Native forest management
New Zealand’s native forests were once abundant, but logging had depleted them. Native trees are slow to grow to maturity and so, to meet the continuing demand for wood, fast-growing exotic forests were planted, mainly by the state.
Also, from the 1920s, to improve the management of native forests, the Forest Service set up research projects to study forest growth, regeneration and ecology.
National forest survey
To assess the amount of timber available in native forests the Forest Service began a national forestry survey in 1946. The survey also assessed the extent of natural regeneration and the effects of introduced animals.
The survey project was an enormous undertaking and fieldwork covered a huge area, including rugged mountain terrain.
The survey was completed in 1955, and was followed by further ecological and high-country surveys. Data collected in all of these surveys was also valuable for water catchment control and soil conservation.
Plotting a survey
The 1946 national forest survey involved measuring all saleable trees within sample plots. In the most intensively sampled areas there was a plot every quarter mile (0.4 kilometre), along grid lines one mile apart through the forest. In the least intensively sampled areas, plots were located every half mile, on lines four miles apart.
Selective logging research
Increasing concern for the environment led to protective legislation for native forests. Before 1975 it was legal to log native forest and convert the land to other uses. From 1975 to 1984, only selective logging (taking just some trees from a forest) was permitted.
Trials studied the impact of selective logging operations, with the aim of reducing damage to the remaining forest. Logging in North Island state native forests ceased in 1984, while it continued in the South Island until the early 2000s.
Growing more native trees
More recent research has emphasised forest ecology and rehabilitation. Crops of native tree species, including kauri, tōtara and beech, have been planted for timber production.