Overstory #14 - Getting Started: Diversity of Species

Natural forests are abundant systems–rich in diversity of species, stored nutrients, and yields. Much agricultural land has been degraded in tropical areas, typified by the loss of those characteristics which make forests so abundant–depleted soils, diminishing yields, lack of diversity. The problems of degraded lands are compounded by broadscale environmental influences such as erosion, watershed depletion, changing climate, and the presence of new diseases and insect pests.

Which species should be planted to help restore the natural abundance of a forest to degraded lands? Once a site has been degraded, it is often very difficult to predict which species will thrive there. The original forest species, if replanted, may not be able to cope in the changed conditions. It is usually unknown how other useful non-native species will behave in such circumstances. In other words, how a species will perform on a particular site is almost impossible to predict.

Whether you are seeking to plant a forest, orchard or garden, one promising step towards restoring a site is to start with a diversity of species. By conducting trials of many species you allow nature to guide you in selecting plants that do well in your area. This beats picking a few species and forcing them to grow! Starting with a diversity of species in initial trials, you can allow for many of them to perhaps do poorly, while a good number will perform very well.

Depending on your goals (forestry, farming, etc.) and the size of your project, an initial trial planting may consist upwards of 100-300 species. Although you may have an idea of the species you want to focus on for commercial use, remember to also trial supporting species such as groundcovers and fertility crops. The initial trial should include trees, shrubs, vines, groundcovers, herbaceous plants, etc. It is a good idea to try at least ten plants from each species to get an idea of their performance on the site. Less than ten might not give a clear picture, more than ten would become too costly during the trial period.

Keep in mind that within a single species there can also be tremendous variation in performance. For example, offspring from an Acacia koa tree that grows well on one site may perform poorly on another site, or it might be susceptible to certain pests and diseases. Therefore, for each species it is best to use several different selections from different sources when possible.

Within 1-2 years you will be able to narrow down your choice of species to those that are exemplary performers, with vigorous growth, resistance to disease and pests, and desirable behavior and products. At this point, a select group of species will become candidates for larger scale plantings. This follows the goal of starting small and expand on successes, as described in Overstory #5. Once you know which species thrive from small trials, you can expand successfully to a larger planting. Your trials will create a very valuable list of prime species that will make it easier and less costly to reestablish diverse and abundant plantings.

List of plants to use in first trials

• Plants that appear to be thriving in surrounding areas with little or no care by people
• Plants that are known to tolerate harsh conditions such as wind, drought, and poor soils.
• Plants that are widely adapted to many different soil and climatic conditions, such as nitrogen fixing trees and other pioneers.
• Plants that have multiple uses to people, such as timber, food, medicine, etc.
• Plants that can be easily propagated from vegetative parts (cuttings, suckers, etc.)
• Native plants, especially those that are known to pioneer degraded sites in your area.
• Plants from many different plant families.
• Variety selections produced by farmers and university research programs.
• Old varieties used by indigenous farmers, that are no longer commonly used.

Avoid:

• Known weedy species, that produce large amounts of seed quickly
• Thorny and spiny species, especially those that are self-seeding
• Poisonous species
• Invasive, and rapidly spreading plants, such as certain running bamboo species.
• Illegal or offensive species

References and Further Reading

Bill Mollison, "Phases of Abundance," appearing in Permaculture, International Journal #40.

Kim Wilkinson and Craig Elevitch, Overstory #5--Start Small...and Expand on Successes.

About the Authors

Kim M. Wilkinson is the Education Director for Permanent Agriculture Resources and editor of The Overstory. She has B.A. degrees in Anthropology and Ecology from Emory University.

Craig R. Elevitch is an agroforestry specialist with more than ten years of public and private sector experience in tropical agroforest and forest management. He has a M.S. degree in Electrical Engineering (Dynamical Systems) from Cornell University.

Related Editions to The Overstory

• The Overstory #42--Improved Fallow
• The Overstory #28--Microlife
• The Overstory #22--Pioneering
• The Overstory #21--Agroforestry and Diversity
• The Overstory #20--Five Fertility Principles
• The Overstory #9--Observation