## 4 Results
Group I includes Rubus idaeus, _Prunus avium_, _Salix caprea_, _Betula pubescens_, _Betula pendula_, _Alnus glutinosa_, _Calluna vulgaris_, _Quercus robur_, _Populus tremula_, _Salix aurita_, _Salix cinerea_, _Salix pentandra_, _Pinus sylvestris_, _Vaccinium myrtillus_, _Salix purpurea_, _Salix alba_, _Salix viininalis_, _Pyrus \begin{table}
\begin{tabular}{c c c c c} \hline  & **2015** & & & **2018** \\ \hline
**PFR–R** & **R–RA** & **RA–FR** & **PFR–R** & **R–RA** & **RA–FR** \\
0.31 & 0.84 & 0.28 & 0.29 & 0.76 & 0.32 \\
**PFR–RA** & **R–FR** & & **PFR–RA** & **R–FR** \\
0.32 & 0.26 & & 0.32 & 0.26 \\
**PFR–FR** & & & **PFR–FR** & \\
0.36 & & & 0.37 & \\ \hline \multicolumn{5}{c}{**TOTAL**} \\ \hline
**PFR–PFR** & **R–R** & **RA–RA** & **FR–FR** & \\
0.91 & 0.85 & 0.89 & 0.81 & \\ \hline \end{tabular}
\end{table} 
Table 5: The Jaccard’s species similarity coefficient for shore sectors of Lake Piaseczno in 2015 and 2018 (extreme values are marked with colours: yellow, min; orange, max). Figure 3: A dendrogram of hierarchical classification for tree and shrub species (**a**) and their similarity for shore sectors of the lake in 2015 and 2018 (**b**) based on Jaccard’s coefficient and the average linkage method. Species composition of tree and shrub vegetation: _Acer platanoides_, _Alnus glutinosa_, _Andromola polifolia_, _Betula pendula_, _Betula pubescens_, _Calluna vulgaris_, _Cordus avellana_, _Frangula ahus_, _Frazius excelsior_, _Malus domestica_, _Oxycoccus pulstris_, _Padus avium_, _Pinus sylvestris_, _Populus tremula_, _Prunus avium_, _Pyrus communis_, _Quercus petneau_, _Quercus robur_, _Rubus caesius_, _Rubus idaeus_, _Salix alba_, _Salix aurita_, _Salix caprea_, _Salix cinerea_, _Salix fragilis_, _Salix pentandra_, _Salix purpurea_, _Salix osmarififolia_, _Salix viininalis_, _Sambucus nigra_, _Sorbus acucuparia_, _Spiraea media_, _Vaccinium myrtillus_, _Vaccinium uliginosum_ and _Vaccinium vitis-idea_. communis, Malus domestica, Spiraea media, Salix fragilis, Padus avium_ and _Quercus petraea_ (Figure 3a). In phytosociological terms, Group I shows considerable diversity, including species from peatland communities: Oxycocco-Sphagnteea (five species) and Scheuzcherio-Caricetea fuscae (three species); from shrub communities: Betuletum pubescentis and Salicetum pentandro-cinereae (three species each); and from the forest community: Querco-Piceetum (one species). The group included a high number of species occurring in different shore sectors of Lake Piaseczno in low numbers (often single individuals) with variable and other phytosociological affinity (13 species). Group II includes _Rubus caesius_, _Frangula alnus_, _Sorbus aucuparia_, _Corylus avellana_, _Sambucus nigra_, _Vaccinium vitis-idaea_, _Frazinus excelsior_, _Salix rosmariniifolia_ and _Acer platanoides_ (Figure 3a). The species show similarly diverse phytosociological affinity (Oxycocco-Sphagnteea, one species; Scheuzcherio-Caricetea fuscae, one species; Salicetum pentandro-cinereae, two species; Querco-Piceetum, three species; other, four species). The small group III includes _Oxycoccus palustris_, _Andromeda polifonia_ and _Vaccinium uliginosum_ (Figure 3a), and was particularly related to the communities Oxycocco-Sphagnteea (two species) and Scheuzcherio-Caricetea fuscae (one species). The hierarchical classification of shore sectors of Lake Piaseczno in terms of species also permitted the determination of a lack of considerable difference in tree and shrub communities for subsequent study years and the determination of the typological similarity for sectors R and RA (Figure 3b). An analysis of the heatmap that ascribed the frequency of co-occurrence of the identified tree and shrub species to the phytocoenoses of the study sectors in subsequent years revealed several other patterns (Figure 4). For example, more than 54% of tree and shrub species were found in the sectors RA and R, and slightly more than 25% of these species occurred in all sectors in both years of research.