Seasonal Shifts in Diversity and Composition of a Tallgrass Prairie Restoration Have Implications for Sampling Time

ABSTRACT Restorations change across the growing season. Because of this, the point in the season that a restoration is sampled may affect the conclusions reached based on the sample. In this study, we explore seasonal changes in a prairie restoration experiment in eastern Kansas and investigate how these changes affect observed composition, biodiversity, and the effects of seeding density treatment on the plant community based on when, and how completely, vegetation is sampled. Free State Prairie was established in 2014 to test the effects of forb seeding density on forb establishment, diversity, and restoration success. We compared absolute cover data collected in early June and early September 2019 to each other and to combined data. We found changes in both composition and biodiversity from early-to-late in the season. Sown forbs decreased in cover and richness, while sown grasses increased in cover and richness. Nonsown species did not change in cover but decreased in richness. Neither individual sample fully represented the overall composition or biodiversity of the community. We detected a significant negative effect of forb seeding density on diversity in June, and with combined data, but not in September. As sampling time can affect both broad patterns of composition and diversity and observed results of establishment and management techniques, sampling multiple times in a year will provide the fullest and most accurate picture of the community. When multiple samples are impractical, sampling time should be selected carefully based on the phenology of the restoration and the variables of interest.