WEED MANAGEMENT AND THE HABITAT PROTECTION OF RARE SPECIES - A CASE-STUDY OF THE ENDEMIC HAWAIIAN FERN MARSILEA-VILLOSA

Assessment of a plan for management and habitat restoration of a rare fern Marsilea villosa endemic to Hawai'i showed that the plant was cap able of reestablishing itself under certain conditions without intensi ve management. In this case degradation of the population was caused b y a series of unusually dry years combined with damage from off-road v ehicles. As a result the litter layer deteriorated and exposed soil wa s colonized mainly by alien weeds. Under near-normal climatic conditio ns, including periodic flooding, the endemic plant was able to grow vi gorously and successfully exclude most competitors. A program of labor -intensive weeding ultimately proved to be an unnecessary measure to p rotect the plant from possible extinction ai the site where the larges t and healthiest population occurs. Reliable data, collected by known and replicable methods, are needed to monitor the condition of rare sp ecies and to plan efficient management or habitat restoration should i t be necessary.