Mineralisation, leaching and stabilisation of C-13-labelled leaf and twig litter in a beech forest soil

作者：Kammer A^*; Hagedorn F

来源：Biogeosciences, 2011, 8(8): 2195-2208.

DOI：10.5194/bg-8-2195-2011

Very few field studies have quantified the different pathways of C loss from decomposing litter even though the partitioning of C fluxes is essential to understand soil C dynamics. Using 0.75 kg m(-2) of C-13-depleted leaf (delta C-13 = -40.8 parts per thousand) and 2 kg m(-2) of twig litter (delta C-13 = -38.4 parts per thousand), we tracked the litter-derived C in soil CO2 effluxes, dissolved organic C (DOC), and soil organic matter of a beech forest in the Swiss Jura. Autotrophic respiration was reduced by trenching. Our results show that mineralisation was the main pathway of C loss from decomposing litter over 1 yr, amounting to 24 and 31% of the added twig and leaf litter. Contrary to our expectations, the leaf litter C was mineralised only slightly (1.2 times) more rapidly than the twig litter C. The leaching of DOC from twigs amounted to half of that from leaves throughout the experiment (2 vs. 4% of added litter C). Tracing the litter-derived DOC in the soil showed that DOC from both litter types was mostly removed (88-96%) with passage through the top centimetres of the mineral soil (0-5 cm) where it might have been stabilised. In the soil organic C at 0-2 cm depth, we indeed recovered 4% of the initial twig C and 8% of the leaf C after 1 yr. Much of the C-13-depleted litter remained on the soil surface throughout the experiment: 60% of the twig litter C and 25% of the leaf litter C. From the gap in the C-13-mass balance based on C mineralisation, DOC leaching, C input into top soils, and remaining litter, we inferred that another 30% of the leaf C but only 10% of twig C could have been transported via soil fauna to soil depths below 2 cm. In summary, over 1 yr, twig litter was mineralised more rapidly relative to leaf litter than expected, and much less of the twig-derived C was transported to the mineral soil than of the leaf-derived C. Both findings provide some evidence that twig litter could contribute less to the C storage in these base-rich forest soils than leaf litter.

• 出版日期2011