The phytosociological structure of monocultures of shrub willows with Salix cordata ‘Americana’ Hort., and with S. viminalis L. in the vicinity of Rudnik and Sarzyna (The Lower San River valley)

Few data have been published on the developing phytocenoses in the monocultures of shrub energy willows. It is possible that this study has described for the first time and in greater detail the floristic-phytosociological and ecological structure of the type of communities in question with an example of monocultures with Salix cordata ‘Americana’ Hort. and with S. viminalis L. The studies were conducted in the left-bank valley of the Lower San river, in the vicinity of Rudnik and Sarzyna (Fig. 1). These plantations were established on very similar alluvial soils, on arable fields, meadows, and pastures (Tables 1-6). In general, monocultures with Salix cordata ‘Americana’ are established on a somewhat wetter substratum than plantations with Salix viminalis. Moreover, plantations of the former yield a volume of biomass more often than plantations of the latter. Probably because of the foregoing reasons, the farms with S. cordata ‘Americana’ are characterized on average, inter alia, by a more varied floral composition than plantations with S. viminalis. Mainly for those reasons, the phytocenoses of monocultures of the two willow species were classified as belonging to separate, main groups of communities: with S. cordata, Americana' and with S. viminalis. Floristic-phytosociological similarities and differences between the identified community groups are highly complex. Above all, they are floristically very heterogeneous phytocenoses (Table 7). In both the main groups of these phytocenoses, worth noting are three similar subgroups of communities termed as segetal and meadow, ruderal, and underdeveloped (non-typical). The first two represent succession forms. The third one, on account of its highly simplified, quantitative composition of its species and also because of their exceptionally heterogeneous floristic composition, is a community developed in a very fragmentary way for various reasons. In the subgroups of segetal-meadow and ruderal communities, secondary forms of communities are observable with similar or different dominant species. Most of these community forms exhibit a greater or lesser resemblance to known phytocenoses, e.g. segetal (with Echinochloa crus-galli and Setaria glauca), meadow (with Agropyron repens, with Deschampsia caespitosa), ruderal (with Solidago gigantea, with Tanacetum vulgare) or wet sites (with Juncus bufonius). Only two of these communities, like those with Geranium palustre and with Equisetum arvense, constitute a certain phytosociological singularity, perhaps most characteristic of the willow monocultures investigated. The phytocenoses examined are characterized by a special combination of the quantitative percentage of the group value coefficients of plants belonging to specific syntaxonomic groups. (Table 8). The characterized phytocenoses with S. cordata, ‘Americana’ and with S. viminalis were provisionally included into the broadly interpreted class of Agropyretea intermedio-repentis. We can also accept th