Hostname: page-component-586b7cd67f-vdxz6 Total loading time: 0 Render date: 2024-11-23T02:24:45.709Z Has data issue: false hasContentIssue false
  • English
  • Français

Germination ecology of forest species from the highlands of Ethiopia

Published online by Cambridge University Press:  10 July 2009

Demel Teketay  and
Anders Granström
Demel Teketay
Affiliation:
Swedish University of Agricultural Sciences, Faculty of Forestry, Department of Forest Vegetation Ecology, S-901 83 Umeå, Sweden.
Anders Granström
Affiliation:
Swedish University of Agricultural Sciences, Faculty of Forestry, Department of Forest Vegetation Ecology, S-901 83 Umeå, Sweden.
Get access Rights & Permissions [Opens in a new window]

Abstract

A comparative study of seed germination was performed on 25 species of trees, shrubs, woody climbers and herbs from the dry Afromontane forest zone of Ethiopia. Despite the restricted geographical range of the species tested, the optimum constant temperature for germination varied considerably. For 17 of the species studied, it was between 20 and 25 °C while for three, germination was highest at 30 °C Germination was virtually inhibited (<20%) for eight of the species at 10 °C and eight of the species at 30 °C. There was no clear division in temperature response between plants differing in habitat. For four out of 12 species tested, fluctuating temperatures (20/12 °C) resulted in significantly higher germination than the constant temperature treatment (20 °C), suggesting that field-germination would be favoured by disturbance to the canopy or soil. Speed of germination was negatively correlated with the logarithum of seed size. Most species lay in the range 3–15 d to reach 50% of final germination at their optimum temperature for germination. Germination was significantly suppressed in darkness for a large number of species, particularly for those with seed size less than c. 3 mg. When these were incubated under leaf-filtered light, germination was in most cases even more effectively suppressed. Most of these species are known to have large soil seed banks. Mechanical scarification improved germination over the control in nine species. Five of these also reponded to heat or sulphuric acid scarification. Circumstantial evidence suggests that the species showing heat-induced germination may be fire adapted, although fire is probably a rare natural phenomenon in the Afromontane forest proper. Only one species, Bersama abyssinica, showed a classic recalcitrant behaviour. Germination dropped from 88% when the seeds were fresh to less than 20% after 1 mo of dry storage and 0% after 3 mo. Germinability of seeds of Ekebergia capensis also declined significantly with increasing storage time, although less rapidly; after 24 mo of dry storage, germination was 4%. In contrast, germinability of Juniperus procera was not significantly altered during 54 mo of storage. The results indicate that dormancy plays a major role in regulating germination in dry Afromontane species. Out of the 25 species studied, 15 (60%) showed some degree of initial dormancy. In most of the species with initially non-dormant seeds, dormancy would evidently be induced if the seeds are dispersed under a closed forest canopy or buried in the soil. These patterns of dormancy may have evolved in response to a highly unpredictable climate and small-scale disturbances, and should make the Afromontane forest flora relatively resilent also to anthropogenic disturbances.

Keywords

dry storagelightregenerationscarificationspeed of germinationtemperature
Type
Research Article
Information
Journal of Tropical Ecology , Volume 13 , Issue 6 , November 1997 , pp. 805 - 831
Copyright
Copyright © Cambridge University Press 1997

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

LITERATURE CITED

Amminuddin, B. M. & Ng, F. S. P. 1982. Influence of light on germination o. Pinus caribaea, Gmelina arborea, Sapium baccatum and Vitex pinnata. Malaysian Forester 45:62–68.Google Scholar
Anonymous. 1969. Climatological normals (CLINO) for climate and climate ship stations for the period 1931–1960. World Meteorological Organization, Geneva. 65 pp.Google Scholar
Anonymous. 1988. National atlas of Ethiopia. Ethiopian Mapping Authority, Addis Ababa. 77 pp.Google Scholar
Asfaw, Hunde & Thulin, M. 1989. Mimosoideae. Flora of Ethiopia, Vol. 3. Pp. 71–96 in Hedberg, I. & Edwards, S. (eds). Addis Ababa University, Addis Ababa and Uppsala University, Uppsala.Google Scholar
Bergsten, U. & Henriksson, G. 1986. Germination of Scots pine seeds under different conditions of temperature and humidity – a description of two test methods. FBVA Berichte, Schriftenreihe der Forstlichen Bundesversuchsanstalt, Wien 12:99–114.Google Scholar
Burger, W. C. 1974. Flowering periodicity at four levels in eastern Ethiopia. Biotropica 6:38–42.CrossRefGoogle Scholar
Cufodontis, G. 1952–1973. Enumeration plantarum Aethiopiae Spermatophyta. Bulletin du Jardin Botanique de l'Etat Bruxelles, Vols. 23–42.Google Scholar
Daniel, Gamachu. 1977. Aspects of climate and water budget in Ethiopia. Addis Ababa University Press, Addis Ababa. 71 pp.Google Scholar
Demel, Teketay. 1987. Revision of the genu. Clematis L. in Ethiopia. Belmontia 19:1–42.Google Scholar
Demel, Teketay. 1992. Human impact on a natural montane forest in south-eastern Ethiopia. Mountain Research and Development 12:393–400.Google Scholar
Demel, Teketay. 1993. Problems associated with raising trees from seeds, the Ethiopian experience. Pp. 91–100 in Lieth, H. & Lohmann, M. (eds). Restoration of tropical forest ecosystems. Kluwer Academic Publishers, Dordrecht.Google Scholar
Demel, Teketay. 1994. Germination ecology of two endemic multipurpose species o. Erythrina from Ethiopia. Forest Ecology and Management 65:81–87.Google Scholar
Demel, Teketay. 1996a. Germination ecology of twelve indigenous and eight exotic multipurpose leguminous species from Ethiopia. Forest Ecology and Management 80:209–223.Google Scholar
Demel, Teketay. 1996b. The effect of different pre-sowing seed treatments, temperature and light on the germination of five Senna species from Ethiopia. New Forests 11:155–171.Google Scholar
Demel, Teketay. 1996c. Seed ecology and regeneration in dry Afromontane forests of Ethiopia. Ph.D. thesis, Swedish University of Agricultural Sciences, Umeå. 36 pp. with 5 appendices.Google Scholar
Demel, Teketay & Granström, A. 1995. Soil seed banks in dry Afromontane forests of Ethiopia. Journal of Vegetation Science 6:777–786.Google Scholar
Demel, Teketay & Granström, A. 1997. Seed viability of Afromontane tree species during storage in forest soil. Journal of Tropical Ecology 13:81–95.Google Scholar
Fenner, M. 1980a. Germination tests on thirty-two East African weed species. Weed Research 20:135–138.CrossRefGoogle Scholar
Fenner, M. 1980b. The inhibition of germination of Bidens pilosa seeds by leaf canopy shade in some natural vegetation types. New Phytologist 84:95–101.CrossRefGoogle Scholar
Fenner, M. 1995. Ecology of seed banks. Pp. 507–528 in Kigel, J. & Galili, G. (eds). Seed development and germination. Marcel Dekker, Inc., New York.Google Scholar
Fichtl, R. & Admasu, Adi. 1994. Honeybee flora of Ethiopia. Margraf Verlag, Weikersheim. 510 pp.Google Scholar
Foster, S. A. (1986) On the adaptive value of large seeds for tropical moist forest trees: a review and synthesis. Botanical Review 52:260–299.CrossRefGoogle Scholar
Friis, I. 1992. Forests and forest trees of North East Tropical Africa. Kew Bulletin Additional Series 15:1–396.Google Scholar
Gardner, C. J., Mclvor, J. G. & Jansen, A. 1993. Passage of legume and grass seed through the digestive tract of cattle and their survival in faeces. Journal of Applied Ecology 30:63–74.CrossRefGoogle Scholar
Garwood, N. C. 1982. Seasonal rhythm of seed germination in a semideciduous tropical forest. Pp. 173–185 in Leigh, E. G., Rand, A. S. & Windsor, D. M. (eds). The ecology of a tropical forest: seasonal rhythms and long-term changes. Smithsonian Institution Press, Washington, D. C.Google Scholar
Garwood, N. C. 1983. Seed germination in a seasonal tropical forest in Panama: a community study. Ecological Monographs 53:159–181.CrossRefGoogle Scholar
Garwood, N. C. 1989. Tropical soil seed banks: a review. Pp. 149–209 in Leek, M. A., Parker, V. T. & Simpson, R. L. (eds). Ecology of soil seed banks. Academic Press, New York.CrossRefGoogle Scholar
Grime, J. P., Mason, G., Curtis, A. V., Rodman, J., Band, S. R., Mowforth, M. A. G., Neal, A. M. & Shaw, S. 1981. A comparative study of germination characteristics in a local flora. Journal of Ecology 69:1017–1059.CrossRefGoogle Scholar
Gutterman, Y. 1993. Seed germination in desert plants. Spring-Verlag, Berlin. 253 pp.CrossRefGoogle Scholar
Hedberg, I. & Edwards, S. (eds). 1989. Flora of Ethiopia, Vol. 3. Addis Ababa University, Addis Ababa and Uppsala University, Uppsala. 659 pp.Google Scholar
Jansen, P. C. M. 1981. Spices, condiments and medicinal plants in Ethiopia, their taxonomy and agricultural significance. PUDOC, Wageningen. 327 pp.Google Scholar
Komarek, E. V. 1972. Lightning and fire ecology in Africa. Proceedings of Tall Timbers Fire Ecology Conference 11:473–511.Google Scholar
Lamprey, H. F., Halvey, G. & Makacha, S. 1974. Interactions betwee. Acacia bruchid seed beetles and large herbivores. East African Wildlife Journal 12:81–85.CrossRefGoogle Scholar
Legesse, Negash. 1992. In vitro methods for the rapid germination of seeds o. Podocarpus falcatus. SINET: Ethiopian Journal of Science 15:85–97.Google Scholar
Legesse, Negash. 1993. Investigations on the germination behaviour of wild olive seeds and the nursery establishment of the germinants. SINET: Ethiopian Journal of Science 16:71–81.Google Scholar
Metcalfe, D. J. & Grubb, P. J. 1994. Seed mass and light requirement for regeneration in Southeast Asian rain forest. Canadian Journal of Botany 73:817–826.CrossRefGoogle Scholar
Moreno-Casasola, P., Grime, J. P. & Martinez, M. L. 1994. A comparative study of the effects of fluctuations in temperature and moisture supply on hard coat dormancy in seeds of coastal tropical legumes in Mexico. Journal of Tropical Ecology 10:67–86.CrossRefGoogle Scholar
Orozco-Segovia, A. & Vazquez-Yanes, C. 1989. Light effect on seed germination i. Piper L. Acta Oecologia Oecologia Plantarum 10:123–146.Google Scholar
Orozco-Segovia, A. & Vazquez-Yanes, C., Coates-Estrada, R. & Pérez-Nasser, N. 1987. Ecophysiological characteristics of the seed of the tropical forest pionee. Urera caracasana (Urticaceae). Tree Physiology 3:375–386.CrossRefGoogle ScholarPubMed
Phillips, J. 1974. Effects of fire in forest and savanna ecosystems of sub-saharan Africa. Pp. 435–481 in Kozlowski, T. T. & Ahlgren, C. E. (eds). Fire and ecosystems. Academic Press, New York.CrossRefGoogle Scholar
Pohjonen, V. & Pukkala, T. 1990. Eucalyptus globulus in Ethiopian forestry. Forest Ecology and Management 36:19–31.CrossRefGoogle Scholar
Pons, T. L. 1992. Seed responses to light. Pp. 259–284 in Fenner, M. (ed.). Seeds: the ecology of regeneration in plant communities. C.A.B International, Wallingford.Google Scholar
Probert, R. J. 1992. The role of temperature in germination ecophysiology. Pp. 285–325 in Fenner, M. (ed.). Seeds: the ecology of regeneration in plant communities. C.A.B International, Wallingford.Google Scholar
Putz, F. E. 1983. Treefall pits and mounds, buried seeds, and the importance of soil disturbance to pioneer tree species in the tropics. Ecology 64:1069–1074.CrossRefGoogle Scholar
Raich, J. W. & Gong, W. K. 1990. Effect of canopy openings on tree seed germination in a Malaysian dipterocarp forest. Journal of Tropical Ecology 6:203–217.CrossRefGoogle Scholar
Russi, L., Cocks, P. S. & Roberts, E. H. 1992. The fate of legume seeds eaten by sheep from a Mediterranean grassland. Journal of Applied Ecology 29:772–778.CrossRefGoogle Scholar
Sabiiti, E. N. & Wein, W. 1987. Fire an. Acacia seeds: a hypothesis of colonization success, Journal of Ecology 74:937–946.CrossRefGoogle Scholar
Swanborough, P. & Westoby, M. 1996. Seedling relative growth rate and its components in relation to seed size: phylogenetically independent contrasts. Functional Ecology 10:176–184.CrossRefGoogle Scholar
Tamrat, Bekele. 1993. Vegetation ecology of remnant Afromontane forests on the Central Plateau of Shewa, Ethiopia. Acta Phytogeographica Suecica 79:1–59.Google Scholar
Tewolde, B. G. Egziabher. 1986. Ethiopian vegetation – past, present and future. SINET: Ethiopian Journal of Science 9 (suppl.):1–13.Google Scholar
Tewolde, B. G. Egziabher. 1988. Vegetation and environment of the mountains of Ethiopia: implications for utilization and conservation. Mountain Research and Development 8:211–216.Google Scholar
Thompson, K. & Grime, J. P. 1983. A comparative study of germination responses to diurnal fluctuating temperatures. Journal of Applied Ecology 20:141–156.CrossRefGoogle Scholar
Thompson, K., Grime, J. P. & Mason, G. 1977. Seed germination in response to diurnal fluctuations of temperature. Nature, London 267:147–149.CrossRefGoogle ScholarPubMed
Vázquez-Yanes, C. & Orozco-Segovia, A. 1982. Germination of the seeds of a tropical rain forest shrub. Piper hispidum Sw. (Piperaceae) under different light qualities. Phyton 42:143–149.Google Scholar
Vázquez-Yanes, C. & Orozco-Segovia, A. 1990. Ecological significance of light controlled seed germination in two contrasting tropical habitats. Oecologia 83:171–175.CrossRefGoogle ScholarPubMed
Vázquez-Yanes, C. & Orozco-Segovia, A. 1993. Patterns of seed longevity and germination in the tropical rain forest. Annual Review of Ecology and Systematics 24:69–87.CrossRefGoogle Scholar
Vázquez-Yanes, C. & Orozco-Segovia, A. 1994. Signals for seeds to sense and respond to gaps. Pp. 209–236 in Caldwell, M. M. & Pearcy, R. W. (eds). Exploitation of environmental heterogeneity by plants: ecophysiological processes above and below ground. Academic Press, New York.CrossRefGoogle Scholar
Vázquez-Yanes, C. & Smith, H. 1982. Phytochrome control of seed germination in the tropical rain forest pioneer tree. Cecropia obtusifolia and Piper auritum and its ecological significance. New Phytologist 92:447–485.CrossRefGoogle Scholar
Vollesen, K. 1989. Sapindaceae. Pp. 490–510 in Hedberg, I. & Edwards, S. (eds). Flora of Ethiopia Vol. 3. Addis Ababa University, Addis Ababa and Uppsala University, Uppsala.Google Scholar
Von Breitenbach, F. 1961. Forests and woodlands of Ethiopia, a geobotanical contribution to the knowledge of the principal plant communities of Ethiopia, with special regard to forestry. Ethiopian Forestry Review 1:5–16.Google Scholar
White, F. 1978. The Afromontane Region. Pp. 463–513 in Werger, M. J. A. (ed.). Biogeography and ecology of Southern Africa. Dr. W. Junk, Publishers, The Hague.CrossRefGoogle Scholar
White, F. 1983. The vegetation of Africa. A descriptive memoir to accompany the UNESCO/AETFAT/UNSO vegetation map of Africa. UNESCO, Paris. 356 pp.Google Scholar
Whitmore, T. C. 1990. An introduction to tropical rain forests. Clarendon Press, Oxford. 226 pp.Google Scholar
Zar, J. H. 1984. Biostatistical analysis. Prentice-Hall, Englewood Cliffs, New Jersey. 718 pp.Google Scholar