Impact of environmental disturbances on hydrology and nitrogen cycling in Central European forest catchments

Climate-related events and bark beetle outbreaks influenced hydrological dynamics and nitrogen cycling in three Central European forest catchments in the GEOMON network. Since 1994, distinct environmental phases were observed at studied catchments. Initially, nitrate (NO 3 ⁻ ) concentrations declined at Anenský potok and Polomka due to reduced acid deposition, while remaining stable at Pluhův bor. From 2015 onwards, drought and extensive spruce dieback caused significant hydrological disruptions, including over a 200% increase in runoff at Anenský potok. In contrast, moderated hydrological impacts due to differences in the evapotranspiration-to-precipitation ratio was observed at Polomka. At Pluhův bor, gradual deforestation combined with climate change effects, such as rising temperatures and decreasing precipitation, resulted in stable runoff compared to the abrupt changes in the other two catchments. Despite these differences, disturbances across all catchments intensified nitrate leaching and disrupted nitrogen retention. This led to substantial dissolved inorganic nitrogen (DIN) export, particularly at Polomka, which is characterized by a low soil carbon-to-nitrogen ratio (C/N). These findings highlight the vulnerability of forest ecosystems to nitrogen loss under environmental stressors and underscore the importance of effective management strategies to mitigate nitrogen cycle disruptions in the context of ongoing climate change.