The life history and population structure of Cycas armstrongii in monsoonal northern Australia

Watkinson, Andrew R. and Powell, Jane C. (1997) The life history and population structure of Cycas armstrongii in monsoonal northern Australia. Oecologia, 111 (3). pp. 341-349. ISSN 0029-8549

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The cycad Cycas armstrongii is endemic to the north-western corner of the Northern Territory in Australia. Here we provide data on its life history and population structure from four populations across its range. Few plants reproduced before they were 1 m in height. There was considerable variation in the proportion of reproductive plants between sites and years, but the sex ratio in all populations was close to 1:1. The growth rate of plants was approximately 4.5 cm year-1 which indicates that most plants are less than 100 years old and that the tallest individuals are likely to be little older than this. The annual fecundity of female plants ranged from 12 to 80 seeds; there was no evidence that fecundity varied with plant height. Dispersal was restricted generally to less than 1 in and the distribution of dispersal distances was fitted well by a gamma distribution. Recruitment occurred through both seedlings and vegetative sprouts and the proportion of juveniles (plants without trunks) in the populations varied between one-quarter and two-thirds. The data indicate that recruitment is episodic, but occurs more frequently under the current fire regime than amongst the canopy trees. It is shown that there is considerable variation in the dynamics of populations between sites and that the long term dynamics of a population cannot readily be inferred from an examination of the size structure at a single point in time.

Item Type: Article
Faculty \ School: Faculty of Science > School of Environmental Sciences
UEA Research Groups: Faculty of Science > Research Centres > Centre for Ecology, Evolution and Conservation
Faculty of Science > Research Centres > Centre for Social and Economic Research on the Global Environment (CSERGE)
Faculty of Science > Research Groups > Resources, Sustainability and Governance (former - to 2018)
Depositing User: Rosie Cullington
Date Deposited: 02 Aug 2011 09:51
Last Modified: 15 Dec 2022 02:04
DOI: 10.1007/s004420050244

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