Significance of Mangroves in the Arid Environment of the Sultanate of Oman

Abstract

Little is known of the ecological role of the only species of mangrove, Avicemnia marina, in Oman. This study provides information on the physical habitat of three mangrove areas( Qurm, Mahout and Shinas) in relation to the main features of each area ( i.e. community structure, soil and water analysis and biota). The climate of three mangrove areas and surrounding regions is hot and arid; all have very low rainfall (less than 100mm yr), high air temperature (mean 27”C), relative humidity (57.8% at Qurm and 72% at Mahout and Shinas) , solar radiation ( more than 500 MVH cm2) and evaporation rates (more than 3000 mm yr2). Mangrove trees folowered during January-March, fruits matured during April- May, seedlings fell in June , seeds germinated in July-August and leaves were produced in September. Difference among sites included areal  extent ( 162 ha in Mabout, 74 ha in Quran and 53 ha in Shinas) and high variability in mangrove structure within and between sites . The most obvious differences between sites related to tree height diameter , density and basal area. The increase in tree diameter was associated with increase in tree height and basal area, but an impressive relationship existed between tree diameter and density. Significant differences in soil texture and chemical analysis were found  within and between the three mangrove sites. Soil texture wasdominated by sand; however, site( highest at Qurm,, 32%) and clay ( highest at Mahout , 10.1%) were present in considerable amounts. Soils of Mhout had the highest organic matter (10.2%) – totall nitrogeon ( 0.2% ), available phosphorus ( 56.2ppm) and sulphate ( 17.1 meq 100g) contents compared to those from Qurm and Shinas. Water temperature ranged 22-38C and salinity showed small variations at Mahout ( 37-40 ) and Shinas ( 37-40) but at Qurm, salinity showed remarkable variation from fresh and brackish water (10) to hypersaline  water ( more than 100). Dissolved oxygen averaged 8.1( 4.8-12.7) mg and PH was  7.8 ( 6.9-8.9). Mangrove communicate included a faunal assemblage of many species of birds ( more than 200 species ), fish ( 54 species) , crustaceans ( 31 species) and mollusks ( 51 species ) . Some group exhibited clear pattern ( e.g, crabs and oysters), others were just visitors ( fish and birds ), but the majority were resident in the mangroves.