Demography, Time to First Flowering and Longevity of 14 Temperate Forest Herbaceous Species, Iowa, USA

ABSTRACT

The ability of temperate forest herbaceous species to recover from anthropogenic disturbance and to colonize new secondary woods is limited by both seed shortage (lack of dispersal) and suitable safe sites (sites where seedling establishment is possible). In this study, which originated in 1998–99, I added seeds of 14 species, including six phylogenetically related pairs classified as common or restricted in distribution, to both occupied and unoccupied upland forest sites. I recorded emergence the first year and followed yearly survival for an additional five years. Adding seeds resulted in flowering individuals for 12 of the 14 species and an additional species established by vegetative spread. I concluded that dispersal, rather than safe sites, was most limiting. Species with restricted distributions, which also have larger seeds than related common species, had higher survivorship over five years. Minimum longevity ranged from 8–18 years, suggesting that once on site, long-term persistence is possible. A practical implication of these results is that limited funding and other resources can be focused on seed addition techniques, particularly for larger-seeded species. Because the mean age to first flowering was six years, a second practical implication is that the traditional monitoring protocol of following plants through to reproduction as a measure of restoration success may be difficult for many long-lived species. Using “citizen scientists” to monitor may help make long-term monitoring more feasible beyond the limited time frame of grant funding.