Phytocoenological researches on the grasslands of the middle and inferior basin of Crişul Negru river

SUMMARY The meadowlands from the middle and inferior basin of Crisul Negru river form an area with rich flora and vegetation suitable for a complex phytocoenological research and an ecologic and bio-economical study of the floor vegetation. After conducting a number of 80 phytocoenological surveys on the meadowlands near Apateu and Satu Nou villages (Arad county, Romania), respectively near Cociuba Mare and Măr ț ihaz villages (Bihor county, Romania) there have been identified a number of fifteen vegetal associations from which one is examined in this work. The paper presents the hygrophilic association Typhetum latifoliae Lang 1973 on the grasslands of the middle and inferior basin of Crişul Negru river, association classified from the coenotaxonomic point of view in the alliance Phragmition communis Koch 1926, order Phragmitetalia Koch 1926, class Phragmitetea australis R. Tüxen et Preising 1942. - chemical reaction of the soil; 2n - karyotype; K - constancy; ADm - abundance-dominance; Hh - helohydatophyte; H - hemicrypthopyte; G - geophytes; Th - euterophytes; Ch - chamaephytes; Cosm - Cosmopolitan; Cp - Circumpolar; Eua - Eurasian; E European; D - diploidy; P - polyploidy; D-P - diplo-polyploidy.


INTRODUCTION
This study aims to analyze the phytocoenoses of the association Typhetum latifoliae Lang 1973 from the point of view of the floristic composition and by analyzing the spectrum of the floristic elements, the life forms spectrum, the karyotype spectrum and the ecological factors.
The territory chosen for research, the meadowlands from the middle and inferior basin of Crisul Negru river, had not been studied thoroughly by those who had floristic and phytocoenological concerns and were not made many scientific communications and publications about this area. Dissipated data on small segments were found in the author's paperwork's Borza (1929), Pop (1968) and Prodan (1956). In their work the cited authors were related to a larger area without having done thorough studies.
The complex study of flora and vegetation is absolutely necessary especially in regions with less or no researches.
The association is also widespread in the Pannonian region (Borhidi, 2003).
The basin of Crişul Negru river is surrounded by the Crişul Repede basin in the north and in the south by the basin of Crişul Alb river. Western limit of the basin is formed by the state border with the Republic of Hungary and the east limit with the basins of Someș and Arieș rivers. Except for the area occupied by the basin of Teuz valley, the basin of Crişul Negru river extends entirely across the Bihor county, representing 60% of its territory.
From the climate perspective, the basin of Crişul Negru river, as part of Crişurilor basin, falls within the Pannonian climate with wide variety of overtones, depending on the complexity and fragmentation of the landscape. The arrangement of the relief steps is in ascending order from west to east, making the whole basin to be under the influence of oceanic air masses from the west and those subtropical wet, especially in winter, on slopes facing southwest (Cristea, 2004).
The soils of the Crişul Negru Plain are characterized by diversity (Barbu, 1987), their genesis being in close connection with the evolution of the Plain of Tisa. The region from the Plain of Crişul Negru is tessellated; the inter-region soils dominate (alluvial, swamp soil, gleic soil and pseudogley, salty soils).
A part of the middle and inferior basin of the Crişul Negru River, being covered with primary herbaceous vegetation, has been broken up and used for agriculture. The meadows which hasn't been broken up, used by humans as pastures and meadows; as a result of canalizations and drainages these meadows suffered a saline progradation, and secondary halophile vegetation appeared, vegetation which is widely spread in this area.
On taking into consideration several papers in the specialty literature (Sanda et al., 1998(Sanda et al., , 2008, the Typhe tum latifoliae association Lang 1973 was classified in the following coenosystem: Class: Phragmitetea australis R. Tüxen et Preising 1942, Order: Phragmitetalia Koch 1926, Alliance: Phragmition communis Koch 1926. For the study of Typhetum latifoliae association from the middle and inferior basin of Crişul Negru river, I used the phytosociological research method of the European Central School, based on the principles and methods elaborated by Braun-Blanquet (1964) and adapted by Borza and Boşcaiu (1965) to the particularities of the vegetation carpet from our country.
After the field research the list of species is drawn up grouped by classes, order, families and ranges alphabetically, specifying the place and habitat where they vegetate, the locality and an ecological summary (bioforms, geo-elements, ecological clues and karyo type). The taxa identified in the field have been recognized by specialty catalogues "Flora României"/Romania's Flora (Ciocârlan, 1952(Ciocârlan, -1976 and "Flora ilustrată a României"/Romania's Illustrated Flora (Ciocârlan, 2000).
The association's synthetic table was structured after the methodology proposed by Braun-Blanquet (1964) and developed by Ellenberg (1974); therefore, in the column header of the table for the association analyzed the following have been entered: the serial number of land surveys, altitude (m.s.m.), area (m²), coverage (%).
Participation of each species to the association table was made with the help of the index of abundancedominance after the evaluation system of Braun-Blanquet and Pavillard (1928). To the end of the table was registered and calculated the constancy (K), the phytocenotical index whose class is between I-V and expresses the coenetic fidelity degree of each species to the ambiance of the association's phytocoenoses.
To realize this study, there were performed a total of ten local incursions, and about eighty phytocoenological surveys on natural grasslands. The sample (survey) surfaces, homogenous in floristic and physiognomic terms, were chosen from the studied natural grasslands. Their size varies between 20-60 m 2 .
The analyzed phytocoenoses were identified on

RESULTS AND DISCUSSION
The floristic and phytocoenological characterization of Typhetum latifoliae association Lang 1973 reveals that the composition includes seventeen varied species (Table 1).
Typha latifolia builds good contoured phytocoenoses, that develops in the form of clusters at the edge of lakes, ponds, water retaining dams and swampy areas where water stagnates almost all vegetable season, not exceeding the depth of 40-50 cm.
The phytocoenoses is dominated by Typha latifolia, that realizes a covering of vegetation of 75%, with a high constancy (V), and is accompanied by the characteristic species of the Phragmition communis alliance, Phragmitetalia order, Phragmitetea australis class, namely: Lycopus europaeus, Alisma plantagoaqua tica, also with a high constancy (IV), Glyceria flui tans, Eleocharis palustris, Lythrum salicaria, Sparga nium erectum ssp. neglectum with a constancy of III in the frame of association.

CONCLUSIONS
The present work report for the first time the Typhe tum latifoliae Lang 1973 association in the studied area.
Analysis of ecological indices for the associations found on the grasslands of the middle and inferior basin of Crisul Negru river highlight in terms of the soil wet the highest weight among mezo-hydrophilic species, in terms of temperature the micro-mesotherm species and in terms of the chemical reaction of the soil the predominant species are the chemical amphitolerant.
The floristic elements spectrum shows that the cosmopolitan species are in a larger number, which means that the floristic composition of the association has a wide geographical spread.
The significance and the practical value of this study emerges from the fact that research results can serve as a guide for local authorities or as a scientific material for researches in biology, ecology, environmental protection, regional geography.