Wetting strengthens transpiration-streamflow coupling and drying decouples their source pools: Dataset

Transpiration moves large portions of water from below ground to the atmosphere and our knowledge of streamflow sources and generation processes is extensive. But it is often unclear if, or when, transpiration and streamflow are fed by the same subsurface water sources. This repository holds isotopic (δ18O and δ2H) and hydrometric measurements collected over 10 months at the Maimai M8 catchment in New Zealand (42° 05' S, 171° 48'). Sampling was conducted at ~monthly intervals, except for in February, when we carried out five sampling events. We did this to understand when transpiration and streamflow sources were connected or disconnected. This composite dataset contains stable isotopic composition data (δ18O and δ2H) of more than 500 water samples of bulk and mobile soil from different hillslope positions and depths in the soil profile, xylem from Pinus radiata, stream water from the M8 stream, bedrock groundwater, and a macropore at the base of the hillslope. The dataset also includes high-resolution tree hydraulic information from stem radius change. Lastly, the repository provides information regarding environmental conditions during the sampling period, such as precipitation amount, modeled air temperature, and soil moisture. Modeled precipitation isotope data used in this study is not included in the data repository due to licensing requirements. This data was used to understand seasonal source dynamics of transpiration and streamflow, their coupling, and provide a mechanistic understanding of seasonal tree water use dynamics.