The role of prescribed burning in maintenance of an endangered plant species, Lomatium bradshawii

Responses of a federally listed endangered plant species, Lomatium bradshaw ii, to the use of fire as a management tool for maintaining remnant wetland prairies were evaluated at two public land areas in the Willamette Valley of western Oregon. Areas containing L. bradshawii were treated with two or three fall season prescribed burns during a nine-year period. Foliar crown area, height, umbellets, and schizocarps of 150 L. bradshawii at Rose Prair ie and 250 at Fisher Butte and the recruitment and density of L. bradshawii in 2-m(2) plots at both sites were documented during 1988-1996. When both sites were considered together, crown area, height, umbellets, and schizoca rps per plant initially responded positively to burn treatments, but increa ses were not consistent across years or sites. Crown area tended to increas e and then decline after each burn. Burning initially enhanced schizocarp p roduction at both sites; schizocarps declined one or two years after burnin g but remained much higher in the burn treatments than in controls until 19 96. Seedling production was not correlated with schizocarp production at ei ther site. Umbellet and schizocarp production were not correlated with Janu ary-June temperatures or precipitation at the nearest weather station. Burn ing accentuated differences in size and reproductive capacity of L. bradsha wii at the two sites and differentially affected recruitment and density. R andom resampling of L. bradshawii in 1997 indicated that effects of repeate d burning during the previous eight years were hard to detect. At Rose Prai rie, foliar crown area, height, number of leaves, umbellets, and schizocarp s in 1997 were similar or lower with burning than in unburned controls. At Fisher Butte, L. bradshawii in the two burn treatment were similar to contr ol plants, but three burns significantly increased foliar crown area, numbe r of leaves, and schizocarps. Monitoring recovery for one or two years afte r a burn may only capture the initial stimulation provided by burning and m ay foster unrealistically high expectations concerning the viability of an endangered plant population.