|The Improvement of Tropical and Subtropical Rangelands (BOSTID)|
|Criteria for plant selection|
After considering the environmental conditions of the site(s) to be revegetated and the purpose(s) for which the revegetation program was designed, the choice of species is the next task. A range management specialist will wish to examine lists of grass, forte, 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 areas of the 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 areas. 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).
Practical procedures for cleaning and handling assure high seed quality. Further information regarding the availability of germ plasm appropriate for range improvement projects in the tropics and subtropics could be obtained from the following sources:
Division of Tropical Crops and Pastures
Commonwealth Scientific and Industrial Research Organization
Private Mail Bag, MSO
Townsville, Queensland 4810
Forest Resources Development Branch
Food and Agriculture Organization of the United Nations
Via delle Terme di Caracalla
International Council for Research in Agroforestry
P.O. Box 30677