Floristic diversity and agricultural value of Phalaridetum arundinaceae ( Koch 1926 n . n . ) Lib . 1931 in the selected river valleys of the Zamość region

The study presents the results of a floristic survey conducted using the Braun-Blanquet method (50 phytosociological relevés) in permanent grasslands in three river valleys of the Zamość region (Por, Huczwa, Wieprz). The goal of the survey was to determine the floristic diversity and fodder value of the Phalaridetum arundinaceae association (Koch 1926 n.n.) Lib. 1931. A total of 93 plant species from 25 botanical families were identified in the areas under study. The species richness of the Phalaridetum arundinaceae differed among river valleys. It was observed that these are often transitional forms similar to the association of the Molinio-Arrhenatheretea class, Molinietalia order. Predominance of hemicryptophytes and a relatively large share of geophytes was recorded. Based on the fodder value score calculated for the dry matter of the association, the community under study can be classified as having a medium or poor nutritional value.


Introduction
Semi-natural Phalaridetum arundinaceae (Koch 1926 n.n.) Lib.1931 phytocoenoses have been recognized as valuable not only from the agricultural but also environmental perspective [1].According to Grynia et al. [2], Phalaris arundinacea is associated with special habitats: it usually grows on very humid organic soils, in periodically flooded riparian habitats.Kozłowski et al. [3] observe that Phalaris arundinacea grass also grows in drier habitats, under heavy nitrogen fertilization, even though its persistence is reduced in such conditions.Grass rushes with the predominance of Phalaris arundinacea also grow in forest meadows [4] and appear at sites where trees have been removed [5].
Phalaridetum arundinaceae in the Ina valley in the Sowno area occurs on brown alluvial soils [6], while in the Ochoża and Bobrówka valleys it grows on peat-loam soils [7].Grass communities with the predominance of Phalaris arundinacea have also developed on peat-muck soils (the Kuwasy peatbog, drained in the 1950s), with medium phosphorus content [8].Some researchers believe that Phalaris arundinacea has a broad range of tolerance to soil pH.It develops well at acidic and neutral sites, showing high persistence [3].
The recent literature on the subject [6,9,10] suggests a growing non-production role of Phalaridetum arundinaceae.The significance of this association in habitat conservation and management is appreciated, namely its role in the protection against soil erosion by wind and water and its role of an ecological filter absorbing considerable amounts of biogenic elements in the water of the streams flowing through this association.Phalaris arundinacea grass also has an enormous significance for avifauna and mammal fauna [11].
The goal of the survey was to determine the floristic diversity and fodder value of the Phalaridetum arundinaceae association (Koch 1926 n.n.) Lib.1931 in three river valleys (Por, Huczwa and Wieprz) in the Zamość region.

Material and methods
Floristic surveys were conducted in permanent grasslands in the valleys of three rivers -the Por, Huczwa and Wieprz (Roztocze National Park) -within Zamość County in southeastern Poland.Fifty phytosociological relevés were made using the commonly applied Braun-Blanquet method [12] in Phalaridetum arundinaceae meadows in late May/early June (before the first hay harvest).Floristic diversity was determined based on the mean number of species per relevé, the Shannon-Wiener index (H'), and the total number of species.The value of the Shannon-Wiener diversity index [13] is relatively stable for samples of varying size and is determined primarily by the value of the share of the species.The index is expressed by the following equation: where: S -number of species in sample; p i -likelihood that a randomly selected specimen represents species i, where: n i -significance coefficient of a given species; N -sum of significance coefficients of all species.
Furthermore, the percentage share of species from the particular botanical families was calculated, species were classified in terms of plant life-forms according to Raunkiaer [14].The ecological indicator values (EIV) were calculated for all the species recognized, using the Ellenberg system [15].Six environmental variables related to ecological indicator values describing the most typical habitat conditions were calculated -light (L), temperature (T), continentality (K), humidity (F), soil/water pH (R), and nitrogen requirements (N).
The agricultural value of Phalaridetum arundinaeae hay was determined based on the fodder value score (FVS) [16].For this purpose, meadow sward (from an area of 0.5 m 2 ) was sampled in the most representative patches of the association and botanical and gravimetric analyses were carried out.The hay yield (t ha −1 ) from the first harvest was also determined.
The syntaxonomy of the association was identified according to Matuszkiewicz [17], while the nomenclature of vascular plants was adopted based on Mirek et al. [18].

Results
The In the analyzed river valleys of the Zamość region, 93 plant species were found to occur in the sward of Phalaridetum arundinaceae meadows, with the greatest number of taxa identified in the sward of Phalaridetum arundinaceae in the Por valley (68 taxa).
Similarly, it was here that the greatest mean number of species per phytosociological relevé was recorded -Tab. 1.
The research of the selected river valleys in the Zamość region revealed the encroachment of species characteristic of the Molinio-Arrhenatheretea class of the Molinietalia order, Calthion and Filipendulion complex (Tab.2).Interestingly enough, this process occurred with the lowest intensity in the Huczwa River valley, which was reflected in the lowest species richness of the phytocoenoses.At the same time, the presence of the largest percentage of species representing the Phragmitetea class (40.91%) indicates that they developed in the most typical form in comparison to those examined in the other river valleys.
It was found that hemicryptophytes represented the highest proportion of plant life-forms according to the Raunkiaer system in the valleys analyzed.Species categorized as geophytes, hydrophytes and helophytes were less numerous (Tab.3).
The plant species recorded belong to 25 botanical families, among which the greatest number of Poaceae, Cyperaceae, Ranunculaceae and Asteraceae species were found (Tab.4).Humid -but not wet -habitat species predominate in all the three river valleys.Furthermore, wet habitat species also grow in the Huczwa valley; hence the mean value of the F index is 8.21.A clear majority of taxa of the Phalaridetum arundinaceae association in all the river valleys under study prefer neutral or slightly alkaline soils (mean R value from 6.09 to 6.78).Most species require moderate and high nitrogen content in the soil (mean N value from 6.33 to 6.58) -Tab. 5.
The dry matter yield of the 1st harvest of the analyzed Phalaridetum arundinaceae sward was the highest in the Wieprz valley (mean 5.27 t ha −1 ).A lower yield was observed for Phalaris grass in the Por valley (mean 3.9 t ha −1 ) and the Huczwa valley (mean 5.81 t ha −1 ).The FVS value of the dry matter of the Phalaridetum arundinaceae sward in the selected river valleys in the Zamość region indicates that the sward is of medium or poor nutritional value [16] -Tab.6.

Discussion
The investigations conducted by the author and other researchers [4,6,10,19,20] show that Phalaridetum arundinaceae meadows are floristically diverse.In comparison with the studied river valleys of the Zamość region, the greatest mean number of species per phytosociological relevé was found in the patches of the Por valley and the lowest one in the Huczwa valley.A smaller number of species per relevé was found in an analogous association in the Ochoża valley (5 to 8) and the Bobrówka valley (4) [7].Phalaridetum arundinaceae meadow patches show greater species richness in more humid habitats than in the sward of phytocoenoses in periodically dry habitats [10].The mean Shannon-Wiener diversity index (H') calculated for Phalaridetum arundinaceae was H' = 3.8 in the Por valley, H' = 3.6 in the Huczwa valley, and H' = 3.2 in the Wieprz valley.Phalaridetum arundinaceae meadows in the Barycz valley showed a greater number of species and a higher floristic diversity index (H' > 4.0) [19].The diversity index calculated for the Phalaridetum arundinaceae association in the Barycz valley was lower, H' = 1.57[21], while for Wielkopolska H' = 1.11 [22].Some researchers believe that the environmental and fodder value of the Phalaridetum arundinaceae association can improve as a result of changes in hydrologic conditions and the consequent reduction in soil humidity.Under Tab. 3 Plant life-forms in the study areas (in pieces) according to the Raunkiaer system.
similar humidity conditions, patches of the Phalaridetum arundinaceae association in the Barycz valley usually occurred in transitional form similar to communities of the Molinio-Arrhenatheretea class, Molinietalia order [19,23,24].In all the three valleys analyzed, species from the Poaceae family had the highest percentage share, namely: 34.21% in the Por valley, 28.57% in the Huczwa valley, and 12.10% in the Wieprz valley.Grasses also had the greatest share (37.8%) in the Phalaridetum arundinaceae typicum association in the selected valleys of the Warta valley [20].Taxa of the Cyperaceae family had a lower percentage share (from 7.89% in the Por valley to 14.28% in the Huczwa valley).The Ranunculaceae and Asteraceae families were the most frequently represented among dicotyledonous species (Tab.4).In the Phalaridetum arundinaceae meadows of the Great Wetlands of the Obra River (Wielki Łęg Obrzański), dicotyledons predominated (44 to 77%) but had a low abundance (coverage) [10].
In the Zamość region, the Phalaridetum arundinaceae meadows of the selected river valleys revealed a varied fodder value for livestock (FVS from 1.60 to 4.06) -Tab.6.The dry matter of Phalaridetum aruindinaceae typicum in the river valleys of the Wielkopolska region [25] had a distinctly higher fodder value score (FVS = 7.1) and higher yields than in the analyzed river valleys of the Zamość region.According to Kryszak et al. [19], a decrease in the yields and fodder value of the Phalaris arundinacea grass sward results in the recession of rush species, loosening up of the turf, appearance of empty areas, and encroachment of low creeping grass or dicotyledonous plant species.

Conclusions
The Phalaridetum arundinaceae meadows in the river valleys of the Zamość region are floristically diverse.The highest species richness is characteristic for patches that correspond to the Molinio-Arrhenatheretea class, while the poorest species richness is observed in patches of the Phragmitetea class.
The Phalaridetum arundinaceae association occurs mainly on nitrogen-rich soils with a pH of 7-8.Soil humidity is the main determinant of its floristic diversity.
Based on the fodder value score, the Phalaridetum arundinaceae association can be regarded as having a poor or medium nutritional value for animals, with the dry matter yield ranging 3.78-5.27ha −1 .
Phalaridetum arundinaceae (Koch 1926 n.n.) Lib.1931 association was distinguished in the grasslands of the Zamość region (SE Poland) in the valleys of three rivers: Por, Huczwa and Wieprz.The syntaxonomy is the following: Class: Phragmitetea R. Tx. et PRSG 1942 Order: Phragmitetalia Koch 1926 Alliance: Magnocaricion Koch 1926 Association: Phalaridetum arundinaceae (Koch 1926 n.n.) Lib.1931 Floristic diversity of Phalaridetum arundinaceae in the river valleys of the Zamość region.Phytosociological diversity of Phalaridetum arundinaceae in the river valleys of the Zamość region.