Algodones Dunes Sunflower - 2005 [ds413]

In 2005, the Bureau of Land Management (BLM) implemented a monitoring program for Peirson's milk vetch (Astragalus magdalenae var. peirsonii; see BIOS dataset 411), Algodones Dunes sunflower (Helianthus niveus spp. tephrodes), and psammophytic vegetation in the Algodones Dunes of Imperial County as part of the Imperial Sand Dunes Recreation Area (ISDRA) Management Plan. This data layer represents the presence of Algodones Dunes sunflower in the study area. Algodones Dunes sunflower is found in seven of the eight designated management areas of the ISDRA. A sample of 510 belt transects, 25m wide and ranging from 2.35km to 7.75km long, were surveyed in the spring of 2005 in 16 sampling areas within the seven management areas. These sampling areas were positioned to encompass most of the Peirson's milk-vetch and Algodones Dunes sunflower habitat in the Dunes. Data were recorded in contiguous 25m segments along each transect, referred to as cells. A total of 123,488 cells were visited. Only the values for the 27,576 occupied cells (represented in this data layer as points, each point being the southeast corner of an occupied cell) are included in this data layer. Counts were made of the number of non-flowering adults, flowering adults, total number (sum of non-flowering and flowering plants), number of plants with evidence of damage from off-highway vehicles (OHVs) and number of plants with damage from other sources. Number of sunflower seedlings in 5m wide belt transects were initially counted; but due to the large number of seedlings present in 2005, it was determined that surveys could not be completed in time and these counts were discontinued. See Willoughby 2005b for discussion of the sunflower seedlings counts from the first two weeks of sampling. An estimated 325,122 adult Algodones Dunes sunflower plants occurred in the seven management areas of the Dunes in 2005, with an estimated density of 15.33 adults/hectare. Achieving estimates within 30% of the true population size at the 95% confidence interval within each management area was a sampling objective. Precision estimates ranged from 9.2% - 29.0%, with a dunes-wide estimate of 8.3%.

For use by California Department of Fish and Wildlife (CDFW) staff and California Natural Diversity Database (CNDDB) subscribers. Due to the sensitive status of the species in this data, CDFW policy restricts its access.