Differential allocation of carbon in fenced and clipped grasslands: a 13C tracer study in the semiarid Chinese Loess Plateau

The objectives of this study were to determine the partitioning pattern of recently fixed carbon in a plant-soil system and the difference in patterns of carbon flux between fenced and clipped grasslands in the Chinese Loess Plateau (CLP). We used an in situ C-13 pulse labeling method and determined the plant biomass, carbon content and delta C-13 value in shoot, root and soil, in order to calculate the C-13 amount in the plant-soil system. Thirty days after labeling, the C-13 incorporated into the shoots did not differ significantly between the fenced (30.6 % of recovered C-13) and clipped (27.0 %) grasslands. However, the amount of C-13 remaining in the roots and soil in fenced grassland (roots, 9.2 %; soil, 14.7 %) was significantly higher than that in clipped grassland (roots, 2.0 %; soil, 2.5 %). By contrast, the total loss of assimilated C-13 was significantly lower in fenced grassland (45.5 %) than that in clipped grassland (68.5 %). We demonstrate that clipping management results in a higher (CO2)-C-13 efflux and a lower C-13 allocated belowground, which has a negative effect on carbon sequestration in typical grasslands in the semiarid CLP.