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Climate change Land Use and Carbon Analysis System (LUCAS) Programme structure Forests Planted forests
Planted forests
Pre-1990 planted forest: young second-
rotation
pine trees in volcanic soils
of the
central North Island, New Zealand
Due to national and international reporting and accounting commitments LUCAS has stratified New Zealand's plantation forest estate into two sub classifications:
- pre-1990 planted forests
- post-1989 forests ('Kyoto forests').
More than 1.4 million hectares of forest was established in New Zealand before 1990: about 5 per cent of the country’s land area. By 1 April 2005, the total planted forest area had grown to 1.8 million hectares.
Pre-1990 planted forests
More than 1.4 million hectares of plantation forest was established in New Zealand between 1920 and 1990. By 1990 these private and government owned forests covered around 5 per cent of the country’s total land area.
Pre-1990 planted forests are inventoried for UNFCCC (Convention) reporting and to provide a biomass carbon estimate for deforestation under the Kyoto Protocol.
New Zealand’s pre-1990 planted forest estate was first measured by LUCAS during the winter of 2010. Almost 200 plots were measured nationwide using field measurements and airborne scanning LiDAR. Total carbon stock and stock change will be calculated for pre-1990 planted forests using the data collected from the pre-1990 planted forest plot network. The pre-1990 planted forests will not be remeasured during the First Commitment Period (CP1:2008-2012). Therefore, stock change will be estimated using growth modelling and assumptions on silviculture treatment. The results of the pre-1990 planted forest data analysis will be available in the 2012 submission of the National Inventory Report.
Post-1989 forests
Post-1989 forests are forests that are planted after 31 December 1989 onto non-forest land. It is estimated that about 569,000 hectares of new forest has been established since 1 January 1990, bringing the total planted forest area to nearly 2 million hectares. The post-1989 forest estate accounts for around 2 per cent of the country’s total land area.
Under the Kyoto Protocol, forests planted after 31 December 1989 onto non-forest lands are eligible to be accounted for as carbon sinks and can be used to offset emissions from other sectors.
An inventory of post-1989 forest was undertaken in 2007/08. This inventory involved the measuring of around 280 permanent sample plots in the field and the acquisition of airborne scanning LiDAR collected in order to estimate carbon stock and for modelling of carbon stock change in this forest estate.
A re-measurement of post-1989 forests will be repeated over the winters of 2011 and 2012. This inventory will include 140 previously unidentified plots increasing the total number of plots to around 400. Re-measurement is required to obtain an accurate estimate of carbon stock change in the post-1989 forest estate through the first Commitment Period. Stock change is currently estimated by growth modelling, but this is particularly difficult in young stands due to unpredictable forest management activities and assumptions on forest growth. Re-measurement of the post-1989 forest estate will validate the LUCAS modelling approach. The results of the analysis of these data will be available for the 2014 submission of the Nation Inventory Report.
Figure above: Annual forest planting in New Zealand from 1920 to 2007. Prior to 1990, there was a mix of private and government-owned forest (the latter shown in blue). All post-1989 forests are privately owned (shown in brown).
Standardised field methods
For measuring the carbon stock and stock change in planted forests, LUCAS has established permanent sample plots on an 8 km grid (pre-1990 planted forests) and a nested 4 km grid (post-1989 forests) overlaid across New Zealand. This grid coincides with the 8 km sampling grid used for natural forests.
Each grid intersect that coincides with mapped planted forest is assigned a permanent sample plot for measurement at regular intervals. A single 0.06ha circular plot is established and sampled at each location. In each plot the diameter at breast height (DBH) and height of crop trees are measured so a volume based estimate of carbon stock can be determined. The inventory is based on standardised forest mensuration procedures and is supplemented with carbon specific measurements, including a silviculture assessment (including treatment and timing), forest health measures and the measurement of non crop understorey trees.
The LUCAS planted forest inventories use a double sampling approach combining airborne scanning laser (LiDAR) data and field measurements to improve the precision of the carbon stock and stock change estimates.
LiDAR
The term LiDAR is an acronym for Light Detection And Ranging; the technique is also known as Laser Scanning. This determines distance to an object or surface using concentrated light pulses. It is an 'airborne mounted technology', that is, it tends to be used from aircraft.
Part of a LiDAR image of a Pinus
radiata forest near Rotorua. This extract is 10 m
wide and clearly shows the profile of nine trees.
The ground surface is shown in blue and the tree
foliage in light blue, green, yellow and red.
Yellow and red denote the highest points above
the ground surface. The absence of any lower
branches indicates the forest has been pruned.
LiDAR is very similar to radar (radio detection and ranging) except it uses light rather than radio. The range (or distance) to an object is determined by measuring the time delay between transmission of a pulse of light and the detection of the reflected signals. One pulse of light can have many reflected signals (returns) as the light pulse hits different heights of an object (e.g. a tree) and finally the ground as it descends. The first return is the highest return from a pulse (e.g. the top of a tree or a high branch) and the last return is the lowest (e.g. the ground). An accurate Digital Terrain Map (DTM) can be established from the last returns and metrics (or parameters) can be extracted from the LiDAR point cloud. These metrics are a height percentile based description of tree/forest characteristics that can be correlated with field measurements. The relationships between LiDAR and field data can then be applied to plots where only LiDAR measurements are available.
LiDAR and field measurements are incorporated in a double sampling inventory approach to increase the precision of the carbon stock and stock change estimate over that of a single sample survey design. Field measurements in combination with LiDAR will also ensure that all plots are sampled. This ensures that an unbiased estimate of carbon can be determined in New Zealand’s pre-1990 and post-1989 planted forest estates.
Last updated: 6 April 2011
