How did Robert Whittaker change classification?

Extremely productive, Whittaker was a leading proponent and developer of gradient analysis to address questions in plant community ecology. He provided strong empirical evidence against some ideas of vegetation development advocated by Frederic Clements. Whittaker was most active in the areas of plant community analysis, succession, and productivity. "During his lifetime Whittaker was a major innovator of methodologies of community analysis and a leader in marshaling field data to document patterns in the composition, productivity and diversity of land plant communities."[1] Thus Whittaker was innovative in both empirical data sampling techniques as well as synthesizing more holistic theories.