Morphological and functional diversity of floodplain water bodies and their classification according to the structure of the surrounding vegetation cover

Abstract

The study identified the indicators of functional and morphological diversity of the Dnipro River floodplain water bodies within the Dnipro-Orilsky Nature Reserve. The database of recorded water bodies of the reserve consists of 302 objects. The total area of the floodplain and the water bodies close to it is 24.2 km2, and the area of the water bodies is 6.03 km2. Thus, the water bodies cover 24.9% of the floodplain area. The water bodies of the Dnipro River channel system account for 17.9% of the number of water bodies in the Reserve and 71.4% of the total area of water bodies and the Dnipro River in the projection of the Reserve. The water bodies of the study system are located at a distance of up to 3.2 km from the main channel of the Dnipro River. The average distance is 1.50 ± 0.04 km. The closest water bodies to the main channel of the Dnipro River are those in the Dnipro riverbed, which were formed as a result of the creation of a reservoir in the floodplain. Three factors with eigenvalues greater than unity were extracted as a result of factor analysis of the morphometric features of the water bodies. These three factors explain 85.8% of the cumulative correlation of morphometric features. Factor 1 reflects a latent variable that can be identified as the total size of the ponds. The total size of the water bodies was the largest for the Orilsky Canal, with slightly smaller sizes in the water bodies of the Dnipro River channel. The smallest water bodies were in the Obukhivka system. Factor 2 as a latent variable can be identified as the level of shoreline development. According to this indicator, the water bodies of different systems did not differ. Factor 3 can be identified as the altitude and variability of the relief surrounding the water bodies. The lowest values of this factor were for the water bodies of the Orilsky Canal and the Obukhivka system. The values were slightly higher for the water bodies of the Taromske and Mykolaivka systems. The highest levels of relief and its variability were characteristic of the areas close to the water bodies of the Dnipro channel system. Cluster analysis allowed us to identify seven clusters that are relatively homogeneous in terms of morphometric features. These clusters can be differentiated based on the results of discriminant analysis. An important aspect of differentiation is the size of the water bodies, the development of the shoreline, and the height of the terrain surrounding the water bodies. The identified clusters correspond well to the types of water bodies, which are selected based on their orientation relative to the preferred direction of water flow. The satellite image classification was used to identify 15 types of vegetation cover within the reserve. The water bodies are characterized by specific spectra of the main types of plant communities in their surroundings. The cluster analysis of the water bodies resulted in nine clusters based on the structure of the vegetation complexes surrounding them. Each cluster contains the entire list of vegetation types that have been established for floodplain ecosystems. The peculiarity of the complexes lies in the specific ratio between different vegetation types. The most important structural factors that distinguish the complexes are the projective cover of oaks, floodplain meadows, and shrubs. At the top level of the hierarchy, the complexes are differentiated by the projective cover of floodplain meadows. At a lower level, the differentiation is based on the projective cover of sands or oaks. The clusters identified on the basis of plant complexes and morphometric features, as well as the types of water bodies in terms of orientation with respect to the prevailing water flows, correspond to each other to a certain extent.