Phenology drives asymmetric responses of ecosystem productivity stability to warming and cooling

Ecosystem productivity stability is a key indicator of ecosystem functioning under climate change, but the role of cooling periods in increasingly variable climates remains poorly resolved. Using a 17‐year reciprocal transplant experiment along an elevational gradient in alpine grasslands, we examined the asymmetric effects of temperature fluctuations, including warming and cooling, on the above‐ground net primary productivity (ANPP) temporal stability. Warming significantly decreased ANPP temporal stability, whereas cooling had no net effect. These asymmetric responses were primarily governed by phenological dynamics. The decline in ANPP temporal stability under warming was primarily driven by advanced leaf‐out phenology. Under cooling, delayed leaf‐out and reduced plant size promoted temporal stability of ANPP, but these effects were offset by direct cooling‐induced suppression and delayed flowering. Our findings indicate that periods of cooling are unlikely to mitigate instability driven by warming, highlighting the necessity to incorporate temperature asymmetry and phenological regulation into predictions of ecosystem stability under increasing climate variability. Read the free Plain Language Summary for this article on the Journal blog.