Articles
NUTRIENT ALLOCATION IN WINTER RAINFALL PROTEACEOUS HEATHLANDS IN RELATION TO NUTRIENT LOSSES THROUGH WILDFLOWER PICKING AND FIRE
Nutrient additions to and losses from these systems are incompletely quantified and even poorly understood.
Based on the limited data available we suggest that intense wildflower picking and frequent veld burning may severely deplete community nutrient reserves.
Data on quantities of wildflowers removed from specific areas and communities are non-existent and therefore accurate quantification of nutrient losses is virtually impossible.
Total Protea repens head contribution to the aerial nutrient pool in Cape coastal fynbos is in the region of 14,1 (N), 12,6 (P), 10,7 (Ca), 9,6 (Mg) and 25,2% (K) while Banksia cones in Kwongan heath, Western Australia represent 25,4 (N), 30,3 (P), 13,5 (Ca), 16,5 (Mg) and 26,3% (K). Casual observations show that moderate picking levels of ±10% per season may remove 4,1 (N) and 9,6% (P) from individual bushes of Banksia hookerana. Estimates for nutrient removal from cultivated fynbos stands give annual losses (live cones only) of between 1,6 (P) and 2,3% (K).
Fire-induced nutrient changes for these systems are also poorly documented although indications are that non-volatilisable elements are generally retained in the ash.
However concern is expressed at the fates of nutrients after fire, particularly during the winter rains.
We conclude that urgent studies are needed to assess the effect of wildflower picking and fire on the nutrient capitals of heathland communities and that the Wildflower Industry can play an extremely constructive role in this regard.