Root Production of Fagus crenata Blume Saplings Grown in Two Soils and Exposed to Elevated CO2 Concentration: an 11-Year Free-Air-CO2 Enrichment (FACE) Experiment in Northern Japan

Abstract

We examined the root production of a set of Fagus crenata (Siebold’s beech) saplings grown in an infertile immature volcanic ash soil (VA) and another set in a fertile brown forest soil (BF) with both sets exposed to elevated CO2. After the saplings had been exposed to ambient (370–390 μmol mol−1) or elevated (500 μmol mol−1) CO2, during the daytime, for 11 growing seasons, the root systems were excavated. Elevated CO2 boosted the total root production of saplings grown in VA and abolished the negative effect of VA under ambient CO2, but there was no significant effect of elevated CO2 on saplings grown in BF. These results indicate the projected elevated CO2 concentrations may have a different impact in regions with different soil fertility while in regions with VA, a higher net primary production is expected. In addition, we observed large elevated CO2-induced fine-root production and extensive foraging strategy of saplings in both soils, a phenomenon that may partly (a) adjust the biogeochemical cycles of ecosystems, (b) form their response to global change, and (c) increase the size and/or biodiversity of soil fauna. We recommend that future researches consider testing a soil with a higher degree of infertility than the one we tested.