Date of Award
J. Stephen Brewer
This study investigated how the carnivorous plant, Drosera capillaris(pink sundew), responded to changes in the resources of its habitat, the fire-prone, nutrient-poor wet savannas. It is of interest to determine what soil nutrient(s), nitrogen or phosphorus, limits the survival and growth of pink sundew, and to what extent, if any, does fire affect the survival and growth of this carnivorous plant. My field experiments had twenty plots with two replicate groups consisting of four pink sundews in each plot. From the fall of 2017 to the fall of 2019, only half of the plots were clipped annually, and there was no clipping in either of the plots in 2020. The clipping of the plots, combined with the removal of clippings and existing leaf litter, was intended to simulate low-intensity surface fires in this system, which cause very little plant mortality but reduce aboveground biomass, reduce leaf litter, and increase the amount of light that reaches the soil surface and the short, flat rosettes of pink sundew. Within each replicate, the pink sundews were assigned one of four treatments to measure how the nutrients affected survival and relative growth rate. In a second experiment, ash was also added to half of the control plants with and without simulated fire in one of the sites to determine whether there was another nutrient that benefits the survival or growth of the pink sundews. Relative growth rate (RGR) was quantified by measuring change in rosette area, which was estimated from digital photographs and calculating the area of polygons drawn around the rosettes using SketchAndCalc. Statistical analyses of survival and RGR were done using R. Results suggested that nitrogen possibly does not limit survival or growth, and additional nitrogen supplied to the soil may actually be harmful. Simulated fire (clipping and litter removal) did not increase the survival or growth of the pink sundews at these sites in the first half of the growing season, despite the fact that fires were previously shown to be important in promoting the emergence and seedling recruitment from a seed bank; however, simulated fire increased RGR of plants in the latter half of the growing season. In addition, there appeared to be an extra benefit of adding phosphorus earlier in the growing season on growth later in the growing season, but only when combined with simulated fire. It is still unclear whether phosphorus is the main nutrient in the ash that is responsible for stimulating the growth when combined with increased light after a fire. These results suggest that nutrients in ash added to the soil (including but not necessarily limited to phosphorus), when combined with increased light associated with fire, increase growth in the carnivorous plant studied here.
Rodriguez Castillo, Karina, "Responses of the Carnivorous Pink Spoonleaf Sundew (Drosera capillaris) to Nitrogen Addition, Phosphorus Addition, and Simulated Fire" (2021). Honors Theses. 1800.
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