Seasonal variations in the calorific values of mangrove plants of the Saudi Arabian Red Sea Coast

الملخص EN

The calorific values of A vicennia marina, by using a phillipson type electronic microbomb calorimeter (model AH 12/EF) was made for material of A.

marina mangrove collected monthly (Jan.-June 1986) from Dhahban about 50 km north of Jeddah; and for material collected in Feb.

1986 from Al- Wajh and Jizan located at North and South of the Saudi Red Sea Coast.

Results of this study elucidate that: 1.

The highest calorific values for seeds and leaves was recorded in Jan.

, and Feb.

and this period was the beginning of fruiting season where the seeds and leaves were young and healthy and very green in colour, while in June (the end of fruiting season) where most seeds and leaves were mature and ripe, the calorific values were lower.

2.

Always, the young seeds and leaves have higher calorific value than the mature ones, which mean that the young seeds and leaves contain more of oxidisable materials, however, pneumatophores did not show this pattern.

3.

The calorific values of the seeds are usually higher than those of the leaves or the pneumatophores.

4.

Plants of A.

marina collected from Jizan showed higher calorific values than plants collected from Al- Wajh, and Dhahban.

This may be related to the healthy growth of Jizan material, where the soil is relatively, containing high organic matter.

5.

There is no relation between the calorific values and the ash-free organic matter which means that not all the ash-free organic matter content is oxidisable.