Recent, record-breaking discharge in the Yenisei River, Siberia, is part of a larger trend of increasing river flow in the Arctic driven by Arctic amplification. These changes in magnitude and timing of discharge can lead to increased risk of extreme flood events, with implications for infrastructure, ecosystems, and climate. To better understand the changes taking place, it is useful to have records that help place recent hydrological changes in context. In addition to an existing network of river gauges, extreme flood events can be captured in the wood anatomical features of riparian trees, which help identify the most extreme flood events. Along the Yenisei River, Siberia we collected willow (Salix spp.) samples from a low terrace that occasionally floods when water levels are extremely high. Using these samples, we use an approach known as quantitative wood anatomy to measure variation in radial cell dimensions, including vessel area, wood fiber size and cell wall thickness. We then compare these measurements to observed records of flood stage. We hypothesize that (1) characteristic patterns of wood fiber size and cell wall thickness in Salix rings are present during flood years, (2) these patterns can be quantified by measuring wood fiber size and cell wall thickness, and (3) quantified variations in cell anatomical properties can be related to flood magnitude and duration. Understanding how riparian vegetation responds to extreme flood events can help us better manage riparian ecosystems and understand changes to the Arctic hydrological regime.

Recent, record-breaking discharge in the Yenisei River, Siberia, is part of a larger trend of increasing river flow in the Arctic driven by Arctic Amplification (AA). These changes in magnitude and timing of discharge can lead to increased risk of extreme flood events, with implications for infrastructure, ecosystems, and climate. To better understand the changes taking place, it is useful to have records that help place recent hydrological changes in context. In addition to an existing network of river gauges, wood anatomical features in riparian trees have been shown to record extreme flooding. Along the lower reaches of the Yenisei River we collected white willow (Salix alba) samples from a fluvial fill flat terrace that occasionally floods when water levels are extremely high. At the end of certain annual growth rings these samples displayed terminal white bands, a type of intra-annual density fluctuation (IADF). To identify the characteristics and causes of these features we use an approach known as quantitative wood anatomy (QWA) to measure variation in fiber cell dimensions across tree rings, particularly fiber lumen area (LA) and cell wall thickness (CWT). We investigate (1) which cell parameters and method to extract intra-annual data from annual tree rings best capture terminal white bands identified in Salix, and (2) if these patterns are related to flood magnitude and/or duration. We find that fiber CWT best captures the IADFs found in Salix rings. For some trees, time series of normalized CWT correlate with July flood durations, which have changed since the 1980s. Understanding how riparian vegetation responds to extreme flood events can help us better manage riparian ecosystems and understand changes to the Arctic hydrological regime.