Scholarly article on topic 'Gravel pads of powerline towers as human-made habitats for ruderal vegetation in some Mediterranean wetlands of Egypt: Implications for management'

Gravel pads of powerline towers as human-made habitats for ruderal vegetation in some Mediterranean wetlands of Egypt: Implications for management Academic research paper on "Biological sciences"

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Abstract of research paper on Biological sciences, author of scientific article — Magdy I. El-Bana

Abstract Despite the widespread of transmission powerlines in many aquatic ecosystems of Egypt, little is known about their ecological impacts. The current study evaluates floristic composition associated with gravel pads constructed for stabilizing powerline towers in the wetlands of Burullus and Manzala. Plant cover was measured for 34 randomly selected in paired gravel pads and adjacent wetlands. Ordination analysis indicated that vegetation on the gravel pads significantly differed from that in wetlands. Thirty-two species were recorded in the gravel pad plots (more than twice the number found in wetlands). Mean species richness was significantly higher in gravel pad plots (3.8 species) than in wetland plots (1.7 species). Gravel pad plots had a significantly lower cover than wetlands of Chenopodiaceae (12.9% vs. 28.7%) and Poaceae (15.7% vs. 32.2%), while Asteraceae showed higher cover in gravel pad plots (25%) than in wetlands (6.7%). Gravel pad plots were consistently occupied by ruderals, weeds and invasive species. Regression analysis showed that total vegetation cover and diversity indices increased significantly with rises in the thickness of the gravel pads. The study highlighted the importance of gravel pad corridors for the abundance of ruderal plant species that could eventually colonize more pristine areas in the adjacent wetlands.

Academic research paper on topic "Gravel pads of powerline towers as human-made habitats for ruderal vegetation in some Mediterranean wetlands of Egypt: Implications for management"

Egyptian Journal of Aquatic Research (2015) xxx, xxx-xxx

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National Institute of Oceanography and Fisheries Egyptian Journal of Aquatic Research

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Egyptian Journal of Aquatic Research

FULL LENGTH ARTICLE

Gravel pads of powerline towers as human-made habitats for ruderal vegetation in some Mediterranean wetlands of Egypt: Implications for management

Magdy I. El-Bana *

Department of Botany, Faculty of Science, Port Said University, Egypt

Received 31 January 2015; revised 3 March 2015; accepted 3 March 2015

KEYWORDS

Anthropogenic habitats; Conservation; Invasive species; Plant cover; Species diversity

Abstract Despite the widespread of transmission powerlines in many aquatic ecosystems of Egypt, little is known about their ecological impacts. The current study evaluates floristic composition associated with gravel pads constructed for stabilizing powerline towers in the wetlands of Burullus and Manzala. Plant cover was measured for 34 randomly selected in paired gravel pads and adjacent wetlands. Ordination analysis indicated that vegetation on the gravel pads significantly differed from that in wetlands. Thirty-two species were recorded in the gravel pad plots (more than twice the number found in wetlands). Mean species richness was significantly higher in gravel pad plots (3.8 species) than in wetland plots (1.7 species). Gravel pad plots had a significantly lower cover than wetlands of Chenopodiaceae (12.9% vs. 28.7%) and Poaceae (15.7% vs. 32.2%), while Asteraceae showed higher cover in gravel pad plots (25%) than in wetlands (6.7%). Gravel pad plots were consistently occupied by ruderals, weeds and invasive species. Regression analysis showed that total vegetation cover and diversity indices increased significantly with rises in the thickness of the gravel pads. The study highlighted the importance of gravel pad corridors for the abundance of ruderal plant species that could eventually colonize more pristine areas in the adjacent wetlands.

© 2015 National Institute of Oceanography and Fisheries. Hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Introduction

The wetlands of the Mediterranean basin occupy about 3 million ha (Pearce and Crivelli, 1994). These wetlands are

* Tel.: +20 10 90075228; fax: +20 66 3657601. E-mail address: mag_bana@yahoo.co.uk. Peer review under responsibility of National Institute of Oceanography and Fisheries.

valuable habitats of biodiversity including many rare and endemic species of halophytes, insects, reptiles, fishes and birds (Balletto and Casale, 1991; El-Bana et al., 2002; Cox et al., 2006; Shaltout and Al-Sodany, 2008; Blondel et al., 2010). However, they are among the most threatened ecosystems on earth due to the long history of interactions between humans and biodiversity loss (Zalidis et al., 1999). During the last few millennia, more than half of the Mediterranean wetlands have been totally drained for controlling water-borne diseases,

http://dx.doi.org/10.1016/j.ejar.2015.03.004

1687-4285 © 2015 National Institute of Oceanography and Fisheries. Hosting by Elsevier B.V.

This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

creating houses, expanding agriculture and installing urban infrastructures and other human welfare (Zalidis et al., 1999; El-Bana et al., 2000; Parra et al., 2005; Blondel et al., 2010; Robledano et al., 2011). Many of the remaining wetlands are threatened by mismanagement and overexploitation of their natural resources (Pardo et al., 2008; Robledano et al., 2011; Eid and Shaltout, 2013; Moreno-Gonzalez et al., 2013).

Human activities such as construction and maintenance of transmission powerlines and their associated rights-of-way create suitable conditions for establishment and growth of ruderal plant species that can threaten biodiversity and other ecological services of the nearby natural ecosystems (Weber, 2003; Diaz et al., 2005; Dube et al., 2011; Wagner et al., 2014). These activities may facilitate the invasion of ruderal vegetation in natural ecosystems through several ways. First, fragmentation of natural habitats and loss of native vegetation increase environmental heterogeneity that facilitates the invasibility and spread of ruderal species (Brothers and Spingarn, 1992; Tewksbury et al., 2002). Second, seeds and propagules of several ruderal species may be transported in constructed soil of pads and foundations for overhead utility line towers and substations (Tyser and Worley, 1992; Cameron et al., 1997). Third, the internal disturbance of native vegetation creates gaps with increased resources that enhance the establishment of less competitive ruderal species (Hessing and Johnson, 1982; Ehrenfeld, 2008). Fourth, establishment and maintenance of transmission line rights-of-way and their connected service tracks closer to access roads may favor seed dispersal and propagules of roadsides ruderal plant species (Tyser and Worley, 1992; Rubino et al., 2002). Fifth, changes in soil physical properties and enhancement of soil nutrients may contribute to the establishment of ruderal plant species which have the ability to grow and thrive in this enriched soil (Grigal, 1985; Cameron et al., 1997).

Researchers have emphasized on the role of establishment and management of rights-of-way when evaluating powerline corridor effects on vegetation composition (Nickerson et al., 1989; Temple, 1996; Clarke et al., 2006; Dube et al., 2011; Wagner et al., 2014). However, much less is known about the impact of the construction of gravel pads, which is a conspicuous landscape-disturbance feature for supporting powerline towers, and forming a network of linear terrestrial patches in wetlands (Fig. 1). Such spatial configuration of benched and graveled pads may facilitate the invasion and spread of ruderal plants into the intersected wetlands. In addition, the installation of these terrestrial barriers in water may induce sediment deposition and nutrient enrichment which change plant community development and create appropriate microhabitats for the establishment of non-native plants in wetlands (Miller and Zedler, 2003; Mahaney et al., 2004; Dube et al., 2011).

Although, urbanization and their attendant effects are obvious features in the Mediterranean wetlands, these effects remain insufficiently studied particularly in those of arid and semi-arid environments of North African countries where there is a rapid rate of uncontrolled urban development (Flower, 2001; Zdruli, 2012; Redeker and Kantoush, 2014). In such fragile environments, there are extensive networks of national and international transmission powerlines, but no studies evaluated the ecological changes that occur in natural ecosystems bisected by these transmission powerlines. The current study examines the following two main hypotheses: (1) that gravel pads constructed for stabilizing transmission towers facilitate the establishment of ruderal vegetation in the Mediterranean deltaic lakes of Egypt (Lake Burullus and Lake Manzala) that have high conservation value (Ramsar sites); and (2) differences exist between the benched gravel pads of powerline towers and the surrounding intersected

wetlands in vegetation composition, species richness and floris-tic diversity.

Methods

Study area

The study area is located along a contiguous 500 kV overhead double circuit high voltage transmission line at the wetlands of Lake Burullus (N 31° 25' 117", E 30° 55' 112") in the west and Lake Manzala (N31° 27' 977'', E 31° 48' 623'') in the east (Fig. 2). In the water of the two lakes, transmission towers are placed on elevated man-made gravel pads with a width of 7.5 m x 7.5 m. The thickness of pad varies according to the water depth in the two lakes. Lake Manzala is the largest of the remaining Nile Delta Lakes with an area of 700 km2, and average water depth of 1.0 m (Rasmussen et al., 2009). Lake Burullus is the second largest lake in north Delta with an area of 410 km2, and average water depth of 1.5 m (Eid and Shaltout, 2013). It is one of the international important wetlands in Egypt under the Wetland Convention (RAMSAR site). Within the two lakes, there are numerous islands and bars that are dominated by several halophytes and glycophytes (El-Bana et al., 2000; Shaltout and Al-Sodany, 2008). Climate is arid, with an aridity index of 0.030.2, and the mean monthly air temperature ranges between 10 °C in mild winter and 30 °C in warm summer (Ayyad et al., 1983). The average annual precipitation is 75 mm, which usually falls during mild winter.

Field sampling

Thirty-four gravel pad sites under transmission towers were selected in the two lakes (16 in Burullus and 18 in Manzala, Fig. 2). The thickness of each constructed gravel pad was calculated as the average of six measurements using a metal ruler that was gently pushed down until it hit the lake bed. Vegetation sampling was conducted twice in 2013 (JuneAugust) and 2014 (March-April) in order to capture the phenology of different plant species. On each selected gravel pad, the percentage cover of plant species and of bare ground were

estimated visually in 4-surveyed plots (2 m x 2 m). The plots were placed systematically in the four cardinal directions at 1.0-m distance from the pad edge resulting in a total of 64 in Lake Burullus and 72 in Lake Manzala. Data from the four cardinal directions were pooled into a composite value, as the preliminary analysis showed no effect of aspect on community structure. For comparison, 40 plots (each of 4 m2) were randomly selected in the surrounding wetlands at least at 20 m from the nearest sampled gravel pad in each lake. Plant species were identified according to Boulos (1999-2005, 2009). The life-form spectra of plants were determined according to the Raunkiaer classification (Raunkiaer, 1934). The alien invasive species was identified according to Shaltout (2014).

Data analysis

Cole and Mao-Tau sample-based rarefaction curves for species richness were constructed in both the wetland and gravel pad plots with Estimates software (Colwell, 2013). Nonmetric multidimensional scaling ordination (NMS) was carried out using Sarenson distance coefficient (autopilot mode) to evaluate variation in vegetation composition between wetland and gravel pad plots (McCune and Mefford, 2011; PC-ORD, version 6.0). A two dimensional solution of NMS was used, because change in stress value was minor with subsequent dimensions. Accordingly, relationships between the first two axes of NMS scores on one hand, and species cover on the other hand, were calculated using Spearman's rank correlation coefficient. Plant species richness and Shannon's diversity index (Huston, 1994) were calculated for the vegetation on the gravel pads. Simple linear regression analysis was undertaken between the thickness of the gravel pad and the total percentage of vegetation cover, bare ground, species richness as well as Shannon's diversity index. These analyses were conducted with SPSS 16.0 (SPSS, Chicago, IL, USA).

Results

Rarefaction curves for species richness differed dramatically between gravel pad and wetland plots (Fig. 3). The curves

Figure 2 Map of the study area showing the location of the surveyed plots in Burullus and Manzala Lakes.

showed that wetland plots reached their asymptote earlier (at the 20th sampling plot) than the gravel pads (at the 32nd sampling plot), indicating the differences in species richness and diversity between the two sites. A total of 32 plant species were recorded in the gravel pad plots versus 15 from all wetland plots (Appendix). Therophytes were the most dominant life forms with 21 species (68.7%) in gravel pad plots, while

-O- Wetland plot > Gravel pad plot

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L /" per p

10 15 20 25 30 35

Sample plot

Figure 3 Cole and Mao-Tau sample- based rarefaction curves for species richness in gravel pad and wetland plots.

wetland plots were dominated by chamaephytes (13 species or 86.7%). Mean species richness was significantly higher in gravel pad plots (3.8 species) than in wetland plots (1.7 species).

Wetland and gravel pad plots were different in number and cover of represented families (Fig. 4a, b). A total of 9 and 13 families were recorded in wetland and gravel pad plots, respectively. Four families were common in both wetland and gravel pad plots (Appendix). Of these, Asteraceae, Convolvulaceae and Poaceae had greater number of species in the gravel pad plots than in the wetland ones, while the number of Chenopodiaceae was higher in the wetlands than in the gravel pad plots (Fig. 4a). Nine families occurred only in gravel pad plots. Of these, Fabaceae was represented by 3 species and Brassicaceae by 2 species, while the other seven families included one species for each (Fig. 4a). Gravel pad plots had a significantly lower cover than wetlands regarding the members of Chenopodiaceae (12.9% vs. 28.7%) and Poaceae (15.7% vs. 32.2%), while Asteraceae (of 8 species) showed higher cover in gravel pad plots (25%) than in wetlands (6.7%) with one species (Fig. 4b).

The first axis of the Nonmetric Multidimensional Scaling (NMS) obtained from the data of species cover explained 74.8% of the compositional variation (Fig. 5), while the second axis explained 15.7%. Species such as Phragmites australis (r = —0.878), Halocnemum strobilaceum (r = —0.952), Arthrocnemum macrostachyum (r = —0.523), Typha domingen-sis (r = —0.762) and Inula crithmoides (r = —0.564) showed strong affinities with the wetland plots along axis 1 (Table 1), while the weedy and ruderal species such as Cynanchum acutum (r = 0.587), Alhagi graecorum (r = 0.863), Bassia indica (r = 0.866), Pluchea dioscoridis (r = 0.753), Conyza bonariensis (r = 0.644) and Polygonum equisetiforme (r = 0.568) were strongly associated with the gravel pad plots.

Solanaceae Portulacaceae Polygonaceae Malvaceae

! Lillaceae ? Fabaceae

Boraginaceae Apocynaceae Zygophyllaceae Typhaceae Juncaceae Cyperaceae Caryophyllaceae Poaceae Convolvulaceae Chenopodiaceae Asteraceae

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Figure 4 Bar plots for number of species (a) and proportional cover (b) of the recorded families in gravel pad and wetland plots.

O Wetland plots # Gravel pad plots

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Figure 5 Nonmetric multidimensional scaling ordination of wetland and gravel pad plots.

Table 1 Spearman's rank correlation coefficients (r) between species cover and values of the first two axes of Nonmetric Multidimensional Scaling (NMS). Only species with correlation coefficients, equal to or greater than half the highest value obtained for each axis are shown.

Species NMDS 1 NMDS 2

Alhagi graecorum 0.863 0.463

Arthrocnemum macrostachyum -0.523 -0.443

Atriplex portulacoides -0.349 0.325

Bassia indica 0.866 -0.353

Centaurea calcitrapa 0.374 -0.232

Conyza bonariensis 0.644 0.454

Cynanchum acutum 0.587 0.315

Halocnemum strobilaceum -0.952 -0.464

Heliotropium curassavicum 0.377 0.254

Inula crithmoides -0.564 0.412

Ipomoea carnea 0.377 0.242

Juncus acutus -0.485 0.335

Phragmites australis -0.878 -0.354

Pluchea dioscoridis 0.753 0.244

Polygonum equisetiforme 0.568 -0.354

SSalsola kali 0.475 -0.232

Sarcocornia fruticosa -0.654 -0.312

Senecio glaucus 0.522 -0.362

Symphyotrichum squamatus 0.474 -0.413

Typha domingensis -0.762 0.292

Zygophyllum album -0.676 -0.283

The four species with greatest cover in wetland plots (Table 2) were P. australis (52.4%), H. strobilaceum (48.2%), Zygophyllum album (45.7%) and T. domingensis (32.6%). The four species with greatest mean cover in gravel pad plots were B. indica (45.8%), A. graecorum (35.9%), P. dioscoridis (28.4%) and C. bonariensis (24.5%). The species with greatest frequency of occurrence in wetland plots were H. strobilaceum (76.5%), P. australis (70.6%) and T. domingensis (62.5%); while those in gravel pad plots were A. graecorum (85.3%), B. indica (70.6%) and Senecio glaucus (52.3%).

Table 2 Most prevalent plant species by frequency (%) and mean cover (%) in wetland and gravel pad plots.

Species

Wetlands

Gravel pads

Cover Frequency Cover Frequency

(%) (%) (%) (%)

Alhagi graecorum 0 0 35.9 85.3

Arthrocnemum 12.8 52.9 0 0

macrostachyum

Bassia indica 0 0 45.8 70.6

Centaurea 0 0 17.5 32.4

calcitrapa

Conyza bonariensis 0 0 24.5 46.1

Cynanchum acutum 0 0 15.8 44.1

Halocnemum 38.2 76.5 0 0

strobilaceum

Heliotropium 0 0 18.4 38.2

curassavicum

Inula crithmoides 15.8 38.2 0 0

Juncus acutus 19.4 44.7 0 0

Phragmites australis 52.4 70.6 0 0

Pluchea dioscoridis 0 0 28.4 20.5

Salsola kali 0 0 12.9 41.1

Senecio glaucus 0 0 14.9 52.3

Typha domingensis 32.6 62.5 0 0

Zygophyllum album 25.7 59.6 0 0

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Figure 6 Linear regression of gravel pad thickness with the percentage of bare substrate (a) and the percentage vegetation cover (b).

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Figure 7 Linear regression of gravel pad thickness with the Shannon-Wiener's diversity index (a) and the species richness index (b).

The percentage of the bare ground decreased with the increase in the thickness of constructed gravel pads

-0.693; P = 0.001) (Fig. 6a). In contrast, the percent-

age of vegetation cover increased with an increase in the thickness of the gravel pad (R2 = 0.745; P = 0.001) (Fig. 6b). Similarly, Shannon-Wiener's diversity index and species richness index increased significantly with rises in thickness of the gravel pad (R2 = 0.721 and R2 = 0.614, respectively) (Fig. 7a, b).

Discussion

Despite the widespread of transmission powerlines in many aquatic ecosystems of Egypt, it seems to us that this is the first effort to assess the effect of construction of the powerline towers on plant communities. The results of the current study support the hypothesis that differences exist in floristic composition and diversity between the gravel pads constructed for stabilizing powerline towers and the surrounding wetlands. Mean plant species richness on the gravel pads was nearly twice that observed in wetland plots. The lower species richness in wetlands may attribute to high soil salinity and homogeneity of habitats (El-Bana et al., 2002; Shaltout and Al-Sodany, 2008). On the other hand, the higher species richness in gravel pad plots apparently resulted from the increase in its thickness. It is possible that the initial impact of the construction of gravel pads with low thickness restricts the colonization of the site to annual species that comes with

transported gravel and capable of tolerating low moisture and nutrient content (Shaltout and Al-Sodany, 2008). With increasing thickness, gravel can trap windblown sediment particles, increases site heterogeneity, and enhances soil moisture and nutrients (Johnson, 1987; Blshop and Chapln, 1989) allowing the establishment of several annual and perennial species. This could be explained by the increase in vegetation cover, species richness and diversity with increase in gravel pad thickness.

The study indicated the association of ruderal plant species with the gravel pad plots. The majority of these species belong to Asteraceae, Poaceae and Fabaceae. These families represent the main bulk of the ruderal plant species in Egypt (Abd El-Ghani et al., 2011) and in the disturbed road networks of Mediterranean climate regions (Di Castri et al., 1990). In addition, they were reported to be the most frequent for the weed flora in the agro-ecosystems of the Nile valley (Abd El-Ghani et al., 2013) and Nile Delta of Egypt (Shaltout et al., 1992). However, the higher vegetation cover of Poaceae in wetland plots may be correlated with the higher frequency and cover of P. australis. This reed was documented as the most dominant vegetation type in the wetlands along the deltaic Mediterranean coast of Egypt (Khedr and Zahran, 1999; Shaltout and Al-Sodany, 2008). On the other hand, the higher number and vegetation cover of Chenopodiaceae in the wetlands plots could be related to its succulence which is a common adaptation strategy for halophytic dicotyledons (Ungar, 1991).

Our results agree with the previous results, where anthropogenic ecosystem such as roads and urban habitats had high abundance of ruderals and weed species in different ecoregions of Egypt (Shaltout and El-Sheikh, 2003; Abd El-Ghani et al., 2011, 2013), in Europe (Sukopp, 2004; Ziarnek, 2007) and in Australia (Johnston and Johnston, 2004; Stenhouse, 2004). Many of these species differ in their degree of establishment in disturbed habitats (Newsome and Noble, 1986). Construction of gravel pads represents a sudden and significant physical disturbance due to the accumulation of large amount of gravel, with the consequent removal of vegetation and soil of wetlands. Such physical disturbance has been reported to encourage the establishment of ruderal and weed species (Wilson and Tilman, 2002).

The dominance of ruderal and weed species in the gravel pad plots is of particular interest. Four of these species (A. graecorum, B. indica, Salsola kali and Symphyotrichum squamatus) are considered as ruderal communities of urban habitats in Nile Delta (Shaltout and El-Sheikh, 2003). In addition, four species (C. bonariensis, C. acutum, S. glaucus and Heliotropium curassavicum) represented invasive segetal weeds in the Mediterranean arable habitats (Prieur-Richard et al., 2000; Abd El-Ghani et al., 2011). El-Sheikh et al. (2012) recognized the dominance of B. indica, C. acutum and S. glaucus during vegetation succession on the constructed landfill along the shore of Lake Burullus. Two woody perennials (P. dioscoridis and Ipomoea carnea) in the gravel pad plots are considered as invasive species in different habitats of Egypt (Shaltout and Slima, 2007; Shaltout et al., 2010; Abd El-Ghani et al., 2013). They have the ability to alter the ecological process and native biodiversity of the invaded habitats through rapid growth and allelopathic effects (Shaltout et al., 2010; Fahmy et al., 2012).

Conclusion and implications for management

The current results demonstrated significant differences in vegetation composition and structure between constructed gravel pads of powerline towers and adjacent wetlands, and highlighted the importance of gravel pad corridors for the growth and abundance ofruderal and weed species. The occurrence ofsuch terrestrial corridors may act as invasion windows and sources of propagules for ruderal species within the Mediterranean wetlands of Egypt, if additional anthropogenic and natural disturbances acting near the constructed gravel pads. Therefore, efforts should be carried out to avoid more human disturbances such as landfill for bordering fish farms in adjacent wetlands. In addition, the study showed that even small terrestrial patches within wetland landscape may have invasive species (e.g.

B. indica, P. dioscoridis and I. carnea) in the flora. The results support an ecosystem approach to vegetation management in wetland environments, in which the nature and impacts of human disturbance should be integrated with the ecological requirements for establishing and conserving native biodiversity (Clarke et al., 2006; Wagner et al., 2014). Human-made habitats such as gravel pads of powerline towers can be utilized for sustainable land use, employing introduced native woody trees on the connected service tracks in combination with herbaceous species on the pads under the overhead towers. This would optimize ecological benefits and values of the constructed patches. The trees can be used for firewood production. Herbaceous productivity on gravel pads can be utilized by livestock grazing. They can also serve important roles in the conservation of wild invertebrates and vertebrates (Wagner et al., 2014).

Appendix A. A list of plant species, including their families, life-form spectra and frequency in gravel pads and wetlands

Family Species Life Invasive Frequency (n = 34)

Forms Species Gravel pads Wetlands

Apocynaceae Cynanchum acutum L. Ph 15 0

Asteraceae Centaurea calcitrapa L. Ch 11 0

Conyza bonariensis (L.) Cronquist Th 16 0

Inula crithmoides L. Ch 0 13

Launaea nudicaulis (L.) Hook. f. H 5 0

lfloga spicata (Forssk.) Sch. Bip. Th 4 0

Pluchea dioscoridis (L.) DC. Ph 10 0

Senecio glaucus L. Th 18 0

Sonchus oleraceus L. Th 7 0

Symphyotrichum squamatus (Spreng.) Nesom Ch Yes 6 0

Boraginaceae Heliotropium curassavicum L. Ch Yes 13 0

Brassicaceae Brassica rapa L. Th 8 0

Eruca ssativa Mill. Th Yes 7 0

Caryophyllaceae Spergularia marina (L.) Griseb. Th 0 6

Chenopodiaceae Arthrocnemum macrostachyum (Moric.) K. Koch Ch 0 18

Atriplex portulacoides L. Ch 0 8

Bassia indica (Wight) A.J. Scott Th Yes 24 0

Chenopodium murale L. Th 8 0

Emex spinosa (L.) Campd. Th 9 0

Halocnemum strobilaceum (Pall.) M. Bieb Ch 0 26

Salsola kali L. Th 14 0

Sarcocornia fruticosa (L.) A.J. Scott. Ch 0 11

Suaeda pruinosa Delile Ch 0 13

Convolvulaceae Convolvulus arvensis L. Th 10 0

Convolvulus hystrix Vahl. Th 6 0

Cressa cretica L. H 0 12

Ipomoea carnea Jacq. Ph Yes 11 0

Cyperaceae Scirpus maritimus L. Ge 0 8

Fabaceae Alhagi graecorum Boiss. Ch 29 0

Medicago ciliaris (L.) All. Th 9 0

Trifolium repens L. Th 6 0

Juncaceae Juncus acutus L. Ge 0 15

Liliaceae Asparagus stipularis Forssk. Ge 7 0

Malvaceae Malva parviflora L. Th 11 0

Poaceae Cynodon dactylon (L.) Pers. Ge 0 14

Digitaria sanguinalis (L.) Scop. Th 8 0

Echinochloa colona (L.) Link Th 12 0

Imperata cylindrica (L.) Raeusch. Ge 0 16

Lolium perenne L. Th 9 0

(continued on next page)

Appendix A. (continued)

Family Species Life Invasive Frequency (n = 34)

Forms Species Gravel pads Wetlands

Phragmites australis (Cav.) Trin. ex Steud. Ge 0 24

Polypogon monspeliensis (L.) Desf. Th 6 0

Rostraria cristata (L.) Tzvelev Th 11 0

Polygonaceae Polygonum equisetiforme Sm. Ge 14 0

Portulacaceae Portulaca oleracea L. Th 10 0

Solanaceae Solanum nigrum L. Th 13 0

Typhaceae Typha domingensis (Pers.) Poir. ex Steud. Ge 0 21

Zygophyllaceae Zygophyllum album L.f. Ch 0 19

Total number of species 32 15

Life form: Th, therophyte; Ch, chamaephyte; H, hemicryptophyte; Ge, geophyte and Ph, phanerophyte.

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