Hydrology as a Determinant of Riparian Habitat Structure in Lowland River Floodplains

Abstract

The objective of the study was to determine the relationship between the structure of phytocenoses in riparian wetland ecosystems and the hydrologic regime in a lowland river floodplain. The hydrobotanical study was conducted over three years 2017, 2018, and 2019, which differed in hydrological conditions (wet, average, and dry) in a middle section of the Supraśl floodplain (NE Poland) as a case study. The results showed that the structure and pattern of phytocenoses in the floodplain are primarily controlled by hydrological regime of the river and the geomorphological features of the area. The reach and duration of the flood contributed to a specific pattern of riparian vegetation. Based on plant community structure and riparian habitat indicators such as soil moisture, fertility, reaction pH, soil granulometry, and organic matter content, four habitat types were identified and supported by discriminant analysis (DA): wet, semi-wet, semi-dry, and dry zones. The indicator species analysis (ISA) revealed species characteristic of the zones with the dominance of reed rush, reed canary grass, anthropogenic or partially natural herbaceous communities along watercourses or riparian meadows, respectively. Natural inundation of the river water is an important driver of site-specific vegetation elements and habitat types and determines habitat availability, biodiversity, and ecosystem functions of wetlands. This knowledge can serve as the basis for conservation efforts, sustainable management practices, and decision-making processes aimed at maintaining the biodiversity and ecological integrity of riparian ecosystems in similar regions.