Soil Ecology and Research Group last update December 16, 2004

ENGELMANN OAK ANNUAL REPORT

Executive Summary
Construction associated with the Rifle/Pistol Range in East Miramar on Marine Corps Air Station (MCAS) Miramar impacted up to nine Engelmann oak (Quercus engelmannii) trees. In accordance with the Station’s Integrated Natural Resources Management Plan (INRMP), impacts to Engelmann oaks require mitigation at a five to one ratio. Therefore, forty-five Engelmann oaks need to be established on the Station at selected locations that meet the appropriate soil and vegetative conditions to support Engelmann oaks. Eight possible restoration sites with the necessary conditions for Engelmann oak establishment were located by the Soil Ecology and Restoration Group (SERG). Final approval for potential sites four, six, and seven was given by the Public Works Department, Environmental Management and Southwest Division.

Acorns were collected in the fall of 2002 from existing Engelmann oaks on the Station as soon as they were mature. Acorns were germinated in a refrigerator at 4°C in sealable plastic bags filled with soil. Soil used was collected below the canopy of mature Engelmann oaks or a potting soil mixture was used that mimics the deep, loamy clay in which they prefer to grow. Germinated acorns were then planted into PVC pipes (10cm diameter x 30-45cm length) to allow for proper development of the taproot.

Prior to out-planting, all sites were treated with herbicide applied by state licensed applicators. Before placing the seedling into the planting hole, a handful of soil taken from beneath selected healthy Engelmann oaks was placed in the bottom to provide necessary mycorrhizal fungi. Additionally, a wire-mesh protector was placed in the planting hole to a depth of approximately 45cm to provide protection from possible gopher damage. The seedlings were installed and provided with approximately one liter of water through a deep-pipe installed at the time of out-planting. Due to potential die-off, 196 seedlings were planted to ensure a minimum survival of forty-five seedlings.

All seedlings will be monitored and maintained for four years after completion of planting. Maintenance will consist of supplemental watering and weed removal.

Introduction
Marine Corps Air Station Miramar, hereafter referred to as the “Station,” is located in San Diego County, California, four miles east of the Pacific Ocean and thirteen miles north of downtown San Diego. Construction associated with the Rifle/Pistol Range in East Miramar on the Station may impact up to nine Engelmann oak (Quercus engelmannii) trees. In accordance with the Station’s Integrated Natural Resources Management Plan (INRMP), impacts to Engelmann oaks require mitigation at a five to one ratio. Therefore, forty-five new Engelmann oaks need to be established at sites with the appropriate soil and vegetative conditions normally associated with oaks.

Background on Engelmann Oak
Engelmann oaks are only found in southern California and the northern portions of Baja California, with more than 90% of the remaining stands located in San Diego County (Pavlick, et al, 2002). Most Engelmann oak woodlands occur between 700 and 1300 meters (2300-4200 feet) and are usually found on southwest facing slopes and mesas dominated by grasslands or coastal sage scrub vegetation (St. John and Scott, 1997). Density of Engelmann oaks can range from 27 trees per hectare up to 147 trees per hectare (Barbour and Major, 1995). These oaks can be found within coast live oak (Quercus agrifolia) woodlands. However, due to their ability to germinate and grow better at low moisture conditions, Engelmann oaks also tend to occupy areas between mesic canyon bottoms and sage scrub/grassland uplands. Engelmann oaks are often found in soil that is deep loamy clay, however they can also grow in sandy or rocky soils if there is some source of summer moisture such as a perennial or intermittent stream (Pavlick, et. al., 2002). Drought and over-grazing, starting near the beginning of the 20th century, have altered the distribution of Engelmann oaks. A reduction in their abundance and decreases in potential habitat has also occurred due to land developments (Barbour and Major, 1995).

A concern when restoring an Engelmann oak community is that this oak readily hybridizes with Quercus berberidifolia and Quercus cornelius-mulleri. Due to this characteristic it is impossible to tell whether collected acorns will result in true Engelmann oaks or hybridized Engelmann oaks.

Methods
Prior to field work, pertinent literature was reviewed to determine the best methods to collect, propagate and maintain the oaks. This review also included information on conditions for site selection. In order to find appropriate locations to plant Engelmann oaks, numerous areas around the Station were surveyed. The Soil Ecology and Restoration Group (SERG) selected several possible sites, starting in the area of Green's Farm Road and working outwards to other areas with deep valley clay soils or with deep moisture conditions that can appropriately support Engelmann oaks. Vegetation that indicates deep soil moisture (Quercus agrifolia, Malosma laurina and Rhus integrifolia) was utilized to determine which sites are most appropriate (St. John, and Scott, 1997). Table 1 and Figures 1 and 2 outline the sites found that were determined to be appropriate for Engelmann oaks. These sites were presented to the Public Works Department, Environmental Management Department and Southwest Division for final approval. GPS coordinates were taken around the edge of each site in order to map the area and determine its overall size. Soil samples were taken from areas that appeared to meet the proper conditions in which these oaks prefer to grow. Soil texture and moisture results were used to select the most appropriate sites. From the eight initially selected, sites four, six and seven were chosen as the locations to be used for Engelmann oak restoration (Figures 3 and 4).

Table 1.
Descriptions of Potential Engelmann Oak Sites.

(Figure 1)
Figure 1. Potential Engelmann Oak Restoration Sites Near Riffle Range Road.

(Figure 2)
Figure 2. Potential Oak Restoration Sites in West Sycamore Canyon.

(Figure 3)
Figure 3. Final Oak Restoration Sites.

(Figure 4)
Figure 4. Final Oak Restoration Sites.

Collection and Germination
Acorns from existing Engelmann oaks located on the Station were collected upon maturation during the fall of 2002. Station personnel were contacted to recommend any known or likely locations of Engelmann oaks. These areas were then surveyed for any existing oaks. Aerial photographs taken of the base were also examined to further pinpoint possible oak locations. Once an Engelmann oak was located, GPS coordinates were recorded and a picture of the tree was taken (Figure 5 and Table 2). Figure 6 shows the Engelmann oaks found on the Station during the survey. More Engelmann oaks may be present than those shown in this survey, since the only areas surveyed were those most likely to support oaks. Due to the low amount of rain in the winter of 2001/2002, acorns were only found on one tree, Engelmann oak 2.

Figure 5. Engelmann Oak Survey (Engelmann Oak 2).

Table 2.
Engelmann Oaks Found on MCAS Miramar

(Figure 6)
Figure 6. Engelmann Oaks Found on MCAS Miramar

Acorns were gathered from Engelmann oak 2 once they were ripe and could easily be removed from the caps (Figure 7). It is preferable to collect acorns directly from the tree as these have less chance of being damaged by insects than those collected from the ground (McGreary, 2000). The acorns were collected from various locations on the tree

Figure 7. Collecting Acorns From Engelmann Oak 2.

in hopes that this would increase the genetic diversity; oaks are wind pollinated species and several Engelmann oaks were in the immediate vicinity. Once collected, acorns were stored in plastic bags and cold stratified in a refrigerator, for approximately one month, until they began to germinate (Figure 8).

Once the acorns began to germinate they were planted in PVC pipes (10cm diam. x 30-45cm) to allow for proper development of the taproot (Figure 9). Half the acorns planted were started inside the SERG greenhouse and then moved outside after three months (Figure 10). The remaining acorns were started outside the greenhouse under shade cloth. Greenhouse conditions encourage plants and their root structures to

Figure 8. Acorns Germinating After Cold Stratification.

Figure 9. Oak Seedlings Growing in 30 - 45 Centimeter Containers.

grow at a faster rate. However, this may also cause the taproot to grow too quickly and reach the bottom of the planting container before the oaks are able to be planted in the field (McGreary, 2000). Starting acorns inside and outside of the greenhouse will determine if the rate of root development in these two conditions has any effect on the long term survival and success of the Engelmann oaks. All oaks were placed behind a cage made of wire-mesh to protect them from rodents which chew-off main stems and leaves for use in nest construction (Figure 10).

Figure 10. Oak Seedlings in the Greenhouse Behind Wire-mesh Cage.

Acorns were either planted in a potting soil mixture that mimics the deep, loamy clay in which they prefer to grow, or in a four to one mixture of potting soil to soil collected from under a mature Engelmann oak. Soil found under oaks contains mycorrhizal fungi necessary for oaks to survive and can be used as a natural innoculum (St. John and Scott, 1997). Planting some acorns into soil with the mycorrhizae and others in soil without will determine whether the mycorrhizal presence is beneficial at the initial stages of germination and growth. It will also determine whether such initial innoculation has any effect on the long term survival and success of Engelmann oaks.

Site Preparation and Planting
Once seedlings reached acceptable size for out-planting (when the taproot has grown the length of the container, estimated at one year), site preparations began. During the last week of October 2003, wildfires swept through Miramar burning all of the approved oak sites. Prior to out-planting in February 2004, all exotic plants on the sites were treated with herbicide, applied by state licensed applicators, to reduce competition for water and nutrients between exotic annuals and the oak seedlings.

Prior to placing a seedling into the planting hole, a handful of soil taken from beneath a healthy Engelmann oak was placed in the bottom. As the seedling's taproot grows through this added soil, it will provide the oak seedling, an obligate mycorrhizal species, the innoculum needed to survive.

Holes for planting were made using a power-auger. A wire-mesh protector (1cm mesh chicken wire) was placed in the planting hole to a depth of approximately 45 cm to provide protection from possible gopher damage. A 1.2 m Tubex plant protector was fastened to a wooden stake and placed over each oak seedling to block grazers such as rabbits and deer. In addition, for supplemental irrigation needs, a 6cm diam. x 0.25-0.5 meter deep-pipe was placed in the ground next to each seedling to allow for below ground irrigation. Figure 11 shows a planting hole being prepared for planting. Once the planting hole had been prepared, the seedling was installed and provided with approximately one liter of water. The deep-pipe allows the plant roots to grow downward and tap into the available groundwater. Deep-pipe irrigation also reduces crown rot, common in oaks, by keeping the surface soil around the base of the plant dry. Due to potential die-off, a total of 196 seedlings were planted to ensure a minimum survival of forty-five seedlings. Each seedling was labeled to denote the different conditions in which it was initially grown (with/without native oak soil and started inside the greenhouse or outside).

Figure 11. Planting Hole Preparations, February 2004.

Monitoring and Maintenance
All out-planted seedlings will be monitored and maintained for four years. Maintenance will consist of supplemental watering and weed removal. Watering has been performed biweekly since the time of transplanting, except for the two weeks immediately following transplanting when rainfall provided sufficient water. Watering has included surface and deep-pipe watering using approximately four liters of water per oak seedling. Appendix 2 includes the complete listings of field work conducted on the three approved oak sites since approval was given in August 2003.

Weed removal has been performed as needed on an area approximately 5m in diameter around each seedling through use of an herbicide (2% RoundUp Pro applied with backpack-sprayers) and through manual or mechanical removal (weed whacker). This will decrease the amount of competition with non-natives for water and nutrients (St. John and Scott, 1997).

Monitoring will be performed on an annual basis through data collection and will consist of determining percent survival, seedling growth (plant volume measured by height x width x width), and rating each seedling’s health on a scale of one to five (one being almost dead and five being robust). Data for the oak sites was collected in April 2004 (Figure 12).

Figure 12. Data Collection, April 2004.

Success Criterion
Success criterion for this project requires that forty-five healthy Engelmann oaks be established at the end of the four year monitoring period. If oak survival falls below the necessary forty-five required by the Agreement, additional seedlings will be planted to meet the established criterion.

Monitoring Results
Survival, growth, and health data were collected on April 19, 2004, approximately two months after out-planting of seedlings. These baseline results will be used as comparison to the annual data collected in the future. Total survival was 100% with the average seedling being 1732 cm³ in size and having a health rating of 4.53. Due to the limited width of the above ground protectors significant increases in volume are not expected until the Tubex are outgrown by the oaks, thus making increases in height the best indicators of growth change during the first few seasons of the project. At the time of data collection the average height was recorded at 27.45 cm.

The various germination techniques utilized at the SERG greenhouse show the average size, in all dimensions, and health numbers are higher for the oaks treated with the oak soil innoculum. The oaks that were kept inside the greenhouse for the first three months following germination in addition to being treated with an innoculum show the best growth numbers so far, with an average height and volume of 32.98 cm and 2261 cm³, respectively. The lowest height and volume data can be seen for the inside oaks that did not receive the innoculum treatment with averages of 19.80 cm and 967 cm³. The same oaks have a lower average health rating of 4.27, whereas oaks that were treated with an innoculum and were immediately placed outside following germination have a higher rating of 4.65. Figure 13 illustrates the size and health data recorded for the germination techniques utilized.

Figure 13. Size and Health Data for Utilized Germination Techniques. OS= Oak Soil, OUT= Seedlings were immediately placed outside following germination, IN= Seedlings were placed in greenhouse for the first three months following germination.

Discussion
Due to the wildfires sweeping across MCAS Miramar in October of 2003, all existing vegetation was burned on the three approved restoration sites. The lack of vegetation revealed the true topography of each site, which was useful information during implementation planning since the possible flow of rainwater could be predicted and oak seedlings could be planted accordingly. At time of data collection, in April of 2004, all out-planted oaks and accompanying protective structures remained intact and there were no indications of water or erosion damage to any of the materials used, affirming that safe placement of the oak seedlings was achieved.

By comparing data from the different germination techniques utilized, long term benefits are expected to be seen in the seedlings grown in native oak soil. Already, seedlings germinated in an oak soil mix are doing better in both size and health compared to the seedlings that germinated in a mimic of the soils typically found where oaks naturally grow. This most likely indicates that mycorrhizae present in the oak soil have been beneficial at the initial stages of germination and growth. Also, when comparing the oaks that were propagated inside the greenhouse to the ones that were propagated outside under a shade cloth, the outside oaks are looking better (indicated by the higher health numbers). Those oaks germinated outside may be better prepared against post transplant shock, as indicated by their healthier appearance.

Although survival is expected to decline as the project prolongs, measures employed to prevent losses due to unsuccessful root establishment, herbivory, and erosion or runoff demonstrate initial success and are expected to remain effective for the duration of the project. This combined with continued monitoring and maintenance of the sites will ensure that the success criterion of 45 surviving Engelmann oaks is met.

Management Implications
Throughout the summer and fall of 2004 several seedlings on all three sites have outgrown the height of their Tubex plant protectors. To eliminate any restraints on growth, protectors will be removed to allow for more lateral growth. Following plant protector removal, some seedlings may need additional support to maintain an upright position until accustomed to the less protective environment seen without the protectors. This will be accomplished by attaching the stem to a thin, but robust stake until oak is self supportive. Due to their limited volume, caused by the restricted width of the protectors, uncovered oaks will be closely monitored for grazing activity to determine if an interim protector, preventing grazing but allowing for unrestricted growth, will be needed. If grazing proves detrimental, or demonstrates any limitations to continued growth, protective measures will be implemented for all uncovered oaks.

Workplan (December 16, 2004)