Sour orange fine root distribution after seventeen years of atmospheric CO2 enrichment

► Elevated CO2 increased both root length (35.6%) and root dry weight (39.1%) densities. ► Fine root length density in the top two depths increased by 64.5 and 57.2%. ► Fine root dry weight density in the top two depths increased by 80.3 and 82.8%. ► Long-term citrus productivity can be enhanced under future levels of atmospheric CO2.