Estimation of Carbon Stocks in New Zealand Planted Forests Using Airborne Scanning Lidar

To meet obligations under Article 3.3 of the Kyoto Protocol, New Zealand is required to estimate, in an unbiased manner, forest carbon stock change, over the Protocol’s first commitment period (2008-2012). New Zealand has three categories of forest, namely: natural forest; forests planted prior to 1990; and forests planted in non-forest land after 1990. Carbon credits can be earned from net carbon accumulated in the last forest category: these forests are referred to as ‘Kyoto forests’. However, field access to these Kyoto forests for sampling is not guaranteed, and a plot-based forest carbon inventory system, which relies on the use of airborne scanning LiDAR, was therefore developed. Circular plots, 0.06 ha in area, will be located within these forests on a systematic 4 km grid. This paper describes investigations to confirm the relationship at the plot scale between LiDAR variables and (a) forest carbon, and (b) the key inputs (namely height, basal area, age, and silvicultural regime) to a New Zealand-specific forest growth model. The study has demonstrated that airborne scanning LiDAR provides an alternative approach to estimate carbon stock change for the first commitment period of the Kyoto Protocol, and can provide inputs to forest growth and carbon models enabling forecasts of carbon sequestration beyond 2012. The paper also describes some considerations for an operational forest carbon inventory system which will be implemented in early 2008.