Rare-Plant Monitoring - 2006
Environmental Report Section 10.10.1.2
More than 100 plant populations of 53 different taxa listed by the Washington Natural Heritage program as
endangered, threatened, sensitive, or on the review or watch list are found at the Hanford Site (for additional
information, see
PNNL-13688
and the following website:
http://www.pnl.gov/ecomon/Veg/Habitat.asp ). The U.S. Fish and Wildlife Service
has designated 4 of these 53 taxa as species of concern in the Columbia River Basin ecoregion: Columbia milkvetch
(Astragalus columbianus), gray cryptantha (Cryptantha leucophaea), Hoover's desert parsley (Lomatium tuberosum), and
persistent sepal yellowcress (Rorippa columbiae). Two species, Umtanum buckwheat (Eriogonum codium) and White Bluffs
bladderpod (Lesquerella tuplashensis) (for additional information, see the website at
http://www.dnr.wa.gov/nhp/refdesk/lists/plantrnk.html)
are proposed as candidates for federal listing as endangered and threatened, respectively. In addition to the rare-plant
populations, several areas on the Hanford Site are designated as special habitat types with regard to potential occurrence
of plant species of concern listed by Washington State. These are areas that potentially support populations of rare
annual forbs.
During May 2006, surveys for rare annual species were conducted within specific areas inside these special habitat types as part of compliance review activities for firebreak construction and maintenance. Several populations of the Washington State sensitive taxa Suksdorf monkeyflower (Mimulus suksdorfii) that were seen in previous surveys in the habitat north of Gable Mountain were found again in 2006. Individuals and/or populations of Piper's daisy (Erigeron piperianus), Columbia milkvetch, and gray cryptantha were also located. Populations of loeflingia (Loeflingia squarrosa var. squarrosa) and rosy pussypaws (Calyptridium roseum) previously identified in the same vicinity were not found in 2006.
During September 2006, monitoring transects originally established in 1994 to examine the condition and status of persistent sepal yellowcress were revisited along the Columbia River shoreline near the 100-F Area. Surveys were also conducted on three Hanford Reach islands (Locke Island [Island 6], Island 18, and Island 16, Figure 10.10.1) in an attempt to relocate populations previously seen at those sites. The number of plants (stems) counted during 2006 at a 100-F Area beach was higher than the number seen in 2005 at the same location (Table 10.10.1). No specimens were located along the original 100-F Area transects (monitored from 1994 through 2001). Monitoring along the shoreline in 2005 and 2006 was accomplished downstream and up the river bank from the original population, and more than 600 stems were counted. Surveys of the islands in the downstream stretch of the Hanford Reach did not locate any persistent sepal yellowcress plants. On Hanford Reach Islands 16 (located just downstream of Wooded Island [Island 14]) and 18 (located near the 300 Area), it appears that the cobble habitats that previously supported persistent sepal yellowcress, have been covered with silt. This change in the substrate may be affecting persistent sepal yellowcress occurrence and/or survival. Data that describe trends in plant numbers and the timing of growth for this species are of interest because large variations in population numbers have been observed. These variations are believed to be linked to natural and Priest Rapids Dam related river-level fluctuations that inundate habitat for this species during a large part of the growing season.
