New paper out: Continuous measurements of soil, root and tree xylem water isotope values are possible!

In multiple field experiments over the last years, we applied novel in situ methods to measure water stable isotopes in soil and tree xylem directly in the field. These new approaches enable us to obtain data from a consistent sampling location in unprecedented temporal resolution. With this we can uncover the temporal variations in tree water uptake and advance our understanding of the complex and highly dynamic water movements at the interface between soils, plants and the atmosphere.

One of the goals of Isodrones is to further develop those methods and to share our experiences and lessons learned. With this we want to make them more accessible to scientists within the interdisciplinary field of ecohydrology but we also want to communicate potential limitations and opportunities for further development.

During our first field campaign 2019 we applied in situ methods at our core site (LINK to sites’) in a tropical dry forest in Costa Rica. The borehole equilibration method in particular has not previously been tested under field conditions and we also used it to measure water stable isotopes in tree root xylem directly in the field for the first time ever. In the experiment we simulated an early onset of the wet season after three months of no rain by irrigating the studied tree individuals with water labelled with heavy hydrogen (deuterium, ²H) at the end of the dry season. This allowed us to investigate changes in tree root water uptake and follow the water added to the system on its path from soils, over roots to tree trunks. Next to in situ data, we collected frequent destructive soil and tree xylem samples throughout the 2.5 month field experiment to validate our method.

In this paper we thoroughly compare data from in situ and destructive sampling, highlight their respective potentials and limitations and identify areas of improvement to further advance the borehole equilibration method.

Check it out! It’s open access :-D

Kathrin Kühnhammer
Kathrin Kühnhammer
Resolve short-term dynamics of plant water uptake in repsonse to varying environmentral conditions.