Exposure to warming and CO 2 enrichment promotes greater above-ground biomass, nitrogen, phosphorus and arbuscular mycorrhizal colonization in newly established grasslands

Aims: In view of the projected increase in global air temperature and CO 2 concentration, the effects of climatic changes on biomass production, CO 2 fluxes and arbuscular mycorrhizal fungi (AMF) colonization in newly established grassland communities were investigated. We hypothesized that above- and below-ground biomass, gross primary productivity (GPP), AMF root colonization and nutrient acquisition would increase in response to the future climate conditions. Furthermore, we expected that increased below-ground C allocation would enhance soil respiration (R soil). Methods: Grassland communities were grown either at ambient temperatures with 375 ppm CO 2 (Amb) or at ambient temperatures +3°C with 620 ppm CO 2 (T+CO 2). Results: Total biomass production and GPP were stimulated under T+CO 2. Above-ground biomass was increased under T+CO 2 while belowground biomass was similar under both climates. The significant increase in root colonization intensity under T+CO 2, and therefore the better contact between roots and AMF, probably determined the higher above-ground P and N content. R soil was not significantly affected by the future climate conditions, only showing a tendency to increase under future climate at the end of the season. Conclusions: Newly established grasslands benefited from the exposure to elevated CO 2 and temperature in terms of total biomass production; higher root AMF colonization may partly provide the nutrients required to sustain this growth response. © 2012 Springer Science+Business Media B.V