THE RELATIONSHIP BETWEEN TUSSOCK TUNDRA SPECTRAL REFLECTANCE PROPERTIES AND BIOMASS AND VEGETATION COMPOSITION

Frequent cloud cover and logistical constraints hamper biophysical remote sensing studies in arctic locations, resulting in a general lack of information regarding relationships between biophysical quantities and the spectral reflectance of arctic vegetation communities. An experiment was conducted on the north slope of Alaska to characterize relationships between the spectral reflectance of three tussock tundra communities (moist tussock, dry heath and water track) and the above ground biomass and vegetation composition of each community. Hand-held radiometric and ground reference data were collected three times during the 1989 growing season. The normalized difference vegetation index (NDVI) was regressed on above ground photosynthetic and non-photosynthetic biomass quantities and individual blue, green red and near-infrared spectral reflectances and the NDVI were regressed on vegetation cover type fractions. Up to 51 per cent of the variance in the NDVI was explained by the amount of photosynthetic biomass in the moist tussock and dry heath communities while no significant relationship was established between the NDVI and non-photosynthetic biomass. Vegetation cover types had a substantial effect on the observed spectral reflectances and NDVI of each of the three communities. A secondary objective of the study was to determine whether the ratio of photosynthetic to non-photosynthetic biomass could be determined using simple point quadrat estimates of these fractions. No substantial relationship was established between the harvested and point quadrat estimates of the biomass fractions.