Tallgrass prairies are among the most imperiled ecosystems globally. Since prairie landscapes and associated species are rapidly disappearing, conservationists have undertaken massive strides toward restoring and creating new prairies using seeds. Despite using diverse native seed mixes, restored prairies are often less diverse and compositionally different from remnant, never-been-plowed prairies. Understanding how seed inputs influence the formation of plant communities not only answers fundamental questions of plant community ecology but is also necessary for achieving restoration goals. In this dissertation, we investigated how vital aspects of seed sources, the seed rain and seed bank, changed during restoration (Chapter 2 and 3) and could be used to inform restoration management (Chapter 4). In an observational study, we resampled seed rain in the same remnant prairie used to conduct the first grassland seed rain study 40+ years ago and expanded to include a chronosequence of nearby restored prairies (Chapter 2). Using the same study sites, we also surveyed the aboveground flora and seed bank to determine the post-dispersal fates of seeds (Chapter 3). Lastly, we used empirical data collected from Chapter 2 to inform a field experiment testing whether species arrival based on dispersal phenology influenced community assembly outcomes (Chapter 4). Overall, we found that tallgrass prairies, especially newly restored prairies, produce record-breaking amounts of diverse seed input. Most prairie seed rain does not survive to germinate from prairie soils, and new desirable species are not recruiting in sufficient quantities for restored prairies to reach composition goals without human intervention. Lastly, when and in what order species arrived to restored communities influenced diversity, cover, and composition outcomes
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