TheImprovement ofTropical and Subtropical Rangelands

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ORJTERIA FOR PLANT SELECTION
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AVAILABRITY or SEEDS AND PLANT MATERIALS
After considering the environmental conditions of the site(s)
to be revegetated and the purpose(s) for which the revegetation
program wu designed, the choice of species is the next task. A
range management specialist will wish to examine lists of grass,
forb, tree, and shrub species in the local flora and become familiar
with the field characteristics of the most desirable species. From
such information sources, comparisons can be made with well-known
species used in other parts of the world that have been successfully
used in revegetation projects.
It may be difficult to obtain the desired and best-adapted species.
If many of the species tentatively chosen for revegetation are native
or "wild- species in the local flora, an established commercial source
of seeds may not exist. Two options are available to those planning
the project. The first is to compare the ecological similarity of the
project site with other areu ofthe world where adequate seed sources
do exist and obtain a mixture of high-performance seeds that meet
project objectives. The species must have a broad genetic base and
meet standards for purity and germination. The rangeland seed
industry generally follows a practice of requiring seeds on a pure live,
seed (PLS) basis, which assures that seeds will be free of trash and
weed seeds and have a live embryo capable of germinating according
to specified percentages (Valentine, 1979).
The second alternative is to develop or assist in developing local
sources of seeds ecologically adapted to site conditions and capable
of productivity and stability under expected project conditions.
The development of such sources may have long-term beneficial consequences
for future projects. With appropriate incentives, local
individuals or small companies may be trained to collect and process
clean seeds from local fields and uncultivated areu. Some grass
species may be grown under field conditions for increased volume
production. Obviously, considerable advance planning is required to
supply the volume of seeds needed for large projects. The assistance
of specialists in native seed production may be needed. Depending
upon seed availability, seed mixtures developed for a revegetation
project may include native species of the project site as well as seeds
obtained from analogous locations elsewhere.
In the western United States, several seed companies have developed
considerable expertise in collecting seeds from native stands
or producing them under field conditions (Crofts and McKell, 1977).