Glossary of Ecology (6th ed.) by Krebs (2009)
- helping another organism, providing positive feedback in a population interaction.
Glossary of "Life (9th ed.)" by Sadava et al. (2011)
- In succession, modification of the environment by a colonizing species in a way that allows colonization by other species. (Contrast with inhibition.)
Glossary of "Environmental Science: Earth as a Living Planet (2nd ed.)" by Botkin & Keller (1998)
- During succession, one species prepares the way for the next (and may even be necessary for the occurrence of the next).
- Botkin, D. B. & Keller, E. A. 1998. Environmental Science: Earth as a Living Planet, 2nd ed. -xxxxii + 649 pp. John Wiley & Sons, Inc., New York.
- Krebs, C. J. 2009. Ecology, 6th ed. -xvi + 655 pp. Pearson Benjamin Cummings, San Francisco.
- Sadava, D., Hillis, D. M., Heller, H. C. & Berenbaum, M. R. 2011. Life: The Science of Biology, 9th ed. -xliv + 1266 pp. Sinauer Associates, Inc., Sunderland.