He made significant contributions to the study of plant ecology throughout the twentieth century, including introducing a vegetation classification scheme, helping define the modern study of ecological succession, and writing the standard reference textbooks for ecologists of the time period.
He studied under Ray C. Freisner, head of the botany department, and Stanley A. Cain, a plant ecologist, who both influenced his eventual career.
[3] He performed an ecological study of the Big Woods, a temperate hardwood forest ecoregion found in Minnesota.
[1][2] In 1948, only one year after joining WSU's faculty, he created a six-week intensive summer field course for surveying in the Rocky Mountains.
He was joined by seven students from universities in Idaho, Michigan, Montana, and Tennessee, as well as his wife Jean Boomer, who was also a botanist.
The Daubenmires travelled to multiple locations, including the Amazon rainforest, the Philippines, Malaysia, and Africa, and Rexford led naturalist trips to Ecuador and Costa Rica.
It proposed that over an area, a plant species would appear, increase in quantity, then decline, and finally disappear, without distinct communities that could be predictably understood.
He criticized Curtis's continuum theory, noting that it was unable to provide any meaningful results because it did not have an organizing principle and could not make predictions.
[6] His work helped pioneer the "ecology of place," understanding how predictions could promote better environmental health and broader ecosystems, while also servicing human needs for natural resources through a scientifically informed process.
[4] In his 1970 book Steppe Vegetation of Washington, he questioned the perceived wisdom of rangeland managers who were in favour of eradicating sagebrush, an economically non-viable plant whose removal provided better growth for valuable grasses in the short-term.
He argued instead that a scientifically informed view of managing those systems would recognize the value of all species, not just those that had resource worth, because of how they had impacts, both direct and indirect, on long-term health of the range.
He noted that sagebrush protected grasses which would be at risk of overgrazing without it; that its removal would have negative effects on mineral recycling into the soil, making for worse yields of other products in the future; that sagebrush provided habitat for birds that controlled insects; and that it increased soil quality in terms of moisture, by holding snow longer into springtime.
[6] Through decades of fieldwork, Daubenmire was able to classify the plant habitats in the forests and steppes of the Columbia Plateau.
This involves recording the amount of cover of each plant along a set length of rope, then summing by species and converting into a percentage.
[11] He discovered a new monotypic genus of Boraginaceae (a family of flowering plants that includes the forget-me-not) which is endemic to only a few square kilometers in northern Idaho.