Abstract
While many studies have reported that drought events have substantial negative legacy effects on forest growth, it remains unclear whether wetness events conversely have positive growth legacy effects. Here, we report pervasive and substantial growth enhancement after extreme wetness by examining tree radial growth at 1929 forest sites, satellite-derived vegetation greenness, and land surface model simulations. Enhanced growth after extreme wetness lasts for 1 to 5 years and compensates for 93 ± 8% of the growth deficit after extreme drought across global water-limited regions. Remarkable wetness-enhanced growths are observed in dry forests and gymnosperms, whereas the enhanced growths after extreme wetness are much smaller in wet forests and angiosperms. Limited or no enhanced growths are simulated by the land surface models after extreme wetness. These findings provide new evidence for improving climate-vegetation models to include the legacy effects of both drought and wet climate extremes.
Highlights
While many studies have reported that drought events have substantial negative legacy effects on forest growth, it remains unclear whether wetness events have positive growth legacy effects
We found that enhanced growth lasted 1–5 years after extreme wetness in the tree-ring chronologies (Fig. 1)
The magnitude of enhanced tree radial growth to wetness was found to be similar when using the Standardized Precipitation-Evapotranspiration Index (SPEI) (22% ± 7% increase in growth above normal conditions, calculated by the difference between observed and predicted growth with a linear model, integrated value of the whole enhanced growth period) and precipitation minus potential evapotranspiration (P−PET) (21% ± 6%), but a smaller increase (10% ± 5%) was found using soil moisture
Summary
While many studies have reported that drought events have substantial negative legacy effects on forest growth, it remains unclear whether wetness events have positive growth legacy effects. We report pervasive and substantial growth enhancement after extreme wetness by examining tree radial growth at 1929 forest sites, satellite-derived vegetation greenness, and land surface model simulations. Enhanced growth after extreme wetness lasts for 1 to 5 years and compensates for 93 ± 8% of the growth deficit after extreme drought across global water-limited regions. Limited or no enhanced growths are simulated by the land surface models after extreme wetness. These findings provide new evidence for improving climate-vegetation models to include the legacy effects of both drought and wet climate extremes. Anderregg et al.[12] analyzed the legacy effects of extreme droughts on tree radial growth using tree-ring records and models and inferred that carbon storage could decrease as a result of extreme droughts in semi-arid forests. Normalized Difference Vegetation Index (NDVI) data together with land surface model simulations from the Coupled Model
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