Floodplain forests are valuable but increasingly endangered landscapes, threatened by human pressures that drive habitat decline and environmental change. The Drava River in Croatia is among the most preserved lowland rivers in the Pannonian Basin with a wide vegetated corridor, yet it is impacted by dam construction that has significantly altered its hydrology and geomorphology. Here, we used Harmonized Landsat- Sentinel (HLS) data to investigate floodplain forest phenology from 2016 to 2024 in two study areas: one located between two accumulation reservoirs and dams, and the other farther downstream in a reach with less pronounced human impacts. Key phenological metrics, start of season (SOS) and end of season (EOS), were derived from EVI2 time series using the R package phenofit. To investigate drivers of spatio-temporal patterns, we analysed climatic variables (temperature, precipitation) and hydrological variables (discharge, groundwater levels). The results showed that SOS varied more strongly between years than between sites and it was significantly negatively associated with mean March temperature. In contrast, EOS occurred, on average, more than 30 days earlier at the upstream dam-impacted site, where river incision and reduced discharge presumably contributed to lower groundwater levels. These findings suggest that, in addition to climate, hydrological conditions strongly influence floodplain forest phenology, highlighting the role of human impacts in shaping riparian ecosystem processes in regulated riverine environments.
Pavlek et al. (Wed,) studied this question.