Kauri Research & Remote Sensing
Current kauri research focuses on their ecological response to a varying climate, as this will be critical moving forward. Cate Macinnis-Ng, a research fellow at the University of Auckland has published two recent papers detailing the kauri response to a recent drought. She found that kauri dropped 72% more litter (leaves, bark, etc) during a drought season, likely in order to conserve water for its remaining parts (Macinnis-Ng et al. 2015). For further information check out her blog to read her posts and publications.
Constant measurement of kauri sap flow and litterfall
Sapflow meters help measure response to drought
Field site with litter baskets
Constant measurement of kauri sap flow and litterfall
This kind of field work is important for quantifying these processes, but requires intensive labor, constant maintenance, and long term funding.
Aerial Photography to Identify Diseased Kauri
In a 2014 publication coordinated by the Auckland Council, Jamieson et al. evaluate the potential of utilizing aerial photography to identify patches of kauri suffering from Kauri Dieback Disease.
In this study, researchers flew a helicopter toward known areas of kauri forest and took pictures with a Nikon camera that were geotagged by GPS. Further ground-truthing studies evaluated which trees were truthfully infected with the pathogen, as seen in the map on the left. The map shows the effectiveness of this method in confirming areas of infected kauri.
Since this method could only identify trees in the latest stages of disease (vastly decreased leaf area or completely bare branches), it is only a moderately effective method for monitoring the spread of the disease. This always requires intensive ground-truthing to confirm suspected areas of disease.
Jamieson et al. 2014
aerialsurveys.co.nz
What more can NZ look to do with remote sensing?
Unfortunately the aerial photography studied highlighted above seems to be the only significant published work using remote sensing to study kauri. Still, there are many options that researchers and officials can consider moving forward, as the situation for kauri grows more and more dire.
There are private companies such as Aerial Surveys in New Zealand that could be contracted to perform a forest health study of the remaining forests. As shown in the image to the right, Aerial Surveys uses LiDAR and near-infrared vegetation analysis to assess the health of a forest.
Additional data from the LANDSAT satellite or MODIS sensor could be used without having to perform additional aerial surveys. If researchers are able to publish a spectral signature for kauri as others have done for maple trees for instance, it could be easier to monitor the kauri populations. See below for details about how this data could be used.
The most exciting information on the horizon will likely come from Jane Jutta Meiforth, a PhD candidate in New Zealand who is focused on Kauri Dieback Disease and Remote Sensing. She plans to use LiDAR, aerial photos, and satellite imagery to identify kauri and the spread of the disease based on canopy features.
Holes in the Canopy
As shown in figure 3 to the right, it has been proven by New Zealand reasearchers Betts et al. that remote sensing using LiDAR can produce digital elevation models (DEMs) capable of showing gaps in the canopy of a forest.
This tool could be used to identify areas of diseased kauri that are experiencing loss of the canopy. This in conjunction with Leaf Area Index studies would be able to map the spread of kauri dieback disease, or kauri trees suffering from increased drought stress.
TeAra.co.nz
Summary
In order to study the health of kauri at a larger scale, it is critical that New Zealand funds research in remote sensing. When kauri are diseased, their leaves yellow, they lose leaves, and will lose water content during drought. All of these symptoms are detectable with remote sensing from typical LANDSAT or MODIS data, and canopy structure can be studied with LiDAR aerial surveys. Coupled with well-established field sampling, we can visualize the health of kauri forests in New Zealand. It will take more involvement and support to continue to protect these amazing kauri forest ecosystems for centuries to come.