Forest management will protect genetic integrity of tree species only if their genetic diversity is understood and considered in decision-making. Genetic knowledge is particularly important for species such as ponderosa pine that are distributed across wide geographic distances and types of climates.
A ponderosa pine study initiated by Gustaf A. Pearson in 1910 at the Fort Valley Experimental Forest (FVEF) is among the earliest ponderosa pine genetic research efforts in the United States. Seed was collected from 18 National Forests, grouped into two ponderosa pine varieties: Scopulorum and Ponderosa. In a provenance experiment, seed is collected from many natural stands (i.e., sources) and then grown in a common environment to study genetic diversity and adaptation patterns. Pearson’s research contributed to the description of ponderosa pine's varietal differences, genetic diversity and adaptation patterns, and helped confirm the importance of using local seed sources.
Researchers are revisiting the 100-year old provenance study in order to assess genetic diversity, adaptation patterns, and improve forest management of ponderosa pine. Researchers hypothesize:
Provenances from climates similar to FVEF will have higher survival rates.
Provenances from climates similar to FVEF will have higher growth rates.
Provenances from wetter sites will show more sensitivity to local climate variations.
For the original provenance study, ponderosa pine survival was monitored until 1919, then subsequently measured in 1928, 1951, 1964, and 1995. Tree heights were measured in 1928 and heights and diameters were measured in 1964 and 1995–1996.
In 2014, researchers measured height and diameter and cored selected trees. Researchers assumed that tree size is a function of age, density, climate, and provenance. Tree data were correlated with long-term weather data at study location and at the original source of the contributed seeds. In 2015, researchers measured density around selected trees.
All ponderosa trees of the Ponderosa variety were dead at the time of re-measurement in 2014.
Provenance from more northerly or higher elevation performed better.
DeWald, Laura E.; Mahalovich, Mary Frances 2008. Historical and contemporary lessons from ponderosa pine genetic studies at the Fort Valley Experimental Forest, Arizona. Pp 150-155 in Olberding, S.D., and Moore, M.M., tech. coords. Fort Valley Experimental Forest-A Century of Research 1908-2008. Conference Proceedings; August 7-9, 2008; Flagstaff, AZ. Proc. RMRS-P-55. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station.