Pink sand verbena monitoring on the Oregon Coast

Abronia umbellata ssp. breviflora

Pink sand verbena (Abronia umbellata ssp. breviflora) is a short-lived perennial in the Nyctaginaceae family that is native to the Pacific Coast.  Individuals of this species only reproduce by seed and many individuals act as annuals, flowering and dying in their first year of growth.  Given their placement on dynamic dune systems, most populations are obliterated during winter storm events but seeds persist and are able to reestablish in the following years.  This pattern leads to highly variable populations (in both size and distribution) from year to year, but shows that a long-lived, persistent seed bank is possible and necessary for survival.   Historically found in widespread populations between British Columbia, Canada and Northern California, the species is now sparsely distributed throughout the range.  Pink sand verbena was thought to be extinct in the northern part of its range until 2 plants were found on Vancouver Island in 2000 and another two plants were found in Washington in 2006.  Existing populations are geographically isolated to the extent that there is little possibility of genetic exchange.  The greatest threat to the verbena habitat is competition with invasive European beachgrass (Ammophila arenaria), which has become widespread throughout pink sand verbena’s range and easily outcompetes native forbs.  The beach grass was introduced to the U.S. coast in the early 1900s and, once established, began stabilizing foredunes and disrupting the dynamic, hummocky dune habitat that pink sand verbena thrives in.   

Staff collected sand for substrate analysis

Research has been conducted since the mid-1990s about methods for reintroduction.  In extensive seeding experiments, over 3.8 million seeds have been distributed across more than 23 Oregon Coast sites.  The sites that had the most successful plant establishment rates were ones where the beach grass populations had been disturbed by bulldozing the top layer of sand and vegetation off the dune.  Following reintroduction in 1997, population numbers were steadily increasing until 2010.  Population surveys by IAE began in 2000 and have extended across lands owned by the US Forest Service, the Bureau of Land Management, the State of Oregon, and private land owners.  In 2012, monitoring occurred at nine populations near Bandon, Coos Bay, and Florence.  Researchers found that the number of plants at several sites had increased since the previous year.  Oregon's largest population of pink sand verbena occurs on the Coos Bay North Spit and is entirely a product of seeding efforts.  Seed was collected from a population in Port Orford in the mid-1990s and was spread across an area identified as ideal sand verbena habitat in 1997.  Seeding at the site resulted in a population of over 185,000 plants in 2011.  In addition, a trip was taken to Floras Lake and the survey crew discovered 67 plants (8 reproductive) at the site, which hasn’t had plants documented since 2006.  This site was last seeded in 2000, so the current population could indicate a small, but long-lived seed bank.

A mat of pink sand verbena sprawls across the dune on the Coos Bay North Spit.  Now the largest population in Oregon, this is entirely a result of seeding by IAE and its partners.

The pink sand verbena produces flowers June through September, but the surveying and monitoring window is limited due to protection of the western snowy plover’s nesting habitat.  The western snowy plover is a small shorebird that has been listed as threatened at the federal level.  It is native to the beaches of the Pacific Coast, but has experienced a drastic decline in numbers over the past several decades, primarily due to habitat degradation and destruction.  The state of Oregon recognized the decline and has included the plover on the state threatened species list since 1975.   The Pacific Coast population of snowy plovers inhabits the same area in which pink sand verbena is found, and their population decline has coincided with the decline of the verbena and several other native beach species.  According to the Western Snowy Plover Recovery Plan there used to be 20 nesting sites along the Oregon Coast, but that number has dwindled to just seven areas that are consistently used.  One of the steps taken to work towards delisting the species is restricting access to known breeding areas during the nesting season, typically between March and late September.  Ideal nesting sites such as dune-backed beaches, sand spits, and sparsely vegetated dunes with active sand movement coincide with ideal habitat for pink sand verbena populations.

Western snowy plover and chick.  Photo source: www.duneguide.com

Kincaid's lupine in Douglas County, Oregon

Lupine leaves and racemes

Lupinus oreganus, commonly known as Kincaid’s lupine, is a perennial forb native to the Pacific Northwest ecoregion.   It is found in wet prairie habitats and open oak woodlands, both of which are habitat types that have experienced extreme degradation and fragmentation due to urban and agricultural development.  Although Kincaid’s lupine is listed as a threatened species by the U.S. Fish and Wildlife Service, approximately 90% of occurrences are located on private land making management and protection difficult.  There are 161 known populations in Oregon, 94 of which cover less than one acre.  Kincaid’s lupine is a member of the legume family (Fabaceae) and has clumping, palmate basal leaves and numerous unbranched stems.  Reproductive stems produce 4-7 inch racemes (flowering stalks) with flowers arranged in a whorled pattern.  This species can be seen flowering between April and June.  There are several other lupine species that exist within the same range as Kincaid’s lupine and hybridization between species can cause difficulty in proper identification.

IAE staff use a grid to census the lupine plants

Ten years ago, IAE began monitoring several lupine populations in Douglas County (the southernmost occurrences of the species) in order to look at trends in population size and reproductive vigor.  Given that Kincaid’s lupine is the obligate larval host plant for the federally endangered Fender’s blue butterfly, researchers conducted butterfly surveys in 2007 at all monitoring locations.  To date, there are no known occurrences of Fender’s blue butterfly within Douglas County.  Current monitoring focuses primarily on measuring foliar cover (translating to abundance) and counting the number of racemes on the individuals monitored (translating to reproductive vigor).  Transects or monitoring grids have been established at six independent sites within the Roseburg BLM district.  Four of the sites are monitored with a full census of the plants, while the remaining two use sub-sample monitoring.

One of the monitoring locations, Callahan Meadows, has a unique population that appears unable to produce successful reproductive individuals.   Plant samples from Callahan Meadows were genetically tested and 100% of the individuals tested were polyploidy and from one maternal haplotype, meaning that the plants are effectively sterile.  Individuals are able to continue reproducing vegetatively but not sexually.  So, while the foliar cover of the plants in this population has continued to increase, the implications of decreased genetic diversity are concerning.  The failure of pollination experiments has reinforced researchers' theories that the population has reached a genetic dead-end and is unable to produce viable seed. This population is the only known Kincaid's lupine population in the Roseburg BLM district that does not occur along a roadside and it also hosts enough nectar species to theoretically be habitat for Fender’s blue butterfly.  Unfortunately, given the chronic reproductive failure, the lupine population would not be able to provide stable reproductive habitat for the butterfly.

Monitoring methods: grid in forest clearing (l), transect on roadside (r)

Aside from concerns about low genetic biodiversity, these lupine populations are vulnerable to encroachment of invasive species, disturbance and competition for resources from associated vegetation.  Kincaid's lupine thrives in areas that receive high levels of sunlight, so decreasing canopy cover can have a positive effect on the populations' health.  In 2010, the BLM treated four of the sites monitored by IAE by significantly thinning small shrubs and trees to open up the canopy around established plots.  At three of the four sites it appears that plants have responded positively, as evidenced by an overall increase in foliar cover and number of inflorescences. Continued monitoring will provide more information about the success of this experimental treatment.