Galella, J.G., M.M. Rahman, A.M. Yaculak, M. Peipoch, J. Kan, M. Sena, B. Joshi, S.S. Kaushal, and S. Inamdar. 2024. Restoration Ecology, early online access.
Abstract
Stream and floodplain restoration is a popular billion-dollar industry in the United States, with many restorations being conducted to satisfy water pollution regulations and nutrient reduction goals. The long-term efficacy of these restorations is, however, not well studied, and key soil metrics that can be used for performance assessments have not been developed. We evaluated a chronosequence of 12 restoration sites spanning an age range of 0–22 years to assess changes in denitrification rates and associated soil parameters. Restored versus unrestored reaches were compared for denitrification rate and functional gene nosZ, bulk soil δ15N, soil organic carbon (SOC), soil organic matter (SOM), bulk density, and soil moisture. Denitrification, SOM, SOC, and soil moisture were all found to increase with site age at restored sites, with the largest increase for the 10–22 age category. Bulk density decreased with time, with a significant decrease in restored floodplain soils. Bulk soil δ15N was highest immediately after restoration, decreased with restoration age, and was not positively correlated with denitrification. This may reduce its potential as a proxy for denitrification. Overall, this study reveals that selected soil metrics (SOC, SOM, soil moisture, and bulk density) could serve as a valuable proxy for denitrification and could help assess the denitrification effectiveness of floodplain restorations at the decadal time scales. Ideally, the soil metrics should be combined with other short-term assessment measures, such as those for stream and groundwaters, for a robust performance assessment of restored floodplains.
