Vegetation community recovery on restored bottomland hardwood forests in northeast Indiana, USA
Authors: Struckhoff Matthew A. , Grabner Keith W. , Albers Janice L. , Hooper Michael J. 
Published: September 2024

Vegetation communities in restored bottomland hardwood forests in northeast Indiana were studied 6–21 years after restoration to assess progress toward restoration objectives. The study focused on four sites that were restored to compensate for resource injuries after contaminant releases. The restored sites were compared with four reference-site conditions, including crops (prerestoration condition), old field communities representing a no-management alternative, locally sampled second-growth mature forests, and forest community types described by the US National Vegetation Classification (USNVC), which represent ideal or defining conditions of recognized vegetation communities. Fixed-area plots provided data on field-sampled environmental variables, vegetation, soil, and hydrological conditions for crops, old fields, restored areas, and mature forests. The USNVC database provided quantitative data for three historically and geographically relevant reference forest community types for comparison with the sampled communities. Results of nonmetric multidimensional scaling based on species cover revealed clear gradients relating to site age and canopy development. Along those gradients, restored areas demonstrated increasing similarity to mature forest reference communities in terms of floristic composition. Specifically, the floristic quality of restored areas was significantly greater than that of crops and old fields. Furthermore, soil health measurements of physical, chemical, and hydrological conditions indicated significant improvements in restored site soils compared with prerestoration conditions represented by cropland soils. Descriptions and data from the USNVC provided ecological context for restoration target conditions and facilitated the assessment of restoration recovery along a trajectory from starting conditions to those target conditions. Descriptions by USNVC also helped identify deviations from the intended restoration objectives (e.g., invasive species recruitment) and potential adaptive management actions to return sites to their intended trajectories. Integr Environ Assess Manag 2024;20:1917–1938. Published 2024. This article is a U.S. Government work and is in the public domain in the USA. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Key Points

Bottomland forest restoration sites were sampled to document the recovery of vegetation communities, soil and hydrological conditions, carbon storage, the return of lost services, and the functional status of the forest ecosystem. Restored sites were compared with a range of reference communities representing starting conditions (cropland), no-management old fields, local mature second-growth forests, and historically and geographically relevant US National Vegetation Classification communities. Vegetation community composition placed the four sampled restoration sites on an age-related gradient between crops and mature forests, driven by indicators of canopy development and shifts in ground flora to species that thrive in shaded conditions. Improved ecological function in restored site soils was reflected in lower bulk density, increased water aggregate stability, and greater infiltration capacity, indicators of increased nutrient processing and reduced runoff, which are known to reduce sediment and nutrient loads in receiving streams.