Ostrya knowltonii

This species is a rare tree. NatureServe reports that the subpopulations are sporadic over its range and may occur as small, isolated subpopulations and classes O. knowltonii as Vulnerable. New Mexico and Texas no longer track O. knowltoni; the 10 element occurrences from Arizona are historic and 16 of Utah’s 37 element occurrences are historic.

Geological research into the fossil record at the Grand Canyon determined that this species was growing throughout the Grand Canyon during the last glacial maximum in mixed woodland – desert community. As the last glacial period came to an end the climate warmed and by 8,000 years ago this and other woodland species disappeared from the deep, inner canyon. Thus, in today’s distribution this species can be considered a glacial relict. It may be assumed that the subpopulations in the Grand Canyon National Park and upper Colorado river have remained stable. 

There are no quantitative data available from which to ascertain if the population trend is increasing, stable or decreasing across its geographic range. However, given the restricted relict habitats, known distribution and lack of human encroachment/development in the area of occupancy it is most likely that the overall population is stable.  Also, there is the potential for the discovery of additional occurrences if funding for the necessary botanical explorations was available.