Plant distributions along mountain gradients
As an Illinois graduate student, Whittaker investigated Great Smoky Mountain vegetation by plotting species along environmental axes such as elevation. Species did not change density or cover in synchronized groups, supporting an individualistic continuum interpretation.
The work formed his 1948 dissertation; the monograph on Great Smoky Mountain vegetation appeared in 1956. The later publication date therefore differs from the period of the original investigation.
References: [1]
Estimating production from plant dimensions
His mountain research expanded to forest biomass and productivity. Besides tree trunks, he measured other tree parts, shrubs and herbs to estimate above-ground plant production.
Using dimensions and growth-ring information, he developed estimation methods and compared forests and deserts with collaborators. This extended studies of composition into material accumulation and ecosystem function.
References: [1]
An ecological approach to classification
Whittaker proposed a classification of kingdoms in 1957 based partly on trophic structures and nutritional energy sources. He subsequently revised it, with the 1969 version becoming particularly influential.
The five-kingdom system became common in late twentieth-century biology textbooks. Historical scholarship identifies ecological influences on its early development and later contributions from cell biology, placing it within a changing scientific context.
Research and teaching syntheses
His work also covered species diversity, vegetation ordination, succession and plant chemical interactions. Communities and Ecosystems appeared in 1970, followed by a second edition in 1975, synthesizing a diverse ecological literature for teaching.
Field studies in different regions connected community composition, environments and ecosystem function. Classification served both to organize the living world and to investigate community patterns.
References: [1]