Vegetation of the Special Zoological Reserve of KopaEki Rit Jasenka Top% Pedagoiki fakultet,
The University of Osijek, Yugoslavia
Received 5 December
1987; in revised form 18 February
Key words: vegetation,
1988; accepted 20 May 1988
Abstract This paper presents the results of several years’ surveys on the vegetation of the Special Zoological Reserve of KopaEki Rit. Over this large floodplain of the Danube and Drava rivers prevail different types of hygro- and hydrophytic communities. Some of them are relatively constant, having persisted in this Reserve for many years with a relatively constant area. Some other communities, particularly aquatic ones, appear periodically, and their area is directly influenced by surface water area and duration of the flood. The vegetation can be divided into 36 plant communities within the classes Lemnetea, Potamogetonetea, Littorelletea, Phragmitetea, Isobto-Nanojuncetea, Bidentetea tripartitae, Chenopodietea, Plantaginetea majoris, Molinio-Arrhenatheretea and Querco-Fagetea.
Introduction The corner between the Danube and Drava rivers, in the vicinity of the Drava’s mouth (Fig. l), represents a large floodplain. The duration of the flood water on the soil surface is the main factor influencing the development of different types of vegetation. Within this area exist various plant communities belonging to different systematic categories. This vegetation is an integral part of the habitat for many animals, particularly birds, making this area very famous throughout Europe. Nowadays, the area is protected as a zoological reserve, and the fauna has been investigated in detail, while the flora and vegetation were surveyed partially (AntiC et al., 1969 RauS et al. 1985. The aim of this paper is to present the concise review of the recent vegetation of the Reserve area of KopaEki Rit. It is necessary not only for botani-
cal science, but also for landscape management, hunting management and nature conservation.
Area of investigation The main factor influencing the vegetation of this area is the microrelief. The area of the Reserve is the lowest part of the Baranja region with altitudes of 80-86 m a.s. The largest depression is KopaCko Lake, located in the central part of the Reserve with an average size of 216.44 ha. It is connected to the Danube and to SakadaS Lake across the channels. These lakes and channels never dry up. The other parts are somewhat higher and sporadically inundated. The whole area has a slightly rolling contour. The highest parts are on the river banks. The Reserve is connected to the Drava only when the water table is high. The water regime of Danube and Drava rivers
1. Position of the Special Zoological
fluctuates. The lowest water noted for the Danube River at Apatin in the period 1958-1977 was - 118 cm, the highest 825 cm, the amplitude was 943 cm. The water of the Danube retains in its bed up to 300 cm at Apatin. At this time the KopaEko and SakadaSko lakes, as well as the deepest channels, are tilled with water. The water area is 28 1.8 1 ha. With the increase of the water height to 350 cm, the lower parts are inundated and the water surface amounts to 815.17 ha. Such a water level persists for 175.85 days on average. At a water level of 400 cm all depressions in the Reserve are inundated, which means that the inundated area is 3025.47 ha. This water remains 13 1.35 days per year on average. At a water table of the Danube of 400-500 cm more than 90% area is under water and it remains 51.15 days on average. In the case of a water table over 500 cm, the whole area of Kopacki Rit is inundated. In some years the inundations completely fail to occur, while in others their duration is consider-
Reserve of KopaEki rit.
able. The relation between the water table and flooded area is shown in Table 1. The prevailing soil types of this area are alphabeta gley (35.5 2) and beta-gley (46.14%) with a considerable amount of calcium carbonate (20-30%) (Mikuska, 1979). The water of Kopa%i Rit is slightly alkaline, approximately 7-8 pH.
Table 1. Water table of Danube river inundated area in KopaEki Rit (Mikuska Water table of Danube river
< 300 300-350 350-400 400-500 > 500
281.81 815.18 3,025.47 5,901.78 6,234.52
(at Apatin) 1979)
area % 4.52 13.08 48.53 94.66 100.00
151 Methods The phytocenological research was made according to the principles of the school ZurichMontpellier (Braun-Blanquet, 1964). The nomenclature is listed according to Ehrendorfer (1973). Characteristic species of the association (Char. Ass.), alliance, order and class (Char. All., O., Cl.), as well as the dominant and important companions (Comp.) are listed on the phytocenological tables, made on the basis of 5-10 vegetational records for each association. Degree of presence is noted for each species (I-V).
Results and discussion On the basis of several years’ surveys of the vegetation in the area of Kopacki Rit, the following plant communities were noted, belonging to 10 vegetational classes: Class: Lemnetea W.Koch et TX. 54 Order: Lemnetalia W.Koch et TX. 54 Alliance: Lemnion R.Tx. et Schwave 72 Ass. : Lemno-Spirodeletum polyrrhizae W.Koch 54 Wo&etum arrhizae J.Tx. 60 Spirodelo-Salvinietum Slav. 50 Lemno-Azolletum Br.-Bl. 52 Lemnetum trisulcae Knapp et Stoffers 62 Riccietum Juitantis Slav. 56 Alliance : Hydrocharition Rubel 3 3 Ass. : Lemno-Utricularietum vulgaris S6o
Myriophyllo-Nupharetum 26 Nymphoidetum peltatae
(All. 22) Oberd. et MUller 60 Trapetum natantis Muller et Gors 60
Ass. Spirodelo-Salvinietum Slav. 50 Horvat et al. 1974) often covers the water surface within the reed stands as well as the open stagnant water in depressions and channels. The dominant and characteristic species of the association is Salvinia natans (Table 2). Ass. Lemno-Azolletum Br.-Bl. 52 appears sporadically in shallow stagnant water, distinguishing it from other related communities by the presence of the smah tropical water fern Azolla Jiliculoides (Topic & Segulja 1978). This plant sometimes dominates the surface with a green carpet in the shade, or with a reddish one on sunny habitats. The floric composition is shown in Table 2. Ass. Lemnetum trisulcae Knapp & Stoffers 62 lies under the water surface, making a layer several centimeters to several decimeters thick in shallow stagnant water. It lies under the other plant communities of the order Lemnetalia such as LemnoSpirodeletum or Lemno-Azolletum (Table 2).
Water and swamp vegetation The shallow depressions with sporadically stagnant water, as well as the deeper ones with permanently stagnant or slowly fluctuating water, are overgrown with different types of vegetation. Ass. Lemno-Spirodeletum polyrrhizae W. Koch 54 covers stagnant or slowly fluctuating water (Oberdorfer 1957). It is very common in the channels outside the floodplain, and within,the Reserve occurs on the margins of shallow ‘gonds. The floric composition is shown in Table 2. Ass. Worfietum arrhizae J.Tx. 60, the community of the smallest water lense is not very widespread, but in a few localities it completely covers the water surface with the dominant species Wolffia arrhiza (Table 2).
Ass. Riccietumfluitantis Slav. 56 appears sometimes sporadically, accompanied by water lenses (Table 2). Ass. Lemno-Utricularietum vulgaris Soo (28) 38 is found in stagnant water, 50-150 cm deep. (Table 2). Ass. Potamogetonetum lucentis Hueck 3 1 appears sometimes fragmentarily developed and mosaitally spread with other communities of the alliance Potamogetonion. The floric composition is presented in Table 3. Ass. Potamogetonetum graminei (W. Koch) Passarge 64 (Table 3) develops in the KopaEko Lake but not regularly every year. In the last six years it was seen only twice, depending on the water regime in the spring and summer. The dominant and characteristic species is Potamogeton gramineus with apparently anisophyllous leaves. The flotant ones are light green, ovate-lanceolate, while the submersed leaves are darker, linear-lanceolate.
2. The vegetation of the class Lemnetea 1
I IV I V
I V V -
V IV -
Char. Ass. Lemna trisulca L. Spirodela polyrrhiza (L.) Schleiden Salvinia natans (L.) All. [email protected] arrhiza (L.) Horkel ex Wim. Azolla filiculoides Lam. Utricularia vulgaris L. Riccia j&tans L. Ricciocarpus natans L.
Char. All., 0. and Cl. Lemna minor L. Hydrocharis morsus-ranae
I I I I II II
I I I
I II I
Comp. Polygonum amphibium L. Nymphoides peltata (Gmel.) Kuntze Alisma plantago-aquatica L. Lycopus europaeus L. Glyceria maxima (Hartman) Holmb. Phragmites australis (Cav.) Trin. ex Mentha aquatica L. Butomus umbellatus L. Rorippa amphibia (L.) Bess. Hippuris vulgaris L. Lythrum salicaria L. Rumex sp. Myosotis scorpioides L. Myriophyllum spicatum L. Sparganium erectum L.
Ass. Najadetum marinae Fukarek 61 was seen only once in the several years of investigation. It develops in shallow, sand depressions with stagnant and very warm water, which means that the thermophilous community is in question. The bottom is partially covered by the species Najas marina, Alisma gramineum and Potamogetonpectinatus.
Ass. Hottonietumpalustris TX. 37 appears in channels outside of the floodplain. The dominant species is Hottonia palustnk (Table 3). Ass. Myriophyllo-Nupharetum W. Koch 26 is characterized by a carpet of large leaves and flowers of the species Nuphar lutea and Nymphaea alba. The community is very common in stagnant water. It covers a large area, especially if the water
154 Table 3. The vegetation of the class Potamogetonetea
2 Char. Ass. Nymphaea alba L. Nymphoides peltata (Gmel.) Kuntze Potamogeton kens L. Potamogeton gramineus L. Hottonia palustris L. Trapa natans L. Ranunculus circinatus L. Hippuris vulgaris L. Myriophyllum verticillatum L. Char. All., 0. and Cl. Polygonurn amphibium L. Nuphar lutea (L.) Sm. Potamogeton natans L. Potamogeton trkhoides Caam. et Schl. Ceratophyllum demersum L. Potamogeton crispus L. Comp. Schoenoplectus lacustris (L.) Palla. Lemna minor L. Utricularia vulgatis L. Veronica anagallis-aquatica L. Sagittaria sagittfolia L. Salvinia natans (L.) All. and others
level is high in the spring. Sometimes, in summer and autumn, one can see the leaves of Nuphar and Nymphaea on the fresh muddy soil, after water regression. The floric composition is shown in Table 3.
of the flowers of Nymphoidespeltata gives the main aspect to water surface. It develops in shallow stagnant water, OS-l.0 m deep. Usually, the cover of characteristic species Nymphoidespeltata is 100% and there are no apparent other species.
Ass. Nymphoidetum peltatae (All. 22) Oberd. et MUller 60 covers the largest area in the summertime, when the water table is high and a large area is flooded. It overgrows the inundated area as well as the fishponds in the vicinity. The yellow carpet
Ass. Trapetum natantis Muller et Gors 60 develops in deeper water than the former community, and usually appears as dense ‘islands’, made of only one species, Trapa natans. The last two communities are sometimes cate-
155 gorized as the same association, Trapo-Nymphoidetum (Oberdorfer 1957) but for our purposes it is necessary to distinguish between Nymphoidetum peltatae and Trapetum natantis (Runge 1980). Ass. Potameto-Ranunculetum circinati Sauer (Antic et al. 1969) develops in shallow ponds within ‘caricetum’ and the characteristic aspect is that of the small white flowers of Ranunculus circinatus (Table 3). Ass. Nymphoideto-Hippuridetum Antic et al.. 69 occurs in shallow water in summer and autumn or on very wet soil remaining without surface water during this period. The floric composition is shown in Table 3. Ass. Eleocharetum acicularis W. Koch 26 develops in dry periods in summer or autumn, when surface water disappears, leaving bare soil. On such a ‘bottom’ with no surface water, but wet enough, develops the vegetation with the dominant species of Eleocharis acicularis accompanied by other species from the class Littorelletea and companions, such as Littorella uniflora, Gnaphalium uliginosum, Agrostis stolonifera, Schoenoplectus lacustris, Veronica anagallis-aquatica etc.
Ass. Scirpo-Phragmitetum W. Koch 26 is one of the most widespread and characteristic communities of the KopaEki Rit. It gives the characteristic landscape to open area without woods, and serves as the refuge and home for many animals. In spite of the common phytocenological table presenting all the aspects as a unique association, Scirpo-Phragmitetum, it is obvious that there are several sharply separated aspects understood nowadays often as distinct associations (Runge 1980, Casper & Krausch 1980). So, there are large areas covered by the dominant and vital, 3-4 m high Phragmites australis, very sparcely accompanied by very few other species. Also, there are ‘islands’ of Typha lattjolia or T. angustifolia. Large stands are characterized by the abundance of Schoenoplectus lacustris. The floric composition is shown in Table 4.
Ass. Phalaridetum arundinaceae Libbert 31 is spread on a wider area of KopaEki Rit, while inside the Reserve it is found only fragmentarily developed. It is not present on the stands with stagnant, but rather underground water. This association often accompanies dried ‘relict’ white willow woods, remaining after drainage. The dominant species is the association characteristic species Phalaris arundinacea (Table 4). Ass. Glycerietum maximae Hueck 31 is not very widely spread in the KopaEki Rit in spite of its commonness in channels and swamps of East Slavonia and Srijem (RauS et al. 1978, 1980). This is a typical community of swamps, being unable to tolerate a great amplitude of water table in inundated areas. The species Glyceria maxima is very tolerant to polluted water, so this community is very common on the channels with waste waters in the surroundings of Kopacki Rit. The floric composition is shown in Table 4. Ass. Oenantho-Rorippetum amphibiae Lohm. 50 is very common community in the investigated area. Some years, when the water table has been low in the previous autumn and winter, the rosettes of the species Rortppa amphibia cover large areas of bare soil, or it is mosaically spread among the bushes of sedges. As the species is tolerant to low temperatures it grows throughout the whole winter and offers a good fresh food for animals. Sometimes in the spring, in May and June, large areas were covered by the yellow flowers of Rorippa amphibia, the dominant species (Table 4). Ass. Caricetum elatae W. Koch 26 (Table 4) develops only fragmentarily on the border of the Reserve, across the dam and in a mixture with other communities of high sedges. Ass. Caricetum vesicariae Br.-Bl. et Denis 26 prevails on a large area covered by high sedges. The floric composition is shown in Table 4. Ass. Caricetum gracilis (Graebn. et Hueck 3 1) TX. 37 is sparsely distributed on the margin of the floodplain, only fragmentarily developed (Table 4).
The vegetation of the class Phragmitetea 1
IV II I II II I
Char. Ass. Schoenoplectus lacustris (L.) Rorippa amphibia (L.) Bess. Oenanthe aquatica L. Typha latifolia L. Typha angustifolia L. Sparganium erectum L. Phalaris arundinacea L. GZyceria maxima (Hartman) Carex elata All. Carex vesicaria L. Carex gracilis L.
Char. All., 0. and Cl. Phragmites australis (Cav.) Trin. ex Steud Sagittaria sagittifolia L. Poa palustris L. Iris pseudacorus L. Butomus umbellatus L. Carex acutiformis Ehrh. Comp. Myosotis scorpioides L. Lythrum salicaria L. Galium palustre L. Polygonurn amphibium L. Stachys palustris L. Urtica dioica L. Mentha aquatica L. Salvinia natans (L.) All. Hydrocharis morsus-ranae L. Rumex hydrolapathum Huds. Veronica anagallis-aquatica L. Solarium dulcamara L. Ranunculus repens L. Veronica longiiolia L. Solidago gikantea Ait. Gnaphalium uliginosum L. Nuphar lutea L. Agrostis stolonfera L. Lycopus europaeus L. and others
157 Alliance Nanocyperion W. Koch 26 is present only in fragments of vegetation, developing on fresh ‘bottoms’ of former ponds and lakes. These stands have partially bare soil and are partially covered by the small plants of Juncus buffinius, Cyperus jiiscus, Gnaphalium uliginosum, Limosella aquatica, Carex bohemica, Lindernia procumbens, Plantago major and others.
5. The vegetation of the class Bidentetea 1
Ass. Ranunculetum scelerati TX. 50 develops sporadically in swamps, within the willow woods and in shallow ponds. The characteristic and dominant species is Ranunculus sceleratus (Table 5). Ass. Alopecuretum aequalis Burrichter 59 could be found sometimes on the dried bottom of swamps and ponds, as well as in fishponds (Table 5). Ass. Descurainietum (= Sisymbrietum) sophiae Krek 35 develops on the dry, warm margins of the dam, as well as on the other ruderal habitats in the surroundings, along the paths, in the yards (RauS et al. 1985). It is characterized by the abundance of the characteristic species Descurainia sophia (Table 6). Ass. Echio-Melilotetum TX. 42 develops on the dry soil along the road, on the southern slopes, in the vicinity of SakadaB Lake. The characteristic species Echium vulgare and Melilotus officinalis are also the dominant ones, giving to the community a blue and yellow aspect.
hydropiper L. sceleratus L. aequalis Sobol minus Huds.
Char. All., 0. and Cl. tripartita cernua
Ass. Polygono-Bidentetum (W. Koch 26) Lohm. 50, distributed all over Croatia (Markovic 1975), occurs here on a few localities, probably where intensive traffic and pasture of animals, particularly wild swine take place. The floric composition is shown in Table 5.
Char. Ass. Polygonum Ranunculus Alopecurus Polygonurn Bidens Bidens
The ruderal vegetation develops on the margins of the Reserve, along the road and dam, on the paths and so on.
Myosotis scorpioides L. Agrostis stolonifra L. Rorippa amphibia (L.) Bess. Ranunculus repens L. Eleocharis acicularis L. Lemna minor L. Spirodela polyrrhiza (L.) Schleiden Ranunculus jlammula L. Gnaphalium uliginosum L. Plantago major subsp. intermedia
Ass. Lolio-Plantaginetum (Lincola 21) Beger 30 develops on the paths intensively treade. Within the Reserve it occurs at the dam only. The floric composition is shown in Table 7. Ass. Sclerochloo-Polygonetum avicularis (Gams 27) Soo 40 could be foundgn the dry, well-treaded places (Markovic 1979, Segulja & Topic 1979), on the margins of roads and on the paths. It develops in the spring and dries up and disappears very early in June.
Meadow vegetation The meadow vegetation is not spread over the territory of Baranja on the whole, due to hydromeliorations, in which the stands are turned into
6. The vegetation of the class Chenopodietea 1
I I V
Char. Ass. Echium vulgare L. Reseda lutea L. Descurainia sophia Melilotus oflcinalis
(L.) Webb. ex Prantl. (L.) Pall. Char. All., 0. and Cl. Chenopodium album L. Sirymbrium officinale (L.) Stop. Datura sramonium L. Polygonum persicaria L. Comp. Cynodon dactylon (L.) Pers. Polygonurn aviculare L. Linaria vutgaris L. Ambrosia artemisi$olia L. Daucus carota L. Capsella bursa-pastoris (L.) Med. Matricaria chamomilla L. Matricaria inodora L. Lepidium ruderale L. Stellaria media (L.) Vill. Sonchus arvensis L. and others 1 Descurainietum
V III I I
I III III II II I I I I I
III III II I I I
arable soil. Only on dams are the grasslands sown and maintained. Ass. Arrhenatheretum elatioris Br.-Bl. 19 is the only meadow community in the Reserve, occur-kg along the dam sides,and is mowed regularly twice a year, with no herbicide treatment. The floric composition depends on the age of the dam, since on the new ones the artificial grasslands are sown, having for a few years many ruderal and weed plants. Later, with regular mowing, the composition becomes more stable and characteristic of a meadow. The floric composition is as follows: Char.Ass.
7. The vegetation of the class Plantaginetea
Char. Ass. dura (L.) PB. squamatus (Forsk.) Asch. inodora L. Char. All., 0. and Cl. Polygonum aviculare L. Poa annua L. Plantago major L. Lolium perenne L. Comp. Triyolium repens L. Capsella bursa-pastoris (L.) Med. Cynodon dactylon (L.) Pers. Hordeum murinum L. and others Sclerochloa Coronopus Matricaria
Pastinaca sativa L. Festuca pratensis Huds. Centaurea jacea L. Poa pratensis L. Taraxacum oficinale Web. Plantago lanceolata L. Ranunculus acris L. Rumex acetosa L. Holcus lanatus L. Leucanthemum vulgare Lam. Dactylis glomerata L. Anthoxanthum odoratum L. Silene alba (Mill.)E.H.L. Trifolium repens L. Trifolium pratense L. Verbena offinalis L. Linaria vulgaris L. Buglossoides arvensis
V V IV IV III III III III III II I IV III II II I I I
Johnst. and others
V IV III IV IV IV IV
IV IV IV I
III II I I
IV I II
Wood vegetation A large part of the Reserve, as well as the whole floodplain of the Danube is overgrown with willow and poplar woods (RauS 1974). Ass. Salicetumpurpureae Wend.-Zel. 52 is spread only along the New Canal and at the foot of the dam. The ground layer of this scrub vegetation is completely covered with herbaceous plants (Table 8).
8. The wood vegetation of the class Querco-Fagetea 1
V V -
I V V -
I I I
II I I I
Char. Ass. Salix alba L. Populus n&a L. Salix purpurea L. Populus alba L. Galium palustre L.
Char. All., 0. and Cl. Crataegus pentagyna W. et K. Viburnum opulus L. Cornus sanguinea L. Ulmus laevis Pall. Quercus robur L. Comp. Rubus caesius L. Myosotis scorpioides L. Fraxinus americana L. Iris pseudacorus L. Urtica dioica L. Lycopus europaeus L. Acer negundo L. Carex vesicaria L. Ranunculus repens L. Mentha aquatica L. Morus alba L. Lythrum salicaria L. Agrostis stolonijera L. Lysimachia vulgaris L. Bidens tripartita L. Potentilla supina L. Euphorbia palustris L. Euphorbia salicijolia Host. Symphytum oficinale L. Cardamine dentata (Schult) Neilr Rorippa amphibia (L.) Bess. Polygonurn hydropiper L. Ranunculus sceleratus L. Rumex hydrolapathum Huds. Glechoma hederacea L. Senecio aquatica L. Leucoium aestivum L. Calystegia sepium (L.) R. Br. Prunella vulgaris L. and others 1 Salicetum purpureae 2 Galio-Salicetum albae 3 Salici-Populetum nigrae 4 Populetum nigro-albae (1-4 Salicion albae, Populetalia)
I III III I I I I II II II II I I I I I
I V I I I I I I I -
V I III II
III I I
I I I I I -
I I -
Ass. Galio-Salicetum albae RauS 76 covers a large area of Kopacki Rit. The wood is monotyic, and wood layer is composed of only one species, Salix alba. It has no bush layer. The inundations of the habitat of this community are frequent, longterm and measuring 2-4 m high. Consequently, characteristic ‘barbs’ of adventive roots hang across the trunk of Salix alba. The floric composition is shown in Table 8. Ass. Salici-Populetum nigrae (TX. 31) MeijerDrees 36 subass. rubetosum caesii RauS 76 (Table 8) develops on the restricted area of the Reserve. It is spread on a somewhat higher position than those of the association Galio-Saliceturn albae (RauS 1974). Consequently, the duration of inundation is shorter and water height is lower. We can find fragments of the association on the channel and river banks which have somewhat higher altitudes on this rolling microrelief. Ass. Populetum nigro-albae Slav. 52 occurs only as fragments on the highest positions, and it is hard to distinguish it from the previously mentioned community because both of them are developed only fragmentarily. There are characteristic formations of grouped specimens of Populus alba. Taking into consideration the areas covered by distinct communities, the largest ones are overgrown with reed and high sedges, as well as the willow woods. The area of some aquatic communities depends on the water table and duration of the inundation. Some communities were always present every year, while some of them appear sporadically. For example, the association Potmogetonetum graminei developed in the spring and summer of 1985 after a six year absense, apparently due to the water regime. For some communities, for example Lemno-Azolletumfiliculoides and WolfJietum arrhizae, it is not yet established what the main reason of periodicity is. Although there are not greater technical interventions in the Reserve influencing the water regime, nevertheless in the near surroundings some meliorations were made, changing the face of the landscape. So, in the last few years the area of
160 Biljski Rit in the village Bilje, only a few kilometers from KopaCki Rit, was drained. Earlier reeds are turned into fields. This tendency is taking place on greater and greater areas in the surroundings and it is hardly possible to predict its influenceupon the water regimeof the wider area of KopaEki Rit. It is a fact that the flora and vegetation of this area become continuously poorer and poorer. So, the community SerrutuloPluntuginetum altissimae Ilijanic 59 (Ilijanic 1959, 1978)is lost, not only in this region,but probably throughoutYugoslavia as a whole. The last large areain the Baranja regioncoveredby the species Iris sibirica was definitively plowed out in 1985. In spite of sevenyearsof field work there were no obvious vegetationalsuccessionsbecausethe relativelyconstantinfluenceof inundational water retains for longer periods natural permanent stages of hydro- and hygrophytic vegetation. However,in placeswherethechannelswereartiticially regulated,on sanddeposits,the initial stage of the wood community, ass. Galio-Salicetum albae, succeededin developing.In contrast,most standswith the old white willow woods reached their terminal stage,persistingthere for the next ten yearsat least. Fortunately, as a protectedand undisturbedareais in question,it will be possible to survey a real vegetationalsuccession. Conclusion
The results of severalyears surveyson the vegetation of the Special Zoological Reserve of Kopaeki Rit can be summarized as follows: 1. The vegetationconsistsof 36 plant communities belongingto the classesLemnetea, Potamogetonetea, Littorelletea, Phragmitetea, IsoPto-Nanojuncetea, Bidentetea tripartitae, Chenopodietea, Plantaginetea majoris, Molinio-Arrhenatheretea and Querco-Fugetea.
2. The largest part of this inundational area cover the associationGalio-Salicetum albae, Scirpo-Phrugmitetum and communities of the order Magnocaricetalia.
3. The areaof aquaticcommunitiesis variable, dependingon the water surfaceareaand duration of the inundation.
4. As the water regimeis rather constant, the vegetation is also constant, with seasonal variations. True successioncould be seenonly on a few sand deposits, artificially made, where the initial stage of willow woods develops. The majority of old woods belonging to the association Galio-Salicetum albae arein their terminal stagewith no renewal. References Antic, M. B., B. Jovanovic, N. Jovic, V. MunkaEeviC, S. Nikolandic, 1969. FitocenoloSko-pedoloSka istraiivanja u plavnom produeju Baranje. Jelen-bilten LSG ‘Jelen’. Beograd 8: a99-114. Braun-Blanquet, J., 1964. Pflanzensoziologie. Dritte Auflage. Springer Verlag. Wien-New York. Casper, S. J. & H. D. Krausch, 1980. Stisswasserflora von Mitteleuropa. 1. Teil. Gustav Fischer Verlag. Stuttgart-New York. Ehrendorfer, F., (ed.), 1973. Liste der Gefasspflanzen Mitteleuropas. Gustav Fischer Verlag. Stuttgart. Horvat, I., V. GlavaE & H. Ellenberg, 1974. Vegetation Stidosteuropas. Geobotanica selecta IV. Fischer Verlag. Stuttgart. istraiivanja Ilijanic, Lj., 1959. EkoloSko fitocenoloSka nizinskih livada Hrvatske (doktorska disertacija). Zagreb. Ilijanic, Lj., 1968. Die Ordnung Molinietalia in der Vegetation Nordostkroatiens. Acta Bot. Croat. 26/2: 161-170. Markovic, Lj., 1975. 0 svezi Bidention tripartiti u Hrvatskoj. Acta Bot. Croat. 34: 103-120. Markovic, Lj., 1979. Das Sclerochloo-Polygonetum avicularis in der Trittvegetation Nordostkroatiens. Acta Bot. Croat. 38: 87-94. Mikuska, J., 1979. EkoloHke osobine i zaStita Specijalnog zooloSkog rezervata ‘KopaEki rit’ s posebnim osvrtom na ekologiju kraljesnjaka (doktorska disertacija). Zagreb. Oberdorfer, E., 1957. Stiddeutsche Pflanzengesellschaften. Pflanzensoziologie 10. Gustav Fischer Verlag. Jena. Rat& D., 1974. Vegetacija ritskih Suma dijela Podunavlja od AljmaSa do Iloka. Glasnik za Sumske pokluse XIX: 5-75. Rat& D., N. Segulja & J. Topic, 1978. Prilog poznavanju mocvarne i vodene vegetacije bara u nizinskim Sumama Slavonije. Acta Bot. Croat. 37: 131-147. RauS, D., N. Segulja & J. Topic, 1980. Vegetacija bara i mocvara u sumama jugozapadnog Srijema. Zbornik za prir. nauke -Matice srpske 58: 2-51. RauS, D., N. Segulja & J. Topic, 1985. Vegetacija sjeveroistocne Hrvatske. Glasnik za Sumske pokuse 23: 235-355. Runge, F., 1980. Die Pflanzengesellschaften Mitteleuropas. Aschendorff, Miinster. Segulja, N. & J. Topic, 1979. Asocijacija Sclerochloetum durae Br.-Bl. 31 u Sremu. Fragm. herbologica Jugosl. VII, 116-125: 39-42. Topic, J. & N. Segulja, 1978. Azollafiliculoides Lam. u Sremu i Slavoniji. Zbornik za prir. nauke Matice srpske 55, 117-118.