Laurie A. Chisholm

Stewardship among lifestyle oriented rural landowners.

Changes in landownership associated with amenity migration are affecting the demographic, cadastral and ecological conditions of rural landscapes. These changes and concerns about their impacts on natural resource management, including ecological conservation, relate to both the structural consequences of landownership change, land subdivision and to the motivations, management ability and attitudes of lifestyle oriented rural landowners. Based on an Australian case study near Sydney, NSW, this paper examines the motivations and practices of such landowners, assesses potential consequences for vegetation and characterises the landowners according to three stewardship types.

Spectral reflectance characteristics of eucalypt foliage damaged by insects

Variables related to foliar damage, leaf morphology, spectral reflectance, chlorophyll fluorescence and chlorophyll content were measured from leaves sampled from mature eucalypts exhibiting symptoms of crown dieback associated with bell miner colonisation located in Olney State Forest, near Wyong, New South Wales. Insect-damaged mature leaves and healthy young expanding leaves of some species exhibited a conspicuous red coloration caused by the presence of anthocyanin pigmentation. For the mature leaves, the level of red coloration was significantly correlated with insect herbivory and leaf necrosis. Significant correlations were also found between the level of red pigmentation and the following four spectral features: maximum reflectance at the green peak (550 nm); the wavelength position and maximum slope of the red edge (690-740 nm) and the maximum reflectance at 750 nm in the near-infrared portion of the electromagnetic spectrum. While it has been shown that anthocyanin pigments are synthesised in some eucalypt species in response to certain abiotic stresses causing photoinhibition and activation of photoprotective mechanisms, this work proposes that biotic agents such as leaf damaging insects and fungal pathogens may induce a similar response in eucalypt foliage resulting in increased levels of anthocyanins. The potential of anthocyanin levels to be related to leaf ontogeny for some eucalypt species was also illustrated in the reflectance spectra. Thus, it is essential that leaf age be considered. This work demonstrates that the identification of a number of key features of leaf spectra can provide a basis for the development of a robust forest health indicator that may be obtained from airborne or spaceborne hyperspectral sensors.

Monitoring live fuel moisture content of heathland, shrubland and sclerophyll forest in south-eastern Australia using MODIS data

Live fuel moisture content is an important variable for assessing fire risk. Satellite observations provide the potential for monitoring fuel moisture across large areas. The objective of this study was to use data from the Moderate Resolution Imaging Spectroradiometer to monitor live fuel moisture content of three fire-prone vegetation types (shrubland, heathland and sclerophyll forest) in south-eastern Australia. The performances of four spectral indices (Normalised Difference Vegetation Index, Visible Atmospherically Resistant Index, Normalised Difference Infrared Index centred on 1650 nm and Normalised Difference Water Index) were compared. Models based on Visible Atmospherically Resistant Index and Normalised Difference Infrared Index centred on 1650 nm provided the best results (R2 values of 0.537 and 0.586). An empirical model based on these two indices was developed and its performance compared with a meteorological index traditionally used in this context, the Keetch–Byram Drought Index. The empirical model (R2 = 0.692) outperformed the meteorological index (R2 = 0.151), showing an enhanced capability to predict live fuel moisture content of the fire-prone vegetation types considered.

Classification of Australian Native Forest Species Using Hyperspectral Remote Sensing and Machine-Learning Classification Algorithms

Mapping forest species is highly relevant for many ecological and forestry applications. In Australia, the classification of native forest species using remote sensing data remains a particular challenge since there are many eucalyptus species that belong to the same genus and, thus, exhibit similar biophysical characteristics. This study assessed the potential of using hyperspectral remote sensing data and state-of-the-art machine-learning classification algorithms to classify Australian forest species at the leaf, canopy and community levels in Beecroft Peninsula, NSW, Australia. Spectral reflectance was acquired from an ASD spectrometer and airborne Hymap imagery for seven native forest species over an Australian eucalyptus forest. Three machine-learning classification algorithms: Support Vector Machine (SVM), AdaBoost and Random Forest (RF) were applied to classify the species. A comparative study was carried out between machine-learning classification algorithms and Linear Discriminant Analysis (LDA). The classification results show that all machine-leaning classification algorithms significantly improve the results produced by LDA. At the leaf level, RF achieved the best classification accuracy (94.7%), and SVM outperformed the other algorithms at both the canopy (84.5%) and community levels (75.5%). This study demonstrates that hyperspectral remote sensing and machine-learning classification has substantial potential for the classification of Australian native forest species.

Effects of leaf age and psyllid damage on the spectral reflectance properties of Eucalyptus saligna foliage

Leaf chlorophyll content is influenced directly by many environmental stress factors. Because leaf pigment absorption is wavelength dependent, numerous narrow-band reflectance-based indices have been proposed as a means of assessing foliar health and condition. Chlorophyll content, however, also varies with leaf developmental stage. In this study, a range of morphological and physiological traits including insect damage, relative chlorophyll content (SPAD values), chlorophyll fluorescence (Fv/Fm) and reflectance spectra was measured of leaves sampled from mature Eucalyptus saligna. Relative differences among three leaf-age cohorts were compared with differences obtained from mature leaves that were either healthy or infested with the psyllid Glycaspis baileyi. Differences in relative chlorophyll content were greater between immature and mature foliage than between damaged and healthy mature leaves. These differences were confirmed in the comparisons of reflectance spectra and indices. As many eucalypt species have opportunistic crown phenology and long-lived leaves, leaf-age composition of crowns needs to be taken into account when applying reflectance-based indices to assess foliar condition of eucalypts.

Differentiation of selected Australian woodland species using CASI data

The potential use of Compact Airborne Spectrographic Imager (CASI II) data for discriminating woodland tree species common to the Southern Brigalow Belt of central Queensland was investigated. For an area near Injune, 1:4000 georeferenced stereo aerial photography, plot data relating to tree species and location, and stand visualisation software were used to identify individual tree crowns of six common woodland species within 1 m spatial resolution CASI data, from which their reflectance values were extracted. Based on transformed divergence and Jefferies-Matuista measures, the spectral separability of species was established. The analysis suggested that most species could be readily distinguished using CASI data, although shadowing within and between crowns was considered a limitation. The research, although preliminary, is anticipated to benefit scaling-up of plot-based estimates of biomass to the landscape and assessment of biodiversity.

A method to dynamically subdivide parcels in land use change models

Spatial simulation models have become a popular tool in studying land use/land cover (LULC) change. An important, yet largely overlooked process in such models is the land subdivision, which is known to govern LULC change and landscape restructuring to a large extent. To fill this gap, we propose an efficient and straightforward method to simulate dynamic land subdivision in LULC change models. Key features in the proposed method are implementing a hierarchical landscape where adjacent cells of the same LULC type form patches, patches form properties, and properties form the landscape and incorporating real subdivision layouts. Furthermore, we use a queue-based modified flood-fill algorithm to dynamically reset LULC patches following a subdivision. The proposed subdivision method is demonstrated in action using a prototype agent-based LULC model developed for an amenity landscape in Australia. Results show that it is computationally feasible to run the subdivision method even as spatial resolution is increased, thus providing a proven means for spatial simulation models to dynamically split parcel land.

Approaches to establishing a metadata standard for field spectroscopy datasets

There is an urgent need within the international remote sensing community to establish a metadata standard for field spectroscopy that ensures high quality, interoperable metadata sets that can be archived and shared efficiently within Earth observation data sharing systems. Careful examination of all stages of metadata collection and analysis can inform a robust standard that is applicable to a range of field campaigns. This paper presents approaches towards a standard that encompasses in situ metadata collection and initiatives towards sharing metadata within intelligent archiving systems.

Assessing eucalypt foliar health with field-based spectra and high spatial resolution hyperspectral imagery

Advances in remote sensing technologies, especially the increasing application of hyperspectral datasets, provide new opportunities to develop reliable, robust indicators of canopy health for Australian eucalypt forests. Leaf reflectance in the visible and near-infrared wavelengths measured using a hand-held spectroradiometer were compared with foliar damage, leaf morphology, chlorophyll fluorescence and chlorophyll content sampled from eucalypt leaves exhibiting symptoms of canopy dieback. Compact Airborne Spectrographic Imager (CASI-2) imagery was also collected over the crowns and spectral signatures extracted from the 80 cm spatial resolution imagery. Results indicate that a number of spectroradiometer derived indices were significantly correlated with leaf variables. These indices were predominantly those that incorporated the spectral red-edge such as changes in slope, the slope of the lower red-edge, the maximum slope, the inflection wavelength and newly proposed red/green indices which specifically target anthocyanins. Mean leaf chlorophyll content, leaf chlorophyll fluorescence, leaf length to width ratio, and estimated percent leaf with red discoloration were all highly significantly correlated to several CASI-2 derived indices. Overall the research has demonstrated strong relationships between eucalypt leaf spectra and leaf damage and morphometry variables.

Spectral and Spatial Variation at Leaf and Patch Scale of Invasive Wetland Weeds

The establishment of invasive weeds in wetland environments is a prominent threat in Australia with adverse impacts on native flora. Current management is hindered by the lack of information available on which to base and justify management interventions, in particular, mapping of weed distributions. Remote sensing is a possible solution to difficulties of this type as illustrated by its successful application to wetland mapping in general. This paper explores the potential of multiscale spectral reflectance to discriminate between two particularly offensive, invasive woody weeds, bitou bush (Chrysanthemoides monilifera ssp rotundata), and lantana (Lantana camara). Spectral reflectance at the leaf and patch-level scales was measured at multiple sites using a field spectrometer. Derivative analyses of spectra as well as t-tests were used to evaluate spectral separability between species across scales. Results suggest further analysis is warranted at the patch level where species are intermixed and structural factors more complex.