Snow Accumulation Increases With Forest Structural Diversity in Low-Relief Catchments

In snow-dominated areas, runoff from winter precipitation can comprise up to 80% of the annual water budget. Warming winters are shifting snow precipitation to rain, shortening the snow accumulation and melt seasons, and increasing midwinter melt events and flooding during rain-on-snow events. At the same time, forests are changing in species composition and geographical extent, and forest-dominated catchments can mediate the effects of increased winter temperatures on snow dynamics. Here, we combine climatic data and high-resolution forest and snow observations to investigate the complex relationships between forest canopy structure and below-canopy snow depth in two low-relief Mississippi headwater catchments. To do so, we use a two-dimensional canopy cover metric (i.e., leaf area index) with forest canopy and understory surveys and catchment terrain (e.g., slope, aspect) to examine their joint influences on snow depth. Results show that (1) co-dominant tree density is a better predictor of peak snow depth over leaf area index, due to representation of both canopy overlap and interception and (2) canopy structural diversity increases peak snow depth. These results suggest that maintaining forest structural diversity not only contributes to forest health but also allows for a deeper snowpack, thereby increasing the potential for water storage in snow-dominated low-relief watersheds.