An environmental group is questioning the effectiveness of some species of trees in aiding the storage of carbon in soil.
The Soil and Health Association says research suggests pinus radiata, a species commonly used by the forestry industry, and eucalyptus do not store carbon as well as native or deciduous trees.
Spokesman Steffan Browning says pinus radiata and eucalypts also tend to leave the soil depleted of nutrients because their leaf litter does not easily decompose into the soil.
He thinks the forestry industry should consider using native or deciduous trees instead, because he says they are less harmful to soil's nutrient levels.
Dr Tim Payn, principal scientist at forestry research institute Scion pinus radiata and eucalypts do take up nutrients at a faster rate, but this can easily be replaced.
He says the organisation's long-term studies have shown no decline in productivity.
Dr Payn says, however, there's a good argument for diversifying the sorts of trees planted within a forestry block, to decrease the risk of pests and diseases attacking the trees.
He says different trees fix different levels of carbon, and some sites may favour certain species over others.