Temperature and snowfall trigger alpine vegetation green-up on the world's roof

Area of Science:

• Ecology
• Climate Science
• Phenology

Background:

• Alpine ecosystems on the Qinghai-Tibetan Plateau face rapid warming, impacting vegetation phenology.
• Satellite data show conflicting trends in vegetation green-up dates, creating uncertainty in climate attribution.
• Ground-based calibration is lacking for remote-sensing phenology estimates, limiting accurate predictions.

Purpose of the Study:

• To investigate spatiotemporal variations in herbaceous plant green-up dates using ground-based data.
• To identify the key climate drivers influencing spring phenology on the Qinghai-Tibetan Plateau.
• To improve predictions of vegetation growth and carbon balance under climate change.

Main Methods:

• Utilized 72 ground-based green-up datasets for 22 herbaceous species (1981-2011).
• Analyzed daily air temperature and precipitation data from 19 climate stations.
• Compared ground data with existing remote-sensing findings on phenological trends.

Main Results:

• Ground data do not consistently support advancing green-up trends or a mid-1990s turning point reported by satellite studies.
• No robust evidence for warmer winters causing later green-up dates was detected; chilling requirements may not be a primary driver.
• Temperature primarily controls green-up at lower elevations with scarce snowfall, while temperature and precipitation interact at higher elevations with abundant snowfall.

Conclusions:

• Snowfall and temperature interactions during late winter/early spring are critical for spatiotemporal variations in green-up dates.
• Chilling requirements appear less influential than previously thought for spring warming responses.
• Accurate prediction of vegetation and carbon balance requires integrating both temperature and snowfall data.