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Assessment of Aspen Defoliation in Canada with MERIS

Joost van der Sanden(1), Vincent Decker(1), Alice Deschamps(1), Robert Landry(1) and Ron Hall(2)

(1) Canada Centre for Remote Sensing, 588 Booth Street, Ottawa K1A 0Y7, Canada
(2) Canadian Forest Service, 5320 – 122 Street, Edmonton T6H 3S5, Canada

Abstract

In most years, insects defoliate several million hectares of forest dominated by trembling aspen in Canada’s boreal forest region. The effects of recurring severe defoliation include reduced radial stem growth, increased susceptibility to other stressors, and mortality. As such, aspen defoliation impacts wood supply and the terrestrial carbon balance. The frequency and severity of defoliation outbreaks are predicted to increase in response to climatic warming. Information needs associated with sustainable development strategies, carbon accounting initiatives and national reporting obligations account for the growing demand for nationally consistent and timely information on the spatial location, extent and severity of insect-induced aspen defoliation.

In this paper we will discuss the results of an ongoing study into the potential of the Medium Resolution Imaging Spectrometer (MERIS) for the mapping and monitoring of aspen defoliation in Northern Alberta, Canada. The strengths of MERIS for the application studied include its two to three day repeat cycle and large, medium-resolution spatial coverage. The results obtained to date (2004 onwards) indicate that MERIS facilitates a national-scale, first-order assessment of the location and extent of severe aspen defoliation. Compared to traditional aerial insect defoliation sketch-maps, MERIS based defoliation products show more detail in terms of the location and extent of defoliation and the variability in defoliation severity. Cloud permitting, MERIS data enable the assessment of the peak defoliation date and the defoliation / refoliation time window. Information on progress and location of defoliation facilitates the selection of high resolution image data for more detailed local-scale, second-order assessment aspen defoliation.

 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry