Abstract
Changes in environmental conditions can lead to rapid shifts in ecosystem state (”regime shifts”), which subsequently returns slowly to the previous state (”hysteresis”). Large spatial, and temporal scales of dynamics, and the lack of frameworks linking observations to models are challenges to understanding, and predicting ecosystem responses to perturbations. The naturally-occurring microecosystem inside leaves of the northern pitcher plant (Sarracenia purpurea) exhibits oligotrophic, and eutrophic states that can be induced experimentally by adding insect “prey.” This regime shift has been modeled previously with difference equations including parameters for pitcher photosynthesis, oxygen diffusion through the pitcher liquid, prey input, and oxygen demand of decomposition. Here, we simplify the model structure, test, and parameterize it using data from a prey addition experiment, and use sensitivity analysis to reveal different model outcomes that are related to plausible values of free parameters. Simulations clearly illustrate that the microecosystem model displays regime shifts, and subsequent hysteresis. Parallel results were observed in the plant itself after experimental enrichment with prey. Decomposition rate of prey was the main driver of system dynamics, including the time the system remains in an anoxic state, and the rate of return to an oxygenated state. Biological oxygen demand influenced the shape of the system’s return trajectory. The combination of simulated results, sensitivity analysis, and use of empirical results to parameterize the model more precisely demonstrates that the Sarracenia microecosystem model displays behaviors qualitatively similar to models of larger ecological systems. Given its scalability, the Sarracenia microecosystem is a valuable experimental platform for rapidly studying ecological dynamics of major importance.