Annual Wetlands Communities of National Nature Park “Pyriatynskyi” (Poltava Oblast, Ukraine)
Kovalenko O.A., Kalista M.S.
Department of Botany, National Museum of Natural History of NAS of Ukraine, Bohdana Khmelnytskoho 15, 01607 Кyiv, Ukraine

Угруповання заплавного ефемеретуму Національного природного парку «Пирятинський» (Полтавська область, Україна)
Коваленко О.А., Каліста М.С. 
Відділ ботаніки, Національний науково-природничий музей НАН України, вул. Б. Хмельницького, 15, 01607, Київ, Україна

Annotation. The results of a comparative structural analysis of the annual wetland herbs vegetation syntaxa (class Isoëto-Nano-Juncetea) of National Nature Park “Pyriatynskyi” (Poltava Oblast, Ukraine) are presented. The critical differentiation of Nano-Cyperion and Eleocharition ovatae alliances and legitimacy of recognition Radiolion linoidis alliance and Polygono recti-Juncetum juzepczukii association as separated syntaxa of the main ranks are emphasized.

Analysis of the syntaxa of the annual wetlands vegetation as multiparameter systems revealed a complex picture of their differentiation in a system of floral, ecological and geographic coordinates. 
The dendrogram of the floristic similarity of phytocenoses mostly coincides with the early classification of vegetation of class Isoëto-Nano-Juncetea developed for NNP “Pyriatynskyi”. 
Based on a complex comparative study of Isoëto-Nano-Juncetea syntaxa analysis on the one hand pointed to the critical nature of the distinction between the Nano-Cyperion and Eleocharion ovatae unions, on the other hand, confirmed the acceptability of the Radiolion linoidis as a separate syntaxon, and the legitimacy of distinguishing associations Eragrostidetum suaveolentis and Polygono-Juncetum. 
Considering the above, we think that a large-scale study of the syntaxon of the annual wetland vegetation allows to make a stable system of the Isoëto-Nano-Juncetea class and shed light on many theoretical and practical problems in the classification of vegetation.