thesis:preciprouting [Hydro-Wiki ]

Problemstellung

Stable isotopes of water are one of the most widely used tools to track the pathways of precipitation inputs from the canopy through soils to streams. In the past, soils have often been treated as black-boxes through which precipitation is routed to streams without much consideration of how, when, and where water is transported along soil water flow paths. In fact, precipitation reaches the forest floor via diffuse (throughfall) and point (stem flow) inputs and throughfall can be highly heterogeneous, partly as a result of variations in canopy coverage, tree stem and branch architecture.

Ziel der Arbeit

The aim of this thesis is to use stable isotopes of water (2H and 18O) of open rainfall, stemflow, throughfall and soil water to evaluate how fast and with which patterns rainfall events (and artificial irrigation events with a deuterated isotope tracer) influence the soil water compartment and which role the canopy plays in terms of altering the isotopic input signal and the above- and below-ground water input and redistribution. The study will be part of the DFG project “Using advances in stable water isotopy to quantify species- and interspecific ecohydrological feedback processes and water transit times of different tree stands” and will be conducted at forest stands near Ettenheim.

Methode

To track the precipitation isotopic input through the canopy into the soil, different types of samplers will be setup and several rainfall/artificial irrigation events will be monitored. Soil water isotope composition (laterally and vertically) will be monitored in-situ and cross-checked via destructive soil sampling and lab-based water extraction for isotope analysis will be performed. Liquid water isotope samples from open rainfall, throughfall, stemflow and extracted soil water will be analyzed for their isotopic composition in the lab.