Nine Step Plan

The Nine Step Revegetation Method is a synthesis of 20 years of full‑time research on riparian vegetation, its associated wildlife and the autecological factors associated with vigorous growth of native riparian plant species (step by step documentation included in Anderson's bibliography). This plan represents a new paradigm for revegetation. Rather brief summaries of this information have been published in two general works (Rosenberg, Ohmart, Hunter and Anderson 1991; Ohmart, Anderson and Hunter 1988). Details concerning wildlife‑vegetation relationships have been presented in Anderson and Ohmart (1984) and in somewhat abbreviated form by Anderson and Ohmart (1985), and Anderson and Ohmart (1987). The suitability of our designs for attracting wildlife have been thoroughly documented in Anderson and Ohmart (1984, 1985) and Anderson, Hunter and Ohmart (1989). The basic steps of The Nine Step Revegetation Method occur in two papers (Anderson 1989 and Anderson and Laymon 1989). Some follow‑up details and important ancillary information occur in Anderson and Miller (1991, 1992). Some of our findings regarding salinity tolerance of riparian plant species have been independently confirmed by Jackson, Ball, and Rose (1990, Assessment of the salinity tolerance of eight Sonoran Desert riparian trees and shrubs. U. S. Bureau of Reclamation Yuma, AZ.) and Busch (1992, Analyses of the structure and function of Lower Colorado River riparian plant communities. PhD. Dissertation, Department of Biological Science, University of Nevada, Las Vegas, 1990). If supportive data (e.g. copies of published material) for the TNSP are required we will make them available upon request. We are also willing to discuss the Method in person if that would be helpful. The objective

was to develop a method that would, in the shortest time possible, lead to a habitat with maximal wildlife value. This, of course, requires maximum survival and growth of the plant species involved. Much of our research effort has been toward maximizing growth rates and minimizing mortality rates.

1. Preliminary Analysis

The preliminary phase involves collection of soil at 13 sample points per 25 acres systematically distributed over a site. At each sample point two soil samples are taken, one near the surface, the other just above the water table or 6‑8 feet below the surface. For each of these samples the soil type, and electroconductivity, as well as surface‑to‑water‑table depth are determined. If possible a water sample is taken and the electroconductivity is determined for it. Preliminary analysis reveals the range of variation for each variable tested thus permitting an assessment of how much success, given the desired outcome, can be realistically expected from planting on the site. Depth to the water table is often critical to survival and will be checked at each sample point. This is a fact finding step where climate, geologic features other than soil, development of roads, and any other ancillary item or action that would be relevant to the outcome of the project are taken into consideration. It also may include a vegetation analysis that provides at least a partial list of plants occurring in the area as well as revealing the soil conditions in which they are found. This analysis is not extensive enough to permit accurate mapping of the distribution of a variable across a site. Final determination of what should be planted should not be made until this step is complete. We can not make guarantees of success until this crucial information is available. This is the step that puts wishful thinking in line with reality.

2. Propagules

We grow many of our own propagules. Cuttings and seeds from local genetic stock are collected, cuttings are treated with rooting hormone and started in one‑gallon pots. Potting material includes a mixture of equal portions of sandy soil from habitats in the area to encourage micorrhizal fungi, vermiculite, and peat moss. Micorrhizal fungi help in the uptake of nutrients from the soil assuming that nutrients are present above certain minimal levels. Propagules are watered daily at our facility and require 8‑12 weeks to develop to a stage adequate for planting, except in the case of mesquite, which require much longer to develop.

3. Site Clearing, Leveling

Site preparation ordinarily involves clearing and leveling the area with a D‑8 or D‑7 Caterpillar dozer (or equivalent) over as much of the area as deemed necessary. This clearing is done in a selective manner thus saving any extant vegetation deemed valuable to wildlife. Surface soils in the Colorado River flood plain are not "natural", salt and debris having built up since construction of major dams or brought to the surface by salt cedar. Leaving this surface salt in place is a potential hazard to revegetation projects.

4. Intensive Soil Sampling

Intensive sampling involves taking soil samples at 10‑30% of all holes on 20 foot centers (roughly 100 per acre, thus10 to 30 samples per acre). Obtaining an adequate sample size of all species to be monitored is the essential feature. Sampling, done with sufficient frequency, allows accurate mapping of the distribution of salts, nutrients, pH values, soil type and depth to the water table across the site. With this information a planting design is developed in such a way that planting will occur only at points where growth can be expected to be at or near maximum for each species. There is often a desire to see a detailed planting design prior to the initiation of a project. A moment's reflection indicates that this cannot be done until intensive soil sampling has been done. Because the site must be nearly ready for planting before intensive soil sampling occurs, it is too costly (and often inappropriate) to be practical prior to initiation of the project. Without intensive soil sampling data however, a planting design is a farce based on nothing but guessing and wishful thinking. Guess work and wishful thinking have no legitimate place in a scientific approach to revegetation; such procedures leave the outcome to chance-growth and survival become matters of luck. TNSP is steeped in extensive, legitimate, scientific investigation. Diligent application of the Method will lead to success. The final product will be of value to wildlife.

5. Tillage

Tillage for trees is accomplished by augering holes a minimum of 15 inches in diameter to a depth of eight feet or to the water table. This, sometimes called vertical tillage, will allow for rapid root penetration to the water table. The need for, and effectiveness of, this step has been documented by Anderson (1988), Anderson and Ohmart (1982, 1985). In some instances and for some species tillage may not be necessary, or, in some cases it may not be possible. This conclusion must not, however, be drawn without serious consideration of all available facts.

6. Irrigation System Design and Installation

The irrigation system for trees will consist of what is commercially referred to as ½ inch black polyethylene drip tubing emanating from black polyethylene main line two inches in diameter. Each lateral drip tube line is supplied with a screen filter and ball shut‑off valve. At about every 15‑20 ft., two‑gallon pressure compensating emitters are installed in the line. Water is ordinarily drawn from existing wells or from the stream channel. Water can also be delivered to drip systems from water trucks. Details of the irrigation system design cannot be made until intensive sampling design is complete. The economy of water associated with drip irrigation is common knowledge. It also keeps weed problems to a minimum and encourages rapid root penetration to the water table.

7. Planting

Trees appropriately distributed on a site are ordinarily planted in densities of roughly 100-135 per acre. This may vary somewhat depending on species and locations. Occasionally one sees plans drawn up or demands made by agencies that call for hundreds or even thousands of trees per acre. Ordinarily planting in such densities is utterly absurd. Shrubs such as mulefat, sandbar willow, etc. are sometimes planted at 10 foot spacing along irrigation lines. Fertilizer is added if soil sampling indicates the need (Anderson and Vasquez 1991). If fertilizer is used, it is applied in such a way that competition from weeds will not become a factor. Trees planted on 20‑foot centers will yield 100% ground cover within three or four years (Anderson 1987, Anderson and Vasquez 1991). Furthermore, wildlife respond to most mixed habitats maximally when the vegetation is planted 10‑20 feet apart (Anderson and Ohmart 1984, 1985). Planting at densities greater than this is wasteful and counterproductive because intraspecific competition is promoted. Planting will occur at roughly 300 per day between March and July. At this time propagules are usually about 15‑20 inches tall. In addition, Tubex, a protective tubing, can be used to protect propagules. This tubing has the beneficial actions of slowing competitor growth, deterring browsing and increasing water use efficiency. Protection from burros may be required.

8. Irrigation/weeding

Irrigation will be done at a basic rate of eight gallons of water per day delivered through two‑gallon per hour pressure compensating emitters for five days each week for 18‑24 weeks. Cottonwood and willow trees will not be planted where the water table or perched water table or permanently wet soil exceeds eight feet unless irrigation can be supplied on a permanent basis. Irrigation during the second year will be done five days per week from May through September on an as needed basis ensure survival and reasonable growth rates. Monitoring will reveal the need for irrigation modifications. Weeding to prevent the negative impact of competition, will be done as needed during the irrigation periods.

9. Monitoring and Reports

Monitoring. Monitoring will begin immediately after planting and will continue for 18 weeks during the year of planting. Plants selected for monitoring will be those planted in the randomly selected sample holes used for the intensive sampling. Sample size of each species monitored will number no fewer than 30 individuals. Monitoring is done by measuring each tree from its base to the top of the tallest up-stretched leaf throughout the first season. Ground cover (crown diameter) and space occupied by vegetation (foliage volume) can be calculated from this measurement (Anderson and Ohmart 1982, 1984). These measurements are entered on the computer the day they are taken. We analyze growth in context of the variation in autecological factors on the site determined from the intensive sampling. If growth of, say, cottonwood or willow is less than expected (.4‑.5 inch/day, depending on area, soil factors and species) we take immediate steps to improve the growth rate; if growth rates are at or exceed expected rates, we strive to achieve even better growth. (For a more in‑depth discussion of monitoring see Anderson 1989). Monitoring in the second growing season will be done May through October by measuring the height of the same trees as during the initial year. We also assess the amount of water that may be available in the soil for the trees. Measurements at these times will reveal the extent to which the project may be in jeopardy. It is reasonable to expect that as time passes mortality will increase cumulatively until in 50 or 60 years‑the natural life expectancy of cottonwood and willow‑most of the original trees will be dead, even with the most intensive care. At the end of three growing seasons, assuming irrigation continues for at least two seasons, mortality will be small, not exceeding 5%. Frequency of monitoring is substantially decreased in follow-up years.

Small increments in mortality can perhaps be expected to be compensated for by natural germination on many revegetation sites.

Reports. We provide substantive reports with quantified data (ecological conditions, monitoring, growth rates) at the end of each growing season. Items such as irrigation and planting designs and results of weekly monitoring will be made available on an "as requested" basis. Reports are based largely on information garnered as a result of the first seven steps.

These steps would remain, although in modified form, if they are to be applied to large scale revegetation projects using land reclamation techniques.

LITERATURE CITED

Anderson, B. W. 1988. Importance of tillage to revegetating with cottonwood trees/Restoration and Mgmt. Notes 6:84‑87.

Anderson, B. W. 1989. Research as an integral part of revegetation projects. In: D. Abell, ed., California riparian systems conference. Gen. Tech. Rpt. U.S. Forest Serv. Gen. Tech. Rpt. PSW‑110:413‑419.

Anderson, B. W. and S. Laymon. 1989. Creating habitat for the Yellow‑billed Cuckoo (Coccyzus americana). In: D. Abell, ed., California riparian systems conference. U.S. Forest Serv. Gen. Tech. Rpt. PSW‑110:468‑472.

Anderson, B. W. and R. D. Ohmart 1982. Revegetation for wildlife enhancement along the lower Colorado River. U.S. Bur. Rec., Lower Colo. Region. Boulder City, NV.

Anderson, B. W. and R. D. Ohmart 1984. A vegetation management study for wildlife enhancement along the lower Colorado River. U.S. Bur. Rec. Lower Colo. Region. Boulder City, NV.

Anderson, B. W. and R. D. Ohmart 1985. Riparian revegetation as a mitigating process in stream and river restoration. In: J. A. Gore, ed., The restoration of rivers and stream. Butterworth Publishers. Boston, MA.

Anderson, B. W. and R. D. Ohmart 1987. Vegetation. In: A. Y. Cooperrider, R. J. Boyd and H. R. Stuart, eds., Inventory and monitoring of wildlife habitat. U.S. Bur. Land Manage. Service Center, Denver, CO.

Anderson, B. W., W. C. Hunter, and R. D. Ohmart. 1989. Status changes of bird species using revegetated riparian habitats on the lower Colorado River from 1977 to 1984. In: D. Abell, ed., California riparian systems conference. U.S. Forest Serv. Gen. Tech. Rpt. PSW‑110:468‑472.

Anderson, B. W., W. C. Hunter, and R. D. Ohmart. 1991. Revegetation and the need to control exotic plant species. In: D. Abell, ed., California riparian systems conference. U.S. Forest Serv. Gen. Tech. Rpt. PSW‑110:468‑472.

Anderson, B. W. and V. R. Vasquez. 1991. Tree growth on revegetation projects: Kern River Preserve. The Nature Conservancy. San Francisco, CA.

Busch, D. E. 1992. Analysis of the structure and function of lower Colorado River riparian plant communities. PhD dissertation. Univ. of Nevada, Las Vegas. Las Vegas, NV.

Jackson, J. J., T. Ball, and M. R. Rose. 1990. Assessment of the salinity tolerance of eight Sonoran Desert riparian trees and shrubs. Desert Research Institute, Univ. of Nevada System, Biological Sciences Center. Reno, NV.

Ohmart, R. D. and B. W. Anderson. 1986. Riparian zones. In: A. Y. Cooperrider, R. J. Boyd and H. R. Stuart, eds., Inventory and monitoring of wildlife habitat. U.S. Bur. Land Manage. Service Center, Denver, CO.

Ohmart, R. D. and B. W. Anderson. 1988. The ecology of the lower Colorado River from Davis Dam to the Mexico‑United States International boundary: A community profile. U. S. Fish and Wildlife Serv. Rep. 85 (7.19).

Rosenberg, K. V., R. D. Ohmart, W. C. Hunter, and B. W. Anderson. 1991. Birds of the lower Colorado River valley. Univ. Az. Press. Tucson, AZ.