Effects of warming on the timing of snowmelt streamflow and seed release by dominant riparian trees

What is it about?

Global warming is changing the timing of many natural springtime events, including snowmelt and plant leaf-out, flowering, and seed release. These changes could make it so that fewer plant resources are available during times when plants need them the most. Riparian trees growing along rivers rely on high snowmelt-driven streamflow during seed release to provide enough moisture and bare ground for seedling establishment. We show that warming is likely to change the timing of snowmelt-driven streamflow more than the timing of seed release, leading riparian trees to release their seeds after floods have receded and soils have dried, potentially reducing seedling survival and forest regeneration.

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Photo by Jack Anstey on Unsplash

Photo by Jack Anstey on Unsplash

Why is it important?

This work provides some of the first evidence that warming could decouple the timing of plant resource requirements from the timing of plant resource availability. Cottonwood and willow forests dominate riparian habitats across the northern hemisphere and provide the foundation for critical riparian ecosystem services, including wildlife habitat, water quality, streambank stabilization, and flood mitigation. By decoupling the timing of seed release from snowmelt streamflow, warming is likely to reduce moisture availability for riparian cottonwood and willow seedlings, which may reduce seedling survival and cottonwood and willow abundance.