Date of Award
M.S. in Biological Science
Carnivorous plants are defined as being able to benefit from the nutrients of prey in the environment, and have at least one trait that either retrieves, ingests, or lures a prey to its traps. The association of carnivorous plants with fire-prone habitats was initially described as a paradox, considering that carnivorous plants are often associated with nutrient-poor soils and fires can increase soil nutrient availability. This apparent paradox assumes, however, that the nutrients that increase in availability following fire are those also provided by prey, which might not be true. In habitats with nitrogen-poor soils, fire has been shown to decrease the amount of available soil nitrogen (N), while increasing the amount of available soil phosphorus (P) from ash. Thus, if prey are an important source of N but not P, then there is no paradox. On the other hand, prey can also be an important source of P, in which case fire-mediated increases in soil P could reduce the benefit of carnivory following fire. Regardless of whether prey provide N and P, neither N nor P limitation may be reduced following fire if neither of these nutrients is limiting before a fire due to severe light limitation and/or if increases in soil nutrients are minimal. In this study, I examined how nutrient limitation of growth and survival in a carnivorous plant, Sarracenia alata, was affected by prey capture and simulated fire (clipping, litter removal, and ash addition) in a wet pine savanna in southeastern Mississippi, USA. Specifically, I measured the responses of relative growth rate, plant tissue N and P concentrations, prey capture potential, and nectar production to soil additions of N, P, or ash, clipping, and prey exclusion. I tested two alternative hypotheses: Hypothesis 1: If prey are primarily a source of N (but not P), and ash produced by fire increases soil P (but not soil N), then the benefit of carnivory should increase following fire to reduce N limitation of growth or survival; Hypothesis 2: If prey are an important source of both N and P, but are not limiting before a fire due to severe light limitation, and fire increases light levels relatively more than it increases soil nutrient levels, then N and P limitation and the benefit of carnivory should increase following fire as a result of reduced light limitation of growth.
Contrary to predictions of hypothesis 1, I found no evidence that prey exclusion increased N limitation of growth, reduced N:P pitcher tissue ratios, or resulted in a compensatory increase in relative prey capture potential or nectar sugar concentration on the lips of the pitchers. Contrary to predictions of hypothesis 2, the exclusion of prey only reduced growth in unclipped plots and did not affect N+P concentrations. Ash was not a significant source of N or P, as it did not alter tissue concentrations of these nutrients either with or without simulated fire. The results of this study suggest that resolving the paradoxical association of carnivorous plants with fire-prone habitats may require examining factors other than the effects of fire on nutrient fluxes.
Holloway, Jalen Christopher, "How do Prey Capture and Simulated Fire Affect Growth and Nutrient Limitation in a Carnivorous Pitcher Plant, Sarracenia alata?" (2021). Electronic Theses and Dissertations. 2104.