On the Tibetan Plateau, where elevations average more than 4,000 meters, snow is far more than just a winter blanket. New research indicates that its impact on vegetation shifts dramatically from spring to summer: while the effect is negative in some areas and positive in others, this transition covers a quarter of the plateau.
In the spring, delayed snowmelt postpones the start of the growing season. Plants are slower to emerge, and their growth during this initial period is notably weaker. Researchers tracked this through snow-clearance dates and phenological shifts, concluding that the later the snow disappears, the later the green season begins, leading to a drop in spring productivity.
The situation changes entirely by summer. The impact of early melting, which seemed to act as a brake in the spring, effectively reverses course. Additionally, moisture stored in the soil from the winter continues to nourish plants during the hotter months. As a result, in those very regions where snow limited growth in the spring, it actually supports it during the summer.
Researchers analyzed satellite data on snow cover and the NDVI vegetation index from 2000 to 2017, using structural equation models to distinguish various impact pathways. It was found that phenological mechanisms dominate in the spring, while soil moisture becomes the key factor in the summer. Most global vegetation models do not yet replicate this seasonal transition.
The Tibetan Plateau is often called the "Water Tower of Asia." It is the source of major rivers that sustain billions of people. Understanding exactly how snow affects grasses and shrubs across different seasons allows for more accurate predictions of the region's evolving green cover and water balance.
