Hostname: page-component-cd9895bd7-p9bg8 Total loading time: 0 Render date: 2024-12-23T14:02:38.878Z Has data issue: false hasContentIssue false
  • English
  • Français

Effect of population size, tree diameter and crown position on viable seed output per cone of the tropical conifer Widdringtonia whytei in Malawi

Published online by Cambridge University Press:  02 August 2011

Tembo F. Chanyenga ,
Coert J. Geldenhuys  and
Gudeta W. Sileshi
Tembo F. Chanyenga*
Affiliation:
Department of Forest and Wood Science, University of Stellenbosch, c/o Forestry Research Institute of Malawi, P.O. Box 270, Zomba, Malawi
Coert J. Geldenhuys
Affiliation:
Department of Forest and Wood Science, University of Stellenbosch, c/o Forestwood cc, P.O. Box 228, La Montagne 0184, Pretoria, South Africa
Gudeta W. Sileshi
Affiliation:
World Agroforestry Centre, P.O. Box 30798, Lilongwe, Malawi
*
1Corresponding author. Email: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract:

The tropical montane conifer tree Widdringtonia whytei is found in small fragments on Mulanje Mountain in Malawi. A study was conducted with the objectives of determining the effect of population size, tree stem diameter and crown position on the proportion of viable seeds per cone produced by W. whytei at three sites (Sombani, Chambe and Lichenya) on Mulanje Mountain. Three population sizes, namely small (fragments with ≤10 cone-bearing trees), medium (fragments with 11–20 cone-bearing trees) and large (fragments with >20 cone-bearing trees) and isolated trees were sampled at each study site. In each fragment, four cone-bearing trees were randomly located, 20 mature cones were collected from each tree and the viability of seeds was tested. Only 23% of the seeds per cone were viable but seed viability per cone was highly variable among fragments. Large fragment populations produced the highest proportion of viable seeds per cone (30%), followed by similar proportions in small fragments (28.3%) and isolated trees (26.1%), with the lowest proportions in medium-sized fragments (18.7%), indicating a non-linear relationship between viable seed output per cone and population size. Tree stem diameter and crown position had no effect on the proportion of viable seeds per cone. Further studies are needed to identify the factors that lead to the low viable seed output per cone, and how this influences whole-tree seed production in W. whytei.

Keywords

crown positioninvasive alienspopulation fragmentationseed viabilitytree stem diameter
Type
Research Article
Information
Journal of Tropical Ecology , Volume 27 , Issue 5 , September 2011 , pp. 515 - 520
Copyright
Copyright © Cambridge University Press 2011

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

AIZEN, M. A. & FEINSINGER, P. 1994. Forest fragmentation, pollination and plant reproduction in a Chaco dry forest, Argentina. Ecology 75:330–351.CrossRefGoogle Scholar
ASHMAN, T. L., KNIGHT, T. M., STEETS, J. A., AMARASEKARE, P., BURD, M., CAMPBELL, D. R., DUDASH, M., JOHNSTON, R. M. O., MAZER, S. J., MITCHELL, R. J., MORGAN, M. T. & WILSON, W. G. 2004. Pollen limitation of plant reproduction: ecological and evolutionary causes and consequences. Ecology 85:2408–2421.CrossRefGoogle Scholar
BAYLISS, J., MAKUNGWA, S., HECHT, J., NANGOMA, D. & BRUESSOW, C. 2007. Saving the Island in the Sky: the plight of the Mount Mulanje cedar Widdringtonia whytei in Malawi. Oryx 41:64–69.CrossRefGoogle Scholar
BOSSUYT, B. 2006. Genetic rescue in an isolated metapopulation of a naturally fragmented plant species, Parnassia palustris. Conservation Biology 21:832–841.CrossRefGoogle Scholar
BRONSTEIN, J. L. 1995. The plant-pollinator landscape. Pp. 256–288 in Hansson, L., Fahrig, L. & Merriam, G. (eds.). Mosaic landscapes and ecological processes. Chapman and Hall, London.CrossRefGoogle Scholar
CASCANTE, A., QUESADA, M., LOBO, J. A. & FISCH, E. J. 2002. Effects of dry forest fragmentation on the reproductive success and genetic structure of the tree, Samanea saman. Conservation Biology 16:137–147.CrossRefGoogle ScholarPubMed
CHAPMAN, J. 1995. The Mulanje Cedar, Malawi's national tree. Society of Malawi, Blanytre. 63 pp.Google Scholar
COCHRAN, W. 1963. Sampling techniques. (Second edition). John Wiley and Sons Inc., New York.Google Scholar
DICK, C. W. 2001. Genetic rescue of remnant tropical trees by an alien pollinator. Proceedings of the Royal Society of London Series B 268:2391–2396.CrossRefGoogle ScholarPubMed
HERRERIAS-DIEGO, Y., QUESADA, M., STONER, K. & LOBO, J. 2006. Effects of forest fragmentation on phonological patterns and reproductive success of the tropical dry forest tree Ceiba aesculifolia. Conservation Biology 20:1111–1120.CrossRefGoogle Scholar
ISTA 1993. International rules for seed testing. Seed Science and Technology, Vol. 21. Supplement.Google Scholar
LAWRENCE, M., OSHINO, A. & CHINGUWO, C. 1994. Mulanje cedar (Widdringtonia cupressoides Endlicher) inventory. FRIM Report 94010 ODC 524.61:174.Google Scholar
O'CONNELL, L., MOSSELER, A. & RAJORA, O. 2006. Impacts of forest fragmentation on the reproductive success of white spruce (Picea glauca). Canadian Journal of Botany 84:956–965.CrossRefGoogle Scholar
PAUW, A. 2007. Collapse of a pollination web in small conservation areas. Ecology 88:1759–1769.CrossRefGoogle ScholarPubMed
PAUW, C. A. & LINDER, H. P. 1997. Tropical African cedars (Widdringtonia, Cupressaceae): systematic, ecology and conservation status. Botanical Journal of the Linnean Society 123:297–319.CrossRefGoogle Scholar
RAJORA, O., MOSSELER, A. & MAJOR, J. 2002. Mating system and reproductive fitness traits of eastern white pine (Pinus strobus) in large, central versus small isolated, marginal populations. Canadian Journal of Botany 80:1173–1184.CrossRefGoogle Scholar
SHEATHER, S. J. & JONES, M. C. 1991. A reliable data-based bandwith selection method for kernel density estimation. Journal of the Royal Statistical Society. Series B 53:683–690.Google Scholar
SNOOK, L. K., CAMERA-CABRALES, L. & KELLY, M. J. 2005. Six years of fruit production by mahogany trees (Swietenia macrophylla King): patterns of variation and implications for sustainability. Forest Ecology and Management 206: 221–235.CrossRefGoogle Scholar
STEPHENSON, A. G. 1981. Flower and fruit abortion: proximate causes and ultimate functions. Annual Review of Ecology, Evolution and Systematics 12:253–279.CrossRefGoogle Scholar
TOMITA, M., SAITO, H. & SUYAMA, Y. 2008. Effect of local stand density on reproductive processes of the sub-boreal conifer Picea jezoensis Carr. (Pinaceae). Forest Ecology and Management 256:1350–1355.CrossRefGoogle Scholar
WANG, H., SORK, V.L., WU, J. & GE, J. 2010. Effect of patch size and isolation on mating patterns and seed production in an urban population of Chinese pine (Pinus tabulaeformis Carr.). Forest Ecology and Management 260: 965–974.CrossRefGoogle Scholar