Soil moisture regime and mound position effects on soil profile properties in a native tallgrass prairie in northwest Arkansas, USA

Prairie, or mima, mound topography often exists in once-abundant, native tallgrass prairie ecosystems throughout North America west of the Mississippi River. However, the abundance of undisturbed prairie mounds is decreasing in many areas due to urbanization and agricultural disturbance. The objective of this study was to evaluate the variations in soil physical, chemical, and estimated hydraulic properties among mound positions (mound summit, backslope, toeslope, inter-mound), soil depths (10-cm intervals from 0 to 90 cm), and soil moisture regimes (udic and aquic) in a native tallgrass prairie in the Ozark Highlands region of northwest Arkansas. Soil samples were collected in mid-April 2017. Soil clay concentrations increased with depth (P < 0.01) at each site position in both soil moisture regimes. The clay concentrations in the mound summits roughly doubled from 0 to 90 cm, while the clay concentrations in the backslope, toeslope, and inter-mound increased by three to six times from 0 to 90 cm. Soil organic matter contents decreased (P < 0.01) with depth at all site positions within both soil moisture regimes and were generally at least numerically largest at respective depth intervals at the inter-mound within the udic soil and at the mound summit within the aquic soil. Estimated saturated hydraulic conductivity decreased (P < 0.05) with depth at each site position and was largest in the inter-mound from 0 to 10 cm (63.4 mm h−1) and numerically smallest at the inter-mound from 70 to 80 cm (4.6 mm h−1). Results clearly indicated that prairie restoration and management practices should consider mounded and inter-mound landscape positions separately to best restore and/or preserve the ecological functioning of the unique mound features in the sparsely remaining tallgrass prairies.