Critical snowpack thresholds and escalating risks for extreme decreases in vegetation productivity across Northern Hemisphere ecosystems

Abstract

Seasonal snowpack is a key driver of vegetation productivity dynamics, but it is unclear at which levels of snowpack changes cause extreme decreases in vegetation productivity (EDVP), increasing the uncertainty in assessing the terrestrial carbon cycle. Here, we investigate the impact of different levels of snowpack changes on EDVP and identify the roles of different ecological processes of snowpack changes in the Northern Hemisphere (NH). The results show that over 30 % of snowpack decrease events are followed by EDVP events in ∼10 % of NH areas (p < 0.05), which is mainly attributed to snowpack’s moisture effect (via altering soil moisture). On average, the response of EDVP to snowpack changes increases rapidly when snow water equivalent (SWE) is –0.85 standard deviations (σ) below the mean, peaking at –1.33σ. Moreover, vegetation in warm and dry regions, especially grasslands, is more vulnerable to decreased SWE, and its resistance significantly increases with increasing precipitation. The future risk of EDVP occurrence will significantly increase in more regions owing to decreased snowpack, with ∼8 % of NH areas experiencing EDVP annually after ∼2083 under SSP5-8.5 scenario. Our findings underscore the significance of decreased snowpack in regulating EDVP and provide insights for better projecting and mitigating ecological consequences of snowpack changes.