ABSTRACT

We evaluated the impacts of the interactions among hydro-aeolian processes and micro-geomorphology on mechanisms controlling the sediment carbon source and sink within a coppice dune. The sediment sampling process was performed within different positions of each dune. Sediment grain size distribution, geometric mean diameter, mean weight diameter, labile SOC, CO₂ flux, and C mineralization ratio were measured. The finest sediments were observed on the dune edge. The labile SOC and CO₂ flux rate showed an increasing trend in the edge, windward, and top positions. However, the C mineralization ratio decreased only in the dune edge. A significant increase of clay fractions at the dune edge can result from the horizontal sediment transport by runoff from the interdune area to the dune. The SOC could bond with clay fractions to contribute toward the formation of soil aggregation, causing less vulnerability of SOC to microbial respiration. A significant increase of sand fractions, transported by the aeolian process, on the top and windward positions could not protect SOC against decomposition. The interactions among hydro-aeolian processes and micro-geomorphology could encourage the hot spots of sediment carbon reservoirs within the dryland landforms that have a significant proportion in the exchange of carbon to the atmosphere.

摘要

我们评估了水-风成过程和微地貌之间的相互作用对控制矮林沙丘内沉积物碳源和汇的机制的影响。沉积物采样过程在每个沙丘的不同位置进行。测量沉积物粒度分布、几何平均直径、平均重量直径、不稳定SOC、CO ₂通量和C矿化率。在沙丘边缘观察到最细的沉积物。不稳定的 SOC 和 CO ₂通量率在边缘、迎风和顶部位置呈增加趋势。然而，碳矿化率仅在沙丘边缘下降。沙丘边缘粘土分数的显着增加可能是由于从丘间区域到沙丘的径流造成的水平沉积物输送。SOC 可以与粘土部分结合，有助于形成土壤聚集体，从而降低 SOC 对微生物呼吸的脆弱性。风沙过程在顶部和迎风位置输送的沙子部分的显着增加不能保护 SOC 免受分解。水-风成过程和微地貌之间的相互作用可以促进旱地地貌中沉积物碳库的热点，这些碳库在碳与大气的交换中占有很大比例。