Raising Peas in Rising Seas: How an increase in soil salinity affects seed germination and seedling survival of the Keys partridge pea (Chamaecrista lineata var. keyensis) a rare Florida Keys endemic
Sabine Wintergerst, Fairchild Tropical Botanic Garden
The only known remaining populations of the Keys partridge pea (Chamaecrista lineata var. keyensis) are found within the imperiled pine rockland habitat on two islands of the Florida Keys. Like other low-lying islands, the Florida Keys are especially threatened by sea level rise. As a consequence, soil salinity levels will likely rise as well, first in areas closer to the coast but eventually salinization will also reach areas further inland. Additionally, more frequent and higher storm surges are also predicted which will temporarily inundate part of the islands in saltwater. Previous research has shown that the impact of 2005’s Hurricane Wilma negatively affected populations of the Keys partridge pea. However, the effect of increased salinity on seed germination and seedling establishment has not been investigated. We established an ex situ collection through which seed bulking provided enough seeds to use for experimental trials which were conducted with the help of high school students as part of Fairchild’s BioTECH internship program. The results show that seed germination remains high at low levels of salinity (<10ppm) but decreases substantially when salinity becomes more similar to ocean water (~30ppm). Although seedling survivorship is also high at low levels of salinity (<10ppm) it is important to note that even at 5ppm, 20% of seedlings died within 2 months of exposure. Above 20ppm, seedling survivorship declined rapidly revealing how even short exposures to ocean water could have detrimental effects on juvenile plants. Our results show how seedlings are especially threatened by storm surges, but further research is needed to investigate how well seeds and seedlings can recover as soil salinity is alleviated by precipitation. Knowing how these critical life stages of the Keys partridge pea are affected by an increase in salinity can inform the future population trajectory and help with management and/or restoration planning.