Using Remote Technology to Provide Better, Cheaper Results

Stephen Rymer, Helena Nermut and Pat Groenhout

One of the challenges being faced by PF Olsen Australia foresters at the moment is how to determine the adequacy of coppice restrike for second rotation blue gum plantations in order to decide whether or not to replant or manage for coppice.

Tasmanian Blue Gum, like many eucalypt species, re-shoots from the stump (coppice). This coppice regrowth can be managed as a second rotation. Re-growing a plantation from coppice has a number of advantages, including a drastic reduction in establishment costs and deferring of other operational costs to later in the rotation, as well as faster initial growth, due to the established root system.

One of the biggest challenges faced when determining if a plantation can be successfully managed from coppice, is determining the stocking of the coppice within the plantation. If the stocking is not adequate, the plantation will not fully utilise the site, and yield will be reduced. Stocking is highly variable, even at a stand level, and is affected by many factors such as season of harvest, position in the landscape and stocking prior to harvest.

The traditional method for assessing coppice stocking is to manually measure plots, usually at a density of one per five hectares of plantation. Using the information from these plots, a forester can then walk the block and determine where the stocking is inadequate. However, due to the high degree of variability in any single forest, this process can provide very inconsistent results.

PF Olsen Australia has been investigating options to reduce the cost and improve the results of coppice assessment. Aerial imagery was considered, but is not cost effective. Instead our foresters have been working with a new, locally based unmanned aerial vehicle (UAV) operator to take aerial images of areas of coppice.

This technology allows a highly accurate stocking map of a plantation to be made to assist making objective decisions about where the stocking of coppice is inadequate for a second rotation. An added advantage is that the data also provides an accurate stump count that can be used as a basis of payment for coppice thinning contractors, rather than relying on the stump counts from the contractors.

One of the major challenges with this technology is that the UAVs are small, made from styrofoam and a desirable target for large wedge-tailed eagles!!! At $40,000 per unit this is a real risk.