Habitat variation throughout the historic range of golden paintbrush, a Pacific Northwest prairie endemic: implications for reintroduction.

摘要

Although golden paintbrush (Castilleja levisecta [Castilla levisecta]) historically inhabited the prairies of the Willamette Valley, Oregon (USA), this Pacific Northwest prairie endemic is currently restricted to 11 sites in the Puget Trough of Washington and British Columbia (Canada). Recovery criteria call for the establishment of new populations throughout the species' historic range, including the Willamette Valley. We described vegetation and soil characteristics of representative golden paintbrush recovery sites in the Willamette Valley and compared them with those of remaining golden paintbrush populations in the Puget Trough. Potential golden paintbrush habitat in the Willamette Valley was ecologically distant from remaining populations. This disparity was likely related to regional differences in geology, climate, ocean proximity, and land use history. Many of the species indicative of remaining populations in the Puget Trough were native perennials, while those of potential reintroduction sites in the Willamette Valley were introduced annuals. Soil characteristics of golden paintbrush sites were also distinct among the two ecoregions. Puget Trough sites were located on sandy soils with generally high levels of magnesium and sulfur, while Willamette Valley sites were found on silty clay soils with high concentrations of potassium and phosphorous. Differences in soil texture, and magnesium and potassium concentrations were associated with plant community divergence among the two regions. We suggest using a plant functional group approach when comparing vegetation assemblages among Puget Trough and Willamette Valley sites, which allows comparison of taxonomically distinct communities that share ecological characteristics..