A new class of the halophytic plant communities in Russia (Climacopteretea crassae Akhani 2004 ex Świerszcz et al. 2021)
Authors: Chuvashov A. V. , Golub V. B. 
Published: December 2023

We argue the presence in the delta of the Volga River of a new class of desert halophyte communities Climacopteretea crassae Akhani 2004 ex Świerszcz et al. 2021. This class was originally presented by H. Akhani (2004) as a syntaxon uniting plant communities with a predominance of annual succulent plants with C4 photosynthesis in Iran. The class was proposed previously, without specifying the nomenclature type.

In 2021, the class Climacopteretea crassae was validated (Świerszcz et al., 2021). S. Świerszcz and his co-authors gave the class a floristic and ecological characterization. The syntaxa of this class remind such of the class Therosalicornietea Tx in Tx. et Oberd. 1958 in terms of the high representation of annual species of the Chenopodiaceae family (although with the participation of perennial species). However, they cannot be called the pioneer communities that usually characterize communities of the class Therosalicornietea. Compared to communities Therosalicornietea they occupy drier habitats. In addition to the strong salinization of the soil, from the surface they can also be solonetzic. Typically, habitats of the class Climacopteretea crassae are significantly affected by grazing by farm animals. The order Psylliostachyetalia spicato-leptostachyae Świerszcz et al. 2021 and the alliance Climacopterion lanatae Berdyev et Golub in Golub 1995 were assigned to the class Climacopteretea crassae.

We proposed a new alliance Petrosimonion oppositifoliae all. nova in the order Psylliostachyetalia spicato-leptostachyae. The ass. Suaedo-Petrosimonietum Golub 1986 was placed in this alliance. This association was originally included in the class Glycyrrhizetea glabrae Golub et Mirkinin Golub 1995 (Golub and Mirkin, 1986; Golub, 1986), and later in Therosalicornietea R. Tx. in R. Tx. et Oberdorfer 1958 (Golub, 1995; Golub and Maltsev, 2013). Plant communities of this association are found in the delta of the Volga River in dry habitats, mainly located on the slopes of Baer hillocks and their foots with a deep level of groundwater. The soils are highly saline and solonetzic. Above the habitats occupied by ass. Suaedo-Petrosimonietum, along the slopes of Baer hills and on their tops, zonal communities of class Artemisietea lerchianae Golub 1994 occur. Various meadow and halophytic plant communities grow below this association. New alliance Petrosimonion oppositifoliae all. nova was suggested.

We suppose that further study of the desert halophytic vegetation of the Caspian Lowland will allow to establish other syntaxa of class Climacopteretea crassae on this territory. Thus, in our opinion, the non-ranking plant communities of Petrosimonia oppositifolia–Suaeda acuminata comm., Suaeda altissima–Suaedaa cuminata comm., Suaeda tragus–Suaeda acuminata comm., occurring in this lowland, including Russia are closely related to this class (Freitag et al., 2001). In addition, a new class of halophyte communities separate from Climacopteretea crassae should be established for this territory on automorphic and similar soils, the floristic composition of which differs significantly from the phytocenoses of hydromorphic soils, such as those belonging to class Therosalicornietea Tx. in Tx. et Oberd. 1958. But the consideration of this issue requires further study of the vegetation of the Caspian lowland and the territories adjacent to it.