How do Wood Anatomical Traits in Salix Vary in Response to Flooding? A Case Study from the Yenisei River, Siberia

Abstract

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 lower reaches of the Yenisei River, Siberia we collected white willow (Salix alba) samples from a fluvial fill flat terrace that occasionally floods when water levels are extremely high. Using these samples, we use an approach known as quantitative wood anatomy (QWA) to measure variation in radial cell dimensions, particularly fiber lumen area and cell wall thickness. We then use Pearson correlations to compare these measurements to observed records of flood stage. We hypothesize that (1) intra-annual changes in wood fiber size (LA) and cell wall thickness (CWT) in Salix rings can be quantified using QWA, and (2) these patterns are related to flood magnitude and/or duration. We find that normalized wood fiber CWT best captures intra-annual density fluctuations (IADFs) found in Salix rings. For some trees, time series of normalized CWT correlate with July flood durations, which have profoundly 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.