How will anticipated changes in climate interact with grassland plant community composition and diversity to affect the performance of seedlings? We ask this question for two reasons. 1) If plant species are to track spatial shifts in the locations of suitable climatic conditions, plant species must invade communities by means of seedling establishment; more diverse plant communities have been shown to be less invasible, but it is not known how warming will interact with diversity to affect invasion. 2) Warming and diversity may affect the performance of seedlings of resident species, which may change their abundance and even lead to local extinctions; we may detect effects of warming on seedling performance before adult abundance is affected.

We seek to answer this question using experimental grassland communities at Cedar Creek Ecosystem Science Reserve (CDR LTER site, Minnesota) that differ in plant species diversity, composition, and level of experimentally imposed warming (the Biodiversity and Climate experiment, BAC). BAC sub-plots receive high warming (2.5-3.0 °C), low warming (1.0-1.5 °C) or unwarmed control treatments, nested within whole-plots of 1, 4, or 16 plant species. Into each BAC subplot, we planted seeds of 26 perennial plant species and seedlings of four of these species. We are monitoring germination and seedling survival of both planted and resident species. We aim to relate seedlings’ traits to their performance in these communities of varying diversity and climate, in order to better predict and manage the response of grassland species, communities and ecosystems to global climate change.