Long-Term Response of Stream and Riparian Restoration at Wilson Creek, Kentucky USA

Abstract

Degradation, impoundment, and channelization of streams is a global problem. Although stream restoration projects have increased in recent years, post-restoration, long-term monitoring is rare. In 2003, a channelized section of Wilson Creek (Nelson Co., Kentucky) was restored by creating a meandering channel, re-connecting the channel to its floodplain, and planting native riparian species: giant cane and bottomland forest species. Our main objective was to conduct a ten-year post-restoration assessment to determine long-term restoration outcomes of channel water quality, growth of trees planted in the riparian area, and soil development. Water quality, soil, and tree data collected in 2013–2015 was compared to 2004–2006 data. Quality of water parameters changed over time: sulfate, magnesium, calcium, potassium, alkalinity, pH, iron, and temperature decreased, whereas dissolved oxygen increased. Overall, soil pH, extractable ammonium, extractable nitrate, total carbon (TC), and total nitrogen (TN) increased over time. Effects were observed in restored riparian areas for pH, extractable ammonium, and TC; while TC and TN exhibited depth-dependent interactions. The carbon-nitrogen ratio in these soils significantly decreased over time for the reference sites, and the treatments recovered to near reference level. Platanus occidentalis (American sycamore) and Fraxinus pennsylvanica (green ash) individuals had higher survival (80% and 79%, respectively) than individuals of Quercus palustris (pin oak; 22%). Shelter and herbicide treatments had no effect on tree survival or height growth; however, height growth varied by species. Platanus occidentalis exhibited a greater than five-fold increase, F. pennsylvanica slightly increased, and Q. palustris decreased in height growth. Overall, water and soil quality improved over time at the restoration site, while tree survival and height growth exhibited species-specific outcomes.