There are many criteria and methods of evaluating success of natural area restorations. As the number of restorations and the ages of restorations increase, evaluation of outcomes becomes more statistically robust as the number of replicates increases. Evidence of poor results has also led to changes in techniques, providing more treatments. We used data collected from 29 sites, including intact remnant vegetation and an array of restoration sites of varying ages and techniques. We analyzed both cover and presence data to detect parameters that could be used to assess restoration quality. The goal was to find properties that varied continuously from remnant sites, considered to have the highest quality, to recently planted sites dominated by exotic and ruderal species. We considered remnant vegetation as the approximate ideal goal of most restoration projects, and limited sampling to mesic and dry-mesic prairies, to minimize differences attributable to hydrologic and edaphic conditions and reflect different seed applications and restoration techniques. We examined species richness at several scales using 0.25m2 quadrats and species accumulation curves, and native/exotic ratios for quality assessment. Classification, ordination and MRPP were used for differences in planting techniques.
Remnants had consistently higher richness, above 10 species at the quadrat scale, with only one restoration achieving that level. Species accumulation curves also distinguished sites at a similar resolution. Sites using the oldest technique, establishing dominant grasses first and adding other species later, gave the poorest results, and were consistently among the species-poorest. Starting with a seed mix with higher richness provided better results, but most of theses sites are relatively new, and may or may not lose species as time progresses. Better results still were achieved by seeding and installation of plugs of species that often don't establish well from seed. The best restorations were older and had nearly annual additions of some species until they established and reproduced, or were intensively managed with hand weeding and plug installation. Burning varied considerably, making assessment of its effect difficult.