The amount of new forestry planting is its lowest level since World War II.
A survey by the Ministry of Agriculture & Forestry has also found 85 years of growth in the total size of forests went into reverse five years ago.
A decline in planting began in 1996.
Forest owners say the figures are disappointing but not surprising. They blame uncertainty over emissions trading as well as poor economic conditions.
The report also shows a further reduction in the total area of forest plantations.
About 1.8 million hectares of forest was standing in April last year, a drop of more than 17,000 hectares on the previous year.
And a trend of not replanting forest after harvesting or conversion to pasture is continuing. This started on a significant scale five years ago.
More than 15,500 hectares of forest is estimated to have been converted to another land use in the year to April 2008.