Abstract
The present paper aims to study the demography and growth strategy of Cornulaca monacantha Delile population under natural and experimental conditions in Asir region, Saudi Arabia (in terms of size structure, natality, mortality, and demographic flux) and to assess its standing crop and the correlation between its population characters and the prevailing environmental variables. Thirty permanent stands were established to represent the microvariations in five habitats, where C. monacantha inhabits. In each stand, the height from the ground and the average diameter of the canopy for each C. monacantha individual were estimated monthly and its volume was calculated as a cylinder. The results showed significant variation in its growth variables in relation to habitat types. The growth follows a seasonal pattern, where the highest values for most growth variables were obtained during Marsh and April, while the lowest during October and November. The plant has two peaks of mortality: the first in January mainly due to heavy death of the seedlings and juveniles, while the second in June associated with the end of its life cycle. Its size structure was characterized by the preponderance of the young individuals comparing with the old ones. Regarding the density effect, the individuals were bigger and had more leaves under low than under high density. Density affected also the pattern of leaf distribution, length and number of branches and internodes.

Key words: Architecture, Competition, Mortality, Natality, Phytomass, Demographic flux