Some differences between the soils ofRhizophora andAvicennia mangrove swamps in sierra leone

Summary

The differences existing between a fibrous mud from aRhizophora mangrove swamp and a non-fibrous mud from a nearbyAvicennia swamp have been examined.

The differences found between the muds are due largely to the kind of mangrove they support.

Compared to the Avicennia swamp mud, that from the Rhizophora swamp had a higher pH value and a higher content of oxidisable sulphur, nitrogen, phosphorus, and carbon. The behaviour of the muds on incubation has helped to explain why the mud under Rhizophora is considered as being more fertile than mud under Avicennia. An apparent high rate of decomposition of the Rhizophora swamp mud as compared to that of mud under Avicennia was due to high oxygen uptake during sulphur oxidation. Rhizophora-bearing mud had a very high C/N ratio and inorganic nitrogen added to it was immobilised. It is suggested that land reclaimed from Rhizophora would respond to nitrogen fertilization. The most important difference between the muds was in their behaviour on drying. The intense acidity produced by sulphur oxidation in the fibrous mud affected all other changes, chemical and microbiological. It was found that if the moisture content of the fibrous mud remained at any point between 40 and 10 per cent for any length of time, then the mud became more acid than if continuously dried.