Several Botrychium species are classified as endangered or threatened. Rare species like B. gallicomontanum and B. pseudopinnatum, have only a few known populations. Conservation management of these rare Botrychium requires knowledge of their life history and population demographics. Using what we know about the species biology we can model population responses to natural and man-made perturbations. Understanding Botrychium population dynamics, (the distribution and actual population size) is complicated by their small size. It is further compounded by the fact that plants do not produce above-ground leaves on an annual basis and may be dormant for several years. High variability in numbers of above-ground plants suggests a high probability of local extinction. Using demographic data collected on Botrychium mormo we have identified the critical life history stages and used a stage-based model to assess the population viability. Stages identified for Botrychium include above-ground stages and several underground stages including spores, gametophytes, juvenile sporophytes and non-emergent sporophytes. Stochastic fluctuations and catastrophic disturbances were examined. The model resulting from this analysis predicts greater stability of populations than might be concluded from monitoring above-ground plants. We believe this is a consequence of having a large proportion of the population existing in underground stages. Even catastrophic elimination of all the underground gametophyte and sporophyte stages does not inevitably lead to population extinction because of the importance of the spore bank. Despite highly variable above-ground population fluctations, below-ground stages provide Botrychium populations with a high degree of buffering against local extinction.

Key words: Botrychium, conservation biology, population viability analysis, stage-based modeling