Species
Achnatherum speciosum Ambrosia dumosa Ambrosia acanthicarpa Amsinkia sp. Astragalus sp. Atriplex polycarpa Eriogonum inflatum Eriogonum deflexum Eriophyllum ambiguum Hymenoclea salsola Larrea tridentata Psathyrotes ramosissima Psorothamnus polydenius Plantago ovata Salsola tragus Schismus barbatus Stephanomeria pauciflora Tiquilia plicata	Native Native Native Native Native Native Native Native Native Native Native Native Native Native Exotic Exotic Native Native	Perennial Perennial Annual Annual Annual Perennial Annual Annual Annual Perennial Perennial Perennial Perennial Annual Annual Annual Perennial Perennial

 

Materials and Methods

Valley of Death

The Valley of Death project was designed to reestablish vegetation on a sloping area above the main road that runs through the area, reducing both wind and water erosion, thus preventing further damage to an already established maneuver/staging area. A second aim of the project was to restrict further damage to the area south of the road by preventing access to the area from the road, through the use of berm plantings, and to enhance the natural revegetation of the area through the use of catchments and island plantings.

Work was begun at this site on 19 May with pre-planting preparations. Construction of catchments, augering of planting holes, trenching and installation of perforated pipes were completed after five site visits. Plants were transported in several large lots and stored in a temporary shade structure to protect container plants pending installation (Figure 4). Planting was begun on 27 May and completed after four site visits on 3 June 1999. A total of 880 native desert shrubs were planted at the VOD site (Figure 5). The total number of plants per species is represented in Table 2.

Forty linear plantings utilizing perforated pipe irrigation were installed. Each of these plantings is approximately 100 feet in length and consists of sixteen native desert shrubs planted adjacent to each perforated pipe at a spacing of approximately six feet. One-half of these plantings were arranged in such a manner as to define the eastern and western limits of the lower portion of the site, and one-half of the plantings were arranged so as to exclude training activities in the upper (southern) portion of the site. Each perforated pipe was installed along the contour of the slope (perpendicular to the slope) to allow water to flow freely from either end. These pipes were placed below grade by means of a trench to facilitate water reaching plant root zones and to encourage deeper percolation (Figure 6A). A gasoline powered, walk behind trencher was employed to cut a trench approximately one foot deep. The machine-dug trenches were cleared of loose soil using trenching shovels and the perforated pipe was laid in the trench. The ends of the pipes

 

Figure 4. Temporary shade structure at Valley of Death site (26 May 1999).

 

Figure 5. Completed plantings along perforated pipe at Valley of Death (28 May 1999).

 

Table 2

Species and quantities planted at the VOD work site.

Species	Quantity
Ambrosia dumosa Atriplex canescens Atriplex polycarpa Encelia farinosa Encelia frutescens Ephedra nevadensisL Eriogonum fasciculatumU Isomeris arborea Hymenoclea salsola Larrea tridentata Lepidium fremontiiL Salazaria mexicanaL Senna armataL Sphaeralcea ambigua Thamnosa montanaU	100 125 80 20 70 40 75 50 125 125 10 30 25 10 5
Total	880

LSpecies restricted to catchment plantings at the lower portion of the site.

USpecies restricted to plantings in the upper portion of the site.

 

Figure 6

 

were leveled and fixed to rebar stakes and the pipes covered with available soil. Plants were then placed in pre-dug, pre-watered holes about one foot from the pipe.

Eight chevron shaped catchments were constructed along the lowest portion of the site utilizing the ITAM tractor. Each catchment is approximately twenty-five feet long on a side. These catchments are expected to collect water and silt runoff from the heavily disturbed training area immediately up-slope. Fifteen native desert shrubs were planted along the inner face of each catchment.Twenty relatively large and intact shrubs were identified in the upper portion of the site. Each of these shrubs was chosen to serve as a focus for the planting of six additional native desert shrubs to create vegetation islands or “Larrea Protection Zones” (LPZ’s) (Figure 7). In consultation with Ruth Sparks of the ITAM Program, LPZ berm construction at the VOD site was modified from the original idea. Instead of building berms around each LPZ, berms were constructed around the perimeter of the southern portion of the site at places of obvious vehicle ingress. It was decided through field observation that this alteration would provide greater protection for the numerous native seedlings and re-sprouts in this area.

During the time that planting was taking place, the ground was also being prepared for seeding. This was done only on the upper portion of the site using a mechanical pitter operated by ITAM personnel. Special care was taken to insure that no pre-existing plants were damaged in the process. Direct seeding was implemented by ITAM personnel the following March (see Appendix C for seed mix description).

Watering was scheduled to take place on a monthly basis, or when needed. During the winter, some rainfall occurred on site as to make watering unnecessary. Also, while watering, drip lines and basins was repaired by hand when required.

Figure 7. Larrea Protection Zone at Valley of Death (28 May 1999).

 

Hill 760 Phase II

The overall aim of the Hill 760 Phase II project was to decrease both sheet and gully erosion that had begun to occur from a disturbed area adjacent to a current helicopter logistics pad and a proposed field Ammo Supply Point (ASP). This was to be accomplished through the use of berm plantings, Larrea Protection Zone plantings and trail closures. Work was begun at this site on 22 June and required ten visits to complete. Planting was completed on 8 July 1999. A total of 810 native desert shrubs were planted at the Hill 760 Phase II site. The total number of plants per species is represented in

Table 3.

 

Nine wedge-shaped berms were constructed at trail intersections to prevent corner cutting. The berms are approximately 200 feet long with each arm being roughly equal in length. Approximately forty native desert shrubs were planted adjacent to and along the interior of each berm. Drip line irrigation was installed along each berm to facilitate the watering of these plantings (Figure 6B). A total of 360 native desert shrubs were planted along the constructed berms (Figure 8). Six additional berms were constructed at trail closures.

An additional 330 native desert shrubs were planted within and adjacent to trail closures as well as open areas adjacent to established trails. Drip line irrigation was installed to facilitate the watering of these plantings (Figure 6C). These plants were laid out in a non-linear manner to give a more natural appearance and provide a greater visual barrier

(Figure 9). The purpose of these plantings was to discourage vehicle traffic through the interior of the site and slow the erosion caused by excessive trail creation.

Hand pitting was performed along the perimeter of the project area, along the closed trails which run through the site and between all berms and catchments (Figure 10). The purpose of pitting is to loosen compacted surface soil and create microsites for seed and litter.

Twenty relatively large and intact shrubs were identified to serve as foci for the planting of vegetation islands (LPZ’s). These shrubs were chosen relatively close to existing roads to provide access for watering. Six additional native desert shrubs were planted in each LPZ (Figure 11). Approximately five mounds were constructed around each island to discourage future disturbance from training activities.

 

Table 3

Species and quantities planted at the Hill 760 Phase II site.

Species	Quantity
Ambrosia dumosa Atriplex canescens Atriplex polycarpa Encelia farinosa Ephedra nevadensis Eriogonum fasciculatum Isomeris arborea Hymenoclea salsola Larrea tridentata Lepidium fremontii Salazaria mexicanaE Sphaeralcea ambigua Thamnosa montana	50 80 100 100 40 100 10 120 150 20 15 20 5
Total	810

E Restricted to catchment plantings at the lower portion of the site.

 

Figure 8. Completed berm planting at Hill 760 II (Encelia fructescens) (13 October 1999).

 

Figure 9. Non-linear planting at Hill 760 II (8 July 1999).

 

Figure 10. Hand pitting between berms (13 October 1999).

 

Figure 11. Larrea Protection Zone planting at Hill 760 II (1 July 1999).

 

In addition to the initially proposed work, an effort was initiated to reduce the fecundity of this year’s generation of Salsola tragus. This species has become a persistent weed in many areas of Fort Irwin, and a large population exists at this site (Figure 12). Timing of this effort was not ideal, as many individual plants had matured to the flowering and fruiting stages. Thus the intention to kill individual plants before flowering shifted to reducing the production of viable offspring. Glyphosate salt herbicide (RoundUpPro) was applied to all individual plants within the study area. Herbicide spraying was conducted by licensed applicator John Ekhoff (QAL# 36714). Application required six site visits. A 1.6% aqueous solution of RoundUpPro was mixed onsite and used immediately. A total of 283 gallons of herbicide was applied at this site. Spraying was conducted on 30 August - 1 September and 7-9 September. It was hoped that the application of herbicide to the maturing plants would degrade the development of seeds such that they would fail to germinate or at least produce less viable progeny.

Watering was scheduled to take place on a monthly basis, or when needed, since during the winter, some rainfall occurred on site as to make watering unnecessary. Also, while watering, drip lines and basins was repaired by hand when required.

Figure 12. Salsola tragus population at Hill 760 II (7 July 1999).

 

Results

Valley of Death

After one year, overall survivorship at the Valley of Death site was 620 plants out of a total of 876 for a survival percentage of 71%. The total of 876 is an adjusted number calculated by subtracting the number of plants killed by vehicular damage from the original contract total of 880 shrubs. These 4 plants were destroyed during training maneuvers, and are therefore not included in the final results (Table 4).

Survival by treatment varied from a low of 40% for the LPZ plantings to a high of 77% for those along perforated pipes. Shrubs planted in the chevron shaped catchments had a survival rate of 67% (Table 5). Using the statistical analysis program Super ANOVA, a significant difference was found between all three of the planting treatments (p-value < 0001). Using Fisher's Protected Least Significant Difference (LSD) test, the greatest

 

Table 4

Survivorship by species at VOD site.

Species	Planted	Survived	% Survival
Ambrosia dumosa Atriplex canescens Atriplex polycarpa Encelia farinosa Encelia frutescens Ephedra nevadensis Eriogonum fascic. Hymenoclea salsola Isomeris arborea Larrea tridentata Lepidium fremontii Salazaria mexicana Senna armata Sphaeralcea ambigua Thamnosa montana	100 125 80 20 70 40 75 125 50 125 10 20 25 10 5	64 112 76 4 54 27 37 82 12 101 7 6 22 9 3	64% 90% 95% 20% 77% 68% 49% 66% 24% 80% 70% 30% 88% 90% 60%
Total	876	617	70%

 

Table 5

Survivorship by treatment at VOD site

Treatment Catchments Perforated Pipe LPZ TOTAL

Planted 120 636 120 876

Survived 80 492 48 620

% Survival 67% 77% 40% 71%

 

difference in survivorship rates was found to be between the plants in the LPZ's and the two other treatments: both with p-values = 0.0001 (Table 6). There was no significant difference in survival between the perforated pipe plantings and the catchments (p-value = 0.0568).

The site was in very good condition considering its proximity to a major roadway (Figure 13). There appeared to be only two minor instances of vehicle travel across the site (Figure 14), and the growth of surviving plants was impressive (Figure 15).

 

Table 6

Valley of Death ANOVA Spreadsheet

 

Figure 13. Training activity at the Valley of Death site.

 

Figure 14. Vehicular damage to a catchment at the Valley of Death site.

 

Figure 15. Plant growth at VOD site one year after planting.

 

Hill 760

After one year overall survivorship at the Hill 760 Phase II site was 595 plants out of a total of 779 for a survival percentage of 76%. The total of 779 is an adjusted number calculated by subtracting the number of plants killed by vehicular damage (Figure 16) from the original contract total of 810. These 31 plants were destroyed during training maneuvers and are therefore not included in survival calculations (Table 7).

Survival by treatment varied from a low of 61% for the LPZ plantings to a high of 82% for plants along irrigation lines with berms. Plants along irrigation lines without berms had a survival rate of 75% (Table 8). Using the statistical analysis program Super ANOVA, a significant difference in individual survivorship rates was found between all three of the planting treatments (p-value < 0.0001). Using Fisher's Protected Least Significant Difference (LSD) test, the greatest difference was found to be between the plants along both types of irrigation lines, with and without berms, and the LPZ plants,

 

Figure 16. Vehicular damage to Larrea Protection Zone at Hill 760.

 

Table 7

Survivorship by species at Hill 760 II site.

Species	Planted	Survived	% Survival
Ambrosia dumosa Atriplex canescens Atriplex polycarpa Encelia farinosa Ephedra nevadensis Eriogonum fascic. Hymenoclea salsola Isomeris arborea Larrea tridentata Lepidium fremontii Salazaria mexicana Sphaeralcea ambigua Thamnosa montana	50 80 100 100 40 100 120 10 150 20 15 20 5	32 57 75 83 31 62 89 1 123 13 10 15 4	62% 71% 75% 83% 78% 62% 74% 10% 82% 65% 67% 75% 80%
Total	779	595	76%

 

Table 8

Survivorship by treatment at Hill 760 II site.

Treatment LPZ Lines with berms Lines w/o berms TOTAL

Planted 102 322 355 779

Survived 62 265 268 595

% Survival 61% 82% 75% 76%

 

with a p-value = 0.0001. The difference between the two irrigation line plantings was smaller, yet still significant, with a p-value = 0.0356 (Table 9).

It was noticed that the constructed berms experienced some erosion from both the wind and from rain events. At a few points on the down slope area of the site, it appears that the berms acted to channel the runoff water across the surface. At these points, the water was able to significantly weaken the berms enough to cause several sections to blow out. However, on a positive note, it also appears that the berms have already begun to be used as habitat by burrowing animals (Figure 17).

The results of the herbicide treatment on the Salsola weeds were notable. One year after application overall numbers were greatly reduced, the size of plants about one quarter of the previous years plants, and the overall vigor and seed production were greatly reduced.

Table 9

Hill 760 ANOVA Spreadsheet

 

Figure 17. Berms showing both wind erosion effects and use by burrowing animals

 

Conclusions

Valley of Death

It appears that both catchment and perforated pipe are, once again, excellent procedures by which to restore desert habitats such as are found at the National Training Center and Fort Irwin.Both procedures provide a method by which water from precipitation events, either during the normal winter rainy season or from the occasional summer events, can be gathered and stored for use by newly planted seedlings. Precipitation can be either caught by a catchment as it runs down a gradient or can be soaked up by the berm formed by the installation of the perforated pipe. Additionally, both allow large amounts of water from supplemental irrigation to be stored for seedling use.

Mortality was highest in the Larrea Protection Zone (LPZ) plantings, with several different factors possibly accounting for such results. First, and most importantly, it has been noted in past SERG studies that environmental conditions and techniques used during planting can greatly affect mortality of individual shrubs. LPZ's were that last treatment planted at this site, having been planted in late May, when temperatures were in excess of 100 degrees. In these conditions, exposure to excessive heat and sunlight during planting, even for brief periods, can greatly reduce a shrub's chances for survival. A second factor possibly involved could be the well established root system of the mature Larrea plant that is the focus for the LPZ's. Such well-established root systems might be drawing up water that would otherwise be available for the transplanted shrubs. These factors, combined with basins that were only 18 inches in diameter and watered individually by hand, could mean that the LPZ plants received less water overall than the plants on irrigation lines.

One mortality factor that could be greatly minimized involves the rebar that is used to hold the tubex plant protectors in place. When rebar that is either to short or to thin is used, it is more likely that the tubex will be knocked around by the wind, or even blown off entirely. When this happens, the tubex can damage the plant in the process, even to the extent of severing the main stem of the shrub. If the plant does not die immediately, it is still then susceptible to secondary mortality factors such as desiccation and herbivory.

 

Hill 760

Due to the proximity of the Hill 760 site to a major roadway, vehicle damage to plants from military training exercises was a large source of mortality, especially for the LPZ plants. A total of 31 plants out of 810, were completely destroyed. Half of this number occurred in LPZ's, roughly 13% of shrubs planted in that treatment.

The difference in survival rates between the two drip line treatments is probably best explained by looking at the weather experienced by Fort Irwin during the late Spring and Summer months. There were several precipitation events that occurred during the summer months, providing off-season rainfall to the newly planted seedlings. The shrubs next to the berms most probably had higher survivorship (82% versus 75% with no berm) because of the berms’ ability to catch and retain run-off water during these precipitation events. It is for this reason that the use of catchments and berms is highly recommended for desert land restoration projects. However, berms can also cause a problem in some instances. Wind erosion of the berms caused sand to deposit around some plants, sometimes crushing the tubex and smothering the shrubs. In some cases, wind blown sand actually filled up tubex to heights of 18 inches. However, from the current results, along with previous project results, it appears that the benefits of berms out weighed the negative side effects.

The problems with the Larrea Protection Zone plantings that occurred at the Valley of Death site also appeared at the Hill 760 site, though much less pronounced, with a survival rate of 61%. The reason for the higher rate at Hill 760 is most probably from the different weather experienced during planting. Even though Hill 760 was planted over one month later than Valley of Death, temperatures were 10-15 degrees cooler during planting and, probably of greatest impact, it rained the day after planting the Hill 760 LPZ's. It has been noted on numerous previous projects that if planting can be timed to occur just prior to a significant rainfall, survival increases tremendously.

 

Recommendations

There were two problems that occurred at both sites that have very simple solutions: water limitations at LPZ's and inneffective rebar. To avoid the first problem of possible water limitations at LPZ's in the future, it is recommended that individual plant basins be constructed at a slightly larger size. While experimenting with basins sizes, it was found that basin diameters between 25-30 inches were able to hold approximately 2 to 2 1/2 gallons of supplemental water, equivalent to what plants on the drip lines received with one half hour of watering. The second problem with the rebar can be easily solved by just using rebar with a minimum size of 3/8 inches in diameter and at least 2 1/2 feet long.

As mentioned above, it is highly recommended that the use of berms and/or catchments be considered as standard restoration procedures for habitat restoration at The National Training Center and Fort Irwin. The high probability of Fort Irwin receiving summer precipitation events, such as occurred this year, leads to berms and catchments, constructed at an appropriate size for the amount of expected runoff that might occur from summer rains, being highly efficient procedures for providing needed water to young seedlings during both winter and summer seasons, leading to increased survivability and project success.

In regard to Salsola weed control at the Hill 760 site, some follow-up treatment should be taken. Regular maintenance of the weed population for a few years is necessary to ensure a positive long-term result. If not, the weed population will soon return to previous numbers, wasting the effort that has already been spent.

---