The Effects of Exotic Forests on Soil, Ground Water, Water Quality, Air Quality and Native Flora and Fauna

Pine trees have the same effects on soil as native trees (except kauri), no more, no less.

There is strong evidence that pine forests improve soils. Approximately two-thirds of the Ngati Hine Forestry Trust land has extremely old, infertile gumland soils. It is of low natural fertility, is highly erodible and has been in short scrub eroding since well before Maori arrived in this country.

This land got this way because it previously carried dense kauri forests, most of the kauri having killed itself off long prior to the arrival of the first Polynesians.

1. All trees remove and return nutrients from and to the soil. Kauri, however returns few nutrients to the soil and makes it so poor and acidic that it eventually kills itself out. (See explanation in Reference 2).

2. Trial work in New Zealand has shown that pine trees do not degrade or kill the soil. Instead, they improve nutrient cycling in the soil and improve internal soil drainage.

3. Pine trees make the soil no more acid than native bush, certainly nothing like kauri, and recycle nutrients in the same way as native trees. Trials on sand dune forests have shownthat pine trees do not ‘leach’ soils of nutrients like kauri trees.

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