World Applied Sciences Journal 1 (2): 097-106, 2006 ISSN 1818-4952 © IDOSI Publications, 2006 Corresponding Author: Dr. A.K. Hegazy, Department of Botany, Faculty of Science, Cairo University, Giza 12613, Egypt 97 Considerations of Demography and Life Table Analysis for Conservation of Acacia tortilis in South Sinai A.K. Hegazy and M. Elhag Department of Botany, Faculty of Science, Cairo University, Giza 12613, Egypt Abstract: Populations of Acacia tortilis (Forssk.) Hayne subsp. tortilis were monitored in South Sinai, Egypt. Age determination was mainly based on canopy volume and stem circumference. Study sites were located in wadi systems in the upstream, midstream and downstream of the wadis. The upstream populations are represented in all size class distribution, while populations in the midstream and the downstream parts have one or more size classes missing due to the variation of water income and human impacts. Phenological monitoring showed that the appearance of new leaves started in December-January. Leaf shedding reaches its peak during November. A. tortilis has two flowering events. The first flowering event begins on old branches in March followed by peak fruiting in May. The second flowering event begins on the new branches in July followed by peak fruiting in September-October. Life table analysis and fecundity schedules showed that the flowers, seeds and seedlings are the shortest stages in the life span. The net reproductive rate was 0.281, the estimated intrinsic rate of increase reached -0.00337 per capita per year and the average generation time of the species attained about 380 years. Population demography, phenology and life table analyses draw the attention towards specific conservation considerations to manage the species population in the protected and nonprotected sites. Key words: Age classes phenology population dynamics Egypt INTRODUCTION A. tortilis is found in the Egyptian deserts and is The dominant Acacia species in South Sinai, Egypt where it occurs as small populations that are thinly is Acacia tortilis (Forssk.) Hayne subsp. tortilis. The scattered over an extensive range [1, 8]. At present the species provides food and shelter for many wild desert species is not endangered, but without immediate animals and is a major source of livestock feed and conservation measures, it is likely to move into the firewood for the native Bedouins [1]. High mortality and vulnerable category due to the continuous decline of low recruitment of Acacia trees in arid lands was reported its populations. by Wiegand [2]. As a multipurpose species, it is subject Most studies on survival and mortality were of intensive human collection and use. In the Negev concerned with the early plant life stages, not only desert and Sinai Peninsula the mortality rates of Acacia because these are generally the most critical stages in trees vary with life stages and may reach 61% in the adult the plant's life span, but also because they are perhaps stage [3] as affected by insect seed attack, drought, high the only stages where manipulative experiments can temperature and human impacts. easily be performed [9, 10]. For most plant populations Desert plants are adapted to the arid environment with overlapping generations, the mortality, survival through various structural and functional characters to and reproduction tend to vary with age or size of the decrease water loss. Among the mechanisms diminishing individual plants [10-17]. water-loss is the reduction of the transpiring surface, The present study covers the phenology, where shedding of leaves and branches is a common demography and dynamics of the plant populations behaviour [4-6]. In A. tortilis, the phenomenon of leaflet in South Sinai, Egypt. Quantitative data on survival, shedding was pointed out by Halevy and Orshan [7] and mortality and reproductive ecology are analyzed as a they related it to the intensification of drought during the base for provision of essential information for dry rainless season. conservation considerations of the species. entirely confined to arid and semi-arid habitats,