Tamarix Nilotica Research Articles

Species identification of plant tissues from the gut of An. sergentii by DNA analysis

There are three commonly used assays to identify plant material in insect guts: the cold anthrone test for fructose, the cellulose staining test for visualizing plant tissue and gas chromatography for seeking unique sugar content profiles. Though sugar and cellulose tests can distinguish between the general sources of sugar meal (nectar versus tissue), they cannot identify the species of plant sources. Even gas chromatography profiles can be problematic; there are reported instances of intra-specific variation as well as inter-specific and intergeneric variation that can mar results. Here, we explore the potential for DNA analysis to help resolve this issue. First, Anopheles sergentii were exposed to branches of two species of highly attractive flowering bushes in the laboratory and the great majority (∼90–98%) were positive for sugar from nectar while very few were positive for cellulose (∼0.5–8%) and DNA (6–19%). Moreover, laboratory An. sergentii showed opposing preferences, tending to obtain sugar from nectar of one plant ( Tamarix nilotica) but to feed more on tissue from the other ( Ochradenus baccatus). An. sergentii are exposed to a wide variety of plants in their natural desert habitats and in the absence of flowers in the dry season, they resort to feeding specifically on tissues of a few plants. According to DNA analysis the favorite plants were Suaeda asphaltica, Malva nicaeensis and Conyza dioscoridis, which are succulents that account for less than 1% of vegetation in the area.

Plant community distribution and variation along the Awash river corridor in the main Ethiopian rift

AbstractThe vegetation along the Awash River (1200‐km long) in the main Ethiopian Rift, and its relationship with environmental factors was studied. Seven plant communities were described from the study area: (1) Acacia nilotica subsp. leiocarpa. – Carissa edulis type; (2) Acacia robusta subsp. usambarensis – Acokanthera schimperi type; (3) Celtis africana – Mimusops laurifolia type; (4) Acacia senegal – Acacia mellifera – Dobera glabra type; (5) Acacia nilotica subsp. indica – Ficus capreaefolia type; (6) Lannea schimperi–Glycine wightii type; and (7) Tamarix nilotica – Acacia hocki community type. It has been shown that the plant communities along the river follow an altitudinal gradient. The vegetation of the Awash River is mainly the result of the interactions between edaphic factors, the hydrology, altitude, slope and climate.

New Monomeric and Dimeric Hydrolyzable Tannins from Tamarix nilotica

Two new ellagitannin monomers, nilotinins M2 (4) and M3 (5), two new dimers, nilotinins D4 (6), D5 (7), and a known dimer (8), were isolated from an aqueous acetone extract of dried leaves of Tamarix nilotica (Ehrenb.) Bunge. Structures of 4-7 were determined based on spectral data and chemical correlations with known tannins. The known dimer 8 was isolated from a plant extract for the first time; its 1 H and 13 C assignments are also reported here.

Do Acacia and Tamarix trees compete for water in the Negev desert?

We investigated the spatial distribution of the three Acacia and two Tamarix tree species and related the spatial distribution of these two genera to their 18O value, i.e. their 18O/ 16O isotopic ratio in the Negev desert, Israel. At the regional spatial scale, there was a significant difference in the overall distributions of these two genera, although there was considerable overlap. At the 1 km 2 scale, there was no deviation from homogeneity. At a finer scale, no deviation from a random distribution was found in three ephemeral rivers between the two largest trees in these two genera, Acacia raddiana and Tamarix nilotica. We found that Tamarix used deep water from aquifers while Acacia trees used an alternate source, most likely surface water. Spatial segregation of Tamarix and Acacia occurs at the large spatial scale but not at the small scale, perhaps because of the high tolerance of Tamarix species for salinity and the low tolerance of Acacia species for saline conditions. It appears that the trees are not spatially segregated on the small scale because they use different water sources.

Population structure of common shrubs and trees in Wadi Allaqi Biosphere Reserve, South‐East Egypt

AbstractThe aim of the present study is to analyze the structure of the populations of eight common shrubs and trees in Wadi Allaqi Biosphere Reserve (South‐East Egypt) through demographic survey of the plants. This study is special important for the populations of trees and shrubs that are continuously subjected to overuses such as cutting, overgrazes and other constraints. For achieving this, 112 stands were selected at 19 locations distributes in the upstream, midstream and downstream parts, including the different Wadi tributaries. The locations and stands were selected to present a wide range of physiographic and environmental variation in each tributary. In each location, sampling stands were situated randomly. For each species in each stand, the height and several crown diameters of each individual depending on its uniformity were measured. The size frequency distributions of Acacia ehrenbergiana, Tamarix nilotica, Salsola imbricata and Leptadenia pyrotechnica populations were either inverse‐J‐shaped or positively skewed which may represent rapidly growing populations with high reproductive capacity. Such distributions may also indicate a high juvenile mortality. In these populations, the younger individuals are preponderant than the older ones, which is an indication of strength and success of the species, it is mostly due to victorious germination and survival of seedlings. On contrast, the other four species, Acacia tortilis subsp. raddiana, Calotropis procera, Acacia tortilis subsp. tortilis and Balanites aegyptiaca have a tendency towards the J‐shaped or negatively skewed distribution. Such distributions characterize the declining population of limited regenerations capacity (the population has higher proportions of large individuals than the smaller ones). (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

3-O-trans-Caffeoylisomyricadiol: A New Triterpenoid from Tamarix nilotica Growing in Saudi Arabia

A detailed chemical study of the aerial parts of Tamarix nilotica (Tamaricaceae) from Saudi Arabia led to the isolation of a new pentacyclic triterpenoid, 3-O-trans-caffeoylisomyricadiol, in addition to nine known compounds. The structures of all isolated compounds were unambiguously elucidated by 1D, 2D NMR, and mass spectrometry. In the radical scavenging (DPPH) assay, 3-O-trans-caffeoylisomyricadiol exhibited potent antioxidant activity with an IC50 value of 3.56 microM, while that for quercetin (standard antioxidant) was 5.72 microM.

Antiviral screening of forty-two Egyptian medicinal plants

Aim of the study Egyptian medicinal plants are well known by their diverse uses in traditional folk medicine to cure various ailments including infectious diseases. Forty-two Egyptian medicinal plant species were selected from local market and were subjected to antiviral screening bioassay to investigate and to evaluate their biological activities. Materials and methods Hydro-alcoholic extracts of each species were separately prepared and tested against three viruses: herpes simplex-1 virus (HSV), poliomyelitis-1 virus (POLIO) and vesicular stomatitis virus (VSV). The antiviral activity were determined by means of the end point titration technique (EPTT) that depends on the ability of plant extract dilutions to inhibit the produced cytopathogenic effect (CPE) and expressed as reduction factor (Rf) of the viral titer. Results Achillea fragrantissima, Jasonia montana and Globularia arabica are found to have antiviral activity against POLIO in a concentration dependent manner at complete non-toxic concentration range 10–100 μg/ml (Rf 10 6), 10–100 μg/ml (Rf 10 5) and 50–100 μg/ml (Rf 10 4), respectively while Tanacetum sinaicum are found to have moderate antiviral activity against POLIO at concentration of 50–100 μg/ml (Rf 10 2). Ephedra alata and Moringa peregrina are found to have antiviral activity against HSV (Rf 10 4). Also, the results revealed that Capparis sinaica, Tamarix nilotica and Cyperus rotundus are found to have virucidal effect against HSV. All the forty-two plant species are found to have no reliable antiviral activity against VSV. Conclusion The specific indications claimed by the traditional healers are confirmed by antiviral test.

Monomeric and dimeric hydrolysable tannins of Tamarix nilotica

An ellagitannin monomer, nilotinin M1 ( 1), and three dimers, nilotinins D1 ( 2), D2 ( 3), and D3 ( 4), were isolated from leaves of Tamarix nilotica (Ehrenb.) Bunge. Structures were elucidated based on analysis of spectroscopic data and chemical correlations with known compounds. In addition, six known tannins, hirtellin A ( 5) (dimer), remurin A ( 6), remurin B ( 7), 1,3-di- O-galloyl-4,6- O-( S)-hexahydroxydiphenoyl-β- d-glucose ( 8), gemin D ( 9), and hippomanin A ( 10) (monomers), were isolated for the first time from this plant species. The reported 13C NMR assignments of the dehydrodigalloyl moiety and glucose cores of 5 are revised, and the 13C NMR spectroscopic data for 6 and 7 are also reported for the first time.

A New Ferulic Acid Ester and Other Constituents from Tamarix nilotica Leaves

Phytochemical investigation of the leaves of Tamarix nilotica (Tamaricaceae) has led to isolation of methyl ferulate 3-O-sulphate (1) for the first time from natural sources. In addition, coniferyl alcohol 4-O-sulphate (2), kaempferol 4'-methyl ether (3), tamarixetin (4) and quercetin 3-O-beta-D-glucupyranuronide (5) were isolated from the n-butanol soluble fraction of the extract. The pentacyclic triterpenoid, 3alpha-(3'',4''-dihydroxy-trans-cinnamoyloxy)-D-friedoolean-14-en-28-oic acid (6) was isolated from the n-hexane soluble fraction of the extract. The structures of these compounds were determined on the basis of spectroscopic analyses including 2 dimensional NMR. Compounds 3, 4 and 6 exhibited 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity with IC(50) values of 35.2, 37.0 and 21.2 muM, respectively.

Antioxidant activity and phenol content of plant germplasm originating in the Dead Sea area

The antioxidative properties of forty-seven plant samples originating from the Ein Gedi Botanical Garden were screened. Their antioxidative activity, determined by DPPH radical scavenging assay and expressed as chlorogenic acid equivalent, ranged from 0.3 to 88 mg/g DW. The total phenol content, determined by the Folin-Ciocalteu assay, ranged from 2-82 mg/g DW. A substantial correlation was found between the antioxidative activity and the total phenol content among species. Tamarix nilotica, Suaeda vera, Acacia raddiana, Lawsonia alba, and Grewia villosa contained the highest antioxidative properties. This work consists of the first screening of the antioxidative properties of indigenous plants from the Dead Sea area. The future introduction of these plants as agricultural crops may provide novel natural sources for antioxidants.

Diversity and distribution of medicinal plants in North Sinai, Egypt

The present study aims to assess plant diversity and distribution of medicinal plants in relation to environmental factors at three geomorphological districts (Mediterranean coast, anticlines, and inland) and five main habitats (salt marshes, sand dunes, sand plains, wadis, and gorges) in North Sinai. The results revealed that North Sinai harbors 281 species with high taxonomic diversity (species/genera = 1.49) and high percentage of rare and very rare species (67%). Mediterranean coastal district and anticlines district are more diverse than inland district. Medicinal plants constitute 43% of North Sinai flora. Species richness, Shannon-Weiner H, and Margalef indices measurements indicated that gorges are the most diverse habitat in North Sinai followed by wadis. Plains have intermediate diversity followed by sand dunes. The lowest diversity indices were recorded at salt marshes habitat. Beta diversity measurements, using Wilson and Schmida index (�T), indicated significant changes in floristic compositions between different habitats. The lowest changes were among sand plain, wadi, and gorge habitats. North Sinai habitats support about 100 to 120 medicinal plant associations. The main dominant species include Artemisia monosperma, Arthrocnemum macrostachyum, Lycium shawii, Retama raetam, Stipagrostis scoparia, Tamarix nilotica, Zygophyllum album, and Zygophyllum dumosum. Soil physical properties in addition to soil salinity and topographic variations are the main driving factors controlling the distribution of medicinal plants in North Sinai. About 60% of medicinal plants are threatened due to intensive collection and other human activities. The threatened medicinal plants including Acacia pachyceras, Acacia tortilis, Anastatica hierochuntica, Asclepias sinaica, Capparis spinosa, Chiliadenus montanus, Citrulus colocynthis, Ephedra alata, and Juniperus phoenicea along with their habitats should have the first priority in management and conservation plan of medicinal plants in North Sinai. Public and private involvement in management and utilization of medicinal plants in sustainable way is essential to combat human pressures on these valuable natural resources.

Archaeobotanical studies at Hierakonpolis Locality HK6: The Pre and Early Dynastic elite cemetery

Plant macroremains were separated from samples taken from nine tombs (1-3, 5-7, 9-11) in an elite cemetery at locality HK6 at Hierakonpolis. These tombs are dated to the Predynastic Naqada IIA period and the Early Dynastic Naqada A2-IIIC1 (c. 3800 – 3650 B. C./ 3200 – 3050 B. C.). Human and/or animal skeletal remains were found in all of these tombs. A total of 1984 plant macroremains were identified. This botanical assemblage has been attributed to 23 plant taxa and classified into wild edible fruits, cultivated crops, wild herbs, wood and charcoal. The highest number and percentage of plant remains as well as the greatest number of plant species were recorded from Tombs 1, 3 and 11. The current study shows that the Predynastic inhabitants depended heavily for wood and fuel on native trees, e. g., Acacia nilotica, Ficus sp, Tamarix aphylla, Tamarix nilotica and Ziziphus spina-christi. From the remains it was also possible to reconstruct the characteristic habitats and plant communities that flourished in the general vicinity of the site : 1) a contracted desert vegetation dominated by Acacia nilotica, Balanites aegyptiaca, Capparis decidua, Fagonia bruguieri, Ficus sycomorus and Tamarix aphylla ; 2) a contracted ground water-bound desert vegetation included Acacia nilotica, Desmostachya/ Imperata and Tamarix ; 3) a swampy habitat characterized by stands of Phragmites, Desmostachya/Imperata, Cyperus alopecuroides and Tamarix nilotica. Remains of conifer trees, e. g., Cedrus libani, Cupressus sempervirens, Pinus halepensis, have been found in very small numbers. They may have been imported into Egypt from the Levant.

Vegetation Composition, Biomass Production, Carrying Capacity and Grassland Types in Odolla Area of Shinile Zone, Eastern Ethiopia

A study was conducted to characterize vegetation composition and grassland types as well as to estimate biomass production and carrying capacity of the rangeland in Ordolla areas of Shinile zone, eastern Ethiopia in October 2004. The Ordolla grasslands covered 22,621ha on alluvial plain composed of sand and silt texture and clay in minor cases in small hydromorophic depressions. Seventeen vegetation types are identified in Orodolla areas based on soil types, vegetation structure and density, and drainage pattern described using LANDSAT image and geographical map of the area. The dominant grass species were Cynodon dactylon, Cynodon nlemfuensis, Eragrostis cilianensis, Cenchrus ciliaris, Andropogon greenwayii, Brachiaria leersiodes, Setaria pumila and Sorghum arundinaceum. Acacia tortilis, Acacia nilotica, Acacia mellifera and Acacia seyal were the most dominant shrubs with scattered Caddaba rotundifolia, Caddaba furmisa, Seddera bagshawei, Tamarix nilotica, Dobera glabra and abundant Parthenium hysterophorus, Cissus rotundifolia and C. quadrangularis . The grass biomass estimated in enclosed site near Ordolla village was 4.5 t DM/ha/yr and the total grass biomass produced in Ordolla rangeland was estimated around 27 534 t DM/year. The theoretical, dry and wet seasons carrying capacities were 0.16, 0.06 and 0.09 TLU/ha, respectively. There were good grazing lands in hydromorphic depression and well drained facets in Ordolla areas but the palatable grasses, trees and shrubs are decreasing due to overgrazing, runoff and drought and replaced by Parthenium, Calotropis, Solanum and Xanthium species, which are invader category of the plant community, indicating overgrazing and rangeland degradation. Keywords : Biomass Production; Carrying Capacity; Grassland Types; Grazing Lands; Vegetation Composition East African Journal of Sciences Vol. 1 (2) 2007: pp. 148-159

Late Holocene upper bounds of flood magnitudes and twentieth century large floods in the ungauged, hyperarid alluvial Nahal Arava, Israel

The impact of large twentieth century floods on the riparian vegetation and channel morphology of the relatively wide anabranching and braided Nahal Arava, southern Israel, was documented as part of developing tools to (a) identify recent large floods, (b) determine these flood's respective magnitudes in alluvial ungauged streams, and (c) determine long-term upper bounds to flood stages and magnitudes. Along most of its course Nahal Paran, a major tributary that impacts the morphology, floods and sediments of Nahal Arava at the study reach, is a coarse-gravel, braided ephemeral stream. Downstream of the Arava–Paran confluence, aeolian and fluvial sand delivered from eastern Arava valley alters the channel morphology. The sand has accreted up to 2.5 m above the distinct current channels, facilitating the recording of large floods. This sand enhances the establishment of denser riparian vegetation (mainly Tamarix nilotica and Haloxylon persicum) that interacts with floods and affects stream morphology. A temporal association was found between specific floods recorded upstream and tree-ring ages of re-growth of flood-damaged tamarix trees (‘Sigafoos trees’) in the past 30 years. This association can be utilized for developing a twentieth century flood chronology in hyperarid ungauged basins in the region. The minimum magnitude of the largest flood that covered the entire channel width, estimated from flood deposits, is approximately 1700–1800 m 3s − 1 . This is a larger magnitude than the largest gauged flood of 1150 m 3s − 1 that occurred in 1970 about 30 km upstream in Nahal Paran. Our estimation agrees with flood magnitude estimated from the regional envelope curve of the largest floods. Based on Holocene alluvial stratigraphy and OSL dating in the study reach we also conclude that flood stages did not reach the late Holocene (∼ 2.2 ka) surface and therefore we estimate a non-exceedance upper bound of ∼ 2000 m 3s − 1 flood magnitudes for Nahal Arava during that interval. This study indicates that in unfavorable areas the combination of hydrology, fluvial morphology and botanic evidence can increase our understanding of ungauged basins and give information crucial for hydrology planning.

Sugar questing mosquitoes in arid areas gather on scarce blossoms that can be used for control

Floral nectar sugars provide energy for mosquito activities. We presumed that scarce flowering trees in arid areas are attractive, central sugar sources and tested the assumption in the southern desert of Israel. In traps baited with flowers of Acacia raddiana, Tamarix nilotica or Ochradenus baccatus the catch of Anopheles sergentii was ∼35–75 times greater than with baits of flowerless branches. At a small isolated oasis, a spray of sugar and food-dye solution on the few flowering A. raddiana trees dye-labelled 80–90% of A. sergentii. At a similar oasis, this spray with addition of oral insecticide, virtually eliminated the local mosquitoes.

Plant succession on abandoned fields after 25 years of shifting cultivation in Assuit, Egypt

The purpose of this study is to introduce the general trends in the various ecological characteristics of secondary succession occurring in abandoned fields after shifting cultivation in the Nile valley at Assuit, Egypt. The study examined, evaluated, and discussed the succession of the secondary growth of the plant communities in the abandoned fields inside Al-Azhar University campus at Assuit (constructed 25 years ago). It assessed the relationships between the environmental gradients, floristic composition, species richness, disturbance level, and size structures of woody plants. Seventy-eight species were recorded (46 annuals and 32 perennials). Four vegetation types were recognized after the application of TWINSPAN, DCA, and canonical correspondence analysis techniques and named after their dominant species as follows: Dichanthium annulatum–Pulicaria crispa, Pluchea dioscorides, Desmostachya bipinnata–Tamarix nilotica, and Desmostachya bipinnata–Ziziphus spina-christi. The notable environmental variables affecting the distribution of vegetation types in the study area were moisture content, disturbance level of stands, percentages of silt, clay, and K.

Vegetation clustering along irrigation and drainage canal banks in an extreme arid area in Upper Egyp

Vegetation analysis of the irrigation and drainage canals of the Aswan Province indicates the dominance of Pluchea dioscoridis, Phragmites australis, Cynodon dactylon, Imperata cylindrica, Alhagi graecorum, Sonchus oleraceus, Ceratophyllum demersum and Polypogon monspeliensis. The classification of stands according to the TWINSPAN technique resulted in seven vegetation clusters at level three. The seven clusters of level three are named after the dominant species as follows: (I) Sesbania sesban, (II) Chenopodium murale-Digitaria sanguinalis-Echinochloa colona, (III) Cyperus alopecuroides, (IV) Cynodon dactylon, (V) Phoenix dactylifera-Oxystelma alpini-Hyphaene thebiaca, (VI) Tamarix nilotica and (VII) Anagallis arvensis-Cuscuta pedicellata-Convolvulus arvensis-Chenopodium album. Among the estimated soil variables in the present study, sand, silt, Mg+2 and organic matter are important in characterising the vegetation clusters.

Assessment of metals in soil extracts and their uptake and movement within Tamarix nilotica at Lake Nasser banks, Egypt

This study aims to determine heavy-metal levels in soil from the banks of Lake Nasser, the ability of Tamarix nilotica to accumulate such metals from soil and hence its potential for phytoextraction. Soil and Tamarix samples were collected from the banks of four bights around Lake Nasser and analysed for Fe, Mn, Ca, Mg, Cr, Cu, Ni, Zn, Cd and Pb by atomic absorption spectrometry, whereas Na and K were measured by atomic emission spectrophotometry. Three different methods of extraction were used for the soil samples. Lead, copper and zinc were equally distributed between the exchangeable phase and Fe/Mn oxide-bound form, while other measured metals were mainly present in the Fe/Mn oxide fraction. With the exception of iron, all metals studied showed total concentrations within the geochemical background values. T. nilotica exhibited elevated concentrations of Na (36.2–48.5 mg g−1) and K (2.74–4.33 mg g−1) in stems, and relatively high concentrations of Pb, Cd and Co (0.39–1.03 µg g−1, 0.24–1.3 µg g−1 and 1.94–5.3 µg g−1, respectively) are found in plant leaves. Bioaccumulation factors of Na and K (9.3 and 12.63, respectively) were high in T. nilotica stems. While the bioaccumulation of Pb, Cd, Co and Ni (2870.1, 2035.4, 10.5 and 5313.2, respectively) was high in plant leaves, Fe, Mn, Ca and Mg were accumulated relatively equally in plant stems and leaves. T. nilotica was found to secrete high amounts of Na, Ca and K, in addition to small amounts of all accumulated metals except Cd and Cu. These secreted metals appeared as salt crystals (67.5% Na; 25.8% Ca; 5% Mg; 1.5% K and 0.16% trace and minor elements) on the plant surface. The concentrations of all the metals studied in T. nilotica were higher than in the salt crystals. Statistical analysis of the database suggests bioaccumulation of these metals from soil to T. nilotica. This reflects the importance of using T. nilotica as a model in the phytoremediation process as an established environmental clean-up technology.

Soil–vegetation relationships in a coastal desert plain of southern Sinai, Egypt

The present study provides an analysis of soil, vegetation types as well as structure and species distribution in 19 sites in El-Qaa plain along the Gulf of Suez (south Sinai, Egypt), and focuses on the environmental factors that control the species distribution. A total of 203 species belonging to 39 families of the vascular plants are recorded. Asteraceae, Fabaceae, Chenopodiaceae and Poaceae are the largest families. Grasses constitute only 9% of the recorded species, while the woody perennials (shrubs and sub-shrubs) are highly dominated (46%). Therophytes and chamaephytes are the most frequent, denoting a typical desert life-form spectrum. Floristic composition in the different geomorphologic landscape units showed differences in species richness. The highest mean species richness of 19.7±1.7 is recorded in the wadi channels. The lowest species richness values are recorded in the coastal shore and playas (6.0±1.4) and in the alluvial fans (mean of 8.4±1.6 species). Chorological analysis revealed that 46% of the studied species are uniregional, being native to the Saharo-Arabian region. On the other hand, about 50% of the recorded species are biregional and pluriregional, extending their distribution all over the Saharo-Arabian, Sudano-Zambezian, Irano-Turanian and Mediterranean regions. Classification of the vegetation is analysed using two-way indicator species analysis (TWINSPAN) techniques resulted in the recognition of five vegetation groups, each of definite vegetation and soil characters, and could be linked to a specific geomorphologic unit. Capparis spinosa var. spinosa occupied the terraces, Cornulaca monacantha, Convolvulus lanatus and Deverra tortuosa inhabited the alluvial plains, Launaea nudicaulis and Artemisia judaica characterized the wadi channels, Acacia tortilis subsp. raddiana and Leptadenia pyrotechnica characterized the alluvial fans and Tamarix nilotica, Zygophyllum album and Nitraria retusa on the playas and the coastal shore. Ordination techniques as detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA) are used to examine the relationship between the vegetation and studied soil parameters. Nine soil variables are included: electrical conductivity, pH, calcium carbonate, gypsum, organic matter, gravel, fine soil fractions and soil saturation percentage. Analysis with DCA gave results similar to CCA, suggesting that there is a relatively high correspondence between vegetation and soil factors. DCA axis 1 showed significant positive correlation with CaCO 3, pH, soil saturation and organic matter, and interpreted as a calcium carbonate—soil saturation gradient. DCA axis 2 showed significant correlation with pH, gypsum and electric conductivity, and interpreted as an electric conductivity—gypsum gradient. Application of CCA indicated that soil surface sediment, CaCO 3, soil saturation, pH and organic matter are the main operating edaphic gradients in the area. These gradients are related closely to the first three canonical axes, and accounted for 67% of the species–environment relationship among the sites.

Phytosociology and size structure of Nitraria retusa along the Egyptian Red Sea coast

The present study aims at analyzing the phytosociological behavior and size structure of Nitraria retusa (Forssk.) Asch shrub along the Egyptian Red Sea coast in relation to the prevailing environmental gradients. The application of TWINSPAN and DCA multivariate techniques led to identifying five vegetation groups associated with the distribution of this plant in this region. These groups are named after their characteristic species as follows: Typha domingensis, Zygophyllum coccineum – Zilla spinosa, Tamarix nilotica– Zilla spinosa, Nitraria retusa– Zygophyllum album and Nitraria retusa. The two groups of Nitraria retusa had, on average, the lowest species diversity and their stands had the highest soil salinity and clay contents. In general, the population of this plant is characterized by relative preponderance of the small-sized individuals (i.e. juveniles) particularly in the sites of medium positions along the prevailing salinity gradient. On the other hand, the juveniles are highly stressed in the stands of hypersalinity. The negative relationship between the density and size of this plant suggests that its size is density-dependent.