Fieldwork and university research
Warming worked for naturalist P. W. Lund in Brazil in 1863–1866 and studied vegetation near Lagoa Santa. After a doctorate in 1871 and a professorship in Stockholm, he moved to Copenhagen in 1886 as professor of botany and director of the botanical garden.
References: [2]
Communities and ecological factors
Plantesamfund (1895), followed by an English edition in 1909, examined plants in relation to light, moisture, temperature and other factors. Similar growth forms could reflect similar conditions rather than close evolutionary relationships.
Plants spreading underground
His 1918 study of underground runners examined horizontal growth and the separation of connected parts into independent units. Such observations complicate the identification of a plant individual with a single visible shoot.
References: [2]
Influence and rediscovery
His community studies influenced Cowles and Tansley. Later historical analysis distinguishes that documented influence from parallels between his clonal-plant observations and modern research, which need not imply direct transmission.
References: [2]