Demonstration of the rapid incorporation of carbon into protective, mineral-associated organic carbon fractions in an eroded soil from the CarboZALF experimental site
The goal of this work was to quantitatively describe the influence of soil erosion on the distribution of recently assimilated carbon (C) within the plant-soil system and different soil fractions.
Surface soil was manipulated in the field to simulate a strong erosion event, and maize plants were cultivated in a growth chamber using soil material from the manipulated (eroded) and non-eroded sites. The maize plants were pulse labeled with 14C-labeled carbon dioxide (CO2) at the start of flowering, and C partitioning within the plants and the distribution of recently assimilated C into organo-mineral soil fractions of different particle size were assessed after 25 days.
The distribution of C differed significantly between the particle size fractions separated from the soil material of the eroded and non-eroded sites. For example, a much higher percentage of 14C was found in macro-aggregate-occluded organic particles of the eroded soil than in the same fraction of soil from the non-eroded site. Furthermore, a significantly higher absolute amount of recently assimilated C was found in the < 20-μ m mineral particles and aggregates of the eroded soil than in the same particle fraction of the non-eroded soil. We show that this C is most likely derived from rhizodeposition or metabolites originating from the microbial decomposition of rhizodeposits.
The findings provide experimental evidence of the concept of the “dynamic replacement” of organic C (OC) losses due to erosion by C derived from crops growing on eroded soils. The rapid and enhanced sorption of recently assimilated C on the surfaces of mineral particles and occlusion in aggregates < 20 μ m confirms the role of erosion processes in creating an immediate terrestrial C sink with the potential to enhance long-term soil C storage.
KeywordsSoil erosion Rhizodeposition Dynamic C replacement
We are grateful to the employees of the ZALF Agricultural Landscape Data Centre (DZA) for their support of the CarboZALF-D field trial. We also thank Andrea Neumann and Chandan C. Kemparaju from the Leibniz Center for Agricultural Landscape Research (ZALF) in Müncheberg (Germany) for preparing the soil, root and shoot samples.
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