The primary research goal is to identify differences and diagnostic features of the phytolith spectra of the steppe and forest phytocoenoses. The paper presents the research results of recent soils from various communities. The authors employ the phytolith analysis method. The isolation of phytoliths from recent soils has been carried out with the help of the maceration method and from plants – the dry ashing method. The authors counted the phytoliths using the Olympus BX-51 light microscope. Additionally, the authors have compiled the spectra using the 2C software. The paper compares the phytolith spectra of plain and mountain steppe phytocoenoses. The comparison reveals that the considered plain communities are more similar in phytolith composition than the mountain ones. The following morphotypes are common for all spectra: low conical rondel particles and psilate ribbed particles. These are the forms that characterize steppe communities. Analysis of phytolith spectra of the mountain forest communities demonstrates that the presence of ribbed particles of psilate is common for all spectra. The common feature of all forest spectra is the presence of psilate symmetrical particles, polylobate trapeziforms, lanceolates (trichomes) with a massive base, and trapeziform bilobate (“Stipa-type”) particles. In the spectra of all pine forests, there is a low content or complete absence of needle phytoliths. Diagnostic features of individual phytocoenoses have not been found. The most significant is the ratio of individual phytolith forms in the phytolith spectrum. The comparative analysis of phytolith spectra of the phytocoenoses in the south of western Siberia is carried out for the first time.

The article deals with the problem of nomenclature and classification of phytoliths. The division of the “crenate” morphotype (ICPN 2.0) into two forms – polylobate and wavy – is substantiated using Pooideae grasses from the south of Western Siberia. An analysis of the literature data confirms the heterogeneity of this morphotype and various interpretations of its variations. The polylobate group includes phytoliths high in lateral projection with distinct lobes, and the wavy group includes flattened forms with a wavy edge. The article details the formation of these two morphotypes in 52 grass species belonging to 25 genera. The main content of the study is an analysis of the occurrence of forms in various tribes and subtribes according to modern information on the phylogeny of cereals. The differences in the formation of these morphotypes at the sectional and subgeneric levels are considered using as examples three genera. The detailed analysis shows that wavy plates are most typical for the subtribe Aveninae(Poeae), polylobed particles are typical for the subtribe Agrostidinae (Poeae) and the tribe Meliceae. For some taxa, for example, the tribe Stipeae, ambiguous data have been obtained that are inconsistent with information from other territories, which indicates the need for further research on this problem. The analysis of occurrence of forms at the intrageneric level shows that in the genera Poa and Festuca there are differences between individual subgenera and sections, while for the genus Calamagrostis there are no such differences. The results obtained point to the prospect of using phylogenetic information in the classification of phytoliths and the need for a more complete study of large genera of grasses in terms of phytolith composition (Festuca, Calamagrostis, Poa, Stipa, etc.).