干旱区生态环境知识资源中心

The formation of coppice dunes (nebkhas) has been attributed to both aeolian and hydrological processes, however, the interactions between these processes and vegetation dynamics are poorly understood. Additionally, a systematic study on the roles of dune geometry, morphology and hydrological processes in relation to sediment grain-size distribution in the coppice dune system is lacking. Here, we analyzed detailed grain-size distribution and saturated hydraulic conductivity for sediments collected from a series of coppice dunes with different morphological features and phases of development in a degraded shrubland in the southwestern US. Our results show that fine-grained dune sediments are associated with the wind-driven accumulation of very fine sand and fine sand (50-250 mu m), irrespective of the height of the dunes. Patterns of grain-size distribution are strongly related to the relative positions along the dune-interdune system and the alignment with the dominant wind direction. Thus, the current notion that dune sediments contain more sand and less silt than interdune soils is over-simplistic. The fact that the grain-size distribution and the saturated hydraulic conductivity are heterogeneous for the dune-interdune system with different morphological features suggests that the relative contributions of aeolian and hydrological processes are distinct in the evolution of coppice dunes.