15-year height of pinus ponderosa is correlated with diurnal temperature variation during bud elongation

An inverse correlation exists between mean diurnal temperature variation (DT) during the bud elongation season and the 15-year height of Pinus ponderosa. Environments with larger DT result in slower growth rates than environments with smaller DT for all families tested. The coefficient of determination (R[squared]) for the mean height of 17 open pollinated families was 0.99. Comparable R[squared] of 0.90 and 0.93, respectively, were found for local trees (same seed zone and similar elevation as the plantations) and general trees (same seed zones but not necessarily similar elevations). In contrast, R[squared] for mean local tree height correlation with the more commonly considered variables of elevation, latitude, mean temperature, and mean daily high temperature for the warmest month of the year were 0.46, 0.73, 0.57, and 0.19, respectively. The available data indicates that the strong correlation between DT and growth rate can be used to select for site fitness, growth rates on untested sites, and adaptation of a species to a site, and to predict the response to climate change. The strong correlation between growth season temperatures and growth rates may be more effective than using geography and elevation in definition of seed and breeding zones.