Drought Impact on Water – Carbon Interaction in Soil: A Stable Isotopic Approach

Tuesday, 16 December 2014
Jobin Joseph, Albert Ludwig University of Freiburg, Freiberg, Germany, Markus Weiler, Albert Ludwig University of Freiburg, Chair of Hydrology, Freiberg, Germany and Arthur Gessler, WSL Swiss Federal Institute for Forest, Snow and Landscape Research, Forest Growth and Climate, Birmensdorf, Switzerland
Extreme climatic conditions like drought introduce drastic changes in carbon and water dynamics in the plant – soil continuum, starting from carbon assimilation till carbon allocation in the soil, root water uptake till transpiration via leaves. Our objective was to study the drought impact on the dynamics of Carbon, and water cycles, as well as the interaction between them under extreme climatic conditions in the plant soil continuum.

The first phase of the experiment involved 13CO2 pulse labeling of drought exposed and well-water beech microcosms, during which we monitored the 13C allocation to roots, and in the soil by measuring the CO2 concentration, ∂13C, and ∂18O of root derived CO2. We found that drought had a significant impact on, a) carbon assimilation, allocation, and translocation rate in the plant – soil system. The drought stressed plants not only assimilated fewer amounts of CO2, but also translocation of those assimilates belowground was extremely slow, and root respiration was low in comparison the well watered control plants.

The second phase involved rewetting of the drought chambers (and the application of similar amounts of water to the controls) using D218O enriched water followed by an additional 13CO2 pulse labeling approach so as to study the effects of drought on the infiltration patterns of a precipitation event as well as the recovery of the carbon relations of previously drought stressed beech saplings.