Photosynthesis as a factor controlling short-term C turnover in the rhizosphere

The effect of different shading periods of wheat or maize on short-term changes of soil organic matter (SOM) decomposition in the rhizosphere was investigated by using 13C natural abundance. Cultivation of wheat (C3 plant) on Haplic Chernozem (C4 soil) increased SOM decomposition intensity (positive priming effect). 13C natural abundance allows tracing of the dynamics of the priming effect depending on the light-on events. In contrast to wheat, cultivation of maize (C4 plant) on Chromic Luvisol (C3 soil) decreased SOM mineralization compared to unplanted soil (negative priming effect). Prolonged and strongly prolonged dark periods reduced the changes of SOM decomposition in the rhizosphere induced by maize under normal day/night cycles. Both investigated plant-soil pairs show tight coupling of short-term SOM decomposition with photosynthesis intensity.