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Understanding how catchment streamflow response varies in time and at different spatial scales is critical to assess runoff production and water availability in mountain areas. Very little work on comparing runoff generation processes in catchments of increasing size has been done in Dolomitic areas. In this research, we adopted a nested catchment (0.14–109 km2) approach to i) assess whether and how streamflow response at the seasonal and the rainfall-runoff event time scale varies with increasing spatial scale, and ii) identify the main factors controlling the temporal variability of streamflow response in three mountain catchments in the Italian Dolomites. We used precipitation and streamflow data from June to September of 13 consecutive years (2005–2017) available for all three catchments, and computed runoff coefficients, stormflow volumes, streamflow peaks and lag times between the rainfall centroid and the streamflow peak for 203 rainfall-runoff events occurred during the study period. Results show that, overall, specific streamflow and runoff coefficients decreased with the increasing spatial scale. However, this pattern was disrupted at the end of spring-beginning of summer due to the relevant snowmelt contribution to streamflow in the intermediate catchment characterized by the largest fraction of high-elevation areas, where deep snowpack accumulated during the winter. The probability distribution of runoff coefficients was very well represented by a Beta-distribution for all three catchments, suggesting that analogous factors controlled the variability of runoff coefficients. This was confirmed by multiple regression analysis that revealed that event rainfall amount, storm duration and 3–12 days antecedent precipitation (assumed as a proxy for antecedent wetness conditions) explained up to 0.81 of the variability of streamflow response, with a minor role of rainfall intensity. Further research is needed to assess whether detailed measurements of hydrological variables collected at the small catchment scale (

Understanding water sources for crop water uptake in agricultural and agroforestry systems is an essential step to develop more efficient and sustainable water management strategies, which is increasingly important in the light of current world population growth, changing climatic conditions and consequent growing pressures on agricultural- and agroforestry production. Stable isotopes of hydrogen and oxygen in the water molecule are powerful and, nowadays, affordable tracers that can help to define the proportion of water sources accessed by plants. Yet, contrary to natural environments, their application is still relatively limited in agricultural and agroforestry research. In this work, we synthesize the advantages and the current knowledge deriving from the use of the stable isotopes of hydrogen and oxygen, in support of more traditional techniques, to understand root water uptake dynamics in agricultural and agroforestry systems. We also underline the practical implications related to the application of this technique for management purposes, and provide a vision for new challenges and future research opportunities in exploring crop and plant water use based on isotopic data.

We used a dual stable isotope approach (2H and 18O) and electrical conductivity data in combination with hydrometric measurements to trace water fluxes in the soil, stream and trees in a small forested watershed in the Italian Pre-Alps. The aim was to understand the main water sources for plant transpiration and runoff generation. The data were collected between events and during rainfall events in order to assess the sources of tree uptake under different conditions. Sampling and analysis are still continuing but preliminary results show that the isotopic composition of tree water was similar to soil water and rain water but statistically different from streamflow and groundwater. This suggests that trees used predominantly soil water, rather than groundwater, during the study period. No marked difference was found between the isotopic composition of the sap of trees in the riparian zone and the sap of trees on the hillslope. However, during dry conditions sap in riparian trees slowly became more similar to deep soil water and groundwater, indicating a possible switch in water uptake from shallow to deeper soil water. In contrast to the quick response of the stream, the composition of tree water did not change immediately after a rainfall event, even though the composition of shallow soil water had changed, which may be caused by storage of water in the tree and the low vapor pressure deficit that suppressed transpiration after the rainfall event. Future work will be carried out to monitor the seasonal variability in water uptake and its response to rainfall events in more detail.