Perspectives on survival, phenology, litter fall and decomposition, and caloric content ofAvicennia marinain the Arabian Gulf region

This study was conducted on a naturally growing population in Al-Khor mangrove swamps in Qatar during the years 1993–1995.Avicennia marinais the only mangrove species growing in Qatar and the Arabian Gulf region. The survivorship curve showed that early reproductive stages, starting from flower buds to seedlings, are at-risk relative to juvenile and adult individuals. The survival of adult plants is age-dependent. The phenological cycle indicated that the reproductive period extends from April to October, while vegetative activity occurs throughout the year with minimum growth during late autumn and early winter. Productivity estimated from litter fall showed considerable differences between seasons. Litter fall is bimodal, with the first peak prior to the start of the reproductive cycle and the second peak before the end of summer or early autumn. Total litter fall decreased from a maximum of 188 g m⁻²month⁻¹to a minimum of 80 g m⁻²month⁻¹. Litter decomposition was lower in winter than in the summer months. Calorific content of the decomposing litter was consistent with over 90% of litter energy lost over a 1-year period. The calorific content of buried leaves decreased from 6.0585 kcal g⁻¹dry weight to 0.0532 kcal g⁻¹dry weight after 1 year. Major human impacts on mangrove ecosystems in the region include oil pollution, solid and liquid waste disposal, coastal development, marine dredging, recreation activities, overgrazing, wood harvest, diversion of fresh water runoff and pest control.