Survivorship and Predation Changes in Five Populations of Botrychium dissectum in Eastern Pennsylvania

Abstract

This study of five populations of Botrychium dissectum was initiated in 1977 as part of a general environmental monitoring program at the Susquehanna Steam Electric Station. The Botrychium populations were discovered in the course of general flora surveys. Plants of this species were remarkably common in old fields and second growth woodlands on the site; therefore, I decided to monitor these populations in several successional habitats and their fate over several years. Part of the rationale of this study was simply that populations of Botrychium dissectum were observed in several plant communities that I could reasonably expect to remain undisturbed at a protected site. The study area is located in the Susquehanna River valley, 8 km north of Berwick, Salem Township, Luzerne County, in east-central Pennsylvania. Botrychium dissectum produces a single leaf each year from a short underground rhizome. This leaf emerges in mid to late summer, unfolds, and, if a fertile segment is present, spores are shed in early autumn. The fertile segment then withers, but the vegetative blade remains throughout the winter and following spring, senescing as the new leaf emerges. It should be emphasized that if this leaf is damaged or lost, the plant has no photosynthetic organ until the next summer. If the first leaf is damaged as soon as it emerges, occasionally plants will produce a small second leaf. Although this study was initiated with the idea of following the fate (longevity) and production of fertile fronds of plants in several populations, the study has been sidetracked by the discovery that many of the plants were eaten in the autumn soon after the leaf emerged and expanded. The plants have high survival under these conditions; this will be the chief topic of this paper.