ORGANIC-CARBON STOCKS IN NEW-ZEALAND TERRESTRIAL ECOSYSTEMS

The organic carbon in New Zealand's vegetation and soils has been esti mated for 1992 from updated national databases of vegetative cover and soil carbon. These databases were augmented by inclusion of vegetatio n and soils information for Stewart Island, and addition of carbon est imates for upland and high-country soils of South Island. Plant biomas s estimates from literature were combined with the Vegetative Cover Ma p of New Zealand to give an estimate of 2420 Mt carbon for vegetation carbon above and below ground, including litter and humus. More than 8 0% of this carbon occurs in indigenous forested ecosystems on less tha n 26% of the land area, with only about 5% in planted forests. Soil or ganic carbon estimates for two depth ranges (0-0.25 m, 0-1 m) were der ived from the N.Z. Land Resource Inventory, the Soil Map of Stewart Is land, and the National Soils Database. Totals were 2500 +/- 77 Mt and 4260 +/- 190 Mt C respectively. Yellow-brown earths made the largest c ontribution, with 727 Mt C in North Island and 489 Mt C in South Islan d, to 1 m depth. Nationally this soil group also contributed most to t he error variance for soil carbon. A 1:1 relationship (R, 0.68) over a wide range of soil C contents for soils sampled recently and 30-50 ye ars ago under pasture suggested that under the same land use, uncertai nties introduced by the use of historical soil data would not be large .