Spatiotemporal dynamics of Floerkea proserpinacoides (Limnanthaceae), an annual plant of the deciduous forest of eastern North America

Because environmental filters are temporally and spatially heterogeneous, t here often is a lack of significant relationship between the spatial patter ns of successive life stages in plant populations. In this study, we determ ined the spatiotemporal relationships between different life stages in two populations of an annual plant of the deciduous forests of eastern North Am erica. Floerkea proserpinacoides. Demographic surveys were done over a 4-yr period, and experiments were performed in the field and under controlled c onditions to test for the effects of various environmental factors on popul ation dynamics. There was a general lock of relationship between the spatia l patterns of seed bank and seedling density, and a lack of similarity betw een their spatial correlograms. This was related mostly to the effects of s patially variable environmental filters operating on germination and emerge nce. However, environmental tilters acting on plant survival were stable th rough time and contributed to stabilize the density and spatial patterns of the populations. Despite density-dependent presenescence mortality, spatia l patterns of seedlings and mature individuals were similar and their corre lograms were alike, suggesting that mortality did not fully compensate for density. Estimated fecundity was negatively correlated with population dens ity over the study period. Although flower production started only 2-3 wk a fter emergence, seed maturation mostly occurred at the end of the life cycl e, just before the onset of plant senescence. Yet, individual fecundity was low for an annual plant, i.e., 3.0 +/- 0.5 mature seeds/plant (mean +/- 1 SE). Seed predation by vertebrates was not significant. Low soil moisture h ad little effect on the total number of seeds germinating, although it slow ed down the germination process. In quadrats where leaf litter was experime ntally doubled, seedling emergence was lower than in control quadrats: in q uadrats where leaf litter was completely removed, emergence did not differ from that in control quadrats. Susceptibility to drought stress was higher for seedlings than for mature plants. Although the species does not maintai n a long-term persistent soil seed bank, other factors, such as density-dep endent fecundity and autogamy, may temper population fluctuations through t ime and reduce the probability of local extinction.