Environmental limits to the distribution of Scaevola plumieri along the South African coast

Peter, C.I. and Ripley, B.S. and Robertson, M.P. (2003) Environmental limits to the distribution of Scaevola plumieri along the South African coast. Journal of Vegetation Science, 14 (1). pp. 89-98. ISSN 1100-9233

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Official URL: http://dx.doi.org/10.1658/1100-9233(2003)014[0089:...

Abstract

Scaevola plumieri is an important pioneer on many tropical and subtropical sand dunes, forming a large perennial subterranean plant with only the tips of the branches emerging above accreting sand. In South Africa it is the dominant pioneer on sandy beaches along the east coast, less abundant on the south coast and absent from the southwest and west coasts. Transpiration rates (E) of S. plumieri are predictably related to atmospheric vapour pressure deficit under a wide range of conditions and can therefore be predicted from measurement of ambient temperature and relative humidity. Scaling measurements of E at the leaf level to the canopy level has been demonstrated previously. Using a geographic information system, digital maps of regional climatic variables were used to calculate digital maps of potential transpiration from mean monthly temperature and relative humidity values, effectively scaling canopy level transpiration rates to a regional level. Monthly potential transpiration was subtracted from the monthly median rainfall to produce a map of mean monthly water balance. Seasonal growth was correlated with seasonal water balance. Localities along the coast with water deficits in summer corresponded with the recorded absence of S. plumieri, which grows and reproduces most actively in the summer months. This suggests that reduced water availability during the summer growth period limits the distribution of S. plumieri along the southwest coast, where water deficits develop in summer. Temperature is also important in limiting the distribution of S. plumieri on the southwest coast of South Africa through its effects on the growth and phenology of the plant.

Item Type:Article
Uncontrolled Keywords:Coastal sand dune; Predictive biogeography; Predictive modelling; Seasonal water balance; Water deficit; coastal zone; environmental factor; geographical distribution; limiting factor; phytogeography; water budget; water relations; Scaevola; Scaevola plumieri; South Africa
Subjects:G Geography. Anthropology. Recreation > GE Environmental Sciences
Q Science > QK Botany
Divisions:Faculty > Faculty of Science > Zoology & Entomology
Faculty > Faculty of Science > Botany
ID Code:1719
Deposited By:INVALID USER
Deposited On:28 May 2010 11:55
Last Modified:06 Jan 2012 16:21
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