| This study takes a causal-explanatory approach to the biology and restoration of Schwalbea americana in New Jersey. Rather than asking general questions about the biology of the species from the outset, I began instead with an interest in explaining the causes of particular patterns and events observed, including the major increase observed in 2001, the lack of seedlings observed in previous years, and the consistent failure of past propagation and restoration efforts. Schwalbea was found to exhibit a distinct clustered distribution that was spatially correlated with a particular range of soil, water, and plant community characteristics relative to adjacent upland and wetland areas. Subsequent experiments found significant effects of these variables on the early life stages of the species, suggesting that they may well explain why the 2001 increase occurred where it did. The temporal dimensions of the increase were explained in terms of the flowering and seed ecology of Schwalbea. Fluctuations in flowering were attributed to prescribed burning, herbivory and size and age class effects. Seed dormancy, release and survival helped explain apparent time-lags between flowering and seedling recruitment events.; The lack of seedlings cited in previous censuses was found to be due to observer error. First-year individuals were mistakenly identified as mature plants emerging from below-ground dormancy due to their larger size compared to seedlings grown in the greenhouse. The lack of success of propagation efforts appeared to be due the presence of unsuitable conditions for Schwalbea, rather than to inbreeding depression, as was previously thought.; By explaining these patterns and events in terms of the particular contexts in which they occurred, insight was gained not only into the causes of important events in the life history of the population, but of the biology and restoration of Schwalbea in general. A lack of attention to such matters of context and causal explanation, in turn, appears to have been responsible for the lack of progress in previous research. These methods, and the knowledge gained from them, therefore stand to contribute to more sound approaches for the ecology and conservation of Schwalbea and other endangered plant species in the future. |
