Development of macrophytic vegetation in the Agmon wetland of Israel by spontaneous colonization and reintroduction

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1 Wetlands Ecology and Management 6: , Kluwer Academic Publishers. Printed in the Netherlands. 143 Development of macrophytic vegetation in the Agmon wetland of Israel by spontaneous colonization and reintroduction D. Kaplan 1,T.Oron 1 & M. Gutman 2 1 Nature Reserves Authority, PO Box 1143, Safed 13111, Israel, Fax: ; 2 Department of Natural Resources, Agricultural Research Organization, PO Box 6, Bet Dagan 50250, Israel, mgutman@shani.net Received 15 May 1997; accepted 23 June 1998 Key words: Cyperus papyrus, Iris pseudacorus, Israel, Nuphar lutea, Nymphaea alba, wetland restoration Abstract The draining of the Lake Hula and swamps, northern Israel, during the late 1950s resulted in the loss of a very diverse and rare ecosystem. Oxidation of the peat soil resulted in ground surface subsidence, while heavy autumn winds have eroded the dry peat. Moreover, agriculture on the peat soils is restricted, because of a nitrate surplus. Predictions that the sinking would continue and that more areas would go out of agricultural production led authorities to re-flood a portion of the Hula Valley in The aim of the present study was to monitor the spontaneous establishment of vegetation in the re-flooded area, the Agmon wetlands, and to reestablish some of the major plant species lost from the valley when Lake Hula was drained. Within the first two years, 74 plant species colonized the wetland spontaneously. Five out of 11 species designated for reintroduction were successfully established. Cyperus papyrus and Cynodon dactylon demonstrated sustainable potential for lake-shore stabilization. Cyperus papyrus was reintroduced from seedlings and rapidly became the dominant riparian species, while Cynodon dactylon established spontaneously. Re-introduced Nymphaea alba clones were established only in enclosures protected from grazing by the semi-aquatic mammal Myocastor coypu. Nuphar lutea and Iris pseudacorus showed better resistance to grazing. These results demonstrate a high potential for successful re-establishment of much of the original Hula swamp macrophytic vegetation by either spontaneous colonization by extant species from the surrounding areas or by introduction of locally extinct species. As such, there is a good chance that the associated faunal components of the former Lake Hula and swamps that have returned to the region since the Hula rehabilitation project commenced will continue to flourish. Introduction The draining of the 6,000 ha Lake Hula and swamps in northern Israel, during the late 1950s resulted in the loss of one of the few aquatic ecosystems in the Middle East, as well an important phyto-geographic meeting zone for holarctic and paleotropic species (Zohary and Orshansky, 1947). Lake Hula and its surrounding marshland were important feeding stations for migrating and wintering birds such as Pelecanus onocrotalus and Porphyrio porphyrioas, as well as a breeding ground for species such as Ardea cinerea, Haliaeetus albicilla and Platalea leucorodia. Numerous fish and hundreds of invertebrate species also inhabited this now extinct ecosystem (Paz, 1975; Dimentman et al., 1992). Much of the high diversity of animal life could be attributed, in part, to the rich floral associations that existed. The rich vegetation described by Jones (1940), Zohary and Orshansky (1947), and others, consisted of nine vascular plants associations: 1) Myriophyllum spicatum,2)myriophyllum spicatum and Potamogeton lucens, 3) Nuphar lutea, 4) Ranunculus aquatilis, 5)Vallisneria spiralis and Najas marina, 6)Potamogeton pectinatus, 7)Potamogeton nodosus, 8)Ceratophyllum demersum, and 9) Potamogeton crispus and Potamogeton perfoliatus. The establishment of the 320 ha Hula Nature Reserve in 1958, did allow for preservation of some of the original habitats but not the ecosystem as a whole, nor did it succeed in preventing the extinction of some species Article: wetlhula11 Pips nr (wetlkap:bio2fam) v.1.1 wethul11.tex; 7/02/1999; 20:35; p.1

2 144 Figure 1. Map showing Lake Agmon, location of sampling transects, and primary reintroduction sites. Table 1. Transect length, number and mean depth of quadrats in each transect used to estimate spontaneous establishment of plant species in Lake Agmon. Refer to Figure 1 for location of transects. Transect Length No. of Mean water no. (m) quadrats depth (cm) , 40, 70, , 30, 70, 70, 80, , 40, 90, 250, 80, 70, , 120, 240, 120, 0 (e.g., Nymphaea alba), some of which were endemic (e.g. Discoglossus nigriventer Paz, 1975). The original aim of draining the Hula swamp to reclaim a large fertile area for cultivation was found to be only partially successful (Hambright and Zohary, 1998). Oxidation of the organic peat soil resulted in soil subsidence while heavy autumn winds have eroded the dry peat. In addition, there have been occasional occurrences of underground fires. Moreover, the fields tended to produce vegetative rather than reproductive growth, due to nitrate surplus, restricting farmers mainly to hay production. Predictions that the sinking would continue and that more areas would go out of production led the authorities in 1994 to re-flood a portion of the Hula Valley. The aim was to reduce both the rate of peat soil deterioration and the input of nitrates downstream to the Lake Kinneret, Israel s largest freshwater reservoir, and at the same time, to create a wetland area conducive to the development of eco-tourism (Shacham, 1994; Livne, 1994; Dimentman et al., 1992). The ecology of restoration has recently received world-wide attention, resulting in more emphasis to endangered species (Bowles and Whelan, 1994). Wetlands, being sensitive and fragmented habitats, are a high priority for restoration (Maltby and Dugan, 1994). The re-introduction of macrophytes plays an important role in the restoration of lakes (Bales et al., 1993). For example, the presence of Potamogeton pectinatus and Nuphar lutea can play an important role in reducing water column nutrient concentrations and thereby improves water quality (Van Donk, 1990; Peltre et al., 1993). Moreover, abundant and diverse macrophyte assemblages provide important habitats for many invertebrate and vertebrate wetland fauna. A literature study of the original Hula ecosystem was carried out, and gave rise to an initial habitat construction program (Kaplan and Vaadia, 1992) which was accepted by the Hula re-flooding project committee. The aim of the present study was to monitor the spontaneous colonization and establishment of vegetation and to reintroduce lost species as a basis of re-establishing as much of a lost ecosystem as possible. wethul11.tex; 7/02/1999; 20:35; p.2

3 145 Table 2. Macrophyte species introduced into the Agmon wetlands, their sources for re-introduction, the original location of the source clones, and the distance from the original source to the site of planting at Lake Agmon. TA Univ. = Tel Aviv University. Species Source Original clone source Distance (km) Marsilea minuta A. Br. Gonen, priv. coll. Hula Valley < 1 Marsilea minuta A. Br. TA Univ.-Bot. Garden Hula Valley < 1 Nymphaea alba L. Bustan Hagalil, priv. coll. Hula swamp 0 Nymphaea alba L. TA Univ.-Bot. Garden Hula swamp 0 Nuphar lutea Sm. Hula Nat. Res. Hula Valley 0 Ludwigia palustris L. Beteiha Nat. Res. Beteiha Nat. Res. 23 Myriophyllum spicatum L. TA Univ.-Bot. Garden Lake Kinneret 34 Methods Spontaneous colonization Colonization and establishment of species naturally was monitored during Four m long transects, were established in Lake Agmon, from the shore toward the lake s center, representing most of the aquatic habitats available for macrophytic vegetation (Figure 1). In each transect 4 to 7 quadrats, 5 5 m each, were located according to the different habitats present, and included quadrats on the dry and the wet sides of the shore line, as well as at the deepest point of the lake (Table 1). In the 22 quadrats examined, water depth, species composition, relative cover and phenology were recorded. Monthly observations were conducted from the start of the flooding in 1994 throughout Reintroduction We conducted a survey of published botanical literature on aquatic habitats in the Hula Valley and its surroundings, such as the Hula Nature Reserve and Ein Teo and Enan springs, to determine appropriate species for reintroduction. Identified species deemed suitable for reintroduction were collected from nearby natural habitats. Specimens of native species that had become extinct were taken from university botanical gardens and private collections. Care was taken that all species reintroduced were indigenous to the Hula Valley (Table 2). All species selected for reintroduction were transplanted to habitats with suitable conditions. The new habitats were classified according to three parameters: water depth, sediment type and the need for enclosures to ensure protection for delicate species such as Myriophyllum spicatum and Utricularia australis from grazing by the semi-aquatic mammal Myocastor coypu. Fence protection was also used for rare species such as Nymphaea alba, of which only limited plant sources were available. Soil types were identified as in Markel et al. (1998) according to relative peat and marl (mineral) content. The m exclosures, were covered with wire net (5 5 cm) and anchored into the sediments. Plants were covered up to the root system and supported with fiberglass poles. Emergent species such as Myriophyllum spicatum and Hydrocotyle ranunculoides were also surrounded by plastic netting. We also performed growth experiments with Cyperus papyrus, in which plants were planted in three locations and monitored for growth and production of flowering stems. Individuals were planted in a) experimental shallow peat ponds; b) mineral sediments on the southern shore of Lake Agmon (two sites); and c) peat sediments on the western shore of Lake Agmon (see Figure 1). The experimental area consisted of shallow pools sloping from 20 cm above water level ( 20) to 20 cm below water level (+ 20). In each location, data regarding height and number of flowering stems of 10 C. papyrus plants located 2 m apart from each other were recorded every 3 months. Paired comparisons of shallow versus deep water or peat- versus mineral-based sediments were performed by t-test. Results Spontaneously established species were classified according to 3 habitat parameters, (aquatic, riparian, ruderal /segetal) by their occurrence in the study area and in different parts of Israel (Zohary, 1966; Feinbrun-Dotan, 1977). In 1995, 53 species had spontaneously established. Of these species, 24 were riparwethul11.tex; 7/02/1999; 20:35; p.3

4 146 Table 3. Plant species that spontaneously colonized various habitats in the Agmon wetlands during and their natural habitats of occurrence. A: aquatic; D: dry shores; M: meadow; R: riparian; Ru: ruderal; SD: semi-dry shores; Se: segetal. Species Natural Agmon Alopecurus myosuroides Huds. Se, R R, M Alternanthera sessilis L. R R, M Amaranthus blitoides L. Ru SD A. graecizans L. Ru SD A. palmeri L. Ru SD A. retroflexsus L. Ru SD A. viridis L. Ru SD Amaranthus sp. L. Ru SD Aster subulatus L. Ru, R SD Atriplex suberecta L. Ru SD Avena sterilis L. Se SD Bromus catharticus Vahl Se SD Calendula arvensis L. Se D Cerastium glomeratum ThuilI. Se D Ceratophyllum demersum L. A A Chenopodium album L. Ru SD Chenopodium ambrosioides L. Ru SD Conyza bonariensis L. Ru SD C. canadensis L. Ru SD Cynanchum acutum L. R R, M Cynodon dactylon L. Pers. R R, M Cyperus alopecuroides Rottb. R, A R, M C. dives Del. R, A A C. papyrus L. R, A A C. pygmaeus Rottb. R R, M C. rotundus L. Ru SD Digitaria sanguinalis L. Scop. Ru SD Echinochloa colonum L. Link Se SD E. crusgalli L. Beauv. R R Eclipta alba L. R R, M Epilobium hirsutum L. R R, M Galium sp. L. R R, M Juncus bufonius L. R R, M Lemna minor L. A A Ludwigia stolonifera L. R R, M Lycopus europaeus L. R R, M Lythrum salicaria L. R R, M Najas delilei L. A A N. minor All. A A Paspalum paspalodes Scibner R R, M Phalaris brachystachys Link Se SD Phragmites australis Cav. Trin. R, A R, M Plantago major L. R R, M Polygonum acuminatum Kth. R R, M P. arenastrum Bor. Ru SD P. lapathifolium L. R R, M P. salicifolium Brouss. R R, M Table 3. Continued. Species Natural Agmon habitat habitat Polypogon monspeliensis L. Desj. R R, M Portulaca oleracea L. Se SD Potamogeton berchtoldii Fieb. R A P. crispus L. A A P. filiformis L. A A P. nodosus Poir. A A P. pectinatus L. A A P. perfoliatus L. A A P. trichoides Cham. A A Ranunculus sceleratus L. R R, M Ricciocarpus natans (L.) R, A A Rumex dentatus L. Ru, R SD Scirpus litoralis Schrad. R A S. maritimus L. R A Scolymus sp L. Se Se Senecio sp L. Se D Sinapis alba L. Se SD Sinapis arvensis l. Se SD Solanum nigrum l. Ru SD Sonchus oleraceus L. Ru SD Sorgum halepense L. Pers. Se SD Triticum aestivum L. Se Se Typha domingensis Pers. Poir. R, A A Urtica sp. L. Ru D Veronica anagallis-aquatica L. A A Veronica lysimachioides Boiss. R R, M Zannichellia palustris L. A A ian, 9 aquatic, 13 ruderal and 7 species were segetal i.e., plants which usually occur in cultivated habitats mostly among crops (Zohary, 1982). In 1996 a total of 74 species had spontaneously established (Table 3). Of these species, 31 were riparian, 13 were aquatic, 17 were ruderal and 13 were segetal. This represents an increase from 1995 to 1996 of 40% in total species number, 29% in riparian species, 44% in aquatic species, 31% in ruderal species and 86% in segetal species. Stands of cattail, Typha domingensis, were established during 1995 that covered 28 ha in the south of Lake Agmon and served as the major roosting and nesting habitat for a large heron colony (Ashkenazi and Dimentman, 1998; Shy et al., 1998). During late 1996 and early 1997, the cattails stands gradually deteriorated and by the end of 1997 had vanished, except for a few plants. wethul11.tex; 7/02/1999; 20:35; p.4

5 147 Table 4. Species reintroduced into the Agmon wetlands, their new habitats (water depth and sediment type) and their establishment success. Species reintroduced Water depth Sediment Protection No. introduced b No. surviving (cm) a type from grazing (duration, mo) Marsilea minuta A. Bn. 0 peat 8 0 (8) mineral 4 0 (6) Nymphaea alba L. 50 peat (18) mineral (24) Nuphar lutea L. 50 peat 65 0 (5) (18) Ludwigia palustris L. 0 peat 0.2 m 2b 1.8 m 2 (26) Myriophyllum spicatum L. 80 peat (20) Utricularia australis L. 80 peat (1) 40 0 (1) Butomus umbellatus L. 0 peat 14 0 (3) 5 1 (4) Potamogeton pectinatus L. 80 peat cm 2b 0(1) Iris pseudacorus L. 30 peat 8 4 (18) peat 42 1 (18) peat (18) Species reintroduced Water depth Sediment Protection No. transplanted b No. surviving (cm) a type from grazing (duration, mo) Cyperus papyrus L. 20 a peat (12) (12) (12) 20 a mineral 24 0 (3) (3) (3) 20 a mineral (12) (13) (12) Hydrocotyle ranunculoides L. 50 peat m 2,b 15 m 2 (7) a Negative values indicate depths above water s surface. b For delicate and complex-structured plants in which identification of individual plants was not practical, we estimated total surface area. The literature survey of extinct species from the Hula Valley, in general, or from the previous swamp in particular, resulted in a list of 11 species with potential for reintroduction (Table 4). The reintroduced species were transplanted to the various types of habitat in the new wetlands. Of the 11 reintroduced species, 4 failed to establish (Marsilea minuta, Myriophyllum spicatum, Potamogeton pectinatus, Utricularia australis) and 2 showed some potential to survive (Nuphar lutea, Butomus umbellatus). The remaining 5 species were established successfully (Nymphaea alba, Ludwigia palustris, Iris pseudacorus, Cyperus papyrus, Hydrocotyle ranunculoides). Most species showed better establishment in grazing-protected areas, with some species (Nymphaea alba, Hydrocotyle ranunculoides, Nuphar lutea) succeeding solely in the enclosures (Table 4, Figure 2). Peat soil seemed to be advantageous for Marsilea minuta and Cyperus papyrus, while Nymphaea alba showed better establishment in mineral soil (Table 3). Cyperus papyrus established better (12 20%) in peat sediment (Figure 3) and showed a tendency for better growth (significantly only in summer) in peat rather than in mineral sediment. Flowering stems appeared with more frequently on the mineral sediment, though the differences were significant only in spring (Table 5). In the experimental ponds, Cyperus papyrus showed a tendency for higher growth in deep wawethul11.tex; 7/02/1999; 20:35; p.5

6 148 Table 5. Cyperus papyrus phenology in the Agmon wetlands: mean height (cm) and mean number of flowering stems in the experimental ponds (shallow versus deep water) or within Lake Agmon (peat- versus mineral-based sediments). Paired monthly treatment means followed by asterisk ( ) are significantly different (P = 0.01). Shallow water = 20 0 cm; Deep water = 0 20 cm. Month Height (cm) No. flowering stems Shallow Deep Shallow Deep Aug Nov Jan Apr Jul Oct Peat Mineral Peat Mineral Jan Apr Jul Oct Figure 2. Percent survival of reintroduced Nymphaea alba (no data available for the last year of peat fenced habitats), Nuphar lutea and Iris pseudacorus in Lake Agmon during 1995 and Figure 3. Percent survival of Cyperus papyrus in experimental plots during 1995 and 1996 in either mineral- or peat-based soils or planted above ( 20 cm), at (0 cm), or below (0 20 the water-shore interface. ter (0 to 20 cm) compared with shallow water (20 to 0 cm), but establishment and survival percentages were higher in shallow water (Figure 3). Discussion In the Northern Galilee of Israel, spontaneous colonization of submergent and emergent species is known (Israel Nature Reserves Authority database), as also in the Camargue (southern France), where Myriophyllum spicatum and Potamogeton pectinatus are common (Van Wijck et al., 1994). However, not all of these species established spontaneously in the Agmon wetlands and therefore some were reintroduced (e.g., Potamogeton pectinatus and Iris psudacorus). In both 1995 and 1996, 60% of all species spontaneously established were aquatic and riparian species, most of which were known to be originally in the Lake Hula swamps prior to draining (Jones, 1940; Zohary and Orshansky, 1947; Dimentman et al., 1992). In less than two years, the fact that most of the spontaneously established species were native gives basis for the hope that additional species will spontaneously establish themselves in the future. The main water source of the Agmon wetlands is fresh water from the Jordan River which could explain the reintroduction of aquatic and riparian species to the area as both a seed carrier, as well as by improving water conditions for macrophytes. Most of these species are present in, or in the vicinity of streams and springs in the Hula Valley. Most interesting is the reappearance of Najas wethul11.tex; 7/02/1999; 20:35; p.6

7 149 minor a species thought to be extinct from Israel since 1949 (Dafni and Agami, 1976). Its seeds may have been preserved in the peat sediments or reintroduced by avian species. The remaining 40% of species were ruderal and segetal species, a phenomenon typical to disturbed areas (Zohary, 1982). Macrophytes have an important role in shore stabilization, nature conservation and tourism. Cyperus papyrus and Cynodon dactylon were found to be plants with sustainable potential for lake shore stabilization. Cyperus papyrus was established rapidly from seedlings and was reintroduced immediately as the dominant riparian species, while Cynodon dactylon established itself spontaneously. Typha domingensis was described in Lake Hula prior to the 1950s draining, but only as a temporary lake-shore association and as a episodic phenomenon (Zohary and Orshansky, 1947). Although T. domingensis revealed great potential for providing an important habitat for the Agmon avifauna for ca. 3 years, the collapse of the population and virtual absence of suitable stands for bird roosting and breeding by the end of 1997 suggest only a transient role for T. domingensis in future years, similar to that in the extinct Hula, but also in the present-day Everglades (Davis, 1994). Several possible factors involved in the collapse have been investigated, including grazing by the semiaquatic mammal Myocaster coypu, and sulfide toxicity (Ashkenazi, Markel and Kaplan, unpublished), but no conclusive evidence is yet forthcoming. Native species that have become extinct are of great importance to nature conservation, and those species with ornamental potential may be important to eco-tourism. Reintroduced Nymphaea alba clones were established only in enclosures protected from grazing by Myocastor coypu. On the other hand, in previous experiments in the Hula Nature Reserve (J. Vaadia, Israel Nature Reserves Authority, pers. com., Nuphar lutea and Iris pseudacorus, which are also very attractive species, showed resistance to grazing. These species are in the first stages of reintroduction to the new lake although, Nuphar lutea was established after only 18 months in enclosures. The original peat swamp habitat of Cyperus papyrus, prior to the 1950s draining was found to be advantageous for the reintroduction and survival of Cyperus papyrus. The survival rate after reintroduction was highest in habitats immediately above the water table and growth was strongest for habitats covered by more than 20 cm of water. Seed germination, after dispersal in autumn, occurred mainly in habitats with the lowest water level. In contrast, faster growth occurred during spring and summer with higher water levels. These results suggest that the reintroduction of Cyperus papyrus would be more successful in habitats similar to those in which the plant grows naturally (i.e., in habitats with seasonally fluctuating water levels). This is a factor to be considered in the Agmon wetlands water table management program. In spite of the impressive number of species spontaneously established, special measures have been, and should continue to be, taken to reintroduce ornamental and extinct species, as well as species important for shore stabilization and bird colonies establishment such as Cyperus papyrus. The rehabilitation program of the vascular plant system described above is a foundation for an ecosystem as close as possible to the original one. Acknowledgments The authors are grateful to Dr. M. Agami (Tel Aviv University Botanical Gardens) for his good advice and for supplying some of the plants reintroduced, to E. Yas ur for his technical assistance and practical advice, to T. Niv for data analysis assistance, to S. Rothman for paper review, to G. Ney for editing the text, and to the Hula Project Committee for financing this study. References Ashkenazi, S. and Dimentman, Ch Foraging, nesting and roosting habitats of the avian fauna of the Agmon wetland, northern Israel. Wetlands Ecol. Managmt. 6: Bales, M., Moss, B., Philips, G., Irvine, K. and Stansfield, J The changing ecosystem of a shallow, brackish lake, Hickling Broad, Norfolk, UK. II. Long-term trends in water chemistry and ecology and their implications for restoration of the lake. Freshwater Biol. 29: Bowles, M.L. and Whelan, C.J Restoration of Endangered Species. Cambridge Univ. Press. Dafni, A. and Agami, M Extinct plants of Israel. Biol. Conserv. 10: Davis, S.M Phosphorus inputs and vegetation sensitivity in the Everglades. In: Davis, S.M. and Ogden, J.C. (eds), Everglades: The Ecosystem and its Restoration. pp St. Lucia Press, Delray Beach. 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