Effects of nutrients on the distribution of dry mass, nitrogen and phosphorus in seedlings of Protea repens (L.) L. (Proteaceae)

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Abstract
The response of seedlings of the sclerophyllous shrub, Protea repens (L.) L., to increasing concentrations of phosphorus (P), nitrogen (N) and a mixture of all essential nutrients excluding N and P (M) was determined in potted Clovelly soil collected from a lowland fynbos site at Pella, south-western Cape, South Africa. Pot culture resulted in increased soil mineral nitrogen, in particular nitrate, and decreased available (resin-extractable) phosphorus concentrations compared to field soil. High amounts of N (4-64 g m-2N) and M addition resulted in seedling mortality. Plant dry mass, leaf area and phosphorus and nitrogen contents increased in response to increasing application of P, but no significant differences were found in response to M. Increasing applications of N resulted in reduced plant dry mass, leaf area and phosphorus content. These patterns of mortality and growth are interpreted as a response to an imbalance between nitrogen and phosphorus availability. These results are compared to the response of mature fynbos shrubs to fertilizer additions in the field and the responses of pot-grown sclerophyllous plants from other Mediterranean-type ecosystems.