The Natural Resources and Environmental Affairs office at the Marine Corps Air Ground Combat Center in Twenty Nine Palms, California initiated a program to develop, test and implement plant community restoration techniques for use throughout the base. Initial work was focused on developing techniques for use in the restoration of the Vertical Short Takeoff and Landing(VSTOL) site located in the Sand Hill region west of the Expeditionary Airfield. The purpose was to test various procedures such as site preparation, soil manipulation, irrigation methods and plant protection to develop the most efficient methods for the restoration of the entire site into useful desert tortoise habitat.

Three plots were established: the Tower Plot to test procedures to be used for restoration of areas disturbed by vehicle use such as roads and staging areas; the Runway Plot to test procedures for use on areas heavily disturbed by construction of the actual runways and aircraft parking areas; and an Undisturbed Plot located outside the VSTOL site to use for comparative analysis. Initial soil analysis was conducted to gain baseline data and to serve as a guideline to what various methods should be tested. Results demonstrated that the Tower Plot was heavily impacted physically, through compaction, but was only slightly disturbed biologically. The Runway Plot, however, though experiencing similar disturbance physically, was heavily impacted biologically with a mineralization process that appeared to be almost totally destroyed.

Both disturbed plots were ripped and contoured and planted with seedlings grown from locally collected seeds. Seedlings in both plots were randomly selected to receive either a plant protective device or to serve as a control. The Runway Plot was treated with a recalcitrant amendment, medium sized wood chips, to work on reestablishing the impacted mineralization system, while the Tower Plot seedlings received either deep pipe or surface irrigation methods. Monitoring continued for one year.

Results demonstrated that the type of irrigation received did have an effect on seedling growth, depending on the species involved. The addition of a soil amendment, however, showed no effect, though previous experiments have shown results only after two growing seasons. No data was able to be collected on the effect of protective devices. Heavier than normal winter rains and later spring rains produced rapid growth in all seedlings and it was decided to remove the protective devices early to prevent damage to the seedlings as they quickly outgrew their protection. Numerous volunteers were seen on the Tower Plot while absolutely no volunteer plants were seen on the Runway Plot, demonstrating the lack of a viable seed bank in the heavily impacted area.

Overall results showed that areas disturbed through vehicle use, such as roads and staging areas, can be efficently restored by concentrating on correcting physical impacts, such as compaction, and using the available seed bank. Areas that have been heavily impacted, such as runways and parking areas, will need more intensive work such as seedling planting, various irrigation methods dependent on species planted, and possibly soil amendment use. A combination of these two approaches would be the most efficient way to restore the VSTOL site to useful desert tortoise habitat.

VSTOL Site: 6 April 1995	VSTOL Site: February 1997