Soil properties of urban streams along a restoration gradient in the Southern Piedmont

Background/Question/Methods

As attention is increasingly focused on the deleterious effects of urbanization on stream health, restoration of degraded streams has increased. Ecologists recognize the integral role soil plays in the successful revegetation of degraded riparian ecosystems. Unfortunately, restoration practices typically focus on stream bank stabilization and channel incision reversal, not remediating soil health. Manipulating soils during stream restoration is common (i.e. grading) but their impact on soil health is frequently overlooked. Our objective was to determine how essential soil properties in urban riparian zones in the Georgia Piedmont are impacted by restoration practices. A gradient of restored river reaches consisting of an unrestored urban stream, a restored urban reach 8+ years post-restoration, and a restored reference site 80+ years post-restoration was selected for study.  We compared soil properties between the reaches to help determine the recovery trajectory of the recently restored reach.  Soil nutrient concentrations (N,P,K), soil organic matter (SOM), and soil compaction were assessed within six 10-m²sites in active channel bars, stream banks, and riparian forests at each reach. Generalized linear models were used to analyze the data and AIC scores were used to select the best model.

Results/Conclusions

Our preliminary results suggest that the recently restored river reach is moving along a reclamation trajectory. Model results indicate that soil nutrient concentrations and the degree of soil compaction of the forested side of the recently restored reach was most similar to the reference site. However, the urban side of the restored reach showed soil nutrient concentrations and a degree of soil compaction that was most similar to the unrestored urban reach. SOM content was highest in the unrestored reach which may suggest a loss of SOM via topsoil manipulation at the restored reaches.

The restoration of Georgia’s urban streams is receiving great interest as communities come to understand the stresses human demands have placed on their resources. However, despite restoration attempts, the frequent disturbance and subsequent environmental changes typical in urban environments reduces the capacity of urban riparian soils to provide valuable ecosystem services. Our results support these findings and suggest that the continuing effects of urbanization may hinder the recovery trajectory of restored urban reaches. Restoration and management practices that include soil rehabilitation may increase the resilience of urban riparian ecosystems to continual urban stressors.