Soil Ecology and Research Group

last update September 20, 2001

 

PLANT SPECIES MANAGEMENT / PROTECTION
ENHANCEMENT OF ORCUTT'S SPINEFLOWER HABITAT
AT POINT LOMA NAVAL COMPLEX


photo from sdnhm.org

Natural History and Biology of Chorizanthe orcuttiana

Chorizanthe orcuttiana, a member of the Polygonaceae family, is a very small and inconspicuous annual that warrants a great deal of natural resource consideration. This plant occurs in sandy openings within chamise-dominated coastal chaparral and is currently endangered in the state of California and on the federal list of endangered plants (cited Bauder).

A brief species description of Chorizanthe orcuttiana follows:

The seeds germinate in late fall after the seasonal winter rains begin, and a small rosette of narrowly oblanceolate leaves develops. Rosettes are often no more than 2 cm in diameter, and the leaves are lightly covered with long, silky trichomes, helping to distinguish it in the early stages of growth from the look-alike species, Mucronea californica, which has sparse, stiff hairs primarily at the leaf margins. Several-to-many decumbent, open-branched inflorescences are produced in late spring. They contain up to several dozen (occasionally more) flowers, each flower surrounded by three, three-angled bracts tipped with recurved spines. The six-lobed perianth is greenish yellow and only 1.5-1.8 mm wide. The breeding system is unknown. One-seeded fruits (achenes) are formed in late spring. (Bauder)

The two identified extant occurrences of Orcutt's spineflower (Chorizanthe orcuttiana) on Point Loma Naval Complex have been closely monitored since 1998. However, little is definitively known about the environmental factors affecting this plant or its reproductive biology (Bauder). In-depth studies of this plant are proving a challenge as numbers of individuals dwindle. Germination experiments have been difficult to carry out with so few seeds available (Bauder). By protecting this plant and its currently occupied habitat, as well as extending potential habitat, we expect to see the population size increase. In addition, some of the plant's biological mysteries may be solved, making management and protection plans more effective.

 

 

 

Introduction

All activities outlined in this project correspond to the Orcutt's spineflower population and encompassing area located south of McClelland Road on the Point Loma Naval Complex. The primary mission of this project is to expand the habitat of and enhance existing habitat for Orcutt's spineflower. The activities that will be implemented under this task will focus largely on eradication of iceplant (Carpobrotus edulis) as well as other invasive non-native plant species. Methods employed for iceplant removal will consist of manual removal, herbicide treatment and solarization. Erosion control measures will also be taken in designated areas to minimize the loss of topsoil and to inhibit further disturbance to the coastal or maritime chaparral plant communities. Sensitive plant species will be surveyed for and protected during all activities.

Many available techniques in iceplant eradication have been investigated. We contacted and communicated with a number of individuals who have been instrumental in large-scale iceplant removal projects in central and southern California. Their advice and suggestions were considered during the development of this research design.

Ecological impacts of soil disturbance will be heavily considered throughout this project. These impacts will be included in the analysis of the eradication treatments. Soil-disturbing activities will be avoided since opportunistic non-native plants are better adapted to infiltrate areas following ground disturbances. Soil bacteria, fungi and other microorganisms create a natural below ground ecosystem that is disrupted when the soil layers are mechanically displaced. Native plants are better adapted to survive in areas where soil health is in a natural state of balance.

Site Preparation

Relevé surveys will be carried out during the months of May and June. These surveys will allow the project team to produce a list of perennial plant species to be propagated during 2001 for out-planting during the winter of 2001-2002. Relative density for the various species will also be noted so that greenhouse seedlings will be out-planted in appropriate numbers representative of the natural plant community. Annual plants encountered will also be carefully documented and considered in this project. Some annual plant species may be direct seeded in open areas following seed collection.

Seed will be collected from the project site and adjacent areas during 2001 as maturing fruits are encountered. This seed will primarily be used to propagate seedlings in our greenhouse facilities for planting during the second phase of the project. Some of the seed may be used in direct-seeding small sections of the project area.

Due to the patchy distribution of the Orcutt's spineflower, its unique habitat and the varied topography found within the designated project site, aerial photos will be instrumental in outlining the project details. In coordination with Dr. Ellen Bauder from San Diego State University, the areas containing and immediately surrounding the Orcutt's spineflower occurrences will be marked on aerial photos as well as physically marked with colored flagging on-site to prevent any disturbance to extant spineflower populations.

Some sensitive and rare plant species are potentially located within the project's perimeters. These will be surveyed for at an appropriate time during their growing seasons when identification can be definitive. Pin flags of different colors will be placed at the individual plants' locations. The orchid, Piperia unalescensis, grows within the iceplant mats and its presence will determine the iceplant removal treatment applied to the surrounding area.

Non-native Plant Eradication/Biomass Removal

The first phase of the project implementation will entail the eradication of iceplant and other non-native plants within the project area and removal of the resultant biomass. Three methods will be employed for non-native plant eradication: manual removal, herbicide application and solarization. Iceplant is removed by hand fairly easily. The large mats can be pulled up and "rolled" with minimal soil disturbance. The proposed herbicide for chemical treatment is Roundup-Pro. Experts in iceplant eradication suggest the application of this glyphosate-based herbicide. The postemergence herbicide targets mature plants with actively growing foliage so that, when applied to the leaves and stem, it is translocated into all parts of the plant (Kuhns). It is inactivated when it contacts soil and does not kill the seed bank within the soil (Kuhns). The herbicide application will be completed at a time late enough as to not affect Orcutt's spineflower in any way (i.e. following the dispersal of seed). Navy Natural Resource Representatives and Dr. Ellen Bauder will determine a time appropriate for chemical treatment. The solarization of iceplant is achieved by covering the plant with a sheet of plastic. The heat from the sun's rays is intensified through the insulating sheet so that the underlying vegetation is killed. This treatment is particularly effective during the hot months of summer.

In coordination with Dr. Ellen Bauder, the areas containing and immediately surrounding the Orcutt's spineflower occurrences will be marked on aerial photos as well as physically marked with colored flagging on-site. All implementation work will take place outside of these identified areas. Dr. Ellen Bauder's team will hand remove any iceplant found within the marked areas. This iceplant will then be placed at a designated site outside of the spineflower area where our project team will transport it off base to a municipal disposal site.

Iceplant located in areas close to or on the historic road leading down to the primary spineflower occurrence will be manually removed. Iceplant will also be hand removed from other areas outside of but near Dr. Bauder's marked project area where plant species of concern are located or where native vegetation is dense. In particular, any iceplant-covered sites found to support the rare orchid, Piperia unalascensis, will be managed by hand. This iceplant removal will open up new habitat for the endangered spineflower and eliminate the primary exotic competitor for available resources in the vicinity of the spineflower. Plastic garbage cans full of the plant material will be moved from these sites to the habitat's perimeter near the road, where they will then be loaded into trucks for transport.

Because of the logistics of the project work site, complete iceplant biomass removal would be difficult and extremely costly to achieve. We propose to kill the iceplant bordering the cemetery fence through both herbicide and solarization and plan to leave the dead mats on-site. These dead mats will help control erosion on the sloped section and act as surface mulch around the native perennials that will be out-planted within the mats. This area appears to be inappropriate for Orcutt's spineflower. It endures run-off from the cemetery grounds and currently supports non-natives that have been introduced from the cemetery. Some on-going maintenance in killing iceplant seedlings may be necessary. The iceplant seedlings will be manually removed or monitored for subsequent herbicide application. We expect the native seedlings to have a much greater chance of surviving with their greatest competitor for resources disabled.

There are other non-native plants that are recognized to varying degrees as threats to the health of the maritime chaparral plant community. We will kill and remove Acacia cultivars, Perez's sealavender (Limonium perezii) and myoporum (Myoporum laetum) from the project site. Perez's sealavender along with acacia seedlings will be manually or mechanically removed. Larger acacia and myoporum will be cut at the base and the resulting stump "painted" with Round-up. The biomass from acacia and myoporum will be removed from the site.

Revegetation

The second phase of the project will involve out-planting the propagated native perennials at two sites within the project area. The planting will take place along the cemetery fenceline within the dead iceplant mats and at an adjacent disturbed open area. Both sites are located above and to the west of the Orcutt's spineflower occurrences. "Plugs" of dead iceplant with a diameter of approximately 80 cm will be removed for each seedling to improve water delivery to the plant during supplemental irrigation. The open area just south of the ice plant that borders the cemetery fence will be hand pitted before being revegetated to reduce soil compaction and improve water infiltration. Basins with an approximate diameter of 60 centimeters will be constructed around seedlings in both areas. Upon approval from the cemetery administration, we will tap into their irrigation line to create a gravity-fed water delivery system to our seedlings at the project site.

The planting of native perennials in the disturbed open area will be designed so that the resultant plant community will be "open" in its coverage. This falls in line with our goal to restore and create potential habitat for Orcutt's spineflower. We will ensure that there is ample open space between planted perennial shrubs of the maritime chaparral for Orcutt's spineflower and its associate annuals to infiltrate. This sparse planting will also be critical for conservation of the substrate vital to the spineflower's survival.

Erosion Control

Various identified slopes within the project area will require erosion control. The historic road will be included in this treatment. Coconut husk fiber rolls, or coir, will be installed at elevational intervals along natural contours of the slopes to inhibit sheet flow of water. Coir mats may also be installed on other adjacent selected slopes. Some areas will be pitted to reduce channeling of water during precipitation events.

Experimental design

The project area referred to in this plan is located south of McClelland Road and surrounds an Orcutt's spineflower population inhabiting a total area of approximately

35 m2 (Bauder). The project area is located within a larger area proposed for the Point Loma Ecological Reserve (Bauder). Within the project area, four subsections where implementation activities will take place are identified: (1) fence line, (2) open space, (3) historic road and (4) surrounding area. Each subsection can be divided into subplots for experimental purposes. The subsections and subplots will be marked on the aerial photos and referred to by correlating numbers in future reports.

Due to the nature of Orcutt's spineflower populations and the distribution of iceplant in the surrounding area, the subsections and subplots will vary in size and shape. We will identify eight subplots in total, two per subsection. Each randomly assigned subplot will have one permanent short transect installed within its boundaries. The ends of the transects will be marked by rebar with colored caps. Each transect will be10 meters in length. The details for transect monitoring will be outlined in the monitoring methods section of this plan.

Topsoil samples will be chosen randomly, with thirty-two sample sites analyzed twice each year. Four samples from each subplot will be analyzed.

Monitoring Methods

The monitoring system for this project will consist of three methods: scientific, visual and photographic. The scientific monitoring will involve surveying of short transects through the treatment sites as well as random topsoil sampling. These surveys will aid in the assessment of the various eradication methods employed. Iceplant re-growth or spreading and native plant germination/survival will be determined through the transect monitoring. To what degree removal of the iceplant mat affects the erosion of topsoil will be answered through the topsoil data. Visual monitoring of the project will be ongoing and all observable changes will be documented in detail. All site preparation and implementation activities will be documented through photography. Several established photo points will also be installed around the experimental sites and at each transect so that changes can be accurately tracked. Photographic documentation will take place at predetermined time intervals following the completion of project implementation activities (this will include photographs taken from the established photo points).

Botanical Transect Monitoring

The vegetation monitoring proposed for this project will be carried out using a modified version of the CNPS point-intercept transect protocol. Each randomly selected10-meter transect will have a metric tape measure pulled from one end to the other (rebar caps will be marked with a "B" for beginning point and an "E" for ending point). Twenty points will be sampled along each transect starting at 0.5 m and ending at 10 m. A one meter long, 1/4 inch round steel bar will be placed vertically at each sampling point, consistently on the same side of the tape. All live species that come in contact with the bar, or its upward extension, are to be counted. Trees are considered >2.5 meters, shrubs between 0.4 and 2.5 meters, and herbs <0.4 meters in height. If no vegetation is intercepted at a sampling point it is recorded as "bare". Total coverage is then determined by how many points are covered by vegetation along the transect. Percent cover for individual species is to be determined by dividing the number of points covered by that species by the total number of sample points (20). Relative cover is to be determined for each species by dividing percent cover for each species by the sum of the percent covers for all species. McClenaghan, et al. 1997 provides a thorough description of the above procedure.

The following questions should be answered from the transect data: Does the iceplant come back if it is sprayed with herbicide or solarized and left in place on site? How quickly does it spread if untreated or if missed during the herbicide/solarization procedure? How do the herbicide and solarization treatments compare in successfully eradicating iceplant? Are native plants able to successfully infiltrate and survive within the dead iceplant mats? Do the dead iceplant mats inhibit growth of exotic plant species? How are the survival and growth rate of the outplanted perennials affected by the type of ice plant controlled (herbicide, solarization, hand removal) used?

Topsoil Sampling

Thirty-two random soil profiles will be taken between the eight subplots twice each year (May and October). The soil strata can then be analyzed using standard soil testing kits. In-field analysis will provide horizon depth and composition data. We will determine soil texture and pH and collect nitrogen, phosphorus and iron content data. Orcutt's spineflower is known to grow in the loose sandy soils derived from ferruginous sandstone from old beach ridges (Bauder). Texture analysis data will then be compared to known site results. By monitoring the soil in the project area, we can assess our progress in soil conservation through erosion control techniques including pitting, installation of coir mats and rolls, and out-planting of native perennials.

Statistical methods for data analysis

The efficacy of the iceplant eradication methods will be analyzed and compared in terms of various factors, including survival and growth rates of out-planted seedlings. ANOVA testing for seedling survival and growth will be completed for the three methods of iceplant eradication. A cost analysis including time and labor involved in the eradication activities will also be completed. Statistical results will be integrated with the cost analysis results to give a cost per/acre finding.

The efficacy of the various erosion control methods will be compared through upper soil horizon data. A cost analysis for the various treatments will also be completed. Texture analysis results from the topsoil sampling will be compared to known soil characteristics from the project area outlined by Dr. Ellen Bauder's team.

The survival of the outplanted greenhouse seedlings in the ice plant areas and the open area will also be analyzed through the use of simple T-testing. The two treatments will be compared to generate data on the value of dead iceplant as surface mulch in the survival and growth of seedlings. Percent seedling survival and growth data will be compared and cost of non-native maintenance around the outplanted seedlings will be included in the analysis for both treatment areas.

Schedule for Implementation

The timeline includes both field work and paper work to be completed. Occasionally the fieldwork might require rescheduling. The proposed date refers to the month within which the work is to commence. All implementation activities will commence upon approval of this restoration plan. Quarterly progress reports will also be submitted.

This project was initiated in October 2000 and is scheduled to continue through October 2002. Areas of interest include the maintenance of iceplant over time (analysis of three methods of eradication: hand removal, herbicide application, and solarization), out-planted seedling survival and growth and erosion control effects on topsoil. The activities under this project will ultimately enhance and create habitat for Orcutt's spineflower.

 

Table 1

Proposed timeline for the commencement of fieldwork and submittal of paper work. Year 1: 2001

DATE

FIELD WORK TO BEGIN

PAPERS TO BE SUBMITTED

29-March - 01

Meeting at project site with Ellen Bauder, Juda Sakrison, David Pivorunas, Kim O'Connor, Dave Bainbridge, Tom Zink and Amy Rusev

1-April-01

Marking of Chorizanthe orcuttiana occurrence perimeters (Dr. Ellen Bauder)

 

1-May-01

Relevé surveys, seed collection, rare plant and annual plant surveys; flagging of rare plants encountered; greenhouse propagation; installation of monitoring transects and photo points; transect monitoring

Research Proposal

1-June-01

Seed collection; greenhouse propagation; iceplant eradication (hand removal and solarization)

Final Research Plan (following corrections and comments on proposal)

1-July-01

Installation of erosion control devices; iceplant eradication (hand removal and herbicide application); seed collection; greenhouse propagation

Quarterly Progress Report

1-August-01

Installation of erosion control devices; continuation of iceplant eradication; seed collection; greenhouse propagation

 

1-September-01

Installation of erosion control devices; continuation of iceplant eradication; seed collection; greenhouse propagation; transect monitoring

 

1-October-01

Pitting of open area; topsoil sampling; seed collection

Quarterly Progress Report

1-November-01

Iceplant monitoring

 

1-December-01

Out-planting of greenhouse seedlings; transect monitoring

 

 

 

Table 2

Proposed timeline for the commencement of fieldwork and submittal of paper work. Year 2: 2002

DATE

FIELD WORK TO BEGIN

PAPERS TO BE SUBMITTED

1-January-02

Outplanting of greenhouse seedlings; supplemental irrigation of seedlings (if necessary)

Quarterly Progress Report

1-February-02

Supplemental irrigation of seedlings (if necessary); monitoring of iceplant; monitoring of erosion control

 

1-March-02

Seed collection, rare plant and annual plant surveys (to catch any missed in 2001); flagging of rare plants encountered; monitoring of erosion control; transect monitoring

 

1-April-02

Monitoring of iceplant; monitoring of erosion control

Quarterly Progress Report

1-May-02

Monitoring of iceplant; monitoring of erosion control; topsoil sampling; supplemental irrigation of seedlings (2X)

 

1-June-02

Transect monitoring; supplemental irrigation of seedlings (2X)

 

1-July -02

Supplemental irrigation of seedlings (2X)

Quarterly Progress Report

1-August-02

Supplemental irrigation of seedlings (2X)

 

1-September-02

Final transect monitoring; supplemental irrigation of seedlings (2X)

1-October-02

Final topsoil sampling

*

* Final report is to be submitted within two months of project completion