The DSL framework was used in two contrasting headwaters in the Mediterranean ecoregion (one with sub-humid climate and the other one with semi-arid climate) and in a temperate forest headwater in central Germany. This work has resulted in three Open Access peer-reviewed publications in scientific journals, one for each of the first three out of four planned work packages. In the first publication we show that during rainfall events of low intensity, hydrological responses at the semi-arid Meditearranean site were more delayed and more variable than at the sub-humid Mediterranean site. By contrast, during rainfall events of moderate and high rainfall intensities (including an extratropical cyclone), hydrological responses were similar in the two sites. Furthermore, at both sites, stream responses were controlled by riparian groundwater table responses, which directly relates to the DSL idea. The results of the second publication suggest that, at the sub-humid Mediterranean site, (i) increased supply of limited resources during storms can sustain the activity of aquatic microorganisms in the stream during high flows, especially during large storm events preceded by dry conditions, and (ii) riparian zones provide organic matter and carbon inputs that are needed for the metabolism of aquatic microorganisms in the stream. Furthermore, in this publication we proposed a conceptual model synthesizing the complex processes driving the mobilization of resources for aquatic microorganisms from riparian zones to streams during storm events based on the DSL framework. In the third publication, we simulated future potential changes in the DSL at the sub-humid Mediterranean site based on future climate scenarios. Nearly all scenarios projected that, together with reductions in stream flow and water exports, the DSL will move down in the future. Consequently, terrestrial organic matter inputs to streams will likely decrease, potentially disrupting stream ecological status. As part of the last work package, work is currently being done to synthetize the understanding of the riparian zone function in the Mediterranean, the temperate, and the boreal catchments based on the DSL framework.
