity. The Ia. Salsoleto-Nitrarietalia P. Quézel 1965 principal difference between these two biogeographical Ia.1 Limoniastreto-Zigophyllyllion P. Quézel 1965. sectors was due more to biological forms than to number Ia.1.1 Tetraenetum gaetulae associatio nova hoc loco. of species. Under more extreme conditions, the floristic Type releve (holotypus): Table 1, releve nº 2; subass. biodiversity of the hyperdesertic Saharan region was euphorbietosum balsamiferae nova, holotypusTable markedly insobra una ferior (Ibf =1.49). 1, rel.14; subass. frankenietosum hirsutae nova, The biodiversity of biotypes expressed more outstan- holotypus holotypusTable 1, rel. 16. dingly the changes noted among the studied floristic regions (Fig. 4a). Loss of biodiversity (Fig. 4b) became A subhalophilous plant community in the ergs that more patent between the Sahelian (Ibf = 1.55) and Sa- border the sabkhas and steppic habitats around the oueds haran (Ibf = 1.12) regions and drastically fell to lower depressions along the west Sahara. The association values in the hyperdesertic areas (Ibf = 0.86). Phanero- presents certain floristic analogies with formerly studied phytes (s.l.) were generally dominant in the sahelian communities in the NW region of the Sahara (Maire, region, while chamephytes and therophytes dominated in 1957; Quézel, 1965). desert regions. Taking into account previous observations about the phytosociological groups for the halophyle vegetation of Plant communities the Sahara, we include the association in the Salsolo- Desertic plant associations have decisive ecological Nitrarietalia order, with a broader floristic and ecological spectrum than that of Juncetalia maritimi for factors in the topographical characteristics of the terrain Sahara W., and in the Al. Limoniastreto-Zigophyllyllion, and soil properties. Lack of biotic relationships and cli- to which it has the best floristic affinity (Tetraena sp, matic severity does not allow any type of succession and Zigophyllum sp. Suaeda vermiculata, Tamarix amplexi- dynamism (Rivas Martinez, 2008). caulis etc., Table 1). Independently of the hierarchical treatment that can Characteristic species (Salsola vermiculata, Nitraria be attributed, it is necessary to point out the difficulties retusa and Tetraena gaetula subs. waterlotii) colonise of distinguishing associations, such as syntaxonomical soils of variable salinity (1.2-2.5% of soluble salts). unities, in spaces in where it is hard to find phanero- Accordingly this factor proposes two sub-associations: phytes and other perennial species with indicative values. euphorbietosum balsamiferae, (Type relevé (holotypus): The phytosociological studies conducted in the Algerian Table 1, relevé no. 14), typical of maritime sands with Sahara (Girgis, 1970; Barry et Faurel, 1974) have shown subhalophylous species (Tetraena simplex, Tamarix the low floristic consistency of communities, where cha- amplexicaulis) and frankenietosum hirsutae (Type relevé racteristic species have a low probability (p ≤ 0.1) of (holotypus); Table 1, relevé no. 16) in sublittoral areas being found in all the relevés. In our study, the synthetic with markedly halophyte species (Frankenia hirsuta and table (Tab. 6) indicates a relatively high presence for Suaeda vermiculata). characteristics species (above 75%). These communities cover the wadis of valleys with The phytosociological unities, which are the result of lower salinity than their beds (with Arthrocnemum sp., a statistical process using a matrix of presence-abundan- Salicornia sp., etc.). This association extends by coastal ce values, provided us with four interrelated groups for sand dunes and valleys near the Mauritania littoral, from Saharan species with a wide chorological range, espe- Nouadhibou (N) to Tiouilit, Nouakchott and Tiguent (S) cially Panicum turgidum and Acacia tortilis subsp. (Fig. 5 A).

Table 1.- Tetraenetum gaetulae ass. nova hoc loco subass. euphorbietosum balsamiferae nova hoc loco (rel. 9-14). ; subass. frankenietosum hirsutae nova hoc loco (rel. 15-18). (Limoniastreto-Zigophyllion, Salsoleto-Nitrarietalia, Sarcocornietea fruticosae) Altitude (m.a.s.l) 265 514 285 332 325 270 448 190 306 260 450 260 245 95 110 190 270 265 Area m2 100 200 200 100 100 200 100 200 200 200 100 200 100 200 100 200 100 100 Cover (%) 60 70 75 55 40 40 30 75 65 50 50 50 50 60 45 20 60 50 Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Ip Characteristics species: Tetraena gaetula subsp. waterlotii 4 1 + 4 3 3 3 1 3 1 3 2 1 3 + 3 3 3 V Charac. All., Ord and Cl.: Tamarix amplexicaulis - 1 4 - - 1 - 4 3 3 1 ------III Nitraria retusa - 4 2 - - + - 2 - - - - 1 1 - - - - III Calotropis procera - + + - - - - + 1 + + + ------III Charac. subassociation euphorbietosum balsamiferae Euphorbia balsamifera ------1 1 2 3 3 3 - - - - III

Tetraena simplex ------2 1 - 1 2 1 - - - - III Cenchrus biflorus ------1 2 - 1 - + - - - - II Stipagrostis plumosa ------1 1 - 1 ------II Farsetia stylosa ------1 1 - - - 1 - - - - II Salvadora persica ------+ - - 1 1 - - - - - II Charac. subassociation frankenitosum hirsutae Frankenia hirsuta ------1 2 - 1 II Suaeda vermiculata ------1 2 1 II Atriplex glauca ------3 1 - 1 II Bassia tomentosa ------1 1 1 II

Other species: Cistanche tubulosa 1 in 2; Salsola vermiculata + in 8; Launaea nudicaulis 1, Heliotropium bacciferum 1 in 9; Maerua crassifolia + in 12; Lycium intricatum + in 13; Panicum turgidum 1 in 14; Lotus glinoides + in 15. Localities.- Mauritania. 1: 20º46'20''N 17º02'44''W; 2: 26º39'32''N 09º0'51''W; 3: 18º37'22''N 15º38'19''W; 4: 18º37'22''N 15º38'19''W; 5: 18º51'54''N 16º09'20''W; 6: 26º36'05''N 09º06'11''W; 7: 27º21'01''N 08º14'54''W; 8: 17º36'02''N 16-01'10''W; 9: 17º41'42''N 15º59'58''W; 10: 20º55'46''N 13º11'23''W; 11: 22º40'52''N 13º11'18''W; 12: 23º27'50''N 12º45'40''W; 13: 18º37'22''N 15º38'19''W; 14: 17º-12'-17''N 16º04'41''W; 15: 20º55'46''N 13º11'23''W; 16: 19º08'27''N 14º59'41''W; 17: 19º40'18''N 14º17'17''W; 18: 20º05'44''N 13º44'59''W. M. Costa, A. Santos, L. Llorens, P. Soriano & H. Boira & H. Soriano P. Llorens, L. A. Santos, M. Costa,

Plant biodiversity, phytosociology and latitudinal ranges in Sahara meridional and Sahelian regions 43

Photo 1.- Halophilous post littoral comunnity (Tetraenetum gaetulae) with Frankenia hirsuta, Suaeda vermiculata, Launaea nuducaulis and Pergularia tomentosa as dominant species. Nouakchot, Mauritania

Photo 2.- Community with Acacia tortilis subsp. raddiana, Panicum turgidum, Launaea nudicaulis, Lycium intricatum (foreground) and Pergularia tomentosa, as characteristic species. Typical of the ergs and W. Sahara dunes, Mauritania. (Ass. Launaeo nudicauli-Pergularietum tomentosi).

II. PANICO TURGIDI-ACACIETEA RADDIANAe classis nova progressive presence of Sahelian characteristic tree hoc loco. species, such as Ceiba pentandra, Adansonia digitata, Typus nominis: Panico turgidi-Acacietalia raddianae. Acacia nilotica and Combretum sp. Northwardly, hyperarid conditions determine low diversity with the charac- II.1. Panico turgidi-Acacietalia raddianae ordo novus teristic presence of Fagonia olivieri, Aerva javanica and hoc loco. Stipagrostis pungens as the best indicators. Typus nominis: Panico turgidi–Maeuruion crassifo- The classic characteristic species are: Panicum turgi- liae. dum, Acacia tortilis subsp. raddiana, Stipagrostis plumo- II.1.1. Panico turgidi–Maeuruion crassifoliae alliance sa, Schouwia purpurea, Maerua crassifolia, Heliotro- nova hoc loco. pium bacciferum, Maerua crassifolia, Lycium intricatum, These classes show a widespread distribution, princi- Gymnocarpos sclerocephalus, Asteriscus graveolens, pally throughout the Saharo-Arabic (Saharan-Arabian) Combretum sp. and Calotropis procera. region, from a Saharo-Mediterrannean hyperdesertic to a Sahelian xeric and hyperxeric bioclimate. II.1.1a. Launaeo nudicauli-Pergularietum tomentosae They represent the characteristic vegetation of ergs, associatio nova hoc loco regs and sand soils. They are present in areas of central Most characteristic species are scattered in Western and southern Sahara, where some communities mark the and Central Sahara, but some (Andrachne telephioides, border with the Sahel (Boscio salicifoliae–Combretum Pergularia tomentosa, Launaea nudicaulis, etc.) have a micranthi). The transition to southern areas shows the distribution restricted to the erg plains of Mauritania

Table 2.- Launaeo nudicaulis- Pergularietum tomentosae ass. nova hoc loco (Panico turgidi–Maeuruion crassifoliae, Panico turgidi–Acacietalia raddianae, Panico turgidi-Acacietea raddianae) Altitude (m.a.s.l.) 445 224 315 223 220 270 327 430 432 395 420 426 460 420 315 264 112 295 295 295 285 304 Area (m2) 400 200 400 400 600 400 600 400 200 200 400 200 200 400 400 600 200 200 200 400 400 200 Cover (%) 80 55 90 80 85 40 70 40 20 20 85 55 65 85 80 85 95 90 60 90 95 90 Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Ip Characteristics species: Launaea nudicaulis + + + 1 1 1 1 2 1 . 2 2 2 1 1 2 . . . 1 . . IV Pergularia tomentosa . . 1 + . 1 1 1 1 1 1 . . . + 1 . 2 2 . 1 1 IV Characteristics of All. and Ord.: Asteriscus graveolens 1 1 1 1 2 1 + . . 1 1 ...... III Echium humile . . 2 1 1 1 ...... + . . . . 1 . . . III Asphodelus tenuifolius 1 . 3 . 1 2 . . . + . . . . . 1 ...... III Lycium intricatum ...... 1 . . 1 . . 2 3 1 ...... II Cullen plicatum . . . 4 . 1 . . . . 2 ...... 1 + II Gymnocarpos sclerocephalus . . . 1 1 1 ...... 1 . . . 1 . . . . II Characteristics of ord. and class: Panicum turgidum . 1 3 2 2 . 3 . . . 2 1 2 2 1 3 4 3 + 3 3 2 V Acacia tortilis subsp. raddiana + . 3 + 1 + 2 1 2 2 3 . + 1 2 1 . . . 3 2 + V Heliotropium bacciferum . 2 . . 1 1 2 . . 1 . . . 1 . 1 1 . . 1 . 1 III Salvia aegyptiaca . . 1 . 1 1 2 ...... + . . . 1 . . . III Anvillea garcinii subsp. radiata . . 1 . . . . . 1 . + . 1 + . + ...... III Maerua crassifolia ...... + . . 1 . . . . . 2 2 II Citrullus lanatus ...... 1 . . . + . . . . . + . . . . + II Stipagrostis plumosa . + ...... 1 . . . . 3 II Schouwia purpurea . . . 1 3 + ...... II Companion: Haloxylon salicornicum ...... 1 + 1 3 ...... II Nucularia perrinii ...... 1 1 2 . . 3 2 . . II Salsola vermiculata 2 ...... 2 1 1 ...... II Farsetia stylosa ...... + . 1 . . 2 3 . 1 . . II Tetraena gaetula subsp. waterlotii 2 3 ...... + . 1 ...... II

M. Costa, A. Santos, L. Llorens, P. Soriano & H. Boira & H. Soriano P. Llorens, L. A. Santos, M. Costa, Andrachne telephioides . . + . 1 1 . . . + ...... II Caylusea hexagyna . . 1 . 1 1 ...... 1 ...... II 44

Euphorbia calyptrata . 1 1 1 1 ...... 1 . . . 1 . . . . III Tetraena simplex . . 1 . . . 1 ...... 1 ...... II Ziziphus lotus ...... 3 ...... + . 3 3 II Lotus glinoides 1 1 1 . . . . + . . . . . 1 ...... II Gymnocarpos decander ...... 1 ...... 1 1 ...... II Plant biodiversity, phytosociology and latitudinal Cotula cinereum 2 1 . . . + ...... + ...... II Trichodesma africanum ...... + . . 1 . . . . 1 . . . II Atractylis aristata . . 1 . . 1 ...... + + . . II Cleome paradoxa ...... 1 . . . . + II Searsia tripartita ...... 2 . . . . . 2 2 ...... II Anastatica hierochuntica 3 . . . 1 + ...... II Atriplex halimus ...... 1 1 1 ...... II Ephedra alata ...... 1 1 1 ...... II Paronychia arabica . . 1 . . 1 ...... 1 ...... II Asparagus altissimus ...... 1 . . . . . 1 + ...... II Convolvulus trabutianus ...... + + ...... II Fagonia arabica . . . . . + ...... 2 . . . . . II ranges in Sahara meridional and Sahelian regions Nitraria retusa ...... 1 . . . . . 1 ...... II Piptadenia flava ...... + . . 1 II

Other species: Pulicaria undulata 1, Aristida caerulescens 1, in 3; Euphorbia balsamifera 1, Indigofera colutea 1, en 18; Neurada procumbens, 1 in 21; Fagonia oliveri 1, Senna italica +, in 23. Localities.- Mauritania. 1: 26º36'05''N 9º06'11''W; 2: 24º10'51''N 11º51'18''W; 3: 25º04'45''N 11º28'26''W; 4: 24º10'51''N 11º51'18''W; 5: 24º10'51''N 11º51'18''W; 6: 26º09'47''N 10º35'16''W; 7: 22º52'41''N 12º49'06''W; 8: 26º39'32''N 09º00'51''W; 9: 26º39'32''N 09º00'51''W; 10: 26º19'50''N 09º37'28''W; 11: 26º19'50''N 09º37'28''W; 12: 26º19'50''N 09º37'28''W; 13: 26º9'28''N 10º33'21''W; 14: 26º09'47''N 10º35'16''W; 15: 26º09'47''N 10º35'16''W; 16: 22º52'41''N 12º49'06''W; 17: 20º05'44''N 14º44'59''W; 18: 22º11'01''N 13º08'24''W; 19: 22º11'01''N 13º08'24''W; 20: 26º08'47''N 11º51'18''W; 21: 22º11'01''N 13º08'24''W; 22: 20º57'13''N 13º10'58''W.

46 M. Costa, A. Santos, L. Llorens, P. Soriano & H. Boira

Table 3. Boscio salicifoliae-Combretum micranthi Panico turgidi–Maeurion crassifoliae, Panico turgidi–Acacietalia raddianae, Panicoturgidi-Acacietea raddianae. Altitude (m.a.s.l.) 310 315 290 285 270 265 275 280 290 375 390 450 Area m2 200 300 300 350 400 300 300 400 300 400 200 400 Cover (%) 45 60 45 40 60 35 55 50 45 55 20 70 Number 1 2 3 4 5 6 7 8 9 10 11 12 Ip Characteristics species: Combretum micranthum 1 1 1 1 1 1 1 1 1 1 . 1 V Boscia salicifolia 1 . . 1 1 1 1 1 1 1 1 . V Adansonia digitata 1 1 . . . . . 1 1 1 + . IV Combretum glutinosum . 1 . 1 1 1 1 1 1 1 . . III Ceiba pentandra ...... 1 1 . + . III Anogeissus leiocarpa 1 ...... 1 1 . . III Commiphora pedunculata 1 . 1 ...... 1 . 3 III Eleusine indica . 1 1 . . . 1 . . . . . III Ficus cordata . . . . 1 1 1 . . . . . III Bauhinia reticulata . 1 . . . . . 1 . . . . II Hyparrhenia hirta . . 1 . 1 . 1 . . 1 . . III Heteropogon contortus 1 . 1 ...... II Characteristics All. and Ord.: Balanites aegyptiaca 1 1 1 1 1 . 1 . 1 1 2 1 V Faidherbia albida . . . . . 1 . 1 . . . . II Indigofera colutea . . . . 1 1 ...... II Calotropis procera . . 1 1 ...... 2 2 III Acacia nilotica . 1 . 1 1 1 ...... III Guiera senegalensis 1 1 . . . . . 1 . 1 . . III Ziziphus jujuba . 1 . 1 . 1 1 . 1 1 . 1 IV Characteristics of Class: Acacia tortilis subsp. raddiana . 1 1 1 . 1 1 1 1 1 1 1 V Maerua crassifolia . 1 1 . . . . 1 1 1 . 1 IV Companion: ...... Euphorbia balsamifera . 1 1 1 1 . . 1 1 . . . IV Acacia seyal 1 1 . . 1 . . . . . + 2 III Leptadenia lancifolia . . . 1 . . 1 1 . 1 . . III Cenchrus biflorus . 1 1 . . . 1 . . 1 . . III Leptadenia pyrotechnica . . . 1 1 ...... II Piptadenia flava . . . . 1 . . . 1 . . . II Aristida caerulescens . . . . 1 . 1 . . . . . II Other species: Panicum turgidum 1 in 2; Chrozophora brocchiana 1 in 3; Boscia senegalensis 2 in 12. Localities.- Mali: 1: 12º 56' 07'' N, 01º 04' 42'' W; 2: 13º23'59''N 1º00'23''W; 3: 13º33'16''N 0º17'27''W; 4: 17º39'40''N 3º9'37''W; 5: 17º53'11''N 3º16'43''W; 6: 17º8'26''N 3º11'17''W; 7: 16º35'29''N 2º58'06''W; 8: 16º8'33''N 2º52'30''W; 9: 15º55'2''N 2º33'34''W; 10: 15º41'28''N 2º31'56''W. Tchad: 11: 13º40'11.6''N 16º24'27.4''E. Niger: 12: 15º58'06''N 06º58'16''E

Photo 3.- Vegetation of the big sandy areas (erg, regs, oueds and sand plains around the mountains) with nanophanerophytes as Salvadora persica, Balanites aegyptiaca and grasses as Leptadenia pyrotecnica and Panicum turgidum (Ass. Salvadoro persicae-Leptadenietum pyrotechnicae). Erg of Iferouane, Niger.

Plant biodiversity, phytosociology and latitudinal ranges in Sahara meridional and Sahelian regions 47

This syntaxon has a good floristic likeness to the ass. areas of the ergs and regs of the Meridional Sahara in- Acacia raddiana, Panicum turgidum and Foleyola billo- cluding the oueds and lower sand areas around big tti proposed by Guinet and Sauvage (1954), and by mountain massifs. Quezel (1961, 1965) for the NW Sahara (oueds and erg Previously, Quezel (1961) proposed for the vegeta- of the hamadas, south Morocco). Moreover, the nume- tion of sand plains (erg and regs of W Sahara, S. Argelie rous presence of optimal tropical and sahelian species and Central Sahara), and from the affinity of the invento- makes it difficult to establish a syntaxonomical scheme. ries published by several authors, only one association This association represents the characteristic vegeta- with Calligonum comosum and Stipagrostis pungens (J. tion of the ergs and sand dunes of the Western Sahara Kyllian, 1961), included in the Ord. Aristidetalia and corresponds to the central and northern regions of (Guinochet et Quézel, 1954). The table of this associa- Mauritania. tion includes only four inventories (20%) with Salvadora They are frequent species that come from the ergs persica and Leptadenia pyrothecnica. It also shows a low and slopes of the Saharan Atlas range (Ziziphus lotus), floristic correlation with all the other inventories, inclu- others from bedrocks near mountain formations (Searsia tripartita), or also, in the most southern ergs, elements ding those with differential species. were widely distributed in the Central and South Sahara The proposed syntaxon include the species of the on the limit with the Sahel (Foleyola billotii, Caylusea major Saharan dispersion. Only some sahalian elements hexagyna etc.). As some of the characteristics species are are present, but scarcely. on the limit of its natural area, they show a low homo- The most important vegetation samples were collec- geneity and abundance index. Type relevé (holotypus) ted from Mali (Tilemsi Valley, Adrar of Tachdaït, Table 2, rel. 16. Tigharghar, Tabrichat and Hamada El Haricha), Niger The area of the association ranges from central (Ergs of the Aïr, Anakom, Iferouane, Tnerere and Bilma regions of Mauritania to Tindouf Sabkha (Ergs de and Adrar Bous, Tenerere du Tafassasset), Chad (ergs Iguidi, El Hammami, (N) and to Maqteir and Adrar (S) and regs of the Barh El Gazel region, Erg Djourab and (Fig. 5, B). Enedi, the Biltine region) and S Mauritanie (Keur Macen (Fig. 5 D). II.1.1b. Boscio salicifoliae-Combretum micranthi association nova hoc loco II.1.1d. Fagonio olliveri-Aervetum javanicae association nova hoc loco This association, which is typically Sahelian, extends on the rocky wadis of the irregular limits across the The group formed by Fagonia olivieri, Aerva java- Southern sector of the Sahara, and comes into contact to nica and Cornulaca monacantha, together with other the South with the Savannah forest. Saharan species of a wide distribution, constitute the The characteristic species of this association are some dispersed populations that are found under hyperxero- typical phanerophytes of the savannah, e.g., Combretum phytic conditions, which extend between 21-23ºC LN. micranthum, Combretum glutinosum, Adansonia digita- (Fig. 2) throughout Central Sahara (Fig. 1, Mali, Chad ta, Ceiba pentandra and other xerophyte species. and Niger). Type relevé (holotypus): Table 5, rel. 7. It is one of the characteristic communities of Sahel, It is the characteristic association of the regions with within general Saharan vegetation, due to the constant a high aridity index. Its irregular area of distribution is presence of xerophyte and hyperxerophyte species of the included between 15ºN and 22ºN, with no exceptions in central and southern Sahara; e.g., Acacia tortilis, Eleu- NW Mauritania and C. Chad (Fig. 5E). sine indica, Maerua crassifolia, Balanites aegyptiaca, Other xerophyte species are frequent, like Citrullus Euphorbia balsamifera, etc. Type relevé (holotypus): lanatus, Stipagrostis pungens and S. plumosa. Table 3, rel. 10. The group formed by Fagonia olivieri, Aerva The study area includes NE Burkina (regions of javanica and Cornulaca monacantha, together with other Mansha, Dori and Markoy), C.S Mali (areas of Azaouad Saharan species of a wide distribution, constitute the and Gourma) and Niger (the Ader region) (Fig. 5 C). dispersed populations that are found under hyperxero- Due to the frequent presence of plants with a high phytic conditions, which extend between 21-23ºC LN. and food forage value (Acacia sp., Maerua crassifolia, (Fig. 2) throughout Central Sahara (Fig. 1, Mali, Chad Combretum sp., Hyparrhenia hirta, Heteropogon sp. and Niger). Type relevé (holotypus): Table 5, rel. 7. etc), this is the plant community that endures the It is the characteristic association of the regions with strongest human and animal impacts. a high aridity index. Its irregular area of distribution is included between 15ºN and 22ºN, with no exceptions in II.1.1c. Salvadoro persicae-Leptadenietum pyrotechni- NW Mauritania and C. Chad (Fig. 5E). cae associatio nova hoc loco Other xerophyte species are frequent, like Citrullus This association contains several species with a lanatus, Stipagrostis pungens and S. plumosa. strong presence in all the inventories. The characteristic Syntaxonomical scheme species of this association, Salvadora persica and Lep- tadenia pyrothecnica, show greater fidelity that others of SARCOCORNIETEA FRUTICOSAE Br.-Bl. &Tüxen ex major ecological and chorological amplitudes (Acacia A. & O. Bolòs 1950 tortilis, Panicum turgidum and Balanites aegyptiaca). ● SALSOLETO-NITRARIETALIA P. Quézel 1965 Type relevé (holotypus): Table 4, rel. 14. ♦ All. Limoniastreto-Zigophyllyllion P. Quézel 1965 Tetraenetum gaetulae ass. nova hoc loco It is the characteristic formation of the big sandy

48 M. Costa, A. Santos, L. Llorens, P. Soriano & H. Boira

PANICO TURGIDI–ACACIETEA RADDIANAE classis nova associatio nova hoc loco. hoc loco (Pergularieto-Pulicarietea P. Quezel, 1965) Fagonio olivieri-Aervetum javanicae associatio nova ● PANICO TURGIDI-ACACIETALIA RADDIANAE ordo novus hoc loco. hoc loco (Sahara W, C and S) Associations proposed for lower slopes of the Atlas ♦ Panico turgidi-Maeuruion crassifoliae alliance nova in Saharan NW (Quezel, P., 1965, Quezel, P. et Simon- hoc loco neau, P. 1962, Guinochet, M. et Quezel, P. 1954), has Launaeo nudicaulis-Pergularietum tomentosae asso- few relations with the communities described. Only Ass. ciatio nova hoc loco. Acacia tortilis and Panicum turgidum (Ord. Pergulario- Boscio salicifoliae-Combretum micranthi associatio Pulicarietalia, Quezel 1965), without syntaxonomic nova hoc loco. typification, has close relations with the class described Salvadoro persicae-Leptadinietum pyrotechnicae in the present study.

Figure 5. Distribution areas of the ass. Tetraenetum gaetulae (A), Launaeo nudicauli- Pergularietum tomentosi (B), Boscio salicifoliae-Combretum micranthi (C), Salvadoro persicae-Leptadinietum pyrotechnicae (D) and Fagonio olliveri-Aervetum javanicae (E).

Photo 4. Fagonia oliveri DC. (Zigophyllaceae) with Stipagrostis pungens. Characteristic species of the hyperxero- phytic communities (Ass. Fagonio oliveri-Aervetum javani), disperses along the Central Sahara (Enedi, Tchad).

Table 4.- Salvadoro persicae-Leptadenietum pyrotechnicae (Balanition aegyptiacae, Maeruetalia, Panico Acacietea raddianae) Altitude (m.a.s.l.) 272 271 310 320 207 299 286 281 282 278 289 288 559 345 275 286 227 25 12 459 450 455 1215 ## ## Area (m2) 300 200 400 400 300 200 200 400 400 200 400 300 400 300 400 400 200 200 ## 200 200 400 300 ## ## Cover (%) 40 20 45 40 20 20 15 30 30 20 70 40 65 60 70 40 60 30 20 30 45 80 60 50 60 Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Ip Plant biodiversity, phytosociology and latitudinal Association characteristics Salvadora persica 1 . 1 1 1 1 1 1 1 1 2 2 . 2 2 1 . 2 1 1 1 1 2 2 1 V Leptadenia pyrotechnica 1 1 1 1 . . 1 1 1 . . 1 1 1 . . 3 1 1 . . . . 1 1 IV Characteristics of all. and ord. Balanites aegyptiaca 1 1 1 1 1 1 1 1 1 1 1 1 . 2 1 . 1 . 1 . 1 2 1 1 2 V Maerua crassifolia 1 . 1 1 1 1 . 1 . . 1 . 2 . 2 2 1 . . 2 1 1 3 . 1 IV Faidherbia albida ...... 1 1 1 . 1 . 1 . . . . . 1 . 2 1 2 1 III Calotropis procera 1 . 1 1 ...... + . . . 1 . . . . . 1 + + 1 . III Aerva javanica . . 1 1 1 . . 1 1 . . . 1 1 + . . . . . 1 2 . . 1 III Stipagrostis pungens . . . . 1 1 . 1 1 . + 1 . . . . 1 ...... III Cenchrus biflorus 1 ...... 1 ...... + . . 1 ...... II Boscia salicifolia 1 . 1 . . . . . 1 ...... II Boscia senegalensis ...... 2 2 ...... 1 II Characteristic class Acacia tortilis subsp. raddiana 1 1 1 1 1 1 1 1 1 1 2 2 2 2 . 1 2 2 1 . 2 3 2 1 2 V Panicum turgidum 1 1 1 1 1 1 1 1 1 . 2 . 2 1 . 1 1 + . 1 1 2 . . 1 V ranges in Sahara meridional and Sahelian regions Aristida caerulescens . . 1 ...... 1 ...... 1 . . . II Stipagrostis plumosa ...... + + . . . + ...... II Companions Ziziphus jujuba . . 1 1 ...... 1 ...... 1 . 1 + . . II Capparis decidua ...... 2 . 2 1 2 1 ...... II Hyphaene thebaica ...... 1 1 2 . . . 2 ...... II Acacia seyal 1 . 1 1 . . . . . 1 ...... II Schouwia purpurea . . 1 1 ...... 1 II Chrozophora brocchiana . . . . . 1 ...... 1 ...... I Leptadenia lancifolia ...... 1 ...... 1 . . . . I Andrachne telephioides ...... + . + . . . I Guiera senegalensis 1 ...... 1 ...... I Other species: in 1, Euphorbia balsamifera 1; in 3, Piptadenia flava 1: in 10, Indigofera colutea 1; in 11, Hyparrhenia hirta 1; in 18, Senna italica 1; in 19, Salsola vermiculata +; Tetraena gaetula subsp. waterlotii, +; Nitraria retusa, 1; in 22, Fagonia arabica, 1; in 24, Trichodesma africanum, 1; in 26, Combretum micranthum 1; in 27, Citrullus lanatus, 1.

Localities.- Burkina: 1: 14º35'26''N 00º02'21''W; 2: 14º43'38''N 00º03'11''W. Mali: 3: 15º02'33''N 00º55'06''W; 4: 15º21'32''N 00º57'54''W; 5: 22º33'58''N 04º00'43''W; 6: 21º28'20''N 03º56'13''W; 7: 19º57'44''N 03º43'00''W; 8: 18º17'47''N 03º23'06''W; 9: 18º13'35''N 03º23'27''W; 10: 17º53'11''N 03º16'43''W; Tchad: 11: 14º47'29.6''N 17º09'60''E; 12: 14º50'15''N 17º15'52''E; 13: 17º15'37.7''N 21º37'31''E; 14: 17º39'30.2''N 19º40'26.5''E; 15: 15º47'46''N 18º20'17.1''E; 16: 14º53'13''N 17º15'57''E. Mauritania: 17: 20º55'46''N 13º11'18''W; 18: 17º12'17''N 16º04'41''W; 19: 16º41'08''N 16º02'51''W. Niger: 20: 17º54'02''N 07º35'59''E; 21: 17º53'17''N 07º37'45''E; 22: 17º52'14''N 07º34'57''E; 23: 19º06'49''N 08º55'48''E; 24: 15º09'33''N 05º45'27''E; 25: 20º10'21''N 12º45'47''E. 49

Tab. 5.- Ass. Fagonio oliveri-Aervetum javanicae (Panico turgidi-Maeurion crassifoliae, Panico turgidi-Acacietalia radianae, Panico turgidi - Acacietea radianae) Altitude (m.a.s.l.) 240 230 274 410 300 292 295 315 560 280 204 320 318 360 320 720 1022 710 735 Area (m2) 200 200 200 200 200 200 200 200 200 100 400 400 200 200 100 200 200 100 100 Cover (%) 15 25 40 25 15 30 20 55 10 15 35 30 15 20 10 45 55 15 35 Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Ip Characteristics Ass. Fagonia olliveri 1 1 . 1 1 . 1 2 + 1 1 1 1 1 1 3 3 1 3 V Aerva javanica . . 2 + . . 1 . . 1 1 1 1 1 1 + + 1 1 IV Cornulaca monacantha . 1 . . 1 1 1 . 1 . 1 . 1 1 . . . . . III Characteristics of all. ord. and class. Panicum turgidum 1 1 2 + . 2 1 . 1 . 1 1 1 1 . + 1 . . IV Acacia tortilis subsp. raddiana . 1 . . . . . 1 1 . 1 1 . 1 . + . . . III Maerua crassifolia . . . + . . . 1 . 1 1 1 ...... III Stipagrostis pungens 1 1 1 1 . 1 1 . 1 ...... 1 . III Citrullus lanatus . . . + . . . . . 1 1 1 1 . . 1 1 . 1 III

Stipagrostis plumosa . . 1 2 1 + 1 3 ...... III Chrozophora brocchiana ...... 1 1 1 1 . . 1 2 . . III Piptadenia flava . 1 ...... 1 1 . 1 . . . . . II Indigofera colutea . 1 . . + ...... II Aristida caerulescens . . + . . + + ...... II Schouwia purpurea ...... 1 1 ...... II Balanites aegyptiaca ...... 1 1 1 ...... II Farsetia stylosa . . . . 1 . . 1 ...... II Senna italica ...... 1 + II Others species: Cenchrus biflorus 2 in 4; Neurada procumbens 1 in 5; Capparis decidua 1 in 8; Acacia seyal 1 in 10; Calotropis procera 1 in 12; Heliotropium bacciferum 3 in 16, Convolvulus trabutianus +. in 18 Localities.- Mali. 1: 22º2'20''N 2º59'16''W; 2: 21º57'26''N 3º59'28''W; 10: 14º57'48'' N, 0º8'58''W; 11: 15º38'11''N, 1º2'49''W; 12: 15º56'39''N, 1º11'46''W; 13: 17º38'24''N, 0º1'29''E; 14: 19º48'31''N 1º8'30''W; 15: 17º38'24''N, 0º1'29''E; Tchad: 3: 15º17'46''N 17º54'51''E; 4: 15º47'40''N 20º02'27''E; 5: 14º00'46N 16º29'35''E; 6: 13º41'52''N 16º29'27''E; 7: 13º42'18''N 16º16'39''E; Mauritania: 8, 22º40'52''N 13º11'18''W; Niger: 9: 20º44'46''N 12º30'26''E; 16: 19º12'43''N 09º00'14''E; 17: 19º22'20''N 9º17'14''E; 18: 19º59'45''N 8º40'21''E; 19: 20º17'24''N 9º00'27''E. M. Costa, A. Santos, L. Llorens, P. Soriano & H. Boira & H. Soriano P. Llorens, L. A. Santos, M. Costa, 50 2

Table 6.- Phytosociological synthesis of Saharan Arabian (W and S) & Sahelian Sudanian vegetation Associations Launaeo Salvadoro Fagonio Boscio salicifoliae- Tetraenaetum nudicauli- persicae- oliveri- Combretum gaetulae Pergularietum Leptadenietum Aervetum micranthi Plant biodiversity, phytosociology and latitudinal tomentosi pyrotechnicae javanicae Characterístics of association 1 2 3 4 5 Tetraena gaetula subsp. waterlotii (Maire) Beier & Thulin V 2,3 Tamarix amplexicaulis Ehrenb. III 2,4 Nitraria retusa (Forssk.) Asch. III 1,7 Calotropis procera (Aiton) Dryand. III 0,3 Atriplex glauca L. II 1,7 Bassia tomentosa (Lowe) Maire & Weiller II 1,0 Frankenia hirsuta L. II 1,3 Suaeda vermiculata Forssk. ex J.F.Gmel. II 1,3 Tetraena simplex (L.) Beier & Thulin. III 1,4 II 1,0 Launaea nudicaulis (L.) Hook.f. IV 1,2 Pergularia tomentosa L. IV 1,0

ranges in Sahara meridional and Sahelian regions Heliotropium bacciferum Forssk. III 1,2 Nucularia perrinii Batt. II 1,8 Anastatica hierochuntica L. II 1,4 Asparagus altissimus Munby II 0,7 Asphodelus tenuifolius Cav. III 1,5 Asteriscus graveolens (Forssk.) Less. III 1,0 Atractylis aristata Batt.ylis prolifera Boiss. II 0,6 Atriplex halimus L. II 1,0 Caylusea hexagyna (Forssk.) M.L.Green II 1,0 Cleome paradoxa R.Br. II 0,6 Convolvulus trabutianus Schweinf. & Muschl. II 0,2 Cotula cinereum Delile II 0,9

Cullen plicatum (Delile) C.H.Stirt. II 1,6 Echium humile Desf. III 1,2 Ephedra alata Decne. II 1,0 Euphorbia calyptrata Coss. & Kralik III 1,0 51

Fagonia arabica L. II 1,6 Gymnocarpos decander Forssk. II 1,0 Gymnocarpos sclerocephalus (Decne.) Dahlgren & Thulin. II 1,0 Haloxylon salicornicum (Moq.) Bunge ex Boiss.. II 1,3 Lotus glinoides Delile II 0,8 Lycium intricatum Boiss. II 1,8 Paronychia arabica (L.) DC. II 1,0 Salsola verniculata L. II 1,5 Salvia aegyptiaca L. III 1,0 Searsia tripartita (Ucria) Moffett II 2,0 Trichodesma africanum (L.) Sm. II 0,7 Ziziphus lotus (L.) Lam. II 2,3 Combretum micranthum G.Don V 1,0 Adansonia digitata L. IV 0,9 Combretum glutinosum Perr. ex DC. III 1,0 Ceiba pentandra (L.) Gaertn. III 0,7 Anogeissus leiocarpa (DC.) Guill. & Perr. III 1,0 Commiphora pedunculata (Kotschy & Peyr.) Engl. III 1,5 Eleusine indica (L.) Gaertn. III 1,0 Ficus cordata Thunb. III 1,0 &H.Boira Bauhinia reticulata DC. II 1,0 Hyparrhenia hirta (L.) Stapf III 1,0 Heteropogon contortus (L.) P.Beauv. ex Roem. & Schult. II 1,0 Salvadora persica L. II 0,7 V 1,3 Leptadenia pyrotechnica (Forssk.) Decne. II 1,0 IV 1,1 1,6 L. Llorens, P. Soriano Capparis decidua (Forssk.) Edgew. II Boscia senegalensis Lam. II 1,7 Hyphaene thebaica (L.) Mart. II 1,5 Fagonia olliveri DC. V 1,4 Cornulaca monacantha Delile III 1,0 Aristida caerulescens Desf. II 0,4 M. Costa, A. Santos, 52

Characterístics of Class, Order and Aliance. Acacia tortilis subsp. raddiana (Savi) Brenan V 1,5 V 1,0 V 1,6 III 0,7 Panicum turgidum Forssk. V 2,2 I 1,0 V 1,2 IV 0,9 Maerua crassifolia Forssk. II 1,3 III 1,0 IV 1,4 III 0,8 Anvillea garcinii subsp. radiata (Coss. & Durieu) Anderb. III 0,6 II 1,0 II 1,0 Plant biodiversity, phytosociology and latitudinal Balanites aegyptiaca (L.) Delile V 1,1 V 1,2 II 1,0 Schouwia purpurea (Forssk.) Schweinf. II 1,7 II 1,0 II 1,0 Farsetia stylosa R.Br. II 1,0 II 1,4 II 1,0 Cenchrus biflorus Roxb. II 1,1 III 1,0 II 0,8 Citrullus lanatus (Thunb.) Matsum. & Nakai II 0,4 III 0,9 Euphorbia balsamifera Aiton III 2,2 IV 1,0 Faidherbia albida (Delile) A.Chev. II 1,0 III 1,2 Indigofera colutea (Burm.f.) Merr. II 1,0 II 0,5 Piptadenia flava (DC.) Benth. II 0,6 II 1,0 II 1,0 Stipagrostis plumosa Munro ex T.Anderson II 1,0 II 1,4 II 0,2 III 1,3 Stipagrostis pungens (Desf.) De Winter III 0,9 III 1,0 Andrachne telephioides L. II 0,6 I 0,2 ranges in Sahara meridional and Sahelian regions Nitraria retusa (Forssk.) Asch. II 1,0 I 0,6 Tetraena gaetula subsp. waterlotii (Maire) Beier & Thulin II 1,6 I 0,6 Calotropis procera (Aiton) Dryand. III 1,5 III 0,7 Boscia salicifolia Oliv. V 1,0 II 1,0 Ziziphus jujuba Mill. IV 1,0 II 0,9 Acacia nilotica (L.) Delile III 1,0 I 1,0 Acacia seyal Delile III 1,0 II 1,0 Guiera senegalensis J.F.Gmel. III 1,0 I 1,0 Leptadenia lancifolia (Schumach. & Thonn.) Decne. III 1,0 I 1,0 Aerva javanica (Burm.f.) Juss. ex Schult. III 1,1 IV 0,8 Chrozophora brocchiana (Vis.) Schweinf. I 1,0 III 1,2 Senna italica Mill. I 0,6 II 0,5

54 M. Costa, A. Santos, L. Llorens, P. Soriano & H. Boira

Human and Saharan plant resources. Bruneau de Mire et Guillet, H., 1956. Contribution a l’ etude de la flore du massif de l’Air.- J. Agr. tropic. et Bot. appl. II. The use of natural resources in Saharan and sub- Saharan ethnics has been the object of numerous stu- Capot- Rey, R. 1952. Les limites du Sahara français. Trav. Inst. Rech. Sah., t. 8. dies. Moving away from the Sahel, sorghum cultiva- tions and increasingly more different species of millet, Capot-Rey, R. 1952. Les limites du Sahara Français. Trab. and the use of natural plant resources becomes less Inst. Rech. Sahar. Univ. Argel. 8, 23-48. evident and meet only domestic feeding, therapeutics Chini, C., Bilia, AR., Keita, A. and Morelli, C., (1992). and medicinal necessities. Protoalkaloids from B. angustifolia. Planta Medica, 58, 476. The different Acacia species are used as rubber Girgis, W.A. 1970. Phytosociological studies of the Vegeta- sources and combustible material. Growing tourism tion of the Maryut area project U.A.R.J. Bot. t. XIII, 234- and is extension are drastically reducing tree popula- 253. tions, which are scarcely found nowadays. Good, R. 1964. The Geography of the Flowering Plants. 3 ed. In the Sahelian-Sudanian region, the common Wiley, New York. 518 pp. applications of Bombacaceae, species of the Combre- Guillet, H. 1968. Le peuplement végétal du massif de l’ taceae family, are used for medicinal purposes: the Ennedi. C.R. Soc. Biogéog., nº 383-388, 95-106. association of the desert bechic and emollient (Com- Guinet, Ph. et Sauvage, Ch. 1954. Les Hammada Sud maro- bretum micranthum and Guiera senegalensis), diuretic caines. Botanique. Trav. Inst. Sci. chérif., Sér. Gén. 2, pp. and cholagogues (Combretum micranthum, Combre- 75- 167. Rabat. tum glutinosum), vasoconstrictors, and also for diffe- Guinochet, M. et Quézel, P. 1954. Reconnaissance phyto- rent injuries. In this region, the use of the natural plant sociologique autour du Grad Erg occidental. Trav. Inst. resources represents 25% of industrial or domestic, Rech. Sah., t. XII, pp. 11- 27. 40% of therapeutic and 25% of feeding purposes. Killian, J. 1960. Contribution a l´etude phytosociologique du In the Saharan-Arabian region, the progressive de- Grand Erg Oriental. Terres et Eaux 37.) crease in agriculture has led to a more widespread use of natural resources for feeding, some of which have a Le Floc´h E. et M. Grouzis. 2003. Acacia raddiana, un arbre des zones arides á usages multiples. In: Un arbre au désert. very high nutritious (Maerua crassifolia with 20% of Acacia raddiana. Grouzis, M. And Le Floch´h, E., Edit. proteins in dry leaves) value. The consumption of fruits (pulp and seeds of Balanites aegyptiaca, Capparis sp., Le Houerou H.N. 1968. La désertisation du Sahara septentrional et des steppes limitrophes (Libye, Tunisie). Ziziphus sp.), and leaves of Salvadora persica and Ann. Algér. Géogr., nº 6. Balanites aegyptiaca is frequent. The presence of toxic alkaloids in the leaves of Maire, 1952- 1968. Flore du l’ Afrique du Nord. Vol. I à XIV, Boscia salicifolia (Chini & al. 1992), allows chamae- Paris. phyte to survive shepherding. However in times of Marie, R. & Monod, Th. 1950. Etudes sur la flora et la ve- shortage or famine, it is consumed by tribes prior to getation du Tibesti. Mem. Inst. Fr. Afr. Noire, 8. p. 140. the maceration and denaturalisation of leaves. Monod, Th. 1944. Tableau d’ ensemble des divisions adoptées The medicinal use of Salvadora persica is constant et remarques sur l’esquisse phytogeographique de M. Murat. in all Saharan territories. Its young stems are em- Mem. of Nat. Antiacridien. 1: 13-14 et 26-31. ployee as tooth brushes for dental hygiene given their Monod, Th. 1957. Les grandes divisions chorologiques de l’ antibacterial properties. Afrique. Comm. For Tech. Cooperation in Afrika Scient. Pressure on biodiversity is stronger due to the Council for Afrika, nº 24 previously indicated circumstances. Of all the species Ozenda, P. 1983. Flore du Sahara. 2 Ed.. C.N.R.S. Paris. 602 mentioned in the biogeographical and phytosociolo- pp gical characterisation (Fig. 2), 47% are the object of Pcord V.4.5 1999. MjM Software Design. Oregon. USA. nutritional use, 47% to medicinal use, and 31% to Quézel, P. 1954. Contribution a l’étude`de la flore et la vègè- industrial or other uses. tation du Hoggar References Quézel, P. 1958. Mision Botanique au Tibesti. Inst. Rech. Sahar. Alger, Mém., 4, 357 pp. Bagnouls, F. et Gaussen, H. 1963. Saison séche et índice xé- Quézel, P. 1961. Contribution a la flore du Sahara. Bull. Soc. rothermique. Doc. Pour la carte des producctions végétales. Hist. Nat. Afr. N. 52. Pp. 225- 232. Vol. I, art. 8, 47 pp. Tolouse. Quézel, P. 1965. La Végétation du Sahara du Tchad á la Barry, J.P. & al. 1987. L’ Adrar mauritanien entre Sahel et Mauritanie. Gustav Fisher Verlag. Stuttgart. 333 pp Sahara. Approches biogéographiques et geomorphologiques. Quézel, P., Bruneau, Ph., et Gillet, H. 1964. Carte inter- Ecologia Medit.: XII (1-2), 131-181. nationale du tapis végétal au 1/1.000.000, feuille Largeau Barry, J.P. et Celles J. Cl. 1973. Le problème des divisions (Tchad). I.G.N. (France). Vincennes bioclimatiques et floristiques au Sahara algérien. Naturalia Quézel, P. & Simonneau, P. 1960. Note sur la vegetation halo- monspeliensia, sér. Bot. Fasc. 23-24. phile du Sahara Occidental. Bull. Res. Council. of Israel. 8, Barry, J.P. et Faurel, L. 1974. Carte de la végétation de l’Al- D 1-4. pp. 253-262. gerie, feuille de Ghardaia au 1/500.000 . Mém. Soc. Hist. Quézel, P. & Simonneau, P. 1962. Contribution a l’ etude phy- Nat. Afr. du N., nº 11, 128 p. tosociologique du Sahara Occidental. L´ action des irriga- Braun–Blanquet, J., 1964. Pflanzensoziologie. Springer- Ver- tions sur la végétation spontanée.- Ann. Agron. 13, pp. 221- lag. Wien. 253.

Plant biodiversity, phytosociology and latitudinal ranges in Sahara meridional and Sahelian regions 55

Quézel, P. 1969. Le Plateaux du Darfour nord- occidental et le Rivas Martinez, S. 2008. Global Bioclimatics. Madrid. Jebel Gourgeil (Rep. du Soudan). Flore et végétation. Rossetti, Ch. 1963. Prospection écologique. Etudes en Dossiers de la Rech. Coopérative sur Programme nº 45, Afrique occidentale. Observations sur la végétation au Mali Marseille. 146 pp. oriental (1959). O.N.U. pour l’ Alimentation et l’Agri- Raunkaier, C. 1937. Plant life forms. Clarendon Press, Oxford, culture, Rome, 68 p. 104 pp. Shannon C. E. and Weaver W. 1998.The Mathematical Rivas Martinez & al., 1999. North American Boreal and Theory of Communication University of Illinois Press. 144 pp WesternTemperate Forest Vegetation. Itinera Geobotánica 12. Pp. 5 - 316

Figure 2. Characteristic bioclimograms of the studied areas in the Saheliana-Sudaniana (Tropical xeric, Niamey) and meridional Saharan-Arabian (Tropical hyperxeric, Bilma) regions