Water availability drives fine root dynamics in a Eucalyptus woodland under elevated atmospheric CO2 concentration

Fine roots are a key component of carbon and nutrient dynamics in forest ecosystems. Rising atmospheric [CO2] (eCO2) is likely to alter the production and activity of fine roots, with important consequences for forest carbon storage. Yet empirical evidence of the role of eCO2 in driving root dynamics in low-nutrient forested ecosystems is limited, particularly for grassy woodlands, an ecosystem type of global importance.

We sampled fine roots across seasons over a two-year period to examine the effects of eCO2 on their biomass, production, turnover and functional traits in a native mature grassy Eucalyptus woodland in eastern Australia (EucFACE).

Fine root biomass, production and turnover varied greatly through time, increasing as soil water content declined. Despite a lack of persistent effects of eCO2 on fine root biomass, production or turnover across the two-year sampling period, we found enhanced production pulses under eCO2 between 10-30 cm soil depth. These eCO2-driven prod...