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Title: Soil pipe collapses in a loess pasture of Goodwin Creek Watershed, Mississippi: Role of soil properties and past land use

Author
item Wilson, Glenn
item Rigby Jr, James
item Dabney, Seth

Submitted to: Earth Surface Processes and Landforms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2015
Publication Date: 3/24/2015
Citation: Wilson, G.V., Rigby Jr, J.R., Dabney, S.M. 2015. Soil pipe collapses in a loess pasture of Goodwin Creek Watershed, Mississippi: Role of soil properties and past land use. Earth Surface Processes and Landforms. DOI: 10.1002/esp.3727.

Interpretive Summary: Little is known about the connection between collapse of large pores in the soil called soil pipes and soil properties or land use history. Three catchments in northern Mississippi were investigated to determine this relationship. Soil pipe collapses were characterized for their size, spatial location, and type feature such as a flute hole, sinkhole, or gully along with soil properties. The soils were wind-blown deposits and contained a layer called a fragipan that perches water during storms, thereby creating lateral flow conditions that can cause erosion of the soil pipes. Although mapped as the same soil, one of the catchments did not contain any observable pipe collapse features while the other two had 29 and 15 pipe collapse features per hectare. The surface layer tended to be non-erodible while layers below, even the fragipan layer, was susceptible to erosion by pipeflow. Soil properties of the lowest fragipan layer were highly variable but tended to prevent further downward erosion of soil pipes and thus formed gully bottoms. Middle to lower landscape positions in one of the piped catchments contained soils that were highly erodible due to man-made impacts. These man-affected soils were previously gullies that were filled-in in the 1950s when forested areas were converted to pasture. Three decades after this land use change, pipe collapses became evident. In contrasts, the adjacent catchment does not have pipe collapse features because severe sheet and rill erosion in the early 1900s while in cotton production had removed the upper layers. The surface horizons above the lower fragipan layer were completely removed during this period, thus the top-soil layer that tends to form a bridge above the more erodible subsoil layers was removed. These results demonstrate the importance of present day soil properties combined with past land use in determining the susceptibility of landscapes to below ground erosion.

Technical Abstract: Little is known about the association of soil pipe collapse features to soil properties or land use history. Three loess covered catchments in northern Mississippi, USA were characterized to investigate this relationship. Soil pipe collapses were characterized for their size, type feature and spatial location along with soil properties across the three catchments. Although mapped as the same soil, one of the catchments did not contain pipe collapse features while the other two had 29.4 and 15.4 pipe collapses per hectare. These loess soils contained fragipan layers that are suspected of perching water, thereby initiating the piping processes. Pipe collapses associated with subsurface flow paths were not always consistent with surface topography. The surface layer tended to be non-erodible while layers below, even the upper fragipan layers, were susceptible to erosion by pipeflow. Soil properties of the lowest fragipan layer were highly variable but tended to prevent further downward erosion of soil pipes and thus formed a lower boundary for gullies. Middle to lower landscape positions in one of the piped catchments contained anthropic soils that were highly erodible. These anthropic soils were previously gullies that were filled-in in the 1950s when forested areas were converted to pasture. Three decades after this land use change, pipe collapses became evident. In contrasts, the adjacent catchment that does not exhibit pipe collapse features experienced severe sheet and rill erosion in the early 1900s while in cotton production. The surface horizons above the lower fragipan layer were completely removed during this period, thus the top-soil layer that tends to form a bridge above the more erodible subsoil layers was removed. This study showed that knowledge of soil characteristics or topography alone do not explain the distribution of soil pipe collapses as past land use can play a definitive role.