Since the nineteenth century, most Wisconsin tributaries have been dammed to generate power and control flood-waters. Approximately 10% of these dams have become obsolete and too expensive to maintain, which has resulted in their removal. The newly exposed sediments have provided a unique opportunity for prairie restoration and studying the integration of belowground properties in ecological restoration. Few have examined the magnitude and spatial structure of belowground properties as controls over the restoration of highly degraded landscapes. Thus, we investigated a recently dewatered basin (after 43 years of impoundment) in southwestern Wisconsin to test hypotheses related to the magnitude, heterogeneity, and spatial dependence of physicochemical properties between sediments and buried soils. A 1.1-ha spatial grid was established in the center of a 2.0-ha basin to sample seven physical and 13 chemical properties across the basin.  

Results/Conclusions

Sediment depths (Sd) averaged 43 cm (SD = 15) across the study area. The mean bulk density (BD) of the buried soils (1.41 g cm-³) was significantly greater than the sediments (0.97 g cm-³), which corresponded with a significantly higher soil moisture content (SMC) and hydraulic conductivity (Ks) in the sediments. Relative to one another, buried soils were significantly higher in the contents of total P, Bray P, Mn, Cu, and Fe, while the sediments had higher contents of S, Ca, and pH. Despite these differences, the sediments were less heterogeneous than the buried soils. Using geostatistics, all physical properties fit a spherical spatial model except for buried soil BD. Sediment BD and SMC displayed both large and fine-scale spatial structure, while Sd and the buried soil SMC displayed only fine-scale variability. Trend analysis revealed that distance away from the dam was positively related to nine physicochemical properties and negatively related to S, SMC, and %clay; no trends were found in the buried soils. These results demonstrate that the disturbance of dam construction, inundation, and removal yielded a spatially distinct and homogenized substrate relative to the soils that were buried. Differences in pedogenic and geomorphic processes, including particle translocation during dewatering likely explain these results. Thus, successful establishment of native plant communities in this system and ones like it may require restoration of soil heterogeneity or the selection of plantings that compliment belowground characteristics. Moreover, understanding the role of soil properties and their spatial distribution in prairie restoration will help educate practitioners and the public about the controls over restoration success.