Impact of a prolonged drought on the seed rain abundance and richness in a semi-arid grassland
Category: Research Poster
Author(s): Giselle Gueddiche, Izabella Rhomberg
Presenter(s): Giselle Gueddiche, Izabella Rhomberg
Mentors(s): Madelyn Amick
Long term extreme droughts are predicted to increase in frequency and severity in semi-arid regions. Thus, understanding how such ecosystems recover from these climate disturbances is essential. Seed rain plays an integral role in plant community recovery by reintroducing locally extinct individuals and species. We aimed to assess how seed rain responded to extreme drought by examining how the diversity and abundances of species changed over time. At the end of the first growing season, after the cessation of an extreme 4-year experimental drought (October 2018 – May 2023), seed traps were placed in the field (October 2023) in a semi-arid grassland in NE Colorado. Six months later they were replaced (May 2024) and then recollected after another six months (October 2024). Seeds were then collected from the traps in the lab, sorted, and identified to species. We found that plots exposed to extreme drought had significantly more seeds deposited than the control (156.32 vs 28.58). Previously droughted plots contained significantly more species (6.18 vs. 4.35) initially and increased over the course of a year (8.46 vs. 4.49) when compared to controls. This may be attributed to seasonality, as the first sample was placed shortly after the growing season ended. Evenness was significantly lower in previously droughted plots (0.45 vs. 0.69) and continued to decrease with time (0.35 vs. 0.64). Extreme drought, and time after drought significantly alters seed deposition dynamics, potentially altering passive mechanisms of recovery. By monitoring seed deposition, we can understand how species in the seed rain interact with grassland recovery after extreme, prolonged drought.