Global Patterns and Drivers of Recent Decoupling Between Extratropical Spring Phenology and Temperature

Area of Science:

• Ecology
• Climate Science
• Remote Sensing

Background:

• Spring phenology and its relationship with thermal cues are critical for ecosystem function.
• The decoupling of vegetation green-up from temperature signals across diverse biomes is not well understood.
• Understanding phenological shifts is vital for predicting ecosystem responses to climate change.

Purpose of the Study:

• To quantify the magnitude and trends of phenological mismatch (ΔSOS) between vegetation green-up onset (GSOS) and thermal growing season onset (TSOS) across extratropical biomes.
• To identify the key drivers influencing the decoupling of GSOS from TSOS.
• To investigate biome-specific pathways of phenological change and their implications for climate-biosphere interactions.

Main Methods:

• Utilized satellite data spanning from 1982 to 2021 to analyze phenological trends.
• Quantified the onset of vegetation green-up (GSOS) and thermal growing season onset (TSOS).
• Analyzed the relationship between phenological shifts and climatic variables including temperature, shortwave radiation, and precipitation, considering biome-specific characteristics.

Main Results:

• The onset of vegetation green-up (GSOS) generally lags behind the thermal growing season onset (TSOS).
• This phenological mismatch (ΔSOS) has significantly increased by 1.51 days per decade since 1996, particularly in shrublands and grasslands.
• Phenological decoupling is biome-dependent: warm-dry grasslands and shrublands show increasing mismatch due to moisture limitation, while temperate forests exhibit dampened mismatch due to warming and increased radiation.

Conclusions:

• Phenology-temperature decoupling is accelerating but heterogeneous across biomes, with significant implications for ecosystem synchrony and carbon cycling.
• Non-thermal drivers, such as precipitation and radiation, play a crucial role in modulating phenological responses, especially in moisture-limited ecosystems.
• Incorporating biome-specific controls and non-thermal drivers into Earth system models is essential for accurately predicting future climate-biosphere interactions.