Aspects of vegetation and soil relationships around athalassohalinelakesof Wadi El-Natrun, Western...

BIOLOGY ORIGINAL ARTICLE

Journal of Biology and Earth Sciences, 201 4, Vol 4, Issue 1 , B21 -B35

Aspects of vegetation and soil relationshipsaround athalassohaline lakes of Wadi El-Natrun,

Western Desert, Egypt

Monier Abd El Ghani, Rim Hamdy*, Azza Hamed

The Herbarium, Faculty of Science, Cairo University, Giza 12613, Egypt

ABSTRACT

The relationship between soil parameters and vegetation around the inland saline lakes of Wadi El-

Natrun in the Western D esert of Egypt was studied. Twenty-five species in 22 stands constituted the

floristic composition included one tree, 3 annuals and 21 perennial herbs. The saline feature of

this habitat enabled some salt tolerant species to grow and flourish. Four species (Juncus acutus L. ,

J. rigidus Desf. , Cyperus laevigatus L. var. laevigatus and Phragmites australis (Cav.) Trin. ex Steud.

subsp. australis) were constantly recorded around the 7 studied lakes which exhibited wide ecologicaland sociological ranges, while 8 species were confined to only one lake (narrowest sociological range).

Based on their frequency values, classification of the recorded resulted in 5 vegetation groups. Each of

these groups was linked to one or more of the soil factors which determines its distribution. Application

of Redundancy Analysis (RDA) indicated that CaCO3, Ca+2, SO4

-2, NO3-, K+ and Cl- were the most

important soil variables affected the vegetation around the studied lakes. I t is recommended that

conservation measures should be taken to protect the remaining populations of Typha elephantinathroughout Wadi El-Natrun which represents its type locality from extinction.

Key words: Egypt; halophytes; Inland salt marshes; Redundancy analysis; Saline lakes; Salinity; Soil-

environment relations.

J Biol Earth Sci 201 4; 4(1 ): B21 -B35

Original Submission: 1 1 November 201 3; Revised Submission: 1 0 January 201 4; Accepted: 1 4 January 201 4

Copyright © 201 4 Author(s). Journal of Biology and Earth Sciences © 201 4 Tomasz M. Karpiński. This is an open-access article

distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction

in any medium, provided the original work is properly cited.

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B21

Journal of Biologyand Earth Sciences

TMKARPIŃSKIPUBLISHER

ISSN: 2084-3577

* Corresponding author:

Rim Hamdy

E-mail : [email protected]

INTRODUCTION

Athalassohaline lakes are inland saline aquatic

environments with ionic proportions quite different

from the dissolved salts in seawater. They are tem-

porary bodies of water with sal inities >3gl-1 and lac-

king any connection to the marine environment [1 ].

Salt lakes are confined to dry regions of the world

where evaporation exceeds precipitation and where

they are often more abundant than fresh waters.

Saline lands are widely distributed globally and

make up about 1 0% of the Earth’s terrestrial surface

[2]. Inland saline lakes have received increased at-

tention in recent years due to their sensitivity to cl i-

matic change. Climatic conditions must reach a

certain degree of aridity effectively to remove water

by evaporation or freeze drying and so produce

progressively concentrated brine. Geochemical and

hydrological features are largely responsible for

control l ing the concentration and composition of the

resulting brine [3, 4]. Changes in evaporation and

precipitation can affect the physical and chemical

conditions in such lakes [5-9].

In Egypt, certain areas are lower than the sea

level and constitute depressions in the desert west

of Nile Delta. They include some water bodies cha-

racterized by high salinity and considered as a va-

luable economic resource that can be developed for

better exploitation. One of these depressions is

Wadi El-Natrun (23 m below sea level) which consi-

dered among the important depressions in the We-

stern Desert for land reclamation and uti l ization.

The presence of irrigation water as underground

water of suitable quality, the existence of natural

fresh water springs and the availabi l ity of some mo-

isture contained in the sandy layers above the shal-

low water table southwest of the depression are the

main reasons for the importance of Wadi El-Natrun

region [1 0].

The inland saltmarshes of the Western Desert of

Egypt are found in the form of Sabkhas around the

lakes, springs and wells of the oases, e.g. Siwa,

Dakhla, Kurkur, Dungul, etc. and the depressions,

e.g. Qattara, Wadi El-Natrun, El-Fayum, etc. Being

lower in level than the surrounding territories, the

inland saltmarshes are characterized by a shallow

underground water table. In certain instances, the

underground water is exposed forming lakes of

brackish or saline water [11 ]. The formation of this

sal ine is due to the uncontrol led spil l ing of water

and flooding of the plains, or to the water table

El Ghani et al. Vegetation and soil relationships around athalassohaline lakes of Wadi El-Natrun, Egypt

Journal of Biology and Earth Sciences, 201 4, Vol 4, Issue 1 , B21 -B35 B22

which is being close to the ground [1 2]. The vege-

tation around these lakes has a patchy structure:

different patches contain different species (or so-

metimes one species) and even different growth

forms [1 3].

Wadi El-Natrun is characterized by small di-

sconnected lakes in its bottom, al igned with its ge-

neral axis in the north-west direction except Lake

Al-Gaar [1 4]. These lakes receive a limited supply

of groundwater which seeps into the depression.

Since the evaporation rate is high and the lakes l ie

in closed basins without outlet, the water in the la-

kes has a high salt concentration and are suscepti-

ble to marked fluctuations in level and salinity.

Although different colourations due to microbial po-

pulations are indicated by some of the lakes names

(Hamra = red, Khadra = green, Bida = white), the

colouration of the lakes is not constant, but is sub-

ject to seasonal changes. There is a discrepancy

regarding the number of lakes in Wadi El-Natrun,

which ranged between two to sixteen [1 5]. Yet, Za-

hran and Wil l is [1 4] reported the presence of 8 prin-

cipal lakes for a distance of about 30 km; perma-

nent water in al l or some of their parts; from south

to north: Fasida, Um Risha, Al-Razoniya, Abu-Gu-

bara, Hamra, El-Zugm, Al-Bida, Khadra and Al-

Gaar, noting that Abu Gubara and Hamra form one

lake in the summer. The Natrun occurs in solution in

the lakes, forms a crust around the edges of the la-

kes and in deposits on their bottom. Natrun deposits

have long been known and were used by the an-

cient Egyptians in the manufacture of glass, rem-

nants of which are sti l l found in the southern part of

the depression.

Compared to studies of coastal marshes, l ittle

attention has been paid to inland saline landscapes

[1 6, 1 7]. The earl iest account of the vegetation of

the salines in Wadi El-Natrun was that of Stocker

[1 8]. The plant growth was studied around some re-

presentative lakes, providing the actual distribution

of plants around the lakes using aerial photos of two

lakes [1 9]. The phytosociology of the wetland vege-

tation revealed the presence of three distinct com-

munities in addition to two species of common

occurrence with no sociological affi l iation (Cyperuslaevigatus and Juncus acutus) [20]. Some studies

were undertaken; focused on the vegetation around

the inland saline lakes of Wadi El-Natrun [21 , 22]

Typha elephantina Roxb. and Cyperus papyrus at

the shore of Um Risha Lake associated with some

water loving plants has been reported [23, 24]. The

human impact revealed that Wadi El-Natrun repre-

sents a raw grazing ecosystem and ecological ly

fragile with unique features and resources [1 0]. In

addition some studies recorded natural and cultiva-

ted land cover types in the area between 1 997 and

2000, as well environmental indices from DEM, cl i-

mate atlas data, land-use observation and soil

sampling were recorded [25, 26].

In a previous work [27], the spatial distribution of

the flora of Wadi El-Natrun within its various habi-

tats, and its changes throughout the last 7 decades

was investigated. This study aims to recognize and

analyze the floristic diversity and variations in the

vegetation around the inland saline lakes of Wadi

El-Natrun, and to assess the environmental factors

that affect their species distribution.

The study area

Wadi El-Natrun is a narrow depression located in

the west of the Nile Delta, approximately 11 0 km

northwest of Cairo between longitudes 30° 80' 20"

and 30° 82' 90"E and latitudes 30° 81 ' 60" and 30°

83' 20"N (Figure 1 ). The total area of Wadi El-Na-

trun is approximately 281 .7 km2, extending in a

NW–SE direction. The origin of the underground

water in Wadi El-Natrun is seepage from the Nile



stream, because of its proximity and low level. A

series of isolated saline lakes occupy the axis of the

depression. The water level in the lakes fluctuates

seasonally along the year rising up in winter and

fal l ing down in summer but never get dry, and ran-

ges from 1 6 m in Zagig Lake to 23 m in Al-Gaar and

Fasida Lakes (Figure 1 ). Wadi El-Natrun area is re-

garded as an extremely arid region where mean

annual rainfal l , evaporation, and temperature are

41 .4 mm, 11 4.3 mm, and 21 °C, respectively (Egyp-

tian Meteorological Authority, 2006).

The water enters the lakes in two ways, as

springs in some of the lakes and as very small stre-

ams or trickles found on the sloping edges of the

lakes which find their way directly to the lakes. The

origin of the water entering the depression has been

discussed [28-31 ].

Also the geology of Wadi El Natrun has been

studied by many authors [29, 32, 33]. In general,

the area is covered by Quaternary lake deposits

and old al luvial deposits of sand and gravel laid

when the sea encroach the area and the Nile flowed

through it. The lake deposits and alluvium are un-

derlain by l imestone of Miocene, Oligocene and

Pliocene ages.

The dominating land-use practice is grazing and

Fig. 1. Schematic map ofWadi El-Natrun, showing the position of the studied lakes.



using the electric conductivity. Sulphates were de-

termined gravimetrical ly and the soluble sulfates

precipitated as barium sulphate. Sodium and po-

tassium ions were determined using a flame photo-

meter. Calcium and magnesium ions were deter-

mined by titration with EDTA. The estimation of

chlorides in the soil extract was carried out by titra-

tion methods against si lver nitrate (AgNO3) using

potassium chromate (K2Cr2O7) as an indicator. So-

luble nitrogen including ammonia and nitrate in soil

was determined using Kjeldahl method.

Data analysis

A floristic data matrix (25 species × 22 stands)

was subjected to classification by cluster analysis of

the computer program CAP (Community Analysis

Package) version 1 .2 [40] using the minimum va-

riance as an algorithm, and a dendrogram had been

presented. The vegetation groups produced from

cluster analysis was then subjected to ANOVA

(One-Way Analysis of Variance) based on soil va-

riables to find out significant variations among gro-

ups. The default option of the computer program

CANOCO software version 4.5 for window was

used for al l ordinations [41 ].

Indirect gradient analysis was performed using

Principal Components Analysis (PCA), and the di-

rect gradient analysis by Redundancy Analysis

(RDA). Seventeen environmental variables were in-

cluded in RDA: pH, electric conductivity (EC), nitra-

tes (NO3-), calcium carbonate (CaCO3), sodium

(Na+), potassium (K+), calcium (Ca+2), magnesium

(Mg+2) , chloride (Cl-), sulphates (SO4-2), ammonium

(NH4+), bicarbonates (HCO3

-), organic matter (OM),

fine sand, coarse sand, si lt and clay. Due to high in-

flation factors, electric conductivity, fine sand, si lt

and clay were excluded from the analysis. Al l data

variables were assessed for normality (SPSS for

windows version 1 7.0) prior to the RDA analysis,

and appropriate transformations were performed

when necessary to improve normality according to

Zar [42]. The relationships between vegetation gra-

dients and the studied environmental variables can

be indicated on the ordination diagram produced by

RDA biplot. The exploratory RDA was evaluated

using interest correlations and RDA axes were eva-

luated statistical ly by means of a Monte Carlo per-

mutation test (499 permutations) [43].

Mapping the vegetation changes around some

selected saline lakes (wet pastures) were based on

the estimation of distances between different belts

cutting. Wadi El-Natrun is a good source of forage,

based on the palatable salt marsh vegetation cover

(77%), and these resources are currently used su-

stainable by the local inhabitants. However, areas of

natural forage that serve as rangelands are subjec-

ted to several types of degradation, overgrazing,

removal for agriculture and fragmentation by roads

network and urban sprawl [1 0]. The wadi can be

best described as a raw grazing ecosystem for ra-

ising l ivestock (such as: goats, sheep, cows and

camels) noting that each type of l ivestock has a

grazing behaviour different from the other. Expan-

ding human demand and economic activities are

putting constantly increasing pressure on land and

other particular natural resources in the area cre-

ating suboptimal use and even destruction.

MATERIALS AND METHODS

Data collection

Between 2008 and 2011 , 22 randomly chosen

stands, with certain degree of homogeneity, were

permanently visited to study the vegetation and flo-

ristic composition around the studied 7 lakes (Figu-

re 1 ). The number of studied stands around each

lake varies and depends on the vegetation hetero-

geneity and species dominance. Due to inaccessi-

bi l ity to Lake Fasida, 2 stands were available.

Within each stand, species present were recorded,

and its frequency (F%) was calculated. Taxonomic

nomenclature fol lows Täckholm and updated by

Boulos [34-38].

Soil samples were collected from each stand at

three depths: 0-1 0, 1 0-25 and 25-50 cm. The sam-

ples were pooled together forming one composite

sample, spread over sheets of paper and left to dry

in the air. Dried soils were passed through 2 mm

sieve to remove gravel and debris, and then packed

in paper bags for physical and chemical analysis.

Soil textural analysis was determined by the hydro-

meter analysis method, and the results were used

to calculate the percentages of sand, si lt and clay).

Organic matter was determined by drying and igni-

tion at 600°C for 3 hours, and CaCO3 content was

determined volumetrical ly using Coll in's calcimeter

apparatus. Soluble bicarbonates were determined

[39]. Soil extracts were prepared and then used in

order to determine chemical analysis. Soil reaction

(pH) was measured in soil water extract (1 :2.5)

using a Beckman pH meter. The electrical conducti-

vity (EC) was measured in soil water extract (1 :5)



(zones) by using a meter tape and walking.

RESULTS

Floristic variations

Table 1 demonstrated the floristic analysis of the

25 species of vascular plants from 22 stands asso-

ciated with the studied seven lakes in the study

area, and distributed as fol lows: one tree, 3 annuals

and 21 perennial herbs. The latter included Juncusacutus, J. rigidus and Cyperus laevigatus var. laevigatus as the common species. I t is obvious that thedesert outskirt surrounding the lakes favor the

growth of some perennials such as Phragmites australis, Imperata cylindrica (L.) Rauesch. , Alhagigraecorum Boiss. and Desmostachya bipinnata (L.)

Stapf. Furthermore, the saline feature of this habitat

enabled some salt tolerant species to grow and flo-

urish such as Typha domingensis (Pers.) Poier. ex

Steud. , Typha elephantina and Spergularia marina(L.) Bessler. Among the less common species Sonchus maritimus, Panicum turgidum Forssk. and Cynodon dactylon L. were noticed. Six species were

occasionally recorded (recorded in one stand)

and/or very modestly represented. These included

xerophytic species such as Sporobolus spicatus(Vahl) Kunth and Centropodia forskaolii (Vahl) Copeand water loving species such as Zannichellia palustris L. , Berula erecta (Koch ex Rchb.) Rchb.f. and

Samolus valerandi L.The performance of species within the different

lakes revealed that four species (Juncus acutus, J.

rigidus, Cyperus laevigatus var. laevigatus and

Phragmites australis subsp. australis) were con-

stantly recorded around the 7 lakes which exhibited

wide ecological and sociological ranges. On the

other hand, 8 species were confined to only one

lake (narrowest sociological range) where Panicumturgidum and Centropodia forskaolii were confinedto Al-Gaar Lake, Samolus valerandi and Berulaerecta to Hamra Lake, Sporobolus spicatus and Digitaria sanguinalis (L.) Scop. to Um Risha Lake,

Solanum elaeagnifolium to El-zagig Lake, and the

water-loving plant Zannichellia palustris to Al-Bida

Lake (Table 1 ).

Classification of the vegetation and soil charac-

teristics around studied lakes

Based on their frequency values, classification of

the recorded 25 species from 22 stands around the

7 lakes resulted in 5 vegetation groups (A-E), and

named after the dominant and highly frequent spe-

cies. Based on the cluster analysis outcome, the

dendrogram in Figure 2 was elaborated, and the

characteristic species of each group was displayed

in Table 2. Clearly, pH (p = 0.006), percentages of

coarse sand (p = 0.020), and silt (p = 0.045), sho-

wed significant differences between the identified

vegetation groups (Table 3).

Group A: Juncus rigidusDesmostachya bipinnataTypha elephantinaArundo donax L. group

It is characterized by the dominance of Juncusrigidus and Desmostachya bipinnata together with

Fig. 2. Cluster analysis of the 22 stands around the studied 7 lakes of Wadi El-Natrun. (A – E) are the

5 separated vegetation groups.



Table 1. Floristic composition of the selected 22 stands of the lakes habitat; + = presence; - = absence.



Table 2. Overall composition and distribution of the associated species

within the five vegetation groups in Lakes habitat of Wadi El-Natrun.

Figures in bold are the leading dominant species with higher presence

percentages (P%).

Typha elephantina and Arundo donax in stands 11 5and 11 6 which located in Al-Gaar and Al-Bida La-

kes. Among the associated species; Tamarix nilotica, Alhagi graecorum, Panicum turgidum, Cyperuslaevigatus var. laevigatus and Imperata cylindricacan be enumerated. Centropodia forskaolii showeda certain degree of fidel ity to this group. Organic

matter, fine sand, coarse sand, pH and bicarbonate

attained their highest values in this group (Table 3).

Group B: Typha domingensis groupThis group (1 2 species) characterized the three

stands (111 , 1 1 8 and 1 20) from Um Risha, El–Ra-

zoniya and El-Zagig Lakes with high soil contents of

sulphates, Ca+2, Mg+2, Na+, K+ and Cl- ions. Typhadomingensis was the characteristic species, while

the common associated species included Alhagigraecorum, Juncus rigidus, Juncus acutus, Cyperuslaevigatus var. laevigatus, Phragmites australis



Table 3. Mean values, standard deviations (±SD) and ANOVA F values of the soil variables, species richness (SR)

and Shannon's index (H’) in the stands representing the five vegetation groups obtained by cluster analysis in the lakes

(* = P ≤ 0.05 and **= P ≤ 0.01 ). CS = Coarse Sand; EC = Electric Conductivity; FS = Fine Sand; OM = Organic Matter.

subsp. australis, Desmostachya bipinnata, Arundodonax and Cynodon dactylon were recorded. Digitaria sanguinalis and Senecio glaucus L. subsp. coronopifolius (Maire) C. Alexander were confined to

this group. I t is interested to note the complete ab-

sence of Typha elephantina.Group C: Juncus acutusCyperus laevigatus var.

laevigatus group

This group characterized by Juncus acutus andCyperus laevigatus var. laevigatus in 7 stands fromfive lakes (Al-Bida, El–Razoniya, Al-Gaar, Fasida

and Um Risha) with soil rich in NH4+ and clay con-

tents (Table 3). Juncus rigidus and Alhagi graecorum were the co-dominant species of this group

(F=85.7% and 71 .4%, respectively). Among the as-

sociated species; Tamarix nilotica, Phragmites australis subsp. australis and Aeluropus littoralis

(Gouan) Parl. were recorded. The complete absen-

ce of Typha elephantina, Arundo donax, Panicumturgidum, Imperata cylindrica, Centropodia forskaolii, Cynodon dactylon, Senecio glaucus subsp. coronopifolius and Digitaria sanguinalis can also be

noticed.

Group D: Juncus acutusImperata cylindrica group

This is the most diversified (1 5 species) among

the recognized groups. I t is characterized by the

dominance of Juncus acutus and Imperata cylindrica in 4 stands (1 03, 1 1 7, 1 1 0 and 1 22) on soil rich inNO3

- content (49.73 ± 3.08). The dominant species

showed their highest abundance in this group, to-

gether with Cyperus laevigatus var. laevigatus and

Phragmites australis subsp. australis. Sporadic

species were Typha domingensis, Desmostachyabipinnata, Sonchus maritimus and Cynodon dacty



Fig. 3. Principal Component Analysis (PCA) scatter plotfor the 22 stands around the lakes habitat in Wadi El-

Natrun along the first two axes, with the vegetation

groups (A-E) superimposed.

lon. Five species showed a degree of consistency tothis group: Zannichellia palustris, Sporobolus spicatus, Samolus valerandi, Berula erecta and Solanumeleagnifolium Cav.

Group E: Juncus rigidusJuncus acutus groupThis group comprised 1 3 species from 6 stands

inhabiting soil rich in CaCO3 and silt content (Table

3), where Juncus rigidus and J. acutus were the do-minant species (Table 2). Typha domingensis was

the most common species. Associated species inc-

luded Imperata cylindrica and Typha elephantina.Occasionally recorded species (present in only one

stand; P=1 6.6%) was Aeluropus littoralis. Notably,Arundo donax, Centropodia forskaolii, Desmostachya bipinnata, Tamarix nilotica (Ehrenb.) Bunge,

Alhagi graecorum, Cynodon dactylon, Senecio glaucus subsp. coronopifolius, Digitaria sanguinalis,Zannichellia palustris, Sporobolus spicatus, Samolusvalerandi, Berula erecta and Solanum eleagnifolium.Ordination of stands

Principal Components Analysis (PCA) scatter plot

showed the segregation of the 5 groups along the

first 2 axes (Figure 3). Stands of group (A) occupied

the highest position in the ordination plan. This gro-

up was dominated with Juncus rigidus, Desmostachya bipinnata, Typha elephantina and Arundodonax. Stands of the vegetation groups (D) and (E)which dominated with Juncus acutus, J. rigidus andImperata cylindrica occupied the positive side of

axis 1 , while stands of the vegetation groups (B)

and (C) that dominated with Typha domingensis,Juncus acutus and Cyperus laevigatus var. laevigatus occupied the other negative end.

Soil-vegetation relationships

The relationships between the results of vegeta-

tion and soil analyses using Redundancy Analysis

(RDA) with the 5 vegetation groups (A-E) were

shown in Figure 4. During this analysis, five varia-

bles showed high inflation values (Ec, Na+, fine

sand, si lt and clay), so they are discarded from the

analysis. I t can be noted that stands of group C

were affected by ammonia; stands of groups D and

E were correlated with pH and CaCO3 while those

of group B were affected by SO4-2 and Ca+2. Two

stands of group A exhibited high correlation to or-

ganic matter and coarse sand. In addition to other

stands of groups C and E were correlated with

HCO3-.

The successive decrease of eigenvalues of the

Fig. 4. The RDA ordination biplot of the first 2 axes

showing the distribution of 22 stands around the lakes,

with the examined soil variables.



four RDA axes (0.1 40, 0.1 1 5, 0.090 and 0.077 for

axes 1 , 2, 3 and 4, respectively) that i l lustrated in

Table 4 suggesting a well structured data set. The

species-environment correlations were high for the

four axes, explaining 67.5% of the cumulative va-

riance. These results suggested an association be-

tween vegetation and the measured soil variables

presented in the biplot. The inter-set correlations

resulted from RDA of the examined soil variables

were shown in Table 4. Axis 1 was positively corre-

lated with CaCO3, while negatively correlated with

Ca+2, SO4-2 and NO3

-. The RDA axis 1 can be inter-

preted as CaCO3-NO3- gradient. Axis 2 was positi-

vely correlated with coarse sand, and negatively

correlated with CaCO3, Ca+2, K+, Cl-, SO4

-2, and

NO3-. The RDA axis 2 can be interpreted as coarse

sand-Cl- gradient. A test for significance with an

unrestricted Monte Carlo permutation test found the

F-ratio for the eigenvalue of RDA axis 1 and the

trace statistics to be significant (p=0.03), indicating

that the observed patterns did not arise by chance.

The ordination biplot diagram (Figure 4) was similar

to the pattern of ordination obtained from the flori-

stic PCA (Figure 3), with most of the sites remaining

in their respective cluster group.

Mapping of vegetation around lakes

Figures 5 and 6 are sketch drawings exemplify

zonation of vegetation around two saline lakes (wet

Table 4. Redundancy analysis results showing the inter-set correlations of the soilvariables, together with eigenvalues and species-environment correlation of the

studied lakes. For abbreviations and units, see Table 2. *= P ≤ 0.05.

Fig. 6. Vegetation mapping around El-Hamara Lake

showing the distribution of the dominant species.

Fig. 5. Vegetation mapping around El-Hamara Lake

showing the distribution of the dominant species.



ties. This difference may be related to the method of

vegetation analysis that fol lowed in each study. The

significant role of abiotic factors that control l ing the

distribution of halophytes in sal ine habitats was stu-

died [47-49]. Redundancy analysis (RDA) of the

present data set demonstrated the effect of edaphic

factors on the spatial distribution of plant communi-

ties around the lakes. CaCO3, Ca+2, K+, SO4

-2, NO3-

and coarse sand were of significant variations

(p<0.05) among the 5 vegetation groups (communi-

ties). RDA axis 1 can be inferred as CaCO3-NO3-

gradient, while RDA axis 2 showed a gradient of

coarse sand and Cl- gradient. These results were in

consistent with those of El-Sawaf and Emad El-

Deen [20]. On the contrary, around the inland sali-

ne lakes in Dakhla and Siwa Oases of the western

Desert [50], 1 2 halophytic plant communities l inked

to two main habitats (wet-moist and dry-mesic)

were identified, with few communities were in com-

mon with Wadi El-Natrun salines. Alhagi graecorum,Tamarix nilotica, Cressa cretica, Juncus rigidus andPhragmites australis were the most common in thetwo oases. Whereas communities of Cyperus laevigatus, Suaeda aegyptiaca, Suaeda vermiculata,Typha domingensis and Aeluropus lagopoides wererecorded from Dakhla Oasis, Cladium mariscus andArthrocnemum macrostachyum communities were

recorded from Siwa Oasis. The most important

edaphic variables affecting the distribution and

structure of the plant communities were: sal inity,

moisture content and fine fractions, yet CaCO3 con-

tent seem to be more effective in the Dakhla Oasis.

When studying the saltmarsh communities of the

western Mediterranean coastal desert [51 ], they

pointed out that sal inity; concentration of different

ions and the periodical variation in the water table

determine the distribution of species and the diffe-

rences between communities. They also conclude

that the saltmarsh vegetation in this part of the co-

untry represents a transition from the western com-

munities in North Africa and those characteristic of

the Eastern Mediterranean region.

From a phytosociological point of view, the pure

community of Typha elephantina existed under the

conditions of deep fresh water (total soluble salts c.

2000 ppm) around Al-Gaar Lake. Typha domingensis replaced T. elephantina when the total soluble

salts reached 4000 ppm coupled with basin eleva-

tion. More accumulation of sand on the bank enco-

uraged Phragmites australis to grow [21 ]. Simpson

stated that Typha domingensis is more sensitive to

pastures); El-Hamra for the former and Um Risha

for the latter. These are the most common among

the lakes of Wadi El-Natrun.

ElHamra LakeA wide bare zone of barren soil devoid of vege-

tation surrounds the southern shore of this lake.

Thickets of Cyperus laevigatus var. laevigatus coverthe ground of the distant zone far away from the

shore. The latter zone was always wet, and the

plants were browed by goats and animals. A narrow

belt of Juncus acutus surrounds the outer l imits of

this zone. Along the eastern side, a pure zone of

Juncus acutus vertical ly traverses these two zones.Um Risha Lake

Apparently, the grass Desmostachya bipinnatalargely contributes to the vegetation zones around

this lake, with the absence of the sedge Cyperuslaevigatus var. laevigatus. Along the western side ofthe shore, Juncus actus zone was represented,

otherwise Alhagi graecorum zone were recognized.

A zone of barren soil separates the outer zone of

Juncus acutus from the inner Desmostachya bipinnata zone.

DISCUSSION

In total, 25 species were recorded, and repre-

sented the species composition around the inland

saline lakes in this study. The fewer number of spe-

cies (mostly salt-tolerant) may be attributed to the

high soil sal inity around the lakes. Such salinity

stress on floristic diversity in the study area and re-

lated areas was documented [44-46]. Application of

multivariate analysis techniques (classification and

ordination) to the floristic composition and soil fe-

atures around the lakes yielded five vegetation gro-

ups (communities):

(A) Juncus rigidusDesmostachya bipinnataTyphaelephantinaArundo donax,(B) Typha domingensis,(C) Juncus acutusCyperus laevigatus var. laevigatus,(D) Juncus acutusImperata cylindrica, and(E) Juncus rigidusJuncus acutus.

None of the obtained vegetation groups has

analogues in other former studies. Despite the dif-

ference in their dominating species, these commu-

nities are undoubtedly having the same floristic

composition of the previously recorded communi-



salt than Phragmites australis as the latter forms

well into Lake Mariut while Typha is present only

where the Lake receives fresh water from Mahmu-

diya canal [52]. El-Sawaf and Emad El-Deen reco-

gnized the disappearance of Typha species from

Hamra Lake where Phragmites australis was scat-

tered among the Juncus acutus plants as well as

higher elevations, near the road [20]. They also re-

cognized 3 distinct communities around the lakes:

(A) Juncus rigidusTamarix nilotica community, in-

habited soil with relatively high contents of Cl-, Na+,

SO4-2, pH and EC with high silt content and low

sand, related to the fairly sal ine habitats.

(B) Phragmites australisTypha elephantina com-

munity inhabiting swampy lands (border of the la-

kes) where there is a rich and continuous feed of

fresh brackish water. Soils showed low content of

Cl-, Na+, SO4-2, relatively high organic matter and

silt and low values of EC and sand.

(C) Nitraria retusaSporobolus spicatus community,

inhabited soil with low content of Cl-, Na+, SO4-2, re-

latively high organic matter and silt and low values

of EC and sand.

Boulos et al [21 ] reported that Juncus acutuscommunities were scattered among Cyperus laevigatus were they distributed as contour l ines paral lelto the lake bank, and both species decreased in

number and vigour by increasing the ground surfa-

ce unti l they disappeared. In the present study, Typha elephantina was represented in vegetation

group (A), with fewer individuals. I t is recommended

that conservation measures should be taken to pro-

tect and secure the remaining populations thro-

ughout Wadi El-Natrun which represents its type

locality from extinction [53].

Two species; Zygophyllum album and Nitraria

retusa deserve special comments. In Egypt, Zygo-

phyllum album is a species of wide ecological am-

plitude. I t was recognized by several habitats of the

country, such as in the l ittoral salt marshs [54], in

the inland desert, in the wadis of the l imestone ha-

bitat [55], in the sand dunes of the oases of the

Western Desert of Egypt [56]. Zygophyllum albumcommunity abounds in the sand formations west of

the lakes (e.g. Hamra and El-Rhazonia Lakes) fur-

ther than area occupied by Sporobolus spicatuscommunity and in water runnels l ined with sand de-

posits and dissecting the gravel deposits where the

salinity is lower [57]. El-Sawaf and Emad El-Deen

[20] recorded Zygophyllum album just as associated

species to community of Nitraria retusaSporobolus

spicatus. Nitraria retusa forms one of the main

scrubland types along the northern part of the Red

Sea littoral of Egypt, and is also common in the wa-

dis of the l imestone desert east of the Nile. Nitrariaretusa was recorded in some of the principal wadis

to the west of Hamra Lake and on terraces east of

El-Khadra and Al-Gaar lakes [58]. Boulos [21 ] re-

ported that Nitraria retusa dominated with increasedsalinity on the surface soil layer, where the under-

ground water table was deep. In this study, it is a

point of importance to recognize the disappearance

of Zygophyllum album and Nitraria retusa around

the studied lakes.

The zonation of saltmarsh vegetation is a uni-

versal phenomenon [1 7, 59, 60]. Concentric zona-

tion of halophytic communities around small lakes

and saltmarshes of the Egyptian oases and the

ring-shaped vegetation formations in NW-Egypt re-

sulting from different habitat gradients were descri-

bed [61 , 62]. The vegetation and flora of Qara Oasis

demonstrated four concentric zones of plant com-

munities bounding the oasis [63]. The zonation pat-

terns of the l ittoral salt marsh vegetation are mainly

influenced by the tidal phenomena, seven salt

marsh zones of plant communities around middle

lakes (Hamra, Zugm, Zagig, Al-Bida and El-Khadra)

of Wadi El-Natrun were observed [54, 57]: Swamps

of Typha elephantina and Phragmites australis, Cyperus laevigatus and Juncus acutus complex (wet

salt marsh), Sporobolus spicatus community, Desmostachya bipinnata community, Zygophyllum album community, Nitraria retusa community and a

community of Tamarix sp. , where the last five com-munity revealed as the dry salt marsh. He also re-

cognized the mosaic pattern of the vegetation which

means that the plant l ife is affected by several inte-

racting factors with no single dominant factor. In

Wadi El-Natrun, the lakes occupy the central part of

this depression, and bordered by saline which may

harbour different plant communities [1 9]. While the

conditions though different, yet vegetation zonation

is control led by seasonal fluctuations of water level

in the lakes and hence that of water table: shal low

in wet season and deeper in dry season. Under the

prevalent arid cl imate, evaporation causes the ac-

cumulation of salts at the ground surface forming

crusts. The other important factor is rel ief [64]. The

soil physical and chemical characteristics are appa-

rently one of the main factors influencing the plant

cover, distribution and also the zonal pattern of the

vegetation types [65].

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9.

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TRANSPARENCY DECLARATION

The authors declare no confl icts of interest.

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MAEG: Conception and design; MAEG and RH:

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