Peirson's Milk-vetch - Algodones Dunes - 2005 [ds411]

In 2004, the Bureau of Land Management (BLM) implemented a monitoring program for Peirson's milk vetch (Astragalus magdalenae var. peirsonii), two other special status plants (Algodones Dunes sunflower and sand food), and dune vegetation in the Algodones Dunes of Imperial County as part of the Imperial Sand Dunes Recreation Area (ISDRA) Management Plan. This monitoring program was conducted again in the spring of 2005 for Peirson's milk-vetch and Algodones Dunes sunflower (due to its somewhat different phenology and the need to more intensively sample Peirson's milk-vetch, sandfood was not monitored in 2005). This data layer represents the presence of Peirson's milk-vetch in the study area. Peirson's milk-vetch (Astragalus magdalenae var. peirsonii) 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 in which Peirson's milk-vetch occurs. These sampling areas were positioned to encompass most of the Peirson's milk-vetch habitat in the Dunes. Data were recorded in contiguous 25m segments along each transect. These segments are called cells. A total of 123,488 cells were visited. Only the values for the 26,116 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 total number of Peirson's milk-vetch plants, and were categorized based upon life stages (seedlings and young non-flowering plants, flowering plants, and plants over 1 year old). The number of plants with evidence of damage from off-highway vehicles and other sources was also noted. Achieving estimates within 30% of the true population size at the 95% confidence interval within each management area was a sampling objective. Precision levels ranged from 7.8 - 44.8%, with the lowest precision occurring in the Buttercup Management area. This was likely due to the high variability in the spatial distribution of plants in this area. Detailed study methodology is described in Willoughby 2005b. (Note that only 12 sampling areas were sampled in 2004. Although the same habitat area within each of the management areas was sampled in 2005 as in 2004, some of the management areas were subdivided into more sampling areas in 2005 to assist in achieving estimates with better precision. The Mammoth Wash, Wilderness, and Ogilby management areas, each of which was organized into one sampling area in 2004, each has two sampling areas in 2005. The Adaptive Management Area, organized with 3 sampling areas in 2004, was subdivided into 4 sampling areas in 2005. Because the total area within each management area was exactly the same in 2005 as in 2004, the Duneswide and management area estimates are directly comparable between 2004 and 2005.)

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.

Disclaimer: The State makes no claims, promises, or guarantees about the accuracy, completeness, reliability, or adequacy of these data and expressly disclaims liability for errors and omissions in these data. No warranty of any kind, implied, expressed, or statutory, including but not limited to the warranties of non-infringement of third party rights, title, merchantability, fitness for a particular purpose, and freedom from computer virus, is given with respect to these data.