In New Zealand, Pinus radiata D. Don is frequently planted on land under pasture primarily for production forestry, but with the added advantage of potentially offsetting carbon dioxide (C[O.sub.2]) emissions from energy and industrial sources. Conversion of pasture to P. radiata plantations can, however, result in lowered contents of soil carbon (C) at some sites. We here examine the effects of this land-use change on soil C and nitrogen (N) pools, and on microbial properties involved in the cycling of these nutrients, at 5 paired sites, each with an established pasture and P. radiata plantation. Four sites had first-rotation trees aged 12-30 years and the other site second-rotation trees aged 20 years. In mineral soil at 0-10 cm depth, total and microbial C and N, extractable C, C[O.sub.2]-C production, and, generally, net mineral-N production were lower under P. radiata than under pasture; differences were significant (P Additional keywords: extractable organic nitrogen, grassland, metabolic quotient, microbial biomass, nitrification, paired sites, land-use change, qC[O.sub.2].