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

Abstract:

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.