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Relationships between ground and aerial photography and geothermal vegetation at Craters of the Moon geothermal area, Waikato

TR 2016/34

Report: TR 2016/34

Author: Kelvin Lloyd, Des Smith, Chris Bycroft, Steve Rate (Wildlands)

About this report

Geothermal ecosystems are some of the most threatened in the Region, having undergone significant reduction in extent and condition. In order to measure change in the extent and condition geothermal vegetation in the Waikato Region, Waikato Regional Council commissioned a test survey at Craters of the Moon to determine whether thermal infra-red, near infrared and visual images of vegetation captured aerially and on the ground could be processed and analysed to determine changes in stress levels in plants due to such factors are changing ground temperatures.

Stressed geothermal vegetation (identified subjectively through percentage cover of dead foliage), and in particular vegetation dominated by geothermal kānuka, can be identified by ground-based NDVI values at a relatively small scale. This suggests that aerial NDVI may also be able to determine geothermal vegetation stress. There was a strong relationship between stressed geothermal kānuka and median ground-based NDVI. Ground-based NDVI was also strongly related to geothermal kānuka height, so long as an outlying value was removed. NDVI and TIR derived from drone-collected imagery have a broadly negative relationship, implying that at higher temperatures leaf density is lower, but this relationship requires further analysis using a larger dataset to establish its true pattern.

Further work is required to validate the relationship between geothermal kānuka height and NDVI, and the relationship between TIR and NDVI. These conclusions are also limited through being interpreted from data collected from just one geothermal site, and at one time of year.


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Relationships between ground and aerial photography and geothermal vegetation at Craters of the Moon geothermal area, Waikato. [PDF, 4.6 MB]


1 Introduction
2 Site description
3 Methods
3.1 Review of information
3.2 Aerial photography with drone
3.3 Ground-based photography
3.4 Analysis of photography
3.4.1 Terrestrial based NDVI calculations
3.4.2 Terrestrial based NDVI analysis
3.4.3 Aerial based NDVI analysis
3.4.4 Analysis of aerial-based TIR versus NDVI
3.4.5 Photopoint analysis of Aerial based TIR versus NDVI
3.5 Statistical analyses
4 Stress and geothermal vegetation
5 Normalised difference vegetation index (NDVI) 
5.1 Overview
5.2 Limitations of NDVI
5.3 NDVI values used to assess vegetation
6 Results
6.1 Ground-based NDVI analyses
6.1.1 Ground-based NDVI and vegetation dieback
6.1.2 Ground-based NDVI and vegetation height
6.1.1 Ground-based NDVI and habitat type
6.2 Aerial TIR and NDVI analyses
6.2.1 Aerial TIR versus aerial NDVI in geothermal kanuka
6.2.2 Aerial TIR versus aerial NDVI for geothermal habitats
6.2.1 Aerial TIR versus geothermal stress and ground-based NDVI
6.3 Soil temperature and geothermal vegetation stress
6.3.1 Soil temperature and geothermal kānuka dieback
6.3.2 Soil temperature and geothermal kānuka height
7 Discussion
8 Conclusions