Soils and Hydrologic Processes Drive Wet Meadow Formation and Approaches to Restoration, Western USA

Abstract

In 1805, the Lewis and Clark Expedition encountered Nez Perce people at a wet meadow that now holds historical significance to both cultures. Over the past two centuries this northern Idaho site, known as Weippe Prairie, was modified by digging of drainage ditches and introduction of exotic plants for livestock forage. From 2013 to 2017 a restoration was implemented that included filling a drainage ditch and planting five native wetland species. Between 2008 and 2018 we analyzed monitoring well data to quantify water levels through time, soil oxidation/reduction stations to measure redox potential, vegetation plots to track community changes, and pits for soil characterization. Seasonal saturation occurred top-down from direct precipitation and sheet flow over fine-grained soil and a low permeability hardpan approximately 60 cm below ground. Resulting hydrologic effects included a mean water level rise of 23 cm and prolonged growing season saturation. Although the restoration appears to be on a desirable trajectory, two years were insufficient for the wet meadow to transition from dominance by exotic pasture grasses to native wetland species. A combination of recurring monitoring, adaptive management, time, and reevaluation of the physical and ecological processes driving wetland function is required to achieve longterm restoration success.