Spatial and temporal complexity in Quaternary desert datasets: implications for interpreting past dryland dynamics and understanding potential future changes

Abstract

Knowledge of desert landscape evolution and related aeolian deposits will increase our understanding of the earth system. Desertification and dust cycle in the middle latitudes are an important part of global change and an important window to understand the earth's climate system. The Hexi Corridor is one of the dust storm centers in northern China and Asia, but the reason of desertification process and its relationship with local aeolian landforms and deposits are still unclear. Based on the extensive survey of aeolian landforms and the analysis of elemental, depositional, and structural properties of diverse aeolian sediments (dune sands, Gobi silts and dust loess), this study explored the genetic connection between dune sands in the study area, gobi erosible silts in the upwind area and dust storms in the downwind area and their relationship with desertification in the Hexi Corridor. The analytical results suggest that the dune sands in the Hexi Corridor are weakly related to the gobi sediments in the upwind area and the dust loess in the downwind area from the perspective of genetic connection, but there is a close relationship between gobi and dust sediments. On the decadal scale, the change trend of dust storm events in the study area is consistent with the variational process of the regional-scale desertification, indicating that the dust storm is an effective indicator of desertification process in the study area on a large scale. Based on the genetic connection and differences between the dust storm, gobi topsoil and dune sand and combined with other environmental parameters, we identified two different processes of desertification in the Hexi Corridor. One is an abnormal, reverse desertification process that occurred on a regional scale, which is inconsistent with the change of global climate and global dust storms. The other is an increased desertification process that occurred in the oasis area on a local scale, which has no relationship to global and regional climate change but is closely related to the decline of groundwater level in the oasis area. This provides good evidence for us to understand the causes of different landsurface processes that occurred in a unified environment in middle latitudes.