THE FUNCTIONAL ECOLOGY OF EMPODISMA-MINUS (HOOK F) JOHNSON AND CUTLER IN NEW-ZEALAND OMBROTROPHIC MIRES

Mires dominated by restionaceous rushes occur in valley and basin sites around New Zealand. The main restiad species is Empodisma minus which produces a surface mat of negative geotropic roots which eventually form a principal part of the underlying peat. Comparison of the peat chemistry of four such mires with a minerotrophic mire was consistent with their suspected ombrotrophic status. The base-exchange capacity achieved (704 +/- 23.3 mequiv m-2 of the surface) by the superficial roots of Empodisma is at least as great as that of the New Zealand Sphagnum cristatum which is not dominant in ombrotrophic conditions. The widespread development of a hummock and hollow microtopography may be associated with higher rainfall regimes and the propensity of Empodisma for directing most incoming rainfall (on which its nutrient economy depends) down its wiry stems.