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

Mires dominated by restionaceous rushes occur in valley and basin site s around New Zealand. The main restiad species is Empodisma minus whic h produces a surface mat of negative geotropic roots which eventually form a principal part of the underlying peat. Comparison of the peat c hemistry of four such mires with a minerotrophic mire was consistent w ith their suspected ombrotrophic status. The base-exchange capacity ac hieved (704 +/- 23.3 mequiv m-2 of the surface) by the superficial roo ts of Empodisma is at least as great as that of the New Zealand Sphagn um cristatum which is not dominant in ombrotrophic conditions. The wid espread development of a hummock and hollow microtopography may be ass ociated with higher rainfall regimes and the propensity of Empodisma f or directing most incoming rainfall (on which its nutrient economy dep ends) down its wiry stems.