Case research on the effects of drought on carbon assimilation within the plant-soil system

Global warming is one of the biggest challenges, the world is facing at the moment and with the current rate of warming, serious consequences to climate have been predicted. Climate change may affect the ecosystem functioning through increased temperatures or changes in precipitation patterns. Water availability is an important driver for various ecosystem processes that may affect the supply of carbon in below-ground pools and alter important ecosystem processes involved in carbon cycling. The objective of this study was to determine the effect of drought stress in the allocation of carbon in different pools within the plant-soil system with Zea mays. The conceptual approach included repetitive 14CO2 pulse labeling of plants grown under drought and optimum moisture levels in order to follow above and below-ground C allocation. After 14C pulse labeling, 14C allocation in different pools such as shoots, roots, soil and soil respiration was traced. Incorporation of fresh assimilates in different soil aggregate fractions were also determined by tracing 14C in different soil aggregates. The study found the drought conditions increased the release of root exudates enhancing the rhizomicrobial respiration (14CO2). Also, an increase in fresh carbon assimilates (14C) into the micro-aggregate fractions compared with optimum moisture levels was found. Thus, maize plants performed quick adaptive response to drought stress by maintaining their biomass and translocating higher photosynthates towards roots for efficient water uptake.