Seed rate study for restoration ecology: What weight of seed should be planted for the best results?

摘要

This study evaluates the weight of dispersed seed per hectare required to produce a successful prairie planting. In December 2006, a planting was established at Nachusa Grasslands, Franklin Grove, IL with a random 3 x 5 block design of four seed treatments, 11.2, 33.6, 56.0, and 78.5 kilograms per hectare (10, 30, 50, and 70 pounds per acre respectively). In 2008, six individual square meter quadrats were used to survey the vegetation composition in the 15 cells. Floristically, the following variables were observed in the months of June, July and August of 2008: species richness, stem density, and percent cover of each species. From this floristic data total plant cover, three diversity indices (Shannon-Weiner Index, Simpson's Index, and the Floristic Quality Index (FQI)), and individual species abundance based on conservation value were viewed to find the best seed weight treatment.;The results from the seed weight experiment for Nachusa Grasslands showed an overall significant difference (One-way ANOVA, p0.05) between the treatments of seed weight. Total plant cover, and the diversity indices gave significant results (One-way ANOVA, p0.05) relating to the exotic and native species ratios during each represented survey month. For example, the nature of exotic species tends to establish and set seed faster than native species. Native species on the other hand are more focused on establishing a strong root foundation which would later benefit them in the growing season. Total plant cover results showed a negative trend in percent cover with seed density treatments for the month of June, while both July and August showed a positive trend in percent cover that became more significant (One-way ANOVA, p0.05) with time and within each seed density treatments used in the experiment. The Shannon-Weiner index indicated that low seed density plots showed only a dominance of a few species, while densities of 50 and 70 lbs per acre showed significant difference (One-way ANOVA, p0.05) which resulted in an increase of evenness amongst multiple species within these treatment plots. The Simpson's index, which represents dominance, showed significant results (One-way ANOVA, p0.05) that were opposite of what the Shannon-Weiner index reported. The results for the FQI represented a significant difference (One-way ANOVA, p0.05) amongst the control compared to the treatments. However, the treatments compared to one another did not show any significant difference (One-way ANOVA, p0.05) amongst each other. This suggests that all the species that emerged, and was counted for in each treatment during the vegetation survey were of the same FQI value. The clearest results from the seed density experiment were evident in the Detrended Correspondence Analysis (DCA). The DCA which represents the entire species composition of the study suggests that 50 pounds per acre yields compositionally similar results to 70 pounds per acre. Thus, suggesting that 70 pounds per acre is not needed when establishing a prairie planting. Also, we see from a few 30 pounds per acre treatments that the vegetation composition is similar to 50 pounds per acre. This suggests that perhaps 30 pounds per acre would be acceptable as a minimum density of seeds to apply in planting prairie. Considering individual species, most species were significantly (One-way ANOVA, p0.05) well established in 50 pounds per acre compared to the other treatments used in the seed density experiment. The findings from both the DCA and the ANOVA tests suggest that the range of 30 to 50 pounds per acre should be used when ever possible in planting prairie at Nachusa Grasslands.