Soil Ecology and Research Group last update November 18, 2001

WEST SLOPE ORCUTT'S SPINEFLOWER
(CHORIZANTHE ORCUTTIANA)
HABITAT RESTORATION
AT POINT LOMA NAVAL COMPLEX

photo from sdnhm.org

 

Ecology of Chorizanthe orcuttiana

Orcutt's spineflower is an herbaceous annual endemic to San Diego County. All known ecology of Ocutt's spineflower is obtained from the "Recovery and Management of Orcutt's Spineflower (Chorizanthe orcuttiana), Final Report" (Bauder, 2000). Once thought to be extinct, this species appears to be restricted to open areas in coastal or maritime chaparral with neutral to slightly acidic, fine, sandy soils derived from eroded ferruginous sandstone where competition for resources is low. Observations made of extant populations found soils that appear to allow establishment of Orcutt's spineflower have increased amounts of nitrogen compared to surrounding areas and often to have iron concretions (Bauder, 2000).

The vegetative stage occurs from late fall until early spring with the reproductive stage occurring in April. One-seeded fruits are produced in late spring and the seeds germinate after the seasonal winter rains. Because of the small population size of Orcutt's spineflower, there is very little known of its biology or reproduction. It is theorized that the possible means of pollination is insects and that it is closely associated with California spineflower (Mucronea californica) although there have been no definitive studies on the breeding or symbiotic relations performed (Bauder, 2000).

It is believed that the causes for rarity of Orcutt's spineflower are the loss of required specialized habitat with few competitors, reduced fitness due to the low number of individuals, and possible germination requirements that may not be met each year causing population size to fluctuate (Bauder, 2000). Orcutt's spineflower is Endangered in the state of California and is listed federally as an endangered plant (CDFG 2000, Federal Register 1996).

Introduction

At the present time, there are only three extant populations of Orcutt's spinflower. Element Occurrence (EO) #10 consists of one individual in Oakcrest Park in Encinitas. The remaining two populations, EO #3 and #12, are both located on the Point Loma Naval Base. Because of the lack of knowledge of reproduction and insufficient amounts of seed for assisted propagation and reintroduction, management of Orcutt's spineflower has focused on both the protection of areas currently supporting the species and the development of surrounding areas to create favorable habitat for its establishment (Bauder, 2000).

Evaluation of the west Chorizanthe site (Figure 1) has suggested that the system has lost the ability to control essential resources and the capacity for autogenic repair. Evidence of biophysical degradation is the dominance of invasive plant species, particularly highway iceplant (Carpobrotus edulis), at the project area. Iceplant, or hottentot fig, is a succulent perennial in the Aizoaceae family. It is an aggressive competitor and superior in direct resource utilization to highly specialized, native plants that are adapted to maritime chaparral communities (State Resource Agency, 1990). There is evidence that iceplant also competes indirectly with native flora. It has been reported that iceplant can lower soil pH and affect the root morphology of some native shrubs (D'Antonio, 1990a; D'Antonio and Mahall, 1991).

The intention of this plan is to repair the damaged ecological cycles thereby crossing the degradation transition threshold of the ecosystem and initiating autogenic repair, hopefully to include an increase in the presence of Orcutt's spineflower. A process-oriented approach to the restoration of the site will focus on vegetation manipulation to increase the ability of the system to conserve essential resources. A benefit to this

Figure 1. Proposed Chorizanthe orcuttiana habitat restoration site.

approach is that once autogenic repair has begun, further maintenance will not be required (Whisenant, 1999).

The means of ecological repair that will be implemented in this plan will be the removal of invasive species, particularly iceplant, installation of erosion control and outplanting of native perennials. These measures will be taken in an attempt to create more space for natural recruitment by the nearby population of Orcutt's spineflower. This will be accomplished by eliminating direct competition for resources, improving the quality of the soil and the mycorrhizal populations present in the soil, and allowing the native flora to utilize water and nutrients.

All activities outlined in this project correspond to the area north of the EO #12 Orcutt's spineflower population. The primary task will be eradication of iceplant and other invasive species. This will be accomplished through herbicide application. Several types of erosion control will also be implemented in order to discourage runoff and reduce soil degradation. Native perennials propagated from seed collected on-site will be planted in an effort to mimic the distribution of plants in the area that currently supports Orcutt's spineflower directly South of the site. Botanical and soil monitoring will be conducted to determine the success of the project in creating a suitable habitat for Orcutt's spineflower.

Site Preparation
Monitoring and Propagation
A reference transect has been established directly West of the area to be restored and point-intercept monitoring was completed to determine the species composition of an undisturbed area of close proximity. A Relevé survey was also conducted and reports on flora associated with Orcutt's spineflower were consulted. From these sources a plant list has been generated and a species palette created. Seed and cuttings of native perennials have been and continue to be collected from the site and propagation has begun at the San Diego State University greenhouse for outplanting during the winter of 2001-2002.

The restoration site will be divided into four subsections; the upper (eastern) open area, the lower (western) open area, the area along the road, and the area to the North of the open clearings (Figure 1). Eight subplots will be established on-site, two subplots per subsection. One permanent modified transect will be established randomly in each subplot for point-intercept and quadrat monitoring. The data collected will be used to determine percent cover and the presence of annuals and invasive species on-site. The transects will be ten meters in length and will be monitored once before implementation to establish base line data and every quarter thereafter to measure progress. The protocol that will be used is discussed in further detail by McClenaghan et al. (1997).

The quality of the soil will be an important aspect of the restoration as Orcutt's spineflower appears to only be able to compete with other members of the coastal sage scrub community where soil conditions are considered harsh. Several types of soil monitoring will be conducted to compare known soil quality data collected by Dr. Ellen Bauder at the Orcutt's spineflower site. Soils will be sampled onsite and both texture and organic content assessed at the soils lab at San Diego State University. Compaction onsite will be determined by measuring bulk density. Soil moisture and pH data will also be collected. Thirty-two samples, two random from each subplot, will be collected, once prior to implementation and twice thereafter, in April 2002 and at the end of the project in October 2002, to determine whether proper soil conditions are being achieved.

Non-native Plant Eradication/Biomass Removal
Once base-line data for all monitoring is collected, invasive species eradication will begin. The species that most threatens the habitat of Orcutt's spineflower, iceplant, will be treated with Roundup-Pro, a glycophosphate-based herbicide that interferes with amino acid production and increases targeted plants' metabolisms (Kuhns). This is the recommended means of iceplant eradication because of its effectiveness and because the agent is inactivated upon contact with soil and therefore does not affect the seed bank. Herbicide application is favored to manual removal because it does not cause soil disturbance that may decrease the ability of native perennials to compete with invading species and can contribute to runoff and erosion. Once treated with herbicide, the resulting mats of dead iceplant will be left onsite in the hopes that they will discourage erosion, act as an organic mulch, and aid in the retention of nutrients and water. Other invasive species found on site will be removed by hand, sprayed with herbicide, or cut and herbicide applied to the resulting stump depending on the size of the plant and presence in each situation. The iceplant that has already been pulled and placed in piles on-site will be removed from the base and disposed of properly along with any other large bio-mass. The area known to support Orcutt's spineflower will be flagged by Dr. Ellen Bauder and the Soil Ecology and Restoration Group will not enter that area or be involved in the eradication or removal of any invasive species within that area. Because of the ability of ice plant to re-sprout from "apparently dead individuals for several months" (Bossard et al. 2000), the site will be closely monitored and any re-emerging invasive species will be removed through out the length of the project.

Erosion Control
It appears that erosion control measures will be required on slopes in several areas around the restoration site. Wattles will be installed in various areas along the declines to prevent sheet flow and run-off. Punched straw and check dams may also be utilized if it is deemed necessary in smaller problem areas. All debris that is currently on the project area will be removed and the disturbed ground beneath will be evaluated to determine if erosion control will be necessary and what types would be most effective. Hand pitting will be performed in the two open areas to reduce soil compaction and increase water retention.

Revegetation
Outplanting
The second phase of the project will be the revegetation of the site with native perennials. Planting will take place in the two open disturbed areas and in the dead iceplant mats on the site. Special consideration will be taken in planning the species distribution to leave open spaces where Orcutt's spineflower could establish. Small, sparse species such as sand aster (Lessingia filaginifolia) and common sun-rose (Helianthemum scoparium) have been favored in the species palette and will be planted throughout the site. Larger species found in the areas surrounding the site such as laurel sumac (Malosma laurina) and red berry (Rhamnus crocea) will be planted in the area along the road and in the access paths to act as a natural barrier and protect the site.

Table 1
Proposed Plant List and Method of Propagation

Holes will be dug with shovels and post-hole diggers and a small amount of the dead iceplant removed from the area surrounding each hole when necessary. Each plant will receive two gallons of water at the time of outplanting. A basin will be constructed around each seedling to collect water during natural rainfall events and supplemental irrigation. Each seedling will receive a plant protector device to discourage herbivory. Treepee shrub shelters will be used on smaller species and plastic mesh will be installed with bamboo sticks around species that would outgrow the treepees to allow for a more natural plant morphology. Evidence of herbivores and browsing will be documented to determine the effectiveness of the plastic mesh plant protectors.

Maintenance
Maintenance of the site will consist of supplemental irrigation of the outplantings and the monitoring of re-emerging invasive species and subsequent eradication or removal. At the time of each visit to the site, all invasive species will be identified, recorded, removed, and disposed of properly. Monitoring of the permanent transects will be used to determine whether the dead iceplant mats favor or discourage the establishment of invasive species. Outplanted seedlings will receive supplemental irrigation one time per month from the time of outplanting in the winter of 2001-2002 until May of 2002. In the months of May 2002 through September 2002 the seedlings will be watered once every two weeks. Each outplanting will receive at least one gallon of water at the time of irrigation. Supplemental irrigation will be discontinued at the end of September 2002.

Schedule for Implementation

The timeline includes both fieldwork and paper work to be completed. This project was initiated in September 2001 and is scheduled to continue through October 2002. Site preparation has begun and is scheduled for completion by the end of November 2001. Revegetation will occur December 2001 through January 2002. Maintenance and monitoring will continue until October 2002. Quarterly reports will be submitted on the first day of the month in which they are due. An Implementation report will be submitted within thirty days of the completion of revegetation and a final monitoring report will be submitted within fifteen days of the completion of the project.

Table 2
Proposed Timeline of Restoration Activities

*Implementation report is to be submitted within 30 days of completion of revegetation
** Final Monitoring report is to be submitted within 15 days of project completion