The combined effects of elevated atmospheric CO2 and nutrient supply rate on plant biomass accumulation were determined for four Leucadendron species (Proteaceae) of the mediterranean climate Fynbos Biome, South Africa. Juvenile individuals were grown for 6 months in experiments comprising 2 X 2 factorial combinations of substrate nutrient supply rate and atmospheric CO2 concentration in open-top chambers in a greenhouse. The four selected Leucadendron species included one pair of species common on extremely nutrientpoor acid sands (typical of the Fynbos Biome), and another pair associated with more nutrient rich substrates (rare in the Fynbos Biome). Plant biomass accumulation data were
Within southern Africa, the socio-economic consequences of droughts are often enormous. For an understanding of the future implications of these droughts an understanding of the variation of the range of possible climates is required. At present regional data sets do not extend back for more than 100 years. Since all climate projections are based on this very limited data set, there are obvious limits to the probable accuracy of estimates. It is therefore important to develop other methods for establishing longer records. Within South Africa, Podocarpus species have been at the centre of dendrochronological research for the past 20 years with many claims for a relationship between ring width and certain climate variables. In the present study, the dendrochronological potential of Podocarpus sp. is re-evaluated. The primary objective is to ascertain whether cross-dating and chronology development are possible for Podocarpus sp. Even though whole-trunk cross-sections were used in the analysis of the 14 trees examined, a combination of poorly defined, locally absent and converging rings, combined with lobate growth, makes cross-dating an impossible task. These results suggest that future dendrochronological research using Podocarpus species is not justifiable, especially since whole-trunk cross-sections have to be used in the analysis and suitable specimens of Podocarpus sp. are rare and endangered.
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