Precision Prairie Reconstruction (PPR): 15 Years of Data

Abstract

Precision Prairie Reconstruction (PPR) is a site-specific application for enhancing native species richness (specifically native forbs) in old fields dominated by exotic grass species. The method consists of establishing native grasses and native forbs in micro-communities in an existing grass matrix. The micro-communities are constructed by broadcast seeding small-scale disturbances (8 m² in size) installed over a given percentage of the site (5%, 25%, or 50%). Here we compared results from PPR treatments with two standard restoration techniques: herbicide application/drill-seeding (H&D) and rototill/broadcast seeding (R&B). In year 15 of the experiment, the 25% PPR had higher native forb density (27 plants m⁻²) and seeded forb density (16 plants m⁻²) than the other treatments with their corresponding averages of 10 plants m⁻² and 4 plants m⁻² respectively. Implementation cost of the 25% PPR treatment was approximately 1/3 of the traditional treatment costs in terms of seed purchase, cultivation, and seeding. Average results across 15 years showed the 25% PPR and R&B treatments were statistically similar in terms of total species richness (22 species), seeded forb richness (8 species), and seeded-forb-richness stability, measured by coefficient of variation (CV of 0.4, where high CV equals low stability). The other treatments were significantly different with corresponding averages: total species richness of 16, seeded forb richness of 3, CV of 0.97. After a 15-year field experiment, we are confident that the PPR technique offers an innovative, cost effective approach for increasing native forb diversity and stability in old fields dominated by exotic grass species.