A study of the growth and distribution ofcolophospermum mopane(kirk ex benth.) Kirk Ex J. Leon: The interaction of nitrogen, phosphorus and soil moisture stress

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Abstract
Eight sites representative of the full diversity of Colophospermum mopane woodland were chosen in Rhodesia, Botswana and South Africa. Mopane performance, as measured by S diameter at breast height times density, over six height classes, was highly correlated (69 per cent of the variation accounted for) with total N and NaHCO3‐extractable P in the surface soil (0–10 cm). Mopane seedlings grown in pots responded to increased N and P supply, though, not significantly, on two soils with over 20 per cent water at 0,33 bars matric suction. Fluctuations in the available water supply from 100 to 0 per cent had no effect on yield or evapotranspiration rate on these soils. On a third soil, with only seven per cent water at 0,33 bars suction, yield decreased significantly (P < 0,01) with increased N and decreasing available water supply. These effects were primarily due to increased soil osmotic suction. Mopane growth was reduced at osmotic suctions less than 3 bars. At higher suctions (6–8 bars) internal osmotic adjustment appeared to enable the plant to continue growing at a reduced rate. These results are discussed in terms of mopane's distribution, and its apparent competitive advantage when induced to grow in “'coppice” habit.