The runoff infiltration partitioning has direct consequences on preservation of water resources in rural territories, both in agricultural plots and uncultivated areas (e.g. ditches, channels, grass strips), and requires a better understanding of the variability of soil infiltration capacity by disentangling the complex links between soil, vegetation and management. The general objective of the study was to investigate the temporal variation in quasi-steady ponded infiltration rates of a fluvisol soil under bare and different cover crop type (a Malvaceae with a tap-root system and a Poaceae with a fibrous root system) and management conditions (burning, mowing, and chemical weeding) that are commonly found in the Mediterranean vineyards. A modified double-ring infiltration method was used to repeat measurement of the quasi-steady ponded infiltration, fcp, on the same location over time. Placed on a 64 m2 plot area with minimal distances between individual measurements of 30 cm, the setup allowed evaluation of variability among measurements that were conducted within the plot. The results showed a significantly lowerfcp for bare soil than covered soil, and a two-fold higherfcp for soil covered by Malvaceae than Poaceae. A seasonal effect in fcp was observed, with the highest fcp in summer and the lowest in winter. The study revealed a strong spatial variability in fcp along a transect of a few tens of centimeter, and showed no significant effect of management strategies compared to the vegetated control. The results revealed the importance of considering both plant traits and season rather than vegetation management strategies to explain quasi-steady ponded infiltration rates.

Perennially frozen soil in high latitude ecosystems (permafrost) currently stores 1330-1580 Pg of carbon (C). As these ecosystems warm, the thaw and decomposition of permafrost is expected to release large amounts of C to the atmosphere. Fortunately, losses from the permafrost C pool will be partially offset by increased plant productivity. The degree to which plants are able to sequester C, however, will be determined by changing nitrogen (N) availability in these thawing soil profiles. N availability currently limits plant productivity in tundra ecosystems but plant access to N is expected improve as decomposition increases in speed and extends to deeper soil horizons. To evaluate the relationship between permafrost thaw and N availability, we monitored N cycling during 5years of experimentally induced permafrost thaw at the Carbon in Permafrost Experimental Heating Research (CiPEHR) project. Inorganic N availability increased significantly in response to deeper thaw and greater soil moisture induced by Soil warming. This treatment also prompted a 23% increase in aboveground biomass and a 49% increase in foliar N pools. The sedge Eriophorum vaginatum responded most strongly to warming: this species explained 91% of the change in aboveground biomass during the 5year period. Air warming had little impact when applied alone, but when applied in combination with Soil warming, growing season soil inorganic N availability was significantly reduced. These results demonstrate that there is a strong positive relationship between the depth of permafrost thaw and N availability in tundra ecosystems but that this relationship can be diminished by interactions between increased thaw, warmer air temperatures, and higher levels of soil moisture. Within 5years of permafrost thaw, plants actively incorporate newly available N into biomass but C storage in live vascular plant biomass is unlikely to be greater than losses from deep soil C pools.