A variety of organisms change their geographic locations during their life
history, and many use the atmosphere to accomplish this shift. Biota that h
ow in the atmosphere range from very small (viruses, bacteria, pollen, and
spores) to quite large (weed seeds, aphids, butterflies and moths, songbird
s, and waterfowl). As these organisms move, they experience meteorological
and ecological conditions that occur at a wide range of spatial and tempora
l scales. We present an ecological scaling approach that integrates concept
s and elements of spatial and temporal scaling to understanding aerobiology
and provide examples of the ecological scales important to the long-distan
ce aerial movement of organisms and associated biological events and proces
ses.
An operational framework for ecological scaling of long distance biota move
ment is achieved by linking spatially-static ecoregion classification syste
ms with temporally-dynamic measures of vegetation phenology. The ecoregions
provide ecological boundaries for the phenological dynamics of plants. Ope
rationally, this approach integrates the bi-weekly vegetation greening indi
ces (NDVI) derived from AVHRR or TM satellite data (representing temporal s
caling) with the less dynamic land cover-land use classification (IGBP) and
the relatively static ecoregion boundaries (representing the spatial scali
ng). We argue that the correlation of the life histories of species, especi
ally the timing of take-off to ecosystem phenology through meteorological-b
ased variables and indices (e.g., degree days and moisture indices), allows
for dynamic characterization of source ecosystems and can be used to param
eterize atmospheric models to forecast the flow of biota in the air.
The scale of these processes, the diversity of the types of biota involved
in long-distance movement, and the complexity of the processes require syst
ems thinking. We anticipate that this paper will stimulate studies to enhan
ce our understanding of the flow of organisms in the biosphere. (C) 1999 Pu
blished by Elsevier Science B.V. All rights reserved.