|ASNER, GREGORY - Carnegie Institute - Stanford|
|MARTIN, ROBERTA - Carnegie Institute - Stanford|
|HELLER, WADE - University Of Hawaii|
|HUGHES, MARC - University Of Hawaii|
|VAUGHN, NICHOLAS - Carnegie Institute - Stanford|
|HUGHES, FLINT - Us Forest Service (FS)|
|BALZOTTI, CHRISTOPHER - Carnegie Institute - Stanford|
Submitted to: Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2018
Publication Date: 3/6/2018
Citation: Asner, G., Martin, R., Keith, L.M., Heller, W., Hughes, M., Vaughn, N., Hughes, F., Balzotti, C. 2018. A spectral mapping signature for the Rapid Ohia Death (ROD) pathogen in Hawaiian forests. Remote Sensing. 10(3):404-417. doi:10.3390/rs10030404.
Interpretive Summary: A study was conducted to develop a quantitative link between leaf and canopy spectroscopy and the chemistry of foliage in ROD-affected trees on Hawaii Island. The results of this study support a new approach to map and monitor the ROD fungal outbreak using LGIS measurements.
Technical Abstract: Pathogenic invasions are a major disruptive source of change in both agricultural and natural ecosystems. In forests, fungal pathogens can kill habitat-generating plant species such as canopy trees, but methods for remote detection, mapping and monitoring of such outbreaks are poorly developed. Ceratocystis wilt has spread rapidly across humid and mesic forests of Hawaii Island, causing widespread mortality of the keystone endemic canopy tree species, Metrosideros polymorpha or Ohia. The process, known as Rapid Ohia Death (ROD), causes browning of canopy leaves in days to weeks; however, the period of time following infection by the pathogen to visible symptom development could take several months or more. An operational mapping approach is needed to track the spread of the disease. We combined field studies of leaf spectroscopy, with laboratory chemical studies and airborne remote sensing, to develop a spectral signature for ROD. We found that more than 80% of ROD-infected plants undergo marked decreases in foliar concentrations of chlorophyll, water and non-structural carbohydrates, which collectively result in strong consistent changes in leaf spectral reflectance in the visible (400-700 nm) and shortwave-infrared (1300-2500 nm) wavelength regions. Leaf-level results were replicated at the canopy level using airborne laser-guided imaging spectroscopy, with quantitative spectral separability of normal green-leaf canopies from suspected ROD-infected brown-leaf canopies in the visible and shortwave-infrared spectrum. Our results provide the spectral-chemical basis for detection, mapping and monitoring of the spread of ROD in native Hawaiian forests.