OPCE-STR.vp Acta Bot. Croat. 69 (1), 31–46, 2010 CODEN: ABCRA 25 ISSN 0365–0588 Vegetation spatial heterogeneity in a hyper arid Biosphere Reserve area in north Africa KAMAL H. SHALTOUT1, MOHAMMED G. SHEDED2*, ASHRAF I. SALEM3 1 Botany Department, Faculty of Science, Tanta University, Tanta, Egypt 2 Botany Department, Faculty of Science at Aswan, South Valley University, Aswan, Egypt 3 National Conservation Sector, Wadi Allaqi Biosphere Reserve, EEAA, Aswan, Egypt Ninety eight species of angiosperms belonging to 34 families were identified in the Wadi Allaqi Biosphere Reserve (S. E. Egypt): 33.7 % annuals and 66.3 % perennials. The mem- bers of Leguminosae contributed 19.4% of the total flora, considering the most dominant family in Wadi Allaqi. Three herbaceous species were recorded for the first time in this re- gion: Iphiona scabra, Chenopodium album and Lotus deserti. Eight vegetation clusters were obtained and categorized into 4 distinct groups according to soil composition and chemical characteristics (concentration of bicarbonates, calcium, magnesium and chlo- rides), and intensity of inundation by the water of Lake Nasser. Key words: Vegetation, Tamarix, Iphiona scabra, Chenopodium album, Lotus deserti, scrubland, life form, diversity, desert, Wadi Allaqi, Egypt Introduction Wadis represent one of the most prominent desert landforms, which exhibit physio- graphic irregularities that lead to parallel variations in species distribution (KASSAS and GIRGIS 1964). Wadi vegetation in the Eastern Desert of Egypt is distinguished into plant communities where the dominant perennial species give the permanent character to the plant cover in each habitat (KASSASS and IMAM 1954). This may be attributed to the scanty rainfall, which is not adequate for the appearance of many annuals. This desert lies in the Saharo-Sindian region and is bounded from the south by Sudano-Zambezian region; it is dominated by Saharo-Sindian species (OZENDA 1958). The South Eastern part belongs to the Saharo-Arabian phytogeographical region. In general, the vegetation is characterized by sparseness of plant cover and the preponderance of a limited number of plant species (SPRINGUEL et al. 1997). The life form distribution is closely correlated with topography and landform (KASSAS and GIRGIS 1965, ZOHARY 1973, ORSHAN 1986). The composition of life forms expresses a typical desert flora, the majority of species being therophytes and ACTA BOT. CROAT. 69 (1), 2010 31 * Corresponding author, e-mail: sheded1960@yahoo.com U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 9. travanj 2010 12:09:40 Color profile: Disabled Composite 150 lpi at 45 degrees chamaephytes. The South Eastern Desert of Egypt is interesting ecologically because of its physiographic variations and environmental gradients. Considerable efforts have been made towards the elucidation of vegetation – environmental relationships in its wadi eco- systems (KASSAS and IMAM 1954, 1959; BATANOUNY 1979; EL-SHARKAWI et al. 1987). Re- cently, the multivariate approach (HILL 1979a,b; DIGBY and KEMPTON 1987) has been used for the study of spatial distribution and classification of the desert vegetation of Wadi Allaqi (SPRINGUEL and SHEDED 1991, SHEDED 2002). The present study aims at analyzing the vegetation of Wadi Allaqi, in the south eastern desert of Egypt, in order to depict the main vegetation types and to assess the role of the soil factors and human interference that influence the vegetation. On the other hand, it is also a diagnostic study to evaluate the recent situation of Wadi Allaqi vegetation in comparison with the previous studies (e.g. SPRINGUEL et al. 1991, ALI et al. 1997). Study area The Wadi Allaqi Biosphere Reserve is situated in the South-Eastern Desert of Egypt (i.e. Egyptian Nubian Desert), about 180 km south of Aswan, on the eastern side of Lake Nasser (22° and 23° N to 33° and 35° E). It forms one of the most extensive drainage sys- tems in Egypt’s Eastern Desert. Its upstream tributaries drain some of the mountains that divide the Red Sea coastal plain from the Nile Valley. The wadi extends for about 350 km, in a NW- SE direction. It has an average width of about 1 km being narrower upstream and considerably broader downstream as it approaches Lake Nasser (Fig. 1). 32 ACTA BOT. CROAT. 69 (1), 2010 SHALTOUT K. H., SHEDED M. G., SALEM A. I. Fig. 1. Map of Wadi Allaqi showing the 19 sampled locations (1–19). U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 9. travanj 2010 12:09:45 Color profile: Disabled Composite 150 lpi at 45 degrees The main course of Wadi Allaqi starts in the area of Gabal Iss. It has a length of 350 km and runs generally west, reaching the Nile at Kurisku. The lower part of the wadi is now in- undated by the water of Lake Nasser. The upstream part is ca 500 m. a.s.l. However the sur- rounding mountains are high; one such mountain is Gabal Eigat in the upstream part, rising to 1400 m. a.s.l. (BELAL and SPRINGUEL 1996). The upstream tributaries may receive occa- sional rainfall and their drainage may accumulate in the main channel of Wadi Allaqi form- ing torrents that are the main source of water in this wadi (KASSAS and GIRGIS 1969). The middle part of Wadi Allaqi on the north side receives large influents. Wadi Abu Murra is one of these influents and lays a more clearly defined channel bounded by high ground on both sides. Its channel was once a part of the main camel- caravan. Wadi Umm Raylan is another influent. It is smaller wadi, of about 30 km. with a few short effluent runnels (KASSAS and GIRGIS 1969).Wadi Allaqi consists of the El Quleib core area, an extreme arid ecosystem comprising a small number of plants and animals. Vegetation is sparse with Acacia ehrenbergiana and Aerva javanica as the characteristic species. The El Quleib core area is located in the downstream part of the reserve, and the Eigat core area is located in the upstream part of Wadi Allaqi in a remote area that is difficult to reach. The impacts of the local community include charcoal formation, collection of medicinal plants, grazing and cutting trees. Soil in Wadi Allaqi consists of wadi fill deposits and varies in depth, physical and chemical composition depending on the soil-forming materials, transport processes and depositions (MOALLA and PULFORD 1991). Tamarix litter has an important effect on surface soils as it accumulates salts and increases soil salinity. The study area is characterized by a hyperarid environment with an aridity index of less than 0.05 (AYYAD and GHABBOUR 1986). Data from the Wadi Allaqi meteorological station between 1996 and 2005 shows the annual mean temperature is 25.8 °C. It can be as low as –2 °C in January. On the other hand, the mean maximum temperature of 41.8 °C has been recorded in July, which can often be as hote as 45 °C or higher, especially in August. The monthly mean relative humidity ranged between 14.0 and 38%, with an annual mean of 22.7%. The annual rainfall rarely exceeds 5 mm and is highly variable in both time and space. The wind speed at Aswan ranged be- tween 4 and 8 km h–1 between 1960 and 1980 with an annual mean of 5.9 km h–1. The an- nual fluctuation of water in Lake Nasser during a forty-year period (1964–2003), reached its first peak of 178 m. a.s.l. in 1978, but by 1988 the level had dropped to 154 m. a.s.l. and 175.6 in 2003 m. a.s.l. (Lake Nasser Authority). Materials and methods One hundred and twelve stands were analyzed at 19 locations within the Wadi Allaqi Biosphere Reserve (upstream, midstream and downstream parts, including the different wadi tributaries), in the period from November 2004 to May 2005. The locations and stands were selected to represent a wide range of physiographic and environmental varia- tion in each tributary. In each location, sampling stands were situated randomly using the réléve method described by MULLER-DOMBOIS and ELLENBERG 1974). Species were identi- fied after TACKHOLM 1974, BOULOS 1999, 2000 and 2002. Species life forms were deter- mined depending upon the location of the regenerative buds and the shed parts during the unfavorable season (RAUNKIER 1934). ACTA BOT. CROAT. 69 (1), 2010 33 DESERT VEGETATION SPATIAL HETEROGENEITY U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 9. travanj 2010 12:09:45 Color profile: Disabled Composite 150 lpi at 45 degrees Soil samples were collected from each stand. Sizes of soil particles were estimated us- ing the pipette method (KILMER and ALEXANDER 1949. Soil water extracts (1:5) were pre- pared for determination of EC and pH using conductivity and pH meters, chlorides by di- rect titration against silver nitrate using potassium chromate as an indicator, carbonates and bicarbonates by direct titration against HCl using phenolphthalein and methyl orange as in- dicators, calcium and magnesium by titration against EDTA (ethylenediamine dihydrogen tetraacetic acid) using ammonium purpurate and eriochrome black T as indicators (JACK- SON 1977). Two-way indicator species analysis (Twinspan), as a classification technique and detrended correspondence analysis (DCA) as an ordination technique, were applied to the presence estimates of 98 species in 112 vegetation stands according to the computer pro- grams of HILL (1979 a, b). The relationship between the vegetation and edaphic variables were assessed by calculating the simple linear correlation coefficient (r) between the DCA axes (reflect the vegetation gradient) and the soil variables. Results Stand classification according to TWINSPAN led to the identification of 8 clusters of stands similar in terms of their species composition (Fig 2); they are named after the domi- nant species as follows: Balanites aegyptiaca – Acacia tortilis subsp. tortilis, Fagonia in- dica – Leptadenia pyrotechnica – Acacia tortilis subsp. tortilis – Solenostemma arghel, Acacia ehrenbergiana – Morettia philaeana, Acacia ehrenbergiana – Aerva javanica – 34 ACTA BOT. CROAT. 69 (1), 2010 SHALTOUT K. H., SHEDED M. G., SALEM A. I. 112 +20-92 Tamarix nilotica Cynodon dactylon Glinus lotoides Acacia ehrenbergiana -23 +69 Acacia tortilis subsp. Tortilis Balanites aegyptiaca Solenostemma arghel Leptadenia pyrotechnica Calotropis procera Aerva javanica Acacia ehrenbergiana +13-7 Hyoscyamus muticusHyoscyamus muticus -3 +20 -4 +16 A st ra g a lu s v o g e li i S a lv a d o ra p e rs ic a S o le n o st e m m a a rg h e l C a y lu se a h e x a g y n a C le o m e d ro se ri fo li a Fagonia indica Leptadenia pyrotechnica Solenostemma arghel Calotropis procera -59 +10 Astragalus vogelii Indigofera argentea -12 +1 Eragrostis aegyptiaca Eragrostis aegyptiaca -6 +6 -5 +2 Astragalus vogelii Astragalus vogelii Chenopodium murale +4-1+7-3 S a ls o la im b ri c a ta -9 +50 -35 +15 M o re tt ia p h il a e a n a C o tu la c in e re a F a g o n ia in d ic a A . to rt il is su b sp . ra d d ia n a P u li c a ri a c ri sp a L o to n o n is p la ty c a rp a H e li o tr o p iu m su p in u m T y p h a d o m in g e n si s B a la n it e s a e g y p ti a c a 13 VIII 7 VII 10 VI 15 V 35 IV 9 III 20 II 3 I Fig. 2. Dendrogram indicating the eight vegetation clusters resulting from the TWINSPAN classi- fication of the 112 sampled vegetation stands in Wadi Allaqi. U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 9. travanj 2010 12:09:46 Color profile: Disabled Composite 150 lpi at 45 degrees Fagonia indica, Acacia ehrenbergiana – Aerva javanica, Acacia ehrenbergiana – Indi- gofera argentea, Hyoscyamus muticus – Tamarix nilotica – Morettia philaeana- Glinus lotoides and Tamarix nilotica – Glinus lotoides – Cynodon dactylon (Tab. 1, Fig. 2). Ninety-eight species recorded in the present study belonging to 34 families and 74 gen- era (Tab. 4). 33 species are annuals (33.7%) and 65 perennials (66.3%). Members of Leguminosae contribute 19.4% of the total flora and so considered the most dominant fam- ily, followed by Gramineae (13.3%), Zygophyllaceae (6.1%) and Compositae (6.1%). Three herbaceous species were recorded for the first time in this region: Iphiona scabra and Lotus deserti at the upstream part, and Chenopodium album the downstream. ACTA BOT. CROAT. 69 (1), 2010 35 DESERT VEGETATION SPATIAL HETEROGENEITY Tab. 1. Floristic composition of the vegetation clusters (I–VIII) identified after the application of TWNISPAN on the 112 sampled stands in Wadi Allaqi. * New recorded species in Wadi Allaqi. The figures represent presence value. Cluster I II III IV V VI VII VIII P% Number of stands per cluster 3 20 9 35 15 10 7 13 Species present in seven clusters Acacia ehrenbergiana 0.0 10.0 88.9 100.0 100.0 100.0 14.3 7.7 64.3 Species present in six clusters Aerva javanica 0.0 0.0 66.7 94.3 100.0 20.0 57.1 46.2 58.9 Species present in five clusters Faidherbia albida 33.3 10.0 11.1 0.0 0.0 0.0 14.3 7.7 5.4 Balanites aegyptiaca 100.0 40.0 11.1 0.0 13.3 0.0 14.3 0.0 13.4 Fagonia indica 0.0 70.0 66.7 94.3 6.7 0.0 42.9 0.0 50.9 Pulicaria crispa 0.0 0.0 22.2 2.9 40.0 0.0 42.9 15.4 12.5 Species present in four clusters Acacia tortilis subsp. raddiana 0.0 50.0 11.1 11.4 66.7 0.0 0.0 0.0 22.3 Astragalus vogelii 0.0 0.0 11.1 0.0 0.0 40.0 28.6 7.7 7.1 Salsola imbricata 0.0 5.0 0.0 0.0 13.3 30.0 42.9 0.0 8.0 Species present in three clusters Fagonia glutinosa 33.3 5.0 22.2 0.0 0.0 0.0 0.0 0.0 3.6 Senna alexandrina 0.0 20.0 44.4 8.6 0.0 0.0 0.0 0.0 9.8 Citrullus colocynthis 0.0 20.0 0.0 0.0 0.0 0.0 57.1 7.7 8.0 Glinus lotoides 0.0 5.0 0.0 0.0 0.0 0.0 57.1 76.9 13.4 Pulicaria incisa 0.0 5.0 33.3 0.0 0.0 0.0 14.3 0.0 4.5 Species present in two clusters Acacia tortilis subsp. tortilis 100.0 55.0 0.0 0.0 0.0 0.0 0.0 0.0 12.5 Cleome chrysantha 33.3 10.0 0.0 0.0 0.0 0.0 0.0 0.0 2.7 Chrozophora oblongifolia 33.3 5.0 0.0 0.0 0.0 0.0 0.0 0.0 1.8 Crotalaria microphylla 33.3 10.0 0.0 0.0 0.0 0.0 0.0 0.0 2.7 Senna italica 0.0 20.0 11.1 0.0 0.0 0.0 0.0 0.0 4.5 Cotula cinerea 0.0 25.0 66.7 0.0 0.0 0.0 0.0 0.0 9.8 Forsskalea tenacissima 0.0 10.0 22.2 0.0 0.0 0.0 0.0 0.0 3.6 U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 9. travanj 2010 12:09:46 Color profile: Disabled Composite 150 lpi at 45 degrees 36 ACTA BOT. CROAT. 69 (1), 2010 SHALTOUT K. H., SHEDED M. G., SALEM A. I. Cluster I II III IV V VI VII VIII P% Number of stands per cluster 3 20 9 35 15 10 7 13 Stipagrostis plumosa 0.0 5.0 44.4 0.0 0.0 0.0 0.0 0.0 4.5 Cynodon dactylon 0.0 0.0 0.0 0.0 0.0 0.0 28.6 61.5 8.9 Tamarix nilotica 0.0 0.0 0.0 0.0 0.0 0.0 85.7 84.6 15.2 Heliotropium supinum 0.0 0.0 0.0 0.0 0.0 0.0 14.3 46.2 6.3 Eragrostis aegyptiaca 0.0 0.0 0.0 0.0 0.0 0.0 28.6 7.7 2.7 Indigofera argentea 0.0 5.0 0.0 0.0 0.0 70.0 0.0 0.0 7.1 Cleome droserifolia 0.0 25.0 0.0 2.9 0.0 0.0 0.0 0.0 5.4 Reseda pruinosa 0.0 5.0 0.0 0.0 0.0 0.0 28.6 0.0 2.7 Haplophyllum tuberculatum 0.0 5.0 0.0 0.0 0.0 0.0 14.3 0.0 1.8 Psoralea plicata 0.0 0.0 11.1 0.0 0.0 0.0 14.3 0.0 1.8 Solenostemma arghel 0.0 55.0 0.0 0.0 0.0 0.0 14.3 0.0 10.7 Trichodesma africanum 0.0 5.0 0.0 0.0 0.0 0.0 14.3 0.0 1.8 Astragualus eremophilus 0.0 0.0 11.1 0.0 0.0 0.0 14.3 0.0 1.8 Morettia philaeana 0.0 0.0 88.9 0.0 0.0 0.0 57.1 0.0 10.7 Lotus sp 0.0 0.0 0.0 0.0 6.7 0.0 14.3 0.0 1.8 Species present in one clusters Euphorbia forsskalii 33.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Tribulus pentandrus 33.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Ziziphus spina-christi 33.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Iphiona scabra* 33.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Euphorbia granulata 33.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Cleome paradoxa 33.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Lupinus digitatus 33.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Zilla spinosa 33.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Dipterygium glaucum 33.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Tribulus ochroleucus 33.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Typha domingensis 33.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Chrozophora tinctoria 33.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Aizoon canariense 0.0 10.0 0.0 0.0 0.0 0.0 0.0 0.0 1.8 Anticharis glandulosa 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Aristida adscensionis 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Arnebia hispidissima 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Asphodelus fistulosus 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Calotropis procera 0.0 45.0 0.0 0.0 0.0 0.0 0.0 0.0 8.0 Caylusea hexagyna 0.0 25.0 0.0 0.0 0.0 0.0 0.0 0.0 4.5 Cistanche phelypaea 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Farsetia aegyptiaca 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Cymbopogon schoenanthus L. Spreng. subsp proximus 0.0 10.0 0.0 0.0 0.0 0.0 0.0 0.0 1.8 Heliotropium pterocarpum 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Tab. 1. – continued U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 9. travanj 2010 12:09:46 Color profile: Disabled Composite 150 lpi at 45 degrees ACTA BOT. CROAT. 69 (1), 2010 37 DESERT VEGETATION SPATIAL HETEROGENEITY Cluster I II III IV V VI VII VIII P% Number of stands per cluster 3 20 9 35 15 10 7 13 Monsonia heliotropoides 0.0 10.0 0.0 0.0 0.0 0.0 0.0 0.0 1.8 Zygophyllum simplex 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Dichanthium foevulatum 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Trianthema triquetra 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Leptadenia pyrotechnica 0.0 65.0 0.0 0.0 0.0 0.0 0.0 0.0 11.6 Lotus deserti * 0.0 10.0 0.0 0.0 0.0 0.0 0.0 0.0 1.8 Maerua crassifolia 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Ochradenus baccatus 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Panicum turgidum 0.0 10.0 0.0 0.0 0.0 0.0 0.0 0.0 1.8 Pergularia tomentosa 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Salvadora presica 0.0 20.0 0.0 0.0 0.0 0.0 0.0 0.0 3.6 Orobanche ramosa 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Cocculus pendulus 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 Fagonia bruguieri 0.0 0.0 22.2 0.0 0.0 0.0 0.0 0.0 1.8 Capparis decidua 0.0 0.0 11.1 0.0 0.0 0.0 0.0 0.0 0.9 Heliotropium arbainense 0.0 0.0 22.2 0.0 0.0 0.0 0.0 0.0 1.8 Crotalaria aegyptiaca 0.0 0.0 0.0 2.9 0.0 0.0 0.0 0.0 0.9 Hyphaene thebaica 0.0 0.0 0.0 2.9 0.0 0.0 0.0 0.0 0.9 Lotononis platycarpa 0.0 0.0 0.0 0.0 40.0 0.0 0.0 0.0 5.4 Chenopodium murale 0.0 0.0 0.0 0.0 0.0 0.0 14.3 0.0 0.9 Hyoscyamus muticus 0.0 0.0 0.0 0.0 0.0 0.0 100.0 0.0 6.3 Rumex dentatus 0.0 0.0 0.0 0.0 0.0 0.0 42.9 0.0 2.7 Tephrosia purpurea 0.0 0.0 0.0 0.0 0.0 0.0 28.6 0.0 1.8 Cyperus laevigatus 0.0 0.0 0.0 0.0 0.0 0.0 28.6 0.0 1.8 Phragmites australis 0.0 0.0 0.0 0.0 0.0 0.0 28.6 0.0 1.8 Zea mays 0.0 0.0 0.0 0.0 0.0 0.0 14.3 0.0 0.9 Polycarpaea repens 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.7 0.9 Aristida mutabilis 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.7 0.9 Sonchus oleraceus 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.7 0.9 Acacia nilotica 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.7 0.9 Imperata cylindrica 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.7 0.9 Chenopodium album * 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.7 0.9 Sesbania sesban 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.7 0.9 Abutilon pannosum 0.0 0.0 0.0 0.0 0.0 0.0 0.0 15.4 1.8 Fimbristylis bis-umbellata 0.0 0.0 0.0 0.0 0.0 0.0 0.0 46.2 5.4 Crypsis schoenoides 0.0 0.0 0.0 0.0 0.0 0.0 0.0 46.2 5.4 Senecio flavus 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.7 0.9 Ricinus communis 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.7 0.9 Tamarix aphylla 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.7 0.9 Tab. 1. – continued U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 9. travanj 2010 12:09:47 Color profile: Disabled Composite 150 lpi at 45 degrees Six life forms of species were recognized (Tab. 4, Fig. 3) phanerophytes (19 species), chamaephytes (22 species), hemicryptophytes (16 species), geophytes (4 species), para- sites (2 species), helophytes (2 species) and therophytes (33 species). Regarding the floristic categories, only one species is a Mediterranean element (Lupinus digitatus) and another one is Saharo-Sindian with extension to the Mediterranean region (Heliotropium supinum). On the other hand, four species are cosmopolitan taxa: Chenopodium album, Chenopodium murale, Crypsis schoenoides and Sonchus oleraceus (Tab. 4, Fig. 4), while 30 species are Sudano-Zambezian with extension to Saharo-Sindian and 18 species belong to the Saharo-Sindian with extension to Sudano-Zambezian region. Three species belong to Saharo-Sindian with extension to Irano-Turanian (Fagonia bruguieri, Haplophyllum tuberculatum and Hyoscyamus muticus). 38 ACTA BOT. CROAT. 69 (1), 2010 SHALTOUT K. H., SHEDED M. G., SALEM A. I. 19 Phanerophytes (19%) 22 Chamaephytes (22%) Hemicryptophytes (16%) 4 Geophytes (4%) 2 Parasites (2%) 33 Therophytes (35%) 2 Helophytes (2%) Fig. 3. Biological spectrum of Wadi Allaqi vegetation. 4% 1% 1% 2% 1% 4% 7% 7% 3%18% 7%2% 10% 1% 31% COSM . Cultivated ME ME+IR-TR ME+SA-SI+IR-TR PAL. PAN. SA-SI. SA-SI+IR-TR. SA-SI+S-Z. SA-SI+S-Z+IR-TR+ME. SA-S-Z S-Z S-Z+ME S-Z+SA-SI. Fig. 4. Floristic category spectrum of Wadi Allaqi vegetation. COSM – Cosmopolitan, Pal – Palaeotropical, Pan – Pantropical, SA-SI – Saharo-Sindian, S-Z – Sudano-Zambezian, ME – Mediterranean and IR-TR – Irano-Turanian. U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 9. travanj 2010 12:09:47 Color profile: Disabled Composite 150 lpi at 45 degrees Sand attains the highest value in cluster I (85.5%) and the lowest in cluster VIII (87.4). Clay has the highest value in cluster VIII (8.1%) and the lowest in cluster III (1.9), while silt has the highest in cluster VIII (12.0) and the lowest in cluster II (10.7). The minimum value of pH is attained in cluster II and IV (7.4) and the maximum in clusters VI, VII and VIII (7.6). EC has a maximum in cluster VIII (413 mS–1) and a minimum in cluster I (83.7 mS–1). Cl attains the highest concentration in cluster VIII [16.0 mg (100 mg)–1] and the lowest in cluster III [10.0 mg (100 mg)–1]. HCO3 has the highest value in cluster II [46 mg (100 mg)–1] and the lowest in cluster IV [29 mg (100 mg)–1]. Ca has a maximum in cluster VIII [20.7 mg (100 mg)–1] and its minimum in cluster IV [9.1 mg (100 mg)–1], while Mg at- tains a maximum in cluster VIII [14.6 mg (100 mg)–1] and a minimum in cluster III [3.0 mg (100 mg)–1]. Organic matter attains the highest in cluster VII (1.7 %) and the lowest in clus- ter I (0.8 %) (Tab. 2). The first DCA axis (AX1) correlated positively with electric conduc- tivity (r = 0.81), calcium (r = 0.59), clay (r = 0.89) magnesium (r = 0.78) and organic matter (r = 0.76); and negatively with sand (r = –0.94). The third axis (AX3) correlated positively with silt (r = 0.76) (Tab. 3). The similarity between the vegetation clusters, as revealed by DCA analysis, shows a distinct pattern along the two-dimensional plane of axes 1 and 2 (using the mean vectors of centroids of each cluster): group of clusters I and II; cluster VI; group of clusters III, IV and V; and group of clusters VII and VIII. Discussion Ninety-eight species were recorded in the present study compared with 127 species re- corded by SPRINGUEL et al. (1991) in the same study area. This may be due to the severe en- vironmental conditions as the area has been completely rainless since 1995/1996. Overex- ploitation of the plant resources (e.g. overgrazing and overcutting) may also responsible for the decrease of species diversity in this region (ALI et al. 2000). The common perennial species are: Acacia ehrenbergiana, Aerva javanica, Fagonia indica, Acacia tortilis subsp. raddiana, Solenostemma arghel, Pulicaria crispa, Acacia tortilis subsp. tortilis, Calo- tropis procera, Morettia philaeana and Leptadenia pyrotechnica. The common annuals are Astragalus vogelii, Pulicaria incisa, Glinus lotoides, Indigofera argentea and Cotula ACTA BOT. CROAT. 69 (1), 2010 39 DESERT VEGETATION SPATIAL HETEROGENEITY Tab. 2. Means of soil characteristics of the eight vegetation clusters identified in Wadi Allaqi. Cluster pH EC mS–1 Physical characteristics Chemical characteristics Silt Clay Total sand Organic matter HCO3 Cl Ca Mg % mg (100 g)–1 I 7.5 83.7 11.5 2.5 85.5 0.8 42.4 13.7 12.1 2.7 II 7.4 105.3 10.7 2.4 85.1 1.1 46.3 11.9 11.4 4.1 III 7.5 122.9 11.0 1.9 85.1 1.2 34.6 10.0 12.2 3.0 IV 7.4 129.9 10.8 2.7 85.1 1.0 29.3 12.9 9.1 7.1 V 7.6 117.5 11.4 3.1 83.6 1.1 38.9 12.8 10.6 5.2 VI 7.6 108.1 10.9 3.4 84.2 1.0 38.0 12.2 13.4 3.2 VII 7.6 166.7 11.9 5.2 80.8 1.7 35.3 11.3 11.1 6.3 VIII 7.6 413.3 12.0 8.1 78.4 1.3 39.8 16.0 20.7 14.6 U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 9. travanj 2010 12:09:47 Color profile: Disabled Composite 150 lpi at 45 degrees 40 ACTA BOT. CROAT. 69 (1), 2010 SHALTOUT K. H., SHEDED M. G., SALEM A. I. Tab. 3. The species recorded in Wadi Allaqi and their families, floristic categories and life forms. COSM – Cosmopolitan, Pal – Palaeotropical, Pan – Pantropical, TR – Tropical, SA-SI – Saharo- Sindian, S-Z – Sudano-Zambezian, ME – Mediterranean, and IR-TR – Irano- -Turanian. The life forms are Ph – phanerophyte, Ch – chamaephyte, H – hemicryptophyte, G – geophyte, He – helophyte, P – parasite, and Th – therophyte. Species Family Floristic Category Life form Aerva javanica (Burm.f) Juss.ex Schult. Amaranthaceae SA-SI+S-Z. Ch Abutilon pannosum (G.Forst. f.) Schltdl. Malvaceae S-Z+SA-SI. Ch Faidherbia albida (Delile). Leguminosae S-Z Ph Acacia ehrenbergiana (Hayne). Leguminosae S-Z+SA-SI. Ph Acacia nilotica L. (Delile) Leguminosae S-Z Ph Acacia tortilis subsp. raddiana Savi Leguminosae S-Z+SA-SI. Ph Acacia tortilis subsp. tortilis (Forssk.) Hayne Leguminosae S-Z+SA-SI. Ph Aizoon canariense L. Aizoaceae S-Z+SA-SI. Th Anticharis glandulosa (Asch). Scrophulariaceae SA-SI+S-Z. Th Aristida adscensionis L. Gramineae PAN Th Aristida mutabilis (Trin. and Rupr.). Gramineae S-Z+SA-SI. Th Arnebia hispidissima (Lehm.) DC Boraginaceae S-Z+SA-SI. Th Asphodelus fistulosus Cav. Liliacaae ME+SA-SI+IR-TR Th Astragalus eremophilus Bioss Leguminosae SA-SI+S-Z. Th Astragalus vogelii (Webb) Bornm. Leguminosae SA-SI+S-Z. Th Balanites aegyptiaca (L.) Del. Balanitaceae S-Z+SA-SI. Ph Calotropis procera (Ait.) Asclepiadaceae SA-SI+S-Z. Ph Capparis decidua (Forssk.) Edgew Capparaceae S-Z+SA-SI. Ph Senna italica (Mill.). Leguminosae S-Z+SA-SI. Ch Senna alexandrina (Mill.). Leguminosae S-Z+SA-SI. Ch Caylusea hexagyna (Forssk.) M. L. Green Resedaceae S-Z+SA-SI. Th Chenopodium album L. Chenopodiaceae COSM. Th Chenopodium murale L. Chenopodiaceae COSM. Th Chrozophora obongifolia (Delile) Spreng. Euphorbiaceae S-Z. Ch Chrozophora tinctoria L.Raf. Euphorbiaceae S-Z+SA-SI. Ch Cistanche phelypaea (L.) Cout. Orobanchaceae SA-SI+S-Z+IR-TR+ME. P Citrullus colocynthis (L.) Schrad. Cucurbitaceae SA-SI+S-Z+IR-TR+ME. H Cleome chrysantha.Decne. Cleomaceae SA-SI. Ch Cleome droserifolia (Forssk.) Delile. Cleomaceae SA-SI+S-Z. H Cleome paradoxa DC. Cleomaceae S-Z. H Cocculus pendulus (J. R. and G. Forst.) Diels Menispermaceae S-Z+SA-SI. Ph Cotula cinerea Del. Compositae SA-SI. Th Crotalaria aegyptiaca Benth. Leguminosae SA-SI+S-Z. H Crotalaria microphylla Vahl Leguminosae S-Z. Th Crypsis schoenoides (L)Lam Gramineae COSM. Th Cymbopogon schoenanthus L. Spreng. subsp proximus A.Rich Gramineae SA-SI. G Cynodon dactylon (L.) Pers Gramineae PAN. G U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 9. travanj 2010 12:09:47 Color profile: Disabled Composite 150 lpi at 45 degrees ACTA BOT. CROAT. 69 (1), 2010 41 DESERT VEGETATION SPATIAL HETEROGENEITY Species Family Floristic Category Life form Cyperus laevigatus L. Cyperaceae PAN. G Dichanthium foevulatum Delile. Gramineae SA-SI+S-Z+IR-TR+ME. H Dipterygium glaucum Decne. Cruciferae S-Z. Ch Eragrostis aegyptiaca (Willd.) Delile. Gramineae S-Z. Th Euphorbia forsskalii J. Gay. Euphorbiaceae S-Z+SA-SI. Th Euphorbia granulata Forssk. Euphorbiaceae S-Z+SA-SI. Th Fagonia bruguieri DC. Zygophyllaceae SA-SI+IR-TR. H Fagonia glutinosa Delile Zygophyllaceae SA-SI. H Fagonia indica Burm.f. Zygophyllaceae SA-SI+S-Z. Ch Farsetia aegyptiaca Cruciferae S-Z+SA-SI. Ch Fimbristylis bis-umbellata (Forssk) Bubani. Cyperaceae PAL. Th Forsskalea tenacissima L. Urticaceae SA-SI+S-Z. H Glinus lotoides L. Molluginaceae PAL. Th Haplophyllum tuberculatum (Forssk.). Juss Rutaceae SA-SI+IR-TR. Ch Heliotropium arbainense (Fresen.) Boraginaceae SA-TR+-S-Z Ch Heliotropium pterocarpum Hochst Boraginaceae SA-TR+-S-Z Th Heliotropium supinum (L.) Boraginaceae S-Z+ME Th Hyoscyamus muticus (L.) Solanaceae SA-SI+IR-TR. Ch Hyphaene thebaica (L.) Mart. Palmae S-Z. Ph Imperata cylindrica L. Gramineae PAN. H Indigofera argentea (Burm.) Leguminosae S-Z+SA-SI. H Iphiona scabra DC. Compositae SA-SI+S-Z. Ch Leptadenia pyrotechnica (Forssk.) Decne Asclepiadaceae S-Z+SA-SI. Ph Lotononis platycarpa (Viv.) Pic Serm. Leguminosae S-Z+SA-SI. Th Lotus sp. L. Leguminosae S-Z+SA-SI. Th Lotus deserti Tackh. et Boulos Leguminosae SA-SI. H Lupinus digitatus Forssk.ssp orientalis sensu. Täckh. Leguminosae ME. Th Maerua crassifolia (Forssk.) Capparaceae S-Z. Ph Monsonia heliotropoides (Cav.) Boiss. Geraniaceae SA-SI+S-Z. H Morettia philaeana (Del.) DC. Cruciferae SA-SI+S-Z. H Ochradenus baccatus Del. Resedaceae SA-SI+S-Z. Ph Orobanche ramosa L. Orobanchaceae ME+IR-TR P Panicum turgidum (Forssk.) Gramineae SA-SI+S-Z+IR-TR+ME G Pergularia tomentosa L. Asclepiadaceae S-Z+SA-SI. Ch Phragmites australis (Cav.)Trin ex Steud Gramineae PAL. He Polycarpaea repens (Forssk.) Asch. et Schweinf. Caryophyllaceae SA-SI+S-Z. H Psoralea plicata Delile Leguminosae SA-SI+S-Z. Ch Pulicaria crispa (Forssk.) Oliv. Compositae S-Z+SA-SI. Ch Pulicaria incisa (Lam.) DC. Compositae S-Z+SA-SI. H Tab. 3. – continued U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 9. travanj 2010 12:09:47 Color profile: Disabled Composite 150 lpi at 45 degrees 42 ACTA BOT. CROAT. 69 (1), 2010 SHALTOUT K. H., SHEDED M. G., SALEM A. I. Species Family Floristic Category Life form Reseda pruinosa (Delile) Resedaceae SA-SI Th Ricinus communis L. Euphorbiaceae PAN. Ch Rumex dentatus L. Polyganacaea ME+IR-TR Th Salsola imbricata (Forssk.) Chenopodiaceae SA-SI+S-Z. Ch Salvadora persica L. Salvadoraceae S-Z+SA-SI. Ph Senecio flavus (Decene) Sch. Bip. Compositae SA-SI+S-Z. Th Sesbania sesban (L) Merr. Leguminosae S-Z. Ph Solenostemma argel (Del.) Hayne Asclepiadaceae SA-SI+S-Z. Ph Sonchus oleraceus L. Compositae COSM. Th Stipagrostis plumosa (L.) Munro ex T. Andersson. Gramineae SA-SI+S-Z+IR-TR+ME. H Tamarix aphylla (L.) H. Karst. Tamaricaceae SA-SI+S-Z+IR-TR+ME. Ph Tamarix nilotica (Ehrenb.) Bunge. Tamaricaceae SA-SI+S-Z+IR-TR+ME. Ph Tephrosia purpura (L.) Pers. Leguminosae S-Z+SA-SI. Ch Trianthema triquetra (Forssk). Aizoaceae PAL. Th Tribulus ochroleucus (Maire) Zygophyllaceae PAN. Th Tribulus pentandrus Forssk. Zygophyllaceae S-Z+SA-SI. Th Trichodesma africanum (L.) R. Br. Boraginaceae S-Z+SA-SI. Ch Typha domingensis (Pers.) poir. ex. Steud. Typhaceae PAN. He Zea mays L. Gramineae Cultivated. Th Zilla spinosa L. Cruciferae SA-SI. Ch Ziziphus spina-christi (L.) Desf. Rhamnaceae S-Z+SA-SI. Ph Zygophyllum simplex L. Zygophyllaceae S-Z+SA-SI. Th Tab. 3. – continued Tab. 4. Simple linear correlation coefficient (r) between the soil variables and DCA axes. *: P < 0.05, **: P < 0.01. Edaphic variable DCA axis pH EC HCO3 Cl Ca Mg Silt Clay Sand AX1 AX2 AX3 mS–1 mg 100 g–1 % AX1 1.00 AX2 –0.22 1.00 AX3 0.33 0.16 1.00 pH 0.65 0.06 0.37 1.00 EC mS–1 0.81** –0.10 0.40 0.34 1.00 HCO3 m g 10 0 g– 1 –0.32 0.67 –0.02 –0.08 0.00 1.00 Cl 0.32 0.09 0.67 0.04 0.69 0.24 1.00 Ca 0.59** 0.24 0.37 0.42 0.88** 0.29 0.67 1.00 Mg 0.78* –0.27 0.40 0.19 0.95** –0.11 0.74* 0.72* 1.00 Silt % 0.70 0.23 0.76* 0.59 0.64 0.08 0.49 0.55 0.58 1.00 Clay 0.89** 0.05 0.50 0.50 0.93** 0.03 0.67 0.80* 0.90** 0.77* 1.00 Sand –0.94* 0.03 –0.45 –0.58 –0.90** 0.02 –0.53 –0.73* –0.86** –0.81* –0.98** 1 O.M 0.76* –0.14 –0.01 0.47 0.38 –0.24 –0.22 0.10 0.37 0.54 0.52 –0.67 U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 13. travanj 2010 9:22:15 Color profile: Disabled Composite 150 lpi at 45 degrees cinerea. These species were also recorded by (KASSAS and GIRGIS 1965, SHEDED 1992) as dominant species in some wadis in the Eastern Desert of Egypt including Wadi Allaqi. Three species were recorded for the first time in Wadi Allaqi: Iphiona scabra, Cheno- podium album and Lotus deserti. However, SHEDED (1992) recorded Iphiona scabra in the Red Sea region (never recorded by other authors, such as ALI et al. 1997& 2000). The ap- pearance of these species may be due to the increasing grazing pressure in Wadi Allaqi that extends to the Sudanese borders, the cultivation of some crops along the shoreline of Lake Nasser, the effects of Lake Nasser itself on the migration of certain species, and the camel trade between Sudan and Egypt (ALI et al. 2000). The life form spectrum reflects a typical desert flora, the majority of species being therophytes and chamaephytes (about 57 %). Life forms of desert plants are also closely related with topography (KASSAS and GIRGIS 1965, ZOHARY 1973 and ORSHAN 1986). According to HASSIB (1951), therophytes are the most common life form in the Egyptian flora. The communities of wadi ecosystems of the basement complex country are demon- strated by KASSAS and GIRGIS (1969) into four types: ephemeral, suffrutescent woody, suffrutescent succulent and scrubland types. In the present study, the ephemeral type is rep- resented by Morettia philaeana and Fagonia indica in the downstream and midstream parts of Wadi Allaqi. The suffrutescent type is represented by the community of Aerva javanica and Senna alexandrina in Wadi tributaries particularly at the middle part. The suffrutescent succulent type is represented by Salsola imbricata and Aerva javanica which clearly appear in the main channel of Wadi Allaqi and some of its tributaries. The scrubland type is represented by the following shrubs and trees (see also SHEDED 1992): 1- Tamarix nilotica community,common in the downstream part, 2- Salvadora persica community, which appears in small scale in the upstream part (associated with Solenostemma arghel, Leptadenia pyrotechnica, Balanites aegyptiaca, Acacia tortilis subsp. raddiana and Aca- cia tortilis subsp. Tortilis), 3- Balanites aegyptiaca community, well represented in the up- stream and midstream parts (associated with Salvadora persica, Acacia tortilis subsp. raddiana, Acacia tortilis subsp. tortilis and Calotropis procera), 4- Leptadenia pyrotech- nica community, well represented in the upstream part (mainly associated with Calotropis procera, Solenostemma arghel and Maerua crassifolia), 5- Acacia ehrenbergiana, which community could be dominant in the downstream part and in some scattered small-sized ACTA BOT. CROAT. 69 (1), 2010 43 DESERT VEGETATION SPATIAL HETEROGENEITY I II III IV V VI VII VIII 0 50 100 150 200 250 300 350 0 100 200 300 400 500 600 700 DCA - Axies 1 (X) D C A - A x ie s 2 (Y ) A B C D Fig. 5. DCA ordination of the eight vegetation clusters identified in Wadi Allaqi. U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 9. travanj 2010 12:09:48 Color profile: Disabled Composite 150 lpi at 45 degrees places. 6- Acacia tortilis subsp. tortilis community, well represented in the upstream part (associated with Acacia tortilis subsp. raddiana and Balanites aegyptiaca), 7- Acacia tortilis subsp. raddiana community well represented in all parts of the Wadi (in the down- stream and midstream parts it is associated with Acacia ehrenbergiana but in the upstream part with Acacia tortilis subsp. tortilis, Leptadenia pyrotechnica, Balanites aegyptiaca, Solenostemma arghel and Salvadora persica). Soil analysis in the present study, indicated that some stands appear to be acidic (it is in- dicative that the pH of some stands in cluster II was 6.7). This is may be due to the inunda- tion of these stands by the water of Lake Nasser, as well as the effects of livestock excreta on the soil characteristics. The soils of Wadi Allaqi are generally not highly saline, salt be- ing brought to the surface by evaporation following surface irrigation (PULFORD et al. 1992). However, the electric conductivity in some stands in Sidinab area (Wadi Umm Hambol is located in the downstream part of Wadi Allaqi) is abnormally high values (up to 2960 mS–1) where tamarisk woodland is common. Tamarix has been identified as a major cause of salt accumulation on the soil surface (ALI 1987, SPRINGUEL and ALI 1990). Tamarix also is known to concentrate a high amount of sodium chloride in specialized glands in its leaves (BOSABALIDIS 1992). In addition, there is a relationship between the amount of tamarix litter and the electric conductivity of soil (ALI 1987, BRIGGS et al. 1993 and ALI et al. 2001). In the downstream part, soil characteristics support the vegetation clusters. This part was inundated by Lake Nasser water due to the rising of water levels and the soil was char- acterized by relatively high contents of clay and silt. In contrast, the soil of the clusters in the other parts was not affected by inundation processes, and consequently, the sand frac- tion was relatively high (see the study of SHEDED 1992). The sand fraction was relatively high in the stands of the upstream part (Eigat core area) compared with the other stands. This may be due to the weathering process of granite components, which distinguished the upstream part of Wadi Allaqi. Organic matter had a wide range of variation in relation to the different vegetation clusters, especially in the downstream part of Wadi Allaqi. Live- stock and birds play an important role, due to the deposition of their dung in the soil, dead fish, due to the activity of anglers in Lake Nasser, as well as the little microbial activity in the soil surface (VOLK and LOEPPERT 1982). The eight vegetation clusters, identified after Twinspan, are categorized along the DCA axes 1 and 2 into 4 distinct groups (HILL 1979 a, b). The stands belonging to group A (clus- ters I and II) are mainly located in the upstream part (Eigat core area) and their soil differs from the that of other areas by a higher concentration of bicarbonates, calcium, magnesium and chlorides, perhaps due to animal grazing, rainfall, floods and their effects on the parent rocks (PULFORD et al. 1992).The stands of group B (cluster VI) are located in the middle part, those of group C (clusters III, IV and V) are located in the downstream and middle parts, while those of group D (clusters VII and VIII) are located in the downstream part (some stands are sometimes inundated by the water of Lake Nasser, and their soils are sandy loam)(SHEDED 1992). References ALI, M. M., 1987: Studies on the shoreline vegetation of Aswan High Dam Lake (Lake Nasser) and impacts of the lake on the desert. MSc. Thesis, Assiut University, Assiut. 44 ACTA BOT. CROAT. 69 (1), 2010 SHALTOUT K. H., SHEDED M. G., SALEM A. I. U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 9. travanj 2010 12:09:48 Color profile: Disabled Composite 150 lpi at 45 degrees ALI, M. A., BADRI, M. A., MOALLA, S. N., PULFORD, I. D., 2001: Cycling of metals in desert soils: effects of Tamarix nilotica and inundation by Lake Water. Environmental Geo- chemistry and Health 23, 373–382. ALI, M. M., BADRI, M. A., HASSAN, L. M., SPRINGUEL, I. V., 1997: Effects of physiogeo- graphical factors on desert vegetation, Wadi Allaqi Biosphere Reserve, Egypt: multi- variate analysis. Ecologie 28, 119–128. ALI, M. M., DICKINSON, G., MURPHY, K. J., 2000: Predictors of plant diversity in a hyper- arid desert wadi ecosystem. Journal of Arid Environments 45, 215–230. AYYAD, M. A., GHABBOUR, S. I., 1986: Hot deserts of Egypt and Sudan. In: EVENARI, M., NOY-MEIR, I., GOODALL, D. W. (eds.), Ecosystems of the world, 12B, Hot desert and arid shrublands, B, 149–202. Elsevier, Amsterdam. BATANOUNY, K. H., 1979: The desert vegetation in Egypt. Cairo University African Studies Revue, Special Publication 1, 9–37. BELAL, A. E., SPRINGUEL, I. V., 1996: Economic value of plant diversity in arid environ- ments. Nature and Resources 32, 33–39. BOSABALIDIS, A. M., 1992: A morphological approach to the question of salt gland lifetime in leaves of Tamarix aphylla L. Israel Journal of Botany 41, 115–121. BOULOS, L., 1999: Flora of Egypt, 1 (Azollaceae – Oxalidaceae). Al Hadara Publishing, Cairo. BOULOS, L., 2000: Flora of Egypt, 2 (Geraniaceae – Boraginaceae). Al Hadara Publishing, Cairo. BOULOS, L., 2002: Flora of Egypt, 3 (Verbenaceae – Compositae). Al Hadara Publishing, Cairo. BRIGGS, J., DICKINSON, G., MURPHY, K., PULFORD, I., BELAL, A. E., MOALLA, S., SPRINGUEL, I., GHABBOUR, S. I., MEKKI, A. M., 1993: Sustainable development and resource man- agement in marginal environments: natural resources and their use in Wadi Allaqi re- gion of Egypt. Applied Geography 13, 259–284. DIGBY, P. C. N., KEMPTON, R. A., 1987: Multivariate analysis of ecological communities. Chapman and Hall, London. EL-SHARKAWI, H. M., SALAMA, P. M., FAYED, A. A., 1987: Vegetation of inland desert wa- dis in Egypt. 8: Vegetation of Wadi Kharit. Feddes Repertorium 98, 543–547. HASSIB, M.,1951: Distribution of plants in Egypt. Bulletin of the Faculty of Science Fouad 1 University. 29, 59–261. HILL, M. O., 1979a.: DECORANA: a FORTRAN Program for detrended correspondence analysis and reciprocal averaging. Cornell University, Ithaca, New York. HILL, M. O., 1979b: TWINSPAN: a FORTRAN program for arranging multivariate data in an ordered two-way table by classification of the individuals and attributes. Cornell University, Ithaca, New York. JACKSON, M. L., 1977: Soil chemical analysis. Prentice-Hall, New Delhi. KASSAS, M., GIRGIS, W. A., 1964: Habitat and plant communities in the Egyptian desert. V: The limestone plateau, Journal of Ecology 52, 107–119. ACTA BOT. CROAT. 69 (1), 2010 45 DESERT VEGETATION SPATIAL HETEROGENEITY U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 9. travanj 2010 12:09:48 Color profile: Disabled Composite 150 lpi at 45 degrees KASSAS, M., GIRGIS, W. A., 1965: The units of a desert ecosystem. Journal of Ecology 53, 715–728. KASSAS, M., GIRGIS, W. A., 1969: Plant life in the Nubian Desert east of the Nile. Bulletin de l’Institute d,Égypte 31, 47–71. KASSAS, M., IMAM, M., 1954: Habitat and plant communities in the Egyptian desert. III. The Wadi Bed Ecosystem. Journal of Ecology 42, 242–441. KASSAS, M., IMAM, M., 1959: Habitat and plant communities in the Egyptian desert. IV. The gravel desert. Journal of Ecology 47, 289–310. KILMER, V. J., ALEXANDER, L. T., 1949: Methods of making mechanical analysis of soil. Soil Science 86, 15 – 24. MOALLA, S. M. N., PULFORD, I. D., 1991: Survey of soil resources in Wadi Allaqi. Allaqi Project working paper 18. University of Glasgow and Faculty of Science at Aswan, Assiut University. MULLER-DOMBOIS, D., ELLENBERG, H., 1974: Aims and methods of vegetation ecology. John Wiley and Sons, New York. ORSHAN, G., 1986: The desert of the Middle East. In: Evenari, M., Noy-Meir, I., Goodall, D. W., (eds.), Ecosystems of the world, 12 B, Hot Deserts and Arid Shrublands, 1–28. El-Sevier, Elsevier, Amsterdam. OZENDA, P., 1958: Flore du Sahara septentrional. C.N.R.S., Paris. PULFORD, I. D., MURPHY, K. J., DICKINSON, G., BRIGGS, J. A., SPRINGUEL, I., 1992: Eco- logical resources for conservation and development in Wadi Allaqi, Egypt. Botanical Journal of the Linnaean Society 108, 131–141. RAUNKIER, C., 1934: Life forms of plants and statistical plant geography. The Clarendon Press, Oxford. SHEDED, M. G., 1992: Environment and vegetation in the South Eastern Desert, Egypt. PhD. Thesis, Faculty of Science at Aswan, Assiut University. SHEDED, M. G., 2002: Vegetation analysis in the South Eastern Desert of Egypt. Journal of Biological Science 2, 573–581. SPRINGUEL, I., ALI, M. M., 1990: Impact of Lake Nasser on desert vegetation in desert deve- lopment. Proceedings 2 International Desert Development Conference, Cairo, 557–568. SPRINGUEL, I., EL-HADIDI, M. N., SHEDED, M. G., 1991: Plant communities in the south- ern part of the Eastern Desert (Arabian Desert) of Egypt. Journal of Arid Environments 21, 307–317. SPRINGUEL, I., SHEDED, M. G., 1991: Spatial analysis of the plant communities in south- ern part of the Eastern Desert of Egypt. Journal of Arid Environments 21, 319–325. SPRINGUEL, I., SHEDED, M. G., MURPHY, J. K., 1997: The plant biodiversity of the Wadi Allaqi Biosphere Reserve (Egypt): Impacts on lake Nasser on a desert wadi ecosystem. Biodiversity and Conservation 6, 1259–1275. TACKHOLM, V., 1974: Student’s flora of Egypt. Cairo University Publication. ZOHARY, M., 1973: Geobotanical foundations of the Middle East Gus. Fischer Verlag, Stuttgart. VOLK, B. G., LOEPPERT, R. H., 1982: Soil organic matter. In KILMER, V. J. (Ed.), Hand- book of soils and climate in agricuture, 211–268. CRC Press, Boca Raton, Florida. 46 ACTA BOT. CROAT. 69 (1), 2010 SHALTOUT K. H., SHEDED M. G., SALEM A. I. U:\ACTA BOTANICA\Acta-Botan 1-10\Sheded.vp 9. travanj 2010 12:09:48 Color profile: Disabled Composite 150 lpi at 45 degrees