Canopy nutrient balance predicts autumn senescence across U.S. forests.

Higher canopy N:P is linked to earlier autumn senescence across U.S. NEON forest sites, occurring in 20 of 25 sites, even after accounting for climate and structure.

• Why it matters: Nutrient enrichment is reshaping ecosystem nutrient limitation, but it is unclear how canopy nutrient balance controls the seasonal end of photosynthesis and carbon cycling.
• What they did: The study combined airborne imaging spectroscopy with remote phenology across NEON sites, testing whether canopy nutrient ratios predict spatial variation in autumn senescence while controlling for climate, elevation, dominant species, and canopy structure.
• The result: Higher N:P predicts earlier senescence in most sites, while higher N:K shows opposite associations in 19 sites; productivity only modestly mediates these links, enabling nutrient-informed phenology forecasts beyond climate alone.

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