Prior to European settlement, tallgrass prairie comprised over 7,000 km2 in Canada. Now considered one of the most endangered ecosystems in North America, less than 1% of tallgrass prairie remains in southern Ontario, and between 1-4% remains in the United States. Although it hosts a large proportion of rare flora and fauna, remaining tallgrass habitat is highly fragmented and threatened by both urbanization and encroachment of woody vegetation. Conservation of this ecosystem therefore requires both preservation of existing remnant prairie and active restoration of habitat. There are excellent manuals for practitioners of ecological restoration of tallgrass prairies, but there is a lack of formal experimental designs and analyses of the practices. To address this, we began an experiment to assess the comparative success of three tallgrass prairie restoration methods: drill seeding, shovel-and-spade transplants, and the “cut and paste” approach of translocating (transplanting) 1m x 1m x 30cm sod mat parcels of remnant tallgrass prairie. Data collection included vascular plant species assessment of study plots consisting of sod mat, high quality remnant, poor quality remnant, transplant/seeded, and drill-seeded sites. Soil samples collected at each site were analyzed for pH, soil moisture, NPK, and texture.
After three growing seasons, the large sod mat translocation plots show the highest similarity to high quality remnant prairie. The sod mat plots had the lowest bare ground cover, the highest density of species at risk including Liatris spicata, three distinct soil horizons (O, A, and B down to 20cm), and the most similar pH, soil moisture, NPK, and texture values to extant high-quality tallgrass prairie plots. At sites where shovel-and-spade transplants of individual plants and corms were combined with drill seeding, the vascular plant community became low-quality remnant prairie. Transplant/drill seeded sites showed a higher proportion of endangered species than drill-seeding alone. However, these two treatments did not differ significantly in non-target weedy cover, bare ground cover, and soil properties to the drill seeded sites, including an absence of horizon development and fine grained, compacted clay substrate. Our key finding is that the sod mat plots most closely resembled remnant prairie conditions and little die-off of individual plants within the sod mat was observable in the third growing season. While it is early in the restoration timeline, our results suggest that the seldom attempted “cut and paste” approach to restoration has merit.