Tree-ring isotopes capture interannual vegetation productivity dynamics at the biome scale

Area of Science:

• Ecology
• Paleoclimatology
• Remote Sensing

Background:

• Long-term, high-resolution data are lacking to understand historical and future net primary productivity (NPP) trends and their sensitivity to global change.
• Tree-ring isotopes offer a potential proxy for reconstructing past NPP, but their efficacy requires validation.

Purpose of the Study:

• To test the utility of annually resolved tree-ring stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotopes as proxies for reconstructing past NPP.
• To compare tree-ring isotope chronologies with satellite-derived NPP estimates across diverse hydroclimatic environments.

Main Methods:

• Collected annually resolved tree-ring stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotope data from four sites in the eastern United States.
• Compared these isotope chronologies with satellite-derived NPP products: Global Inventory Modeling and Mapping Studies (GIMMS3g) NPP, Landsat NPP, and Moderate Resolution Imaging Spectroradiometer (MODIS) NPP.
• Analyzed temporal and spatial correlations between tree-ring isotopes and satellite NPP estimates.

Main Results:

• Tree-ring isotopes, particularly δ¹⁸O, showed strong correlations with satellite-derived NPP estimates.
• These correlations were consistent across local and large geographical scales in the eastern United States.
• The findings validate the use of tree-ring isotopes for NPP reconstruction.

Conclusions:

• Tree-ring stable isotopes, especially δ¹⁸O, are effective proxies for reconstructing past terrestrial net primary productivity (NPP).
• This method provides a breakthrough for estimating interannual variability and long-term changes in NPP at the biome scale.
• The study enhances our ability to understand ecosystem responses to global change using paleoclimatological proxies.