Permanent grassland provides ecosystem services such as protection of soil quality, preservation of ground and surface water quality and regulation of climate through soil carbon sequestration. Intensification of management practices through changes of mowing, fertilization and grazing intensity may threaten these services as well as climate variability through increasing drought intensity and frequency. In grassland, root activity (growth, mortality) contributes to the main inputs of C and N compounds into the soil. Understanding how root activity and soil C stock respond to management is of prime importance for the ecosystem C sequestration service. We studied during two years the dynamics of root mass production of an upland grassland subjected to different grazing intensity (abandonment, low and high stocking density with respectively 0, 6.9 and 13.8 LSU ha-1, livestock unit) and to ambient climate variability. We expected to have lower below-ground net primary production in intensive than in extensive grazing treatments due to stimulation of shoot mass at the expense of roots. The site is part of the long-term observatory network (ACBB-SOERE) located at St-Genès-Champanelle, France and included 12 plots, in which four ingrowth cores were inserted at 20 cm and collected 10 times each year during two following years. In addition root mass was measured three times during the first year to calculate root turnover. We showed strong seasonal root production in spring and autumn for all treatments either during a wet (first) or a dry (second) year. Root production started earlier in spring for both grazing treatments than in abandonment, which can be explained by higher soil temperature. However at the annual scale, root production and root stock were similar between treatments, leading to unchanged root turnover. Thus grazing intensity did not lead to change of root stock, although root dynamics, above-ground biomass and species composition were affected.