Variations in Soil Phosphorus in the Fynbos Biome, South Africa

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Abstract
(1) The phosphorus composition of the main soils of the dominant vegetation categories of the fynbos biome, south-western Cape, South Africa was studied. (2) Total, Bray No. 2 and resin-extractable phosphorus, pH and organic matter varied significantly between the soils with the Fernwood soils of the strandveld vegetation containing the highest total (338-422 .mu.g g-1 dry mass) and resin-extractable (13-40 .mu.g g-1 dry mass) phosphorus concentrations. (3) Organic phosphorus was only 10-15% of total phosphorus in the Fernwood soils of strandveld but was 58-77% in the soils of the other vegetation categories. (4) On the west coast, a gradient of soil texture, bulk density and phosphorus status occurred along a 2-km transect from the coastal dunes inland, through strandveld vegetation, vegetation infested with Acacia cyclops and into sand plain lowland fynbos. (5) A significant decrease in the proportion of calcium-bound and increases in iron-bound and saloid fractions of inorganic phosphorus and organic phosphorus occurred along the 2-km transect. (6) Litter phosphorus concentrations declined from the coastal dunes inland through strandveld and sand plain lowland fynbos but there were peaks in foliage projective cover, ground litter mass and soil phosphorus concentrations in A. cyclops invaded strandveld. (7) The phosphorus status of the soils of the south-western Cape excluding the Fernwood soils of the strandveld and the alluvial soils of limestone lowland fynbosis is low.