Effects of experimental storm surge and sedimentation on pitcher plants (Sarracenia purpurea) in a coastal pine savanna

Background/Question/Methods

Sea-level rise and stronger hurricanes associated with global climate change will likely result in farther reaching storm surges that will greatly affect coastal ecosystems. These surges can transport nutrients, salt water, and sediment to nutrient poor, fresh (i.e. low salinity) pine savannas. Purple pitcher plants (Sarracenia purpurea) are pine savanna inhabitants that could potentially be at a disadvantage because their pitcher morphology and stout structure may leave them prone to collecting saline water and sediment after a surge. We hypothesize that the combination of saline water inundation and sedimentation will cause significant decline in pitcher plant cover. Plots (each containing ≥1 genet of S.  purpurea) were established in a coastal pine savanna in northwest Florida; half received saline while the other half received fresh water experimental storm surge treatments. One of four levels of ‘sediment treatment’ (local, foreign, fertilized foreign, or no sediment) was randomly assigned to each plot. We documented pitcher plant percent cover, percent cover of neighboring plant species, and collected soil samples before and on three separate occasions after surging. Short term pitcher plant mortality and changes in soil characteristics (soil-water conductivity and nutrients) were compared among treatments.

Results/Conclusions

Our results show that saline water inundation resulted in significantly higher pitcher plant mortality than the fresh water treatment combinations 23 days after the study was initiated (F = 33.91, p < 0.0001). The effects of surge salinity remained significant for the rest of the growing season but were no longer detectable in the following growing season. The soil data revealed that the combination of salt water and fertilized sediment resulted in significantly higher soil-water conductivity and nutrient availability throughout the first growing season. A subsequent prescribed fire and regional drought greatly affected the study area during the next growing season and they may have been influential in the decline of all the pitcher plants to zero or near zero percent cover. Interestingly, though, S. purpurea decreased significantly more than some of the other neighboring species a year after the treatment applications, suggesting, that pitcher plants are more vulnerable to the cumulative effects of multiple stressors operating in this system. Our data show that storm surges can have dramatic, short term effects on S. purpurea survival and indicate that global climate change may indirectly contribute to the further decline of southeastern purple pitcher plant populations in the future.