He graduated in Freiburg in 1928 with a doctorate which he wrote under the direction of Friedrich Oltmanns and the ecophysiologist Bruno Huber, about the relationship between the places where different algae grew on the rock faces of the Überlinger See and the light conditions at different depths.
This work was supported by the Notgemeinschaft der Deutschen Wissenschaft, a forerunner organization of the German Research Foundation, and was undertaken, among other things, because the Schluchsee was to be dammed up to generate electricity.
Oberdorfer mainly examined the large remains, which he took from depths of up to seven meters using soil auger, and established pollen profiles of the different layers.
In doing so, he had to write reports and descriptions of the nature reserves between Lake Constance and the Tauber area, and his trips made him a profound expert on the vegetation of what was then Baden.
He had experience with the vegetation of Southeastern Europe as a botanist at the "Research Season zbV" where the Lieutenant Schulz-Kampfhenkel used and mapped including in Thessaly, Macedonia, Albania, and Thrace, where he made with colleagues phytosociological recordings and auswertete soil profiles.
After the end of the war Oberdorfer was initially only given occasional jobs due to his membership of the SA and the NSDAP, for example as a research assistant to Heinrich Walter at the University of Hohenheim.
From 1950 Oberdorfer held a teaching position for plant-sociological site studies at the Forestry Faculty of the University of Freiburg and was appointed honorary professor there in 1962.
With this work, Oberdorfer has made a significant contribution to the shift in field botany from pure floristry to a site-ecological consideration of the vegetation.