Ground and Aerial Photography of Geothermal Vegetation at Craters of the Moon Geothermal Area, Waikato

Abstract

Near-infrared (NIR) imagery has been used elsewhere to detect stressed vegetation, and could be used to automate detection of changes in the stress levels experienced by geothermal vegetation, e.g. those caused by changes in heat flow. NIR contains wavelengths that are used to calculate Normalised Difference Vegetation Index (NDVI). Recent drone-captured imagery at Craters of the Moon area, Wairakei, New Zealand, including RGB (normal colour aerial imagery), near infrared (NIR), and thermal infrared (TIR), was used to generate NDVI values and investigate their use in assessing stressed geothermal vegetation.
By assessing geothermal vegetation stress on the ground, and relating it to NDVI by taking downward-focused NIR images of geothermal vegetation, the potential link between NDVI and vegetation stress was examined in geothermal vegetation, with a view to investigating the relationship between changes in heat flow and vegetation stress.
Stressed geothermal vegetation (identified subjectively through percentage cover of dead foliage), and in particular vegetation dominated by geothermal k?nuka, can be identified by ground-based NDVI values at a relatively small scale. Aerial TIR had a surprisingly poor relationship with geothermal k?nuka dieback or stature, and was also poorly related to ground-based NDVI.