PS 46-178 - Precision prairie reconstruction (PPR): 15-year case study results for sustaining forb species richness and diversity in restorations

Wednesday, August 9, 2017
Exhibit Hall, Oregon Convention Center


Carolyn E. Grygiel, North Dakota State University; Jack E. Norland, North Dakota State University; Mario E. Biondini, North Dakota State University


Precision Prairie Reconstruction (PPR) is a site specific, minimal disturbance, cost effective, low maintenance technique for addressing a notable problem in grassland reconstruction: the decline in species richness over time. The method consists of establishing native grass and native forb micro-communities in an existing grass matrix. The working hypothesis is that by installing and seeding specific quantities of small-scale-disturbances with native species, a self-sustaining community will be established that will generate a constant source of propagules which in time will colonize the surrounding vegetation matrix (by taking advantage of suitable environmental conditions that can occur over the years) and thus increase native species diversity. The micro-communities in this experiment were created by broadcast seeding simulated small-scale disturbances (8.06 m2in size) installed systematically over an empirically determined percentage of the site (5%, 25%, or 50%). The PPR results were compared with two standard restoration techniques: herbicide application/drill-seeding (H&D) and roto-till/broadcast seeding (R&B). The experiment was organized as a randomized block design with 6 treatments (including a control) and 5 replications per treatment. The study was initiated in 2001 and sampled over the next 5 growing seasons. In spring 2007 the site was burned followed by sampling in 2010 and 2016.


Across all years sampled, the 25% and R&B treatments were statistically similar (P>0.05) in terms of total species richness (22 species for both), seeded forb richness (7 vs. 8 species), seeded forb richness stability (CV of 0.4 vs. 0.5, where high CV represents low stability), and seeded forb density (10 vs. 8 plants/m2). All the other treatments were significantly different (P<0.05) with corresponding averages of: 16 species, 3 species, CV of 0.97 (the 50% was similar to the 25% and RB with 0.4), and density of 3 plants/m2. The PPR technique involved less cost, and less overall disturbance than the traditional H&D or R&B methods with installation costs of $3,196/ha for the 25% treatment vs. $8,556/ha for the H&B and $9,649 for the R&B treatments. Outcomes from this field experiment after 15 years show that the PPR technique results in sustainable native forb species micro-communities visually comparable to a native prairie and offers an alternative approach for increasing native grass and forb density and richness in old fields dominated by an exotic grass matrix.