Significance of mangroves in the arid environment of the Sultanate of Oman

Abstract EN

Little is known of the eeological role of the only species of mangrove, Avicennia 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 analyses and biota).

The climate of the three mangrove areas and the surrounding regions is hot and arid: all have very low rainfall (<100 mm yr’), high air temperahtre (mean 27°c yr'1), relative humidity (57.8% at Qurm and 72% at Mahout and Shinas), solar radiation (>500 MWH cm 2) and evaporation rates (>3000 mm yr1 ).

Mangrove trees flowered during January-March, fruits matured during April-May, seedlings fell in June, seeds germinated in July-August and leaves were produced in September.

Differences among sites included areal extent (162 ha in Mahout, 74 ha in Qurm 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 inverse 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 was dominated by sand; however, silt (highest at Qurm, 32%) and clay (highest at Mahout, 10.1 %) were present in considerable amounts.

Soils of Mahout had the highest organic matter (10.2%), total nitrogen (0.2%), available phosphorus (56.2 ppm) and sulphate (17.1 meq 100 g"،) contents compared to those from Qurm and Shinas.

Water temperature ranged 22 - 3^c and salinity showed small variations at Mahout (37-40°/دم and Shinas (36-37ده/م, but at Qurm, salinity showed remarkable variation from fresh and brackish water (مم/°0ا) to hypersaline water (> 100°/هم).

Dissolved oxygen averaged 8.1 (4.8 - 12.7) mg 1؛ and pH was 7.8 (6.9 - 8.9).

Mangrove communities included a faunal assemblage of many species of birds (>200 species), fish (54 species), crustaceans (31 species) and mollusks (51 species).

Some groups exhibited clear zonation pattern (e.g.

crabs and oysters), others were just visitors (fish and birds), but the majority were resident in the mangroves.