Detection of canopy water stress in conifers using the Airborne Imaging Spectrometer

George A. Riggs, Steven W. Running

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56 Scopus citations


Imagery was acquired by the Airborne Imaging Spectrometer (AIS-2) over adjacent plots of control (natural) and water-stressed canopies of Norway spruce and white pine, and analyzed for differences in near-infrared reflectance features. Water stress had been induced in the trees by severing the sapwood and was assessed with shoot water potential (ψ) and relative water content (RWC) measurements. Stressed Norway spruce was found to have approximately 20% greater relative reflectance in the 1.0-1.3 μm region compared to the control canopy in the image obtained at 0925 h 13 days after stress induction. The difference in ψ and RWC between stressed and control was measured at 1.2 MPa and estimated at 7%, respectively. However, the difference in reflectance decreased to insignificance in the image taken at 1219 h that same day when the differences in ψ and RWC were approximately 0.72 MPa and 5%. In white pine, no significant differences in reflectance between stressed and control canopies were found in images obtained 14 days and 20 days after treatment with estimated differences in ψ and RWC of 0.3 MPa and 6%. Because extensive ground data was required at times of AIS-2 overflights to detect these small reflectance differences, we believe that water stress in conifer canopies may not be routinely detectable at an operational landscape scale.

Original languageEnglish
Pages (from-to)51-68
Number of pages18
JournalRemote Sensing of Environment
Issue number1
StatePublished - Jan 1991


Funding for this research was provided by the NASA Graduate Student Researchers Program, Training Grant NGT 27-003-800 and NASA Grant #NAGW-829. Many thanks to Dr. Georg Kritikos, Dr. Manfred Schramm, Martin Lamberty and crew, Dr. Barbara Koch, and Dr. U. Ammer for their assistance in site selection, data collection, and the hospitality they extended to us while we were in Germany. We are also grateful to Dr. Barrett Rock for his assistance and for providing us with a set of pressure volume data for Norway spruce from his study area in Germany. Thanks also to Lisa Barge and Alex Zack at JPl~ who patiently assisted with the initial AIS-2 image data display and analysis. Also a debt of appreciation goes to tars Pierce and Dr. Ray Hunt for their many constructive comments and suggestions, and to Dr. Carol Wessman for her suggestions and comments that improved the manuscript.

FundersFunder number
National Aeronautics and Space Administration-829, NGT 27-003-800


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